diff --git a/.forgejo/workflows/build.yaml b/.forgejo/workflows/build.yaml
index 4441b4dd8..6271cb72a 100644
--- a/.forgejo/workflows/build.yaml
+++ b/.forgejo/workflows/build.yaml
@@ -314,26 +314,29 @@ jobs:
 
           # Docs image is a Sphinx static site (deploy/Dockerfile.docs)
           # that also bundles the paradoc-backed FEA verification report.
-          # Rebuild on docs/**, the report source tree, pixi env files,
-          # the Dockerfile, or the workflow itself. Fast = only the doc
-          # sources changed (re-run fea-doc + sphinx on the env base);
-          # env/Dockerfile/workflow changes need the full build.
+          # It is by far the slowest image to build, so it is OPT-IN: it
+          # builds only when the head commit message carries a ``[docs]``
+          # marker, regardless of what changed. Viewer/worker builds are
+          # unaffected. Works for push and workflow_dispatch (GITHUB_SHA is
+          # the branch tip either way; fetch-depth:0 above makes the message
+          # available).
           docs=false
           docs_full=false
-          if match_scope "$DOCS_CHANGED" '^docs/' || \
-             match_scope "$DOCS_CHANGED" '^src/ada/' || \
-             match_scope "$DOCS_CHANGED" '^pixi\.(toml|lock)$' || \
-             match_scope "$DOCS_CHANGED" '^pyproject\.toml$' || \
-             match_scope "$DOCS_CHANGED" '^verification/' || \
-             match_scope "$DOCS_CHANGED" '^deploy/Dockerfile\.docs(-fast)?$' || \
-             match_scope "$DOCS_CHANGED" '^\.forgejo/workflows/build\.yaml$'; then
+          COMMIT_MSG=$(git log -1 --format=%B "$GITHUB_SHA" 2>/dev/null || echo "")
+          if printf '%s' "$COMMIT_MSG" | grep -qiF '[docs]'; then
             docs=true
-          fi
-          if match_scope "$DOCS_CHANGED" '^pixi\.(toml|lock)$' || \
-             match_scope "$DOCS_CHANGED" '^pyproject\.toml$' || \
-             match_scope "$DOCS_CHANGED" '^deploy/Dockerfile\.docs$' || \
-             match_scope "$DOCS_CHANGED" '^\.forgejo/workflows/build\.yaml$'; then
-            docs_full=true
+            # Fast build (re-run fea-doc + sphinx on the cached env base)
+            # unless the pixi env / Dockerfile / workflow changed — those
+            # need a full rebuild off a fresh env base.
+            if match_scope "$DOCS_CHANGED" '^pixi\.(toml|lock)$' || \
+               match_scope "$DOCS_CHANGED" '^pyproject\.toml$' || \
+               match_scope "$DOCS_CHANGED" '^deploy/Dockerfile\.docs$' || \
+               match_scope "$DOCS_CHANGED" '^\.forgejo/workflows/build\.yaml$'; then
+              docs_full=true
+            fi
+            echo "[docs] present in the head commit message — building docs (full=$docs_full)."
+          else
+            echo "docs build is opt-in — add [docs] to the head commit message to build it. Skipping."
           fi
 
           {
diff --git a/.gitattributes b/.gitattributes
index 8f61a8e77..16d52b221 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -1,2 +1,3 @@
 # SCM syntax highlighting
 pixi.lock linguist-language=YAML linguist-generated=true
+files/ifc_files/beam-standard-case-gz.ifc binary
diff --git a/.github/workflows/ci-pages.yml b/.github/workflows/ci-pages.yml
index 00e7a96f4..0694c5aad 100644
--- a/.github/workflows/ci-pages.yml
+++ b/.github/workflows/ci-pages.yml
@@ -50,7 +50,7 @@ jobs:
         with:
           fetch-depth: 0 # otherwise, you will fail to push refs to dest repo
 
-      - uses: prefix-dev/setup-pixi@v0.9.6 # https://github.com/prefix-dev/setup-pixi
+      - uses: prefix-dev/setup-pixi@v0.10.0 # https://github.com/prefix-dev/setup-pixi
         with:
           pixi-version: v0.68.0
           environments: docs
diff --git a/.github/workflows/main-profiling.yml b/.github/workflows/main-profiling.yml
index 5e964e18f..973ac7ebe 100644
--- a/.github/workflows/main-profiling.yml
+++ b/.github/workflows/main-profiling.yml
@@ -27,7 +27,7 @@ jobs:
           fetch-depth: 0
 
       - name: Setup Pixi
-        uses: prefix-dev/setup-pixi@v0.9.6
+        uses: prefix-dev/setup-pixi@v0.10.0
         with:
           pixi-version: v0.68.0
           environments: profile
diff --git a/.github/workflows/pr-profiling.yml b/.github/workflows/pr-profiling.yml
index 627671883..f94c229df 100644
--- a/.github/workflows/pr-profiling.yml
+++ b/.github/workflows/pr-profiling.yml
@@ -29,7 +29,7 @@ jobs:
           persist-credentials: false
 
       - name: Setup Pixi
-        uses: prefix-dev/setup-pixi@v0.9.6
+        uses: prefix-dev/setup-pixi@v0.10.0
         with:
           pixi-version: v0.68.0
           environments: profile
diff --git a/.github/workflows/pr-tests.yml b/.github/workflows/pr-tests.yml
index a0e5f6997..d604d5ef2 100644
--- a/.github/workflows/pr-tests.yml
+++ b/.github/workflows/pr-tests.yml
@@ -19,7 +19,7 @@ jobs:
             with:
               ref: ${{ github.event.pull_request.head.sha || github.ref }}
 
-          - uses: prefix-dev/setup-pixi@v0.9.6 # https://github.com/prefix-dev/setup-pixi
+          - uses: prefix-dev/setup-pixi@v0.10.0 # https://github.com/prefix-dev/setup-pixi
             with:
               pixi-version: v0.68.0
               cache: true
@@ -41,7 +41,7 @@ jobs:
           with:
             ref: ${{ github.event.pull_request.head.sha || github.ref }}
 
-        - uses: prefix-dev/setup-pixi@v0.9.6
+        - uses: prefix-dev/setup-pixi@v0.10.0
           with:
             pixi-version: v0.68.0
             environments: tests
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 6032b0b67..2f58c0995 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -19,7 +19,7 @@ jobs:
         with:
           ref: ${{ github.event.pull_request.head.sha || github.ref }}
 
-      - uses: prefix-dev/setup-pixi@v0.9.6 # https://github.com/prefix-dev/setup-pixi
+      - uses: prefix-dev/setup-pixi@v0.10.0 # https://github.com/prefix-dev/setup-pixi
         with:
           pixi-version: v0.68.0
           environments: tests
@@ -39,7 +39,7 @@ jobs:
         with:
           ref: ${{ github.event.pull_request.head.sha || github.ref }}
 
-      - uses: prefix-dev/setup-pixi@v0.9.6
+      - uses: prefix-dev/setup-pixi@v0.10.0
         with:
           pixi-version: v0.68.0
           environments: >-
@@ -64,7 +64,7 @@ jobs:
         with:
           ref: ${{ github.event.pull_request.head.sha || github.ref }}
 
-      - uses: prefix-dev/setup-pixi@v0.9.6
+      - uses: prefix-dev/setup-pixi@v0.10.0
         with:
           pixi-version: v0.68.0
           environments: >-
@@ -85,7 +85,7 @@ jobs:
         with:
           ref: ${{ github.event.pull_request.head.sha || github.ref }}
 
-      - uses: prefix-dev/setup-pixi@v0.9.6
+      - uses: prefix-dev/setup-pixi@v0.10.0
         with:
           pixi-version: v0.68.0
           environments: >-
@@ -122,7 +122,7 @@ jobs:
         with:
           ref: ${{ github.event.pull_request.head.sha || github.ref }}
 
-      - uses: prefix-dev/setup-pixi@v0.9.6
+      - uses: prefix-dev/setup-pixi@v0.10.0
         with:
           pixi-version: v0.68.0
           environments: >-
diff --git a/deploy/Dockerfile.viewer b/deploy/Dockerfile.viewer
index 0478d8714..fdc26df7f 100644
--- a/deploy/Dockerfile.viewer
+++ b/deploy/Dockerfile.viewer
@@ -47,10 +47,11 @@ RUN npm run build:serve
 COPY --from=adacpp-wheel /out/ /build/dist/wheels/
 COPY --from=adapy-wheel  /out/ /build/dist/wheels/
 
-# The no-pyodide STEP->GLB embind module (adacpp_step_glb.js + .wasm) ships in the same adacpp base
-# image under /out/wasm/, so the copy above lands it at dist/wheels/wasm/. Promote it to /wasm/ — where
-# the in-browser "Load STEP" converter (LocalStepLoader -> stepConverter.worker) fetches it. Guarded so
-# the build still works against older base images that predate the module.
+# The no-pyodide embind modules (adacpp_step_glb / adacpp_ifc_glb / adacpp_brep_writer / adacpp_glb_diff
+# .js + .wasm) ship in the same adacpp base image under /out/wasm/, so the copy above lands them at
+# dist/wheels/wasm/. Promote the whole dir to /wasm/ — where the in-browser converters (cadGlbConverter
+# / brepWriterConverter workers) and the diff utility fetch them. Guarded + globbed so the build works
+# against older base images that predate any given module.
 RUN mkdir -p /build/dist/wasm && \
     if [ -d /build/dist/wheels/wasm ]; then \
         mv /build/dist/wheels/wasm/* /build/dist/wasm/ && rmdir /build/dist/wheels/wasm; \
diff --git a/deploy/Dockerfile.worker b/deploy/Dockerfile.worker
index c9b548dde..d620162a3 100644
--- a/deploy/Dockerfile.worker
+++ b/deploy/Dockerfile.worker
@@ -6,6 +6,15 @@
 # (the build runner has no egress to Ubuntu mirrors). The conda env
 # itself dominates final image size, so a multi-stage trim wouldn't
 # meaningfully shrink things.
+#
+# Rebuild marker (bump to re-pull the ADACPP_BRANCH overlay fresh):
+#   2026-07-13e — adacpp feat/lazy-shape-store @ 3e18e9f: curved-surface fidelity fixes. Respects the
+#   curved trim on near-rectangular B-spline faces (bevels no longer render as straight-edged
+#   rectangles) and adds scale-invariant angular refinement so curved interiors aren't faceted
+#   (cylinders/holes were tessellating as prisms/squares; bevels were internally inconsistent). Also
+#   opt-in per-face clickable regions (face_ranges_node via ADA_STREAM_TESS_FACE_REGIONS). Still carries
+#   the linear-extrusion face fix, dropped-face health counter, IFC linear placement + opening voids,
+#   the bogus-SI-prefix guard (empty tanks), GLB-spill RAM buffering, tri-count logging, parent malloc_trim.
 
 ARG PIXI_VERSION=0.68.0
 # CI passes --build-arg IMAGE_TAG=sha-XXXXXXX so the worker can publish
@@ -19,9 +28,11 @@ ARG IMAGE_TAG=dev
 # CI stages the branch source into ./adacpp-src (clone) or an empty dir, and passes the branch
 # name so the builder stage below knows whether to build. Built with adacpp's own pinned env
 # (occt ==7.9.3), which matches what the released ada-cpp links → ABI-compatible .so.
-# The feat/ngeom-alignment-sweep overlay HEAD carries: alignment fixed-reference swept solid
-# (SweepN), the step_parity single-parse fan-out (STEP parity), and incremental meshopt in the
-# native GLB writer (halves peak RSS on large merged GLBs — fixes the STEP→GLB OOM).
+# The feat/lazy-shape-store overlay HEAD carries: the z=0 face-set plane-fit (IfcFacetedBrep /
+# Triangulated- + PolygonalFaceSet no longer render as a flat sheet), parallel native IFC→GLB,
+# a B-spline-weighted LPT cost estimate + per-solid audit instrumentation (spearman_est_ms/tris),
+# the NAUO-gate fix for the crane STEP→GLB regression, and a moderate 4 MB malloc mmap/trim that
+# trims streaming-tessellation peak RSS.
 ARG ADACPP_BRANCH=""
 
 # ---- optional adacpp-branch overlay (gated by ADACPP_BRANCH) -----------------------
diff --git a/deploy/helm/adapy-viewer/templates/_helpers.tpl b/deploy/helm/adapy-viewer/templates/_helpers.tpl
index 02fc4ee50..208034e05 100644
--- a/deploy/helm/adapy-viewer/templates/_helpers.tpl
+++ b/deploy/helm/adapy-viewer/templates/_helpers.tpl
@@ -202,6 +202,33 @@ spec:
           {{- with $w.resources }}
           resources: {{- toYaml . | nindent 12 }}
           {{- end }}
+          # Liveness: the worker touches /tmp/worker-alive on every JetStream pull-loop iteration
+          # (<=5s when idle) and on conversion progress (~2s). If the pull loop stalls — the durable
+          # consumer wedges after a NATS restart, leaving the pod "Running" but no longer fetching
+          # (num_waiting=0) — the file goes stale and k8s restarts the pod, instead of it sitting
+          # silently broken while jobs pile up unconsumed.
+          #
+          # This heartbeat probe ONLY works on pools running the adapy worker image, which writes the
+          # file. Capability pools that run a foreign image (abaqus, weld-gen) never write it, so the
+          # probe would fail every time and SIGKILL-crashloop them. Hence it is OPT-IN: emitted only
+          # when the pool sets `heartbeatLiveness: true` (the adapy worker default) or supplies its own
+          # `livenessProbe:`. Pools that do neither get no liveness probe.
+          {{- if or $w.livenessProbe $w.heartbeatLiveness }}
+          livenessProbe:
+            {{- with $w.livenessProbe }}
+            {{- toYaml . | nindent 12 }}
+            {{- else }}
+            exec:
+              command:
+                - sh
+                - -c
+                - 'test $(( $(date +%s) - $(stat -c %Y /tmp/worker-alive 2>/dev/null || echo 0) )) -lt 120'
+            initialDelaySeconds: 120
+            periodSeconds: 30
+            failureThreshold: 4
+            timeoutSeconds: 5
+            {{- end }}
+          {{- end }}
           {{- with $w.securityContext }}
           securityContext: {{- toYaml . | nindent 12 }}
           {{- end }}
diff --git a/deploy/helm/adapy-viewer/values.yaml b/deploy/helm/adapy-viewer/values.yaml
index ec5c39c90..30fb64a6b 100644
--- a/deploy/helm/adapy-viewer/values.yaml
+++ b/deploy/helm/adapy-viewer/values.yaml
@@ -49,6 +49,11 @@ strategy:
 worker:
   enabled: true
   replicaCount: 1
+  # This pool runs the adapy worker image, which writes /tmp/worker-alive on
+  # every pull-loop iteration, so the heartbeat livenessProbe applies (restarts
+  # a wedged pull loop). Capability pools on foreign images must leave this
+  # unset — see the livenessProbe note in _helpers.tpl.
+  heartbeatLiveness: true
   image:
     repository: ghcr.io/krande/adapy-viewer-worker
     tag: ""
diff --git a/files/ifc_files/bath-csg-solid.ifc b/files/ifc_files/bath-csg-solid.ifc
new file mode 100644
index 000000000..d66a47edc
--- /dev/null
+++ b/files/ifc_files/bath-csg-solid.ifc
@@ -0,0 +1,70 @@
+ISO-10303-21;
+HEADER;
+FILE_DESCRIPTION(('ViewDefinition [NotAssigned]'),'2;1');
+FILE_NAME(
+/* name */ 'bath-csg-solid.ifc',
+/* time_stamp */ '2016-02-04T08:47:55',
+/* author */ ('redacted'),
+/* organization */ ('redacted'),
+/* preprocessor_version */ 'redacted',
+/* originating_system */ 'redacted - redacted - 3.14159',
+/* authorization */ 'None');
+
+FILE_SCHEMA (('IFC4X3_ADD2'));
+ENDSEC;
+
+DATA;
+/* general entities required for all IFC data sets, defining the context for the exchange */
+#1= IFCGEOMETRICREPRESENTATIONCONTEXT($,'Model',3,0.0001,#3,$);
+#2= IFCCARTESIANPOINT((0.0,0.0,0.0));
+#3= IFCAXIS2PLACEMENT3D(#2,$,$);
+#4= IFCGEOMETRICREPRESENTATIONSUBCONTEXT('Axis','Model',*,*,*,*,#1,$,.MODEL_VIEW.,$);
+#5= IFCGEOMETRICREPRESENTATIONSUBCONTEXT('Body','Model',*,*,*,*,#1,$,.MODEL_VIEW.,$);
+/* defines the default building (as required as the minimum spatial element)  */
+#50= IFCBUILDING('39t4Pu3nTC4ekXYRIHJB9W',#56,'IfcBuilding',$,$,$,$,$,$,$,$,$);
+#51= IFCPERSONANDORGANIZATION(#52,#53,$);
+#52= IFCPERSON('redacted','redacted',$,$,$,$,$,$);
+#53= IFCORGANIZATION($,'redacted',$,$,$);
+#54= IFCAPPLICATION(#55,'redacted','redacted','redacted');
+#55= IFCORGANIZATION($,'redacted',$,$,$);
+#56= IFCOWNERHISTORY(#51,#54,$,.ADDED.,1454575675,$,$,1454575675);
+#57= IFCRELCONTAINEDINSPATIALSTRUCTURE('3Sa3dTJGn0H8TQIGiuGQd5',#56,'Building','Building Container for Elements',(#225),#50);
+#58= IFCAXIS2PLACEMENT3D(#2,$,$);
+#100= IFCPROJECT('0$WU4A9R19$vKWO$AdOnKA',#56,'IfcProject',$,$,$,$,(#1),#101);
+#101= IFCUNITASSIGNMENT((#102,#103,#104));
+#102= IFCSIUNIT(*,.LENGTHUNIT.,.MILLI.,.METRE.);
+#103= IFCSIUNIT(*,.PLANEANGLEUNIT.,$,.RADIAN.);
+#104= IFCSIUNIT(*,.TIMEUNIT.,$,.SECOND.);
+#105= IFCRELAGGREGATES('091a6ewbvCMQ2Vyiqspa7a',#56,'Project Container','Project Container for Buildings',#100,(#50));
+#200= IFCBLOCK(#201,2000.0,800.0,800.0);
+#201= IFCAXIS2PLACEMENT3D(#2,$,$);
+#202= IFCROUNDEDRECTANGLEPROFILEDEF(.AREA.,'VoidProfile',$,1800.0,600.0,200.0);
+#203= IFCAXIS2PLACEMENT3D(#204,$,$);
+#204= IFCCARTESIANPOINT((1000.0,400.0,100.0));
+#205= IFCDIRECTION((0.0,0.0,1.0));
+#206= IFCEXTRUDEDAREASOLID(#202,#203,#205,700.0);
+#207= IFCBOOLEANRESULT(.DIFFERENCE.,#200,#206);
+#208= IFCCSGSOLID(#207);
+#209= IFCREPRESENTATIONMAP(#210,#211);
+#210= IFCAXIS2PLACEMENT3D(#2,$,$);
+#211= IFCSHAPEREPRESENTATION(#5,'Body','SolidModel',(#208));
+#212= IFCMATERIAL('Ceramic',$,$);
+#213= IFCRELASSOCIATESMATERIAL('0Pkhszwjv1qRMYyCFg9fjB',#56,'MatAssoc','Material Associates',(#214),#212);
+#214= IFCSANITARYTERMINALTYPE('1HarmwaPv3OeJSXpaoPKpg',#56,'Bath',$,$,$,(#209),$,$,.BATH.);
+#215= IFCRELDEFINESBYTYPE('1lO$X3e3j9lfVMhNy4MzKB',#56,$,$,(#225),#214);
+#216= IFCRELDECLARES('1acQrDhur9399Xqs2jQs4t',#56,$,$,#100,(#214));
+#217= IFCDIRECTION((1.0,0.0,0.0));
+#218= IFCDIRECTION((0.0,1.0,0.0));
+#219= IFCCARTESIANPOINT((0.0,0.0,0.0));
+#220= IFCCARTESIANTRANSFORMATIONOPERATOR3D(#217,#218,#219,1.0,#221);
+#221= IFCDIRECTION((0.0,0.0,1.0));
+#222= IFCMAPPEDITEM(#209,#220);
+#223= IFCSHAPEREPRESENTATION(#5,'Body','MappedRepresentation',(#222));
+#224= IFCPRODUCTDEFINITIONSHAPE($,$,(#223));
+#225= IFCSANITARYTERMINAL('3$$o7C03j0KQeLnoj018fc',#56,$,$,$,#227,#224,$,$);
+#226= IFCAXIS2PLACEMENT3D(#2,$,$);
+#227= IFCLOCALPLACEMENT($,#226);
+ENDSEC;
+
+END-ISO-10303-21;
+
diff --git a/files/ifc_files/beam-extruded-solid.ifc b/files/ifc_files/beam-extruded-solid.ifc
new file mode 100644
index 000000000..992e131c2
--- /dev/null
+++ b/files/ifc_files/beam-extruded-solid.ifc
@@ -0,0 +1,50 @@
+ISO-10303-21;
+HEADER;
+FILE_DESCRIPTION(('ViewDefinition [NotAssigned]'),'2;1');
+FILE_NAME(
+/* name */ 'beam-extruded-solid.ifc',
+/* time_stamp */ '2016-02-04T08:11:04',
+/* author */ ('redacted'),
+/* organization */ ('redacted'),
+/* preprocessor_version */ 'redacted',
+/* originating_system */ 'redacted - redacted - 3.14159',
+/* authorization */ 'None');
+
+FILE_SCHEMA (('IFC4X3_ADD2'));
+ENDSEC;
+
+DATA;
+/* general entities required for all IFC data sets, defining the context for the exchange */
+#1= IFCGEOMETRICREPRESENTATIONCONTEXT($,'Model',3,0.0001,#3,$);
+#2= IFCCARTESIANPOINT((0.0,0.0,0.0));
+#3= IFCAXIS2PLACEMENT3D(#2,$,$);
+#4= IFCGEOMETRICREPRESENTATIONSUBCONTEXT('Axis','Model',*,*,*,*,#1,$,.MODEL_VIEW.,$);
+#5= IFCGEOMETRICREPRESENTATIONSUBCONTEXT('Body','Model',*,*,*,*,#1,$,.MODEL_VIEW.,$);
+/* defines the default building (as required as the minimum spatial element)  */
+#50= IFCBUILDING('39t4Pu3nTC4ekXYRIHJB9W',$,'IfcBuilding',$,$,$,$,$,$,$,$,$);
+#51= IFCRELCONTAINEDINSPATIALSTRUCTURE('3Sa3dTJGn0H8TQIGiuGQd5',$,'Building','Building Container for Elements',(#211),#50);
+#52= IFCAXIS2PLACEMENT3D(#2,$,$);
+#100= IFCPROJECT('0$WU4A9R19$vKWO$AdOnKA',$,'IfcProject',$,$,$,$,(#1),#101);
+#101= IFCUNITASSIGNMENT((#102,#103,#104));
+#102= IFCSIUNIT(*,.LENGTHUNIT.,.MILLI.,.METRE.);
+#103= IFCSIUNIT(*,.PLANEANGLEUNIT.,$,.RADIAN.);
+#104= IFCSIUNIT(*,.TIMEUNIT.,$,.SECOND.);
+#105= IFCRELAGGREGATES('091a6ewbvCMQ2Vyiqspa7a',$,'Project Container','Project Container for Buildings',#100,(#50));
+#200= IFCCARTESIANPOINTLIST2D(((2.8,-79.5),(2.8,79.5),(6.31471899999999,87.985281),(14.8,91.5),(50.0,91.5),(50.0,100.0),(-50.0,100.0),(-50.0,91.5),(-14.8,91.5),(-6.31471899999997,87.985281),(-2.79999999999999,79.5),(-2.8,-79.5),(-6.31471899999999,-87.985281),(-14.8,-91.5),(-50.0,-91.5),(-50.0,-100.0),(50.0,-100.0),(50.0,-91.5),(14.8,-91.5),(6.31471899999997,-87.985281)),$);
+#201= IFCINDEXEDPOLYCURVE(#200,(IFCLINEINDEX((1,2)),IFCARCINDEX((2,3,4)),IFCLINEINDEX((4,5,6,7,8,9)),IFCARCINDEX((9,10,11)),IFCLINEINDEX((11,12)),IFCARCINDEX((12,13,14)),IFCLINEINDEX((14,15,16,17,18,19)),IFCARCINDEX((19,20,1))),.F.);
+#202= IFCARBITRARYCLOSEDPROFILEDEF(.AREA.,'IPE200',#201);
+#203= IFCCARTESIANPOINT((0.0,0.0,0.0));
+#204= IFCDIRECTION((0.0,1.0,0.0));
+#205= IFCDIRECTION((1.0,0.0,0.0));
+#206= IFCAXIS2PLACEMENT3D(#203,#204,#205);
+#207= IFCDIRECTION((0.0,0.0,1.0));
+#208= IFCEXTRUDEDAREASOLID(#202,#206,#207,1000.0);
+#209= IFCSHAPEREPRESENTATION(#5,'Body','SweptSolid',(#208));
+#210= IFCPRODUCTDEFINITIONSHAPE($,$,(#209));
+#211= IFCBEAM('0EF5_zZRv0pQPddeofU3KT',$,'ExampleBeamName','ExampleBeamDescription',$,#213,#210,'Tag',$);
+#212= IFCAXIS2PLACEMENT3D(#2,$,$);
+#213= IFCLOCALPLACEMENT($,#212);
+ENDSEC;
+
+END-ISO-10303-21;
+
diff --git a/files/ifc_files/beam-standard-case-gz.ifc b/files/ifc_files/beam-standard-case-gz.ifc
new file mode 100644
index 000000000..490f86d57
Binary files /dev/null and b/files/ifc_files/beam-standard-case-gz.ifc differ
diff --git a/files/ifc_files/bs_samples/column-straight-rectangle-tessellation.ifc b/files/ifc_files/bs_samples/column-straight-rectangle-tessellation.ifc
new file mode 100644
index 000000000..7d3b027ea
--- /dev/null
+++ b/files/ifc_files/bs_samples/column-straight-rectangle-tessellation.ifc
@@ -0,0 +1,64 @@
+ISO-10303-21;
+HEADER;
+
+FILE_DESCRIPTION(('ViewDefinition [ReferenceView]'),'2;1');
+FILE_NAME('column-straight-rectangle-tessellation.ifc','2014-07-08T19:20:14',('redacted'),(''),'redacted','redacted - redacted - 3.14159','');
+FILE_SCHEMA(('IFC4X3_ADD2'));
+ENDSEC;
+
+DATA;
+
+/* set the default units - and the units used for geometric representations                       */
+/* here imperial units (inch) are used                                                            */
+/* ---------------------------------------------------------------------------------------------- */
+#12= IFCSIUNIT(*,.LENGTHUNIT.,$,.METRE.);
+#13= IFCMEASUREWITHUNIT(IFCLENGTHMEASURE(0.0254),#12);
+#14= IFCDIMENSIONALEXPONENTS(1,0,0,0,0,0,0);
+#15= IFCCONVERSIONBASEDUNIT(#14,.LENGTHUNIT.,'inch',#13);
+#36= IFCUNITASSIGNMENT((#15));
+
+/* set the context of the IFC4 exchange file                                                      */
+/* name, units and geometric representation context                                               */
+/* note: IfcOwnerHistory is not in scope of the IFC4 reference view                               */
+/* ---------------------------------------------------------------------------------------------- */
+#37= IFCPROJECT('0CxDbxzA1B4eLeOw9eIjQx',$,'Project',$,$,$,$,(#40),#36);
+
+/* set the representation context for 3D body, and 2D axis representation                         */
+/* no north direction and no geo-spatial coordinates are provided                                 */
+/* ---------------------------------------------------------------------------------------------- */
+#38= IFCCARTESIANPOINT((0.,0.,0.));
+#39= IFCAXIS2PLACEMENT3D(#38,$,$);
+#40= IFCGEOMETRICREPRESENTATIONCONTEXT('3D','Model',3,1.0E-05,#39,$);
+#41= IFCGEOMETRICREPRESENTATIONSUBCONTEXT('Body','Model',*,*,*,*,#40,$,.MODEL_VIEW.,$);
+
+/* defines the default site (as required as the minimum spatial element)                          */
+/* ---------------------------------------------------------------------------------------------- */
+#44= IFCSITE('0M0akNk9f3hOH9u2awmtre',$,'Site #1',$,$,#67,$,$,.ELEMENT.,$,$,$,$,$);
+#45= IFCRELAGGREGATES('2y_abP04108BvIhy2WfsHm',$,$,$,#37,(#44));
+#67= IFCLOCALPLACEMENT($,#69);
+#68= IFCCARTESIANPOINT((0.,0.,0.));
+#69= IFCAXIS2PLACEMENT3D(#68,$,$);
+
+/* defines the column with rectangular cross section as a model element                           */
+/* using tessellated geometry                                                                     */
+/* ---------------------------------------------------------------------------------------------- */
+#71= IFCCOLUMN('2WUGYBphrFv8aLIFJCmiIk',$,'Column #1',$,$,#121,#111,$,.COLUMN.);
+#111= IFCPRODUCTDEFINITIONSHAPE($,$,(#154));
+#116= IFCRELCONTAINEDINSPATIALSTRUCTURE('0F1oUoJsr5ZwxKAxiD1Vep',$,$,$,(#71),#44);
+#119= IFCDIRECTION((0.,0.,1.));
+#120= IFCDIRECTION((1.,0.,0.));
+#121= IFCLOCALPLACEMENT(#67,#126);
+#125= IFCCARTESIANPOINT((432.,288.,48.));
+#126= IFCAXIS2PLACEMENT3D(#125,#119,#120);
+#154= IFCSHAPEREPRESENTATION(#41,'Body','Tessellation',(#288));
+
+/* the triangulated tessellation also includes the normals per face and vertex                    */
+/* in this case, the vertex list and the normal list are corresponding lists,                     */
+/* hence no separate normal index has to be provided at IfcTriangulatedFaceSet                    */
+/* it generated longer lists, but is in line with many graphic APIs using a single buffer list    */
+/* ---------------------------------------------------------------------------------------------- */
+#287= IFCCARTESIANPOINTLIST3D(((-4.,4.,0.),(-4.,-4.,0.),(4.,-4.,0.),(4.,4.,0.),(-4.,4.,120.),(-4.,-4.,120.),(4.,-4.,120.),(4.,4.,120.),(-4.,4.,0.),(-4.,-4.,0.),(-4.,-4.,120.),(-4.,4.,120.),(-4.,-4.,0.),(4.,-4.,0.),(4.,-4.,120.),(-4.,-4.,120.),(4.,-4.,0.),(4.,4.,0.),(4.,4.,120.),(4.,-4.,120.),(4.,4.,0.),(-4.,4.,0.),(-4.,4.,120.),(4.,4.,120.)),$);
+#288= IFCTRIANGULATEDFACESET(#287,((0.,0.,-1.),(0.,0.,-1.),(0.,0.,-1.),(0.,0.,-1.),(0.,0.,1.),(0.,0.,1.),(0.,0.,1.),(0.,0.,1.),(-1.,0.,0.),(-1.,0.,0.),(-1.,0.,0.),(-1.,0.,0.),(0.,-1.,0.),(0.,-1.,0.),(0.,-1.,0.),(0.,-1.,0.),(1.,0.,0.),(1.,0.,0.),(1.,0.,0.),(1.,0.,0.),(0.,1.,0.),(0.,1.,0.),(0.,1.,0.),(0.,1.,0.)),.T.,((1,3,2),(1,4,3),(5,6,7),(5,7,8),(9,10,11),(9,11,12),(13,14,15),(13,15,16),(17,18,19),(17,19,20),(21,22,23),(21,23,24)),$);
+ENDSEC;
+
+END-ISO-10303-21;
diff --git a/files/ifc_files/bs_samples/curve-parameters-in-degrees.ifc b/files/ifc_files/bs_samples/curve-parameters-in-degrees.ifc
new file mode 100644
index 000000000..65c8d7649
--- /dev/null
+++ b/files/ifc_files/bs_samples/curve-parameters-in-degrees.ifc
@@ -0,0 +1,155 @@
+ISO-10303-21;
+HEADER;
+FILE_DESCRIPTION(('ViewDefinition [NotAssigned]'),'2;1');
+FILE_NAME(
+/* name */ 'curve-parameters-in-degrees.ifc',
+/* time_stamp */ '2017-06-28T23:09:53',
+/* author */ ('redacted'),
+/* organization */ ('redacted'),
+/* preprocessor_version */ 'redacted',
+/* originating_system */ 'redacted - redacted - 3.14159',
+/* authorization */ 'None');
+
+FILE_SCHEMA (('IFC4X3_ADD2'));
+ENDSEC;
+
+DATA;
+#10= IFCCARTESIANPOINT((0.0,0.0,0.0));
+#11= IFCAXIS2PLACEMENT3D(#10,$,$);
+#12= IFCLOCALPLACEMENT($,#11);
+/* defines the default building (as required as the minimum spatial element)  */
+/* These profile curves are intentionally expressed in a more complicated manner than necessary to test parameterization */
+#13= IFCBUILDING('39t4Pu3nTC4ekXYRIHJB9W',$,'IfcBuilding',$,$,#12,$,$,$,$,$,#18);
+#14= IFCRELCONTAINEDINSPATIALSTRUCTURE('3Sa3dTJGn0H8TQIGiuGQd5',$,'Building','Building Container for Elements',(#77,#131,#180),#13);
+#15= IFCCARTESIANPOINT((0.0,0.0,0.0));
+#16= IFCAXIS2PLACEMENT3D(#15,$,$);
+#18= IFCPOSTALADDRESS($,$,$,$,('Unknown'),$,'Unknown',$,'Unknown','Unknown');
+/* general entities required for all IFC data sets, defining the context for the exchange */
+#20= IFCPROJECT('0$WU4A9R19$vKWO$AdOnKA',$,'IfcProject',$,$,$,$,(#31),#21);
+#21= IFCUNITASSIGNMENT((#22,#23,#24,#27,#29));
+#22= IFCSIUNIT(*,.LENGTHUNIT.,.MILLI.,.METRE.);
+#23= IFCSIUNIT(*,.AREAUNIT.,$,.SQUARE_METRE.);
+#24= IFCSIUNIT(*,.VOLUMEUNIT.,$,.CUBIC_METRE.);
+#25= IFCSIUNIT(*,.PLANEANGLEUNIT.,$,.RADIAN.);
+#26= IFCMEASUREWITHUNIT(IFCPLANEANGLEMEASURE(0.0174532925199433),#25);
+#27= IFCCONVERSIONBASEDUNIT(#28,.PLANEANGLEUNIT.,'DEGREE',#26);
+#28= IFCDIMENSIONALEXPONENTS(0,0,0,0,0,0,0);
+#29= IFCSIUNIT(*,.TIMEUNIT.,$,.SECOND.);
+#30= IFCRELAGGREGATES('091a6ewbvCMQ2Vyiqspa7a',$,'Project Container','Project Container for Buildings',#20,(#13));
+#31= IFCGEOMETRICREPRESENTATIONCONTEXT($,'Model',3,0.0001,#33,#34);
+#32= IFCCARTESIANPOINT((0.0,0.0,0.0));
+#33= IFCAXIS2PLACEMENT3D(#32,$,$);
+#34= IFCDIRECTION((0.0,1.0));
+#35= IFCGEOMETRICREPRESENTATIONSUBCONTEXT('Body','Model',*,*,*,*,#31,$,.MODEL_VIEW.,$);
+/* Example data for CurveParametersDegrees */
+#50= IFCMATERIAL('Steel',$,$);
+#52= IFCCARTESIANPOINT((-1000.0,1000.0));
+#53= IFCDIRECTION((0.70710678,-0.70710678));
+#54= IFCVECTOR(#53,1414.2135623731);
+#55= IFCLINE(#52,#54);
+#56= IFCTRIMMEDCURVE(#55,(IFCPARAMETERVALUE(0.292893218813453)),(IFCPARAMETERVALUE(1.70710678118655)),.T.,.PARAMETER.);
+#57= IFCCOMPOSITECURVESEGMENT(.CONTINUOUS.,.T.,#56);
+#58= IFCCARTESIANPOINT((0.0,0.0));
+#59= IFCAXIS2PLACEMENT2D(#58,$);
+#60= IFCCIRCLE(#59,1000.0);
+#61= IFCTRIMMEDCURVE(#60,(IFCPARAMETERVALUE(315.0)),(IFCPARAMETERVALUE(135.0)),.T.,.PARAMETER.);
+#62= IFCCOMPOSITECURVESEGMENT(.CONTINUOUS.,.T.,#61);
+#63= IFCCOMPOSITECURVE((#57,#62),.U.);
+#64= IFCARBITRARYCLOSEDPROFILEDEF(.AREA.,'SemiCircle',#63);
+#65= IFCMATERIALPROFILE('SemiCircle',$,#50,#64,$,$);
+#67= IFCMATERIALPROFILESET('SemiCircle',$,(#65),$);
+#68= IFCRELASSOCIATESMATERIAL('1gdVo5TjPETPZlW8HSRupM',$,'MatAssoc','Material Associates',(#69),#67);
+#69= IFCCOLUMNTYPE('24mq0gwVr7bgEMXPmo$TrF',$,'SemiCircle',$,$,$,$,$,$,.COLUMN.);
+#70= IFCRELDEFINESBYTYPE('0devdSRyf3uBEQbSqWTDjo',$,'NameNotAssigned',$,(#77),#69);
+#71= IFCRELDECLARES('1Cjr05W9T0fx0M3_mdVqMd',$,$,$,#20,(#69,#124,#173));
+#72= IFCMATERIALPROFILESETUSAGE(#67,5,$);
+#73= IFCRELASSOCIATESMATERIAL('35z8gDFbb6gvrCOz$24tUJ',$,'MatAssoc','Material Associates',(#77),#72);
+#74= IFCCARTESIANPOINT((0.0,0.0,0.0));
+#75= IFCAXIS2PLACEMENT3D(#74,$,$);
+#76= IFCLOCALPLACEMENT(#12,#75);
+#77= IFCCOLUMN('0RGc8lepr7BRF_EtHrWJ45',$,'SemiCircle',$,$,#76,#85,$,$);
+#78= IFCCARTESIANPOINT((0.0,0.0,2000.0));
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+#80= IFCGEOMETRICREPRESENTATIONSUBCONTEXT('Axis','Model',*,*,*,*,#31,$,.MODEL_VIEW.,$);
+#81= IFCSHAPEREPRESENTATION(#80,'Axis','Curve3D',(#79));
+#82= IFCEXTRUDEDAREASOLID(#64,$,#83,2000.0);
+#83= IFCDIRECTION((0.0,0.0,1.0));
+#84= IFCSHAPEREPRESENTATION(#35,'Body','SweptSolid',(#82));
+#85= IFCPRODUCTDEFINITIONSHAPE($,$,(#81,#84));
+#100= IFCCARTESIANPOINT((0.0,1000.0));
+#101= IFCAXIS2PLACEMENT2D(#100,#102);
+#102= IFCDIRECTION((-1.0,0.0));
+#103= IFCCIRCLE(#101,1732.05081);
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+#105= IFCCOMPOSITECURVESEGMENT(.CONTINUOUS.,.T.,#104);
+#106= IFCCARTESIANPOINT((-866.0254,-500.0));
+#107= IFCAXIS2PLACEMENT2D(#106,#108);
+#108= IFCDIRECTION((0.0,-1.0));
+#109= IFCCIRCLE(#107,1732.05081);
+#110= IFCTRIMMEDCURVE(#109,(IFCPARAMETERVALUE(90.0)),(IFCPARAMETERVALUE(150.0)),.T.,.PARAMETER.);
+#111= IFCCOMPOSITECURVESEGMENT(.CONTINUOUS.,.T.,#110);
+#112= IFCCARTESIANPOINT((866.0254,-500.0));
+#113= IFCAXIS2PLACEMENT2D(#112,#114);
+#114= IFCDIRECTION((0.0,1.0));
+#115= IFCCIRCLE(#113,1732.05081);
+#116= IFCTRIMMEDCURVE(#115,(IFCPARAMETERVALUE(30.0)),(IFCPARAMETERVALUE(90.0)),.T.,.PARAMETER.);
+#117= IFCCOMPOSITECURVESEGMENT(.CONTINUOUS.,.T.,#116);
+#118= IFCCOMPOSITECURVE((#105,#111,#117),.U.);
+#119= IFCARBITRARYCLOSEDPROFILEDEF(.AREA.,'CurviLinearTriangle',#118);
+#120= IFCMATERIALPROFILE('CurviLinearTriangle',$,#50,#119,$,$);
+#122= IFCMATERIALPROFILESET('CurviLinearTriangle',$,(#120),$);
+#123= IFCRELASSOCIATESMATERIAL('1qSyS$HSb8TRu4PVnIUzZM',$,'MatAssoc','Material Associates',(#124),#122);
+#124= IFCCOLUMNTYPE('0JgmY6eGLC9AwX_nMFf5CT',$,'CurviLinearTriangle',$,$,$,$,$,$,.COLUMN.);
+#125= IFCRELDEFINESBYTYPE('1N1PpBCJLB4QMrIjidnGaj',$,'NameNotAssigned',$,(#131),#124);
+#126= IFCMATERIALPROFILESETUSAGE(#122,5,$);
+#127= IFCRELASSOCIATESMATERIAL('00Bah4pIPCa9jB2F34kUX_',$,'MatAssoc','Material Associates',(#131),#126);
+#128= IFCCARTESIANPOINT((2500.0,0.0,0.0));
+#129= IFCAXIS2PLACEMENT3D(#128,$,$);
+#130= IFCLOCALPLACEMENT(#12,#129);
+#131= IFCCOLUMN('3vcm8ZmFfDwhpgzzT7EP8n',$,'CurviLinearTriangle',$,$,#130,#137,$,$);
+#132= IFCCARTESIANPOINT((0.0,0.0,2000.0));
+#133= IFCPOLYLINE((#15,#132));
+#134= IFCSHAPEREPRESENTATION(#80,'Axis','Curve3D',(#133));
+#135= IFCEXTRUDEDAREASOLID(#119,$,#83,2000.0);
+#136= IFCSHAPEREPRESENTATION(#35,'Body','SweptSolid',(#135));
+#137= IFCPRODUCTDEFINITIONSHAPE($,$,(#134,#136));
+#150= IFCCARTESIANPOINT((0.0,0.0));
+#151= IFCAXIS2PLACEMENT2D(#150,$);
+#152= IFCELLIPSE(#151,1000.0,500.0);
+#153= IFCTRIMMEDCURVE(#152,(IFCPARAMETERVALUE(0.0)),(IFCPARAMETERVALUE(45.0)),.T.,.PARAMETER.);
+#154= IFCCOMPOSITECURVESEGMENT(.CONTINUOUS.,.T.,#153);
+#155= IFCCARTESIANPOINT((0.0,0.0));
+#156= IFCDIRECTION((0.89442719,0.4472136));
+#157= IFCVECTOR(#156,1.0);
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+#159= IFCTRIMMEDCURVE(#158,(IFCPARAMETERVALUE(0.0)),(IFCPARAMETERVALUE(790.569415042095)),.F.,.PARAMETER.);
+#160= IFCCOMPOSITECURVESEGMENT(.CONTINUOUS.,.T.,#159);
+#161= IFCCARTESIANPOINT((0.0,0.0));
+#162= IFCDIRECTION((1.0,0.0));
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+#164= IFCLINE(#161,#163);
+#165= IFCTRIMMEDCURVE(#164,(IFCPARAMETERVALUE(0.0)),(IFCPARAMETERVALUE(1000.0)),.T.,.PARAMETER.);
+#166= IFCCOMPOSITECURVESEGMENT(.CONTINUOUS.,.T.,#165);
+#167= IFCCOMPOSITECURVE((#154,#160,#166),.U.);
+#168= IFCARBITRARYCLOSEDPROFILEDEF(.AREA.,'PartialEllipse',#167);
+#169= IFCMATERIALPROFILE('PartialEllipse',$,#50,#168,$,$);
+#171= IFCMATERIALPROFILESET('PartialEllipse',$,(#169),$);
+#172= IFCRELASSOCIATESMATERIAL('2V$PMUw5f3PgVGq_LG8lb7',$,'MatAssoc','Material Associates',(#173),#171);
+#173= IFCCOLUMNTYPE('32anvmJgjFPOL650_UAlfM',$,'PartialEllipse',$,$,$,$,$,$,.COLUMN.);
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+#175= IFCMATERIALPROFILESETUSAGE(#171,5,$);
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+#177= IFCCARTESIANPOINT((5000.0,0.0,0.0));
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+#181= IFCCARTESIANPOINT((0.0,0.0,2000.0));
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+#185= IFCSHAPEREPRESENTATION(#35,'Body','SweptSolid',(#184));
+#186= IFCPRODUCTDEFINITIONSHAPE($,$,(#183,#185));
+ENDSEC;
+
+END-ISO-10303-21;
+
diff --git a/files/ifc_files/bs_samples/curve-parameters-in-radians.ifc b/files/ifc_files/bs_samples/curve-parameters-in-radians.ifc
new file mode 100644
index 000000000..b3df78341
--- /dev/null
+++ b/files/ifc_files/bs_samples/curve-parameters-in-radians.ifc
@@ -0,0 +1,152 @@
+ISO-10303-21;
+HEADER;
+FILE_DESCRIPTION(('ViewDefinition [NotAssigned]'),'2;1');
+FILE_NAME(
+/* name */ 'curve-parameters-in-radians.ifc',
+/* time_stamp */ '2017-06-28T23:09:53',
+/* author */ ('redacted'),
+/* organization */ ('redacted'),
+/* preprocessor_version */ 'redacted',
+/* originating_system */ 'redacted - redacted - 3.14159',
+/* authorization */ 'None');
+
+FILE_SCHEMA (('IFC4X3_ADD2'));
+ENDSEC;
+
+DATA;
+#10= IFCCARTESIANPOINT((0.0,0.0,0.0));
+#11= IFCAXIS2PLACEMENT3D(#10,$,$);
+#12= IFCLOCALPLACEMENT($,#11);
+/* defines the default building (as required as the minimum spatial element)  */
+/* These profile curves are intentionally expressed in a more complicated manner than necessary to test parameterization */
+#13= IFCBUILDING('39t4Pu3nTC4ekXYRIHJB9W',$,'IfcBuilding',$,$,#12,$,$,$,$,$,#18);
+#14= IFCRELCONTAINEDINSPATIALSTRUCTURE('3Sa3dTJGn0H8TQIGiuGQd5',$,'Building','Building Container for Elements',(#77,#131,#180),#13);
+#15= IFCCARTESIANPOINT((0.0,0.0,0.0));
+#16= IFCAXIS2PLACEMENT3D(#15,$,$);
+#18= IFCPOSTALADDRESS($,$,$,$,('Unknown'),$,'Unknown',$,'Unknown','Unknown');
+/* general entities required for all IFC data sets, defining the context for the exchange */
+#20= IFCPROJECT('0$WU4A9R19$vKWO$AdOnKA',$,'IfcProject',$,$,$,$,(#28),#21);
+#21= IFCUNITASSIGNMENT((#22,#23,#24,#25,#26));
+#22= IFCSIUNIT(*,.LENGTHUNIT.,.MILLI.,.METRE.);
+#23= IFCSIUNIT(*,.AREAUNIT.,$,.SQUARE_METRE.);
+#24= IFCSIUNIT(*,.VOLUMEUNIT.,$,.CUBIC_METRE.);
+#25= IFCSIUNIT(*,.PLANEANGLEUNIT.,$,.RADIAN.);
+#26= IFCSIUNIT(*,.TIMEUNIT.,$,.SECOND.);
+#27= IFCRELAGGREGATES('091a6ewbvCMQ2Vyiqspa7a',$,'Project Container','Project Container for Buildings',#20,(#13));
+#28= IFCGEOMETRICREPRESENTATIONCONTEXT($,'Model',3,0.0001,#30,#31);
+#29= IFCCARTESIANPOINT((0.0,0.0,0.0));
+#30= IFCAXIS2PLACEMENT3D(#29,$,$);
+#31= IFCDIRECTION((0.0,1.0));
+#32= IFCGEOMETRICREPRESENTATIONSUBCONTEXT('Body','Model',*,*,*,*,#28,$,.MODEL_VIEW.,$);
+/* Example data for CurveParametersRadians */
+#50= IFCMATERIAL('Steel',$,$);
+#52= IFCCARTESIANPOINT((-1000.0,1000.0));
+#53= IFCDIRECTION((0.70710678,-0.70710678));
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+#64= IFCARBITRARYCLOSEDPROFILEDEF(.AREA.,'SemiCircle',#63);
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+#67= IFCMATERIALPROFILESET('SemiCircle',$,(#65),$);
+#68= IFCRELASSOCIATESMATERIAL('1gdVo5TjPETPZlW8HSRupM',$,'MatAssoc','Material Associates',(#69),#67);
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+#80= IFCGEOMETRICREPRESENTATIONSUBCONTEXT('Axis','Model',*,*,*,*,#28,$,.MODEL_VIEW.,$);
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+#100= IFCCARTESIANPOINT((0.0,1000.0));
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+#104= IFCTRIMMEDCURVE(#103,(IFCPARAMETERVALUE(1.0471975511966)),(IFCPARAMETERVALUE(2.0943951023932)),.T.,.PARAMETER.);
+#105= IFCCOMPOSITECURVESEGMENT(.CONTINUOUS.,.T.,#104);
+#106= IFCCARTESIANPOINT((-866.0254,-500.0));
+#107= IFCAXIS2PLACEMENT2D(#106,#108);
+#108= IFCDIRECTION((0.0,-1.0));
+#109= IFCCIRCLE(#107,1732.05081);
+#110= IFCTRIMMEDCURVE(#109,(IFCPARAMETERVALUE(1.5707963267949)),(IFCPARAMETERVALUE(2.61799387799149)),.T.,.PARAMETER.);
+#111= IFCCOMPOSITECURVESEGMENT(.CONTINUOUS.,.T.,#110);
+#112= IFCCARTESIANPOINT((866.0254,-500.0));
+#113= IFCAXIS2PLACEMENT2D(#112,#114);
+#114= IFCDIRECTION((0.0,1.0));
+#115= IFCCIRCLE(#113,1732.05081);
+#116= IFCTRIMMEDCURVE(#115,(IFCPARAMETERVALUE(0.523598775598299)),(IFCPARAMETERVALUE(1.5707963267949)),.T.,.PARAMETER.);
+#117= IFCCOMPOSITECURVESEGMENT(.CONTINUOUS.,.T.,#116);
+#118= IFCCOMPOSITECURVE((#105,#111,#117),.U.);
+#119= IFCARBITRARYCLOSEDPROFILEDEF(.AREA.,'CurviLinearTriangle',#118);
+#120= IFCMATERIALPROFILE('CurviLinearTriangle',$,#50,#119,$,$);
+#122= IFCMATERIALPROFILESET('CurviLinearTriangle',$,(#120),$);
+#123= IFCRELASSOCIATESMATERIAL('1M5oofzjD3IOM43brXW6wT',$,'MatAssoc','Material Associates',(#124),#122);
+#124= IFCCOLUMNTYPE('3N_qc_BjX1hvEgwfRvVcb_',$,'CurviLinearTriangle',$,$,$,$,$,$,.COLUMN.);
+#125= IFCRELDEFINESBYTYPE('3tGocD1N51oOvSvHbJI_qD',$,'NameNotAssigned',$,(#131),#124);
+#126= IFCMATERIALPROFILESETUSAGE(#122,5,$);
+#127= IFCRELASSOCIATESMATERIAL('0gnTzVmkbE9hPsJDxOUOL3',$,'MatAssoc','Material Associates',(#131),#126);
+#128= IFCCARTESIANPOINT((2500.0,0.0,0.0));
+#129= IFCAXIS2PLACEMENT3D(#128,$,$);
+#130= IFCLOCALPLACEMENT(#12,#129);
+#131= IFCCOLUMN('0bmIILAwj8$PLHK1jcmad0',$,'CurviLinearTriangle',$,$,#130,#137,$,$);
+#132= IFCCARTESIANPOINT((0.0,0.0,2000.0));
+#133= IFCPOLYLINE((#15,#132));
+#134= IFCSHAPEREPRESENTATION(#80,'Axis','Curve3D',(#133));
+#135= IFCEXTRUDEDAREASOLID(#119,$,#83,2000.0);
+#136= IFCSHAPEREPRESENTATION(#32,'Body','SweptSolid',(#135));
+#137= IFCPRODUCTDEFINITIONSHAPE($,$,(#134,#136));
+#150= IFCCARTESIANPOINT((0.0,0.0));
+#151= IFCAXIS2PLACEMENT2D(#150,$);
+#152= IFCELLIPSE(#151,1000.0,500.0);
+#153= IFCTRIMMEDCURVE(#152,(IFCPARAMETERVALUE(0.0)),(IFCPARAMETERVALUE(0.785398163397448)),.T.,.PARAMETER.);
+#154= IFCCOMPOSITECURVESEGMENT(.CONTINUOUS.,.T.,#153);
+#155= IFCCARTESIANPOINT((0.0,0.0));
+#156= IFCDIRECTION((0.89442719,0.4472136));
+#157= IFCVECTOR(#156,1.0);
+#158= IFCLINE(#155,#157);
+#159= IFCTRIMMEDCURVE(#158,(IFCPARAMETERVALUE(0.0)),(IFCPARAMETERVALUE(790.569415042095)),.F.,.PARAMETER.);
+#160= IFCCOMPOSITECURVESEGMENT(.CONTINUOUS.,.T.,#159);
+#161= IFCCARTESIANPOINT((0.0,0.0));
+#162= IFCDIRECTION((1.0,0.0));
+#163= IFCVECTOR(#162,1.0);
+#164= IFCLINE(#161,#163);
+#165= IFCTRIMMEDCURVE(#164,(IFCPARAMETERVALUE(0.0)),(IFCPARAMETERVALUE(1000.0)),.T.,.PARAMETER.);
+#166= IFCCOMPOSITECURVESEGMENT(.CONTINUOUS.,.T.,#165);
+#167= IFCCOMPOSITECURVE((#154,#160,#166),.U.);
+#168= IFCARBITRARYCLOSEDPROFILEDEF(.AREA.,'PartialEllipse',#167);
+#169= IFCMATERIALPROFILE('PartialEllipse',$,#50,#168,$,$);
+#171= IFCMATERIALPROFILESET('PartialEllipse',$,(#169),$);
+#172= IFCRELASSOCIATESMATERIAL('2OfhB1Dcz2cAdV$CDh9PHV',$,'MatAssoc','Material Associates',(#173),#171);
+#173= IFCCOLUMNTYPE('0dtemVu1P2682BcO3CPWAy',$,'PartialEllipse',$,$,$,$,$,$,.COLUMN.);
+#174= IFCRELDEFINESBYTYPE('0rNx6sqCH2mOt1cWOT6zSU',$,'NameNotAssigned',$,(#180),#173);
+#175= IFCMATERIALPROFILESETUSAGE(#171,5,$);
+#176= IFCRELASSOCIATESMATERIAL('3bTNkVsf9099xrALHA6WhF',$,'MatAssoc','Material Associates',(#180),#175);
+#177= IFCCARTESIANPOINT((5000.0,0.0,0.0));
+#178= IFCAXIS2PLACEMENT3D(#177,$,$);
+#179= IFCLOCALPLACEMENT(#12,#178);
+#180= IFCCOLUMN('1JCvykjKH71R7_uck4n6hN',$,'PartialEllipse',$,$,#179,#186,$,$);
+#181= IFCCARTESIANPOINT((0.0,0.0,2000.0));
+#182= IFCPOLYLINE((#15,#181));
+#183= IFCSHAPEREPRESENTATION(#80,'Axis','Curve3D',(#182));
+#184= IFCEXTRUDEDAREASOLID(#168,$,#83,2000.0);
+#185= IFCSHAPEREPRESENTATION(#32,'Body','SweptSolid',(#184));
+#186= IFCPRODUCTDEFINITIONSHAPE($,$,(#183,#185));
+ENDSEC;
+
+END-ISO-10303-21;
+
diff --git a/files/ifc_files/bs_samples/extruded-solid.ifc b/files/ifc_files/bs_samples/extruded-solid.ifc
new file mode 100644
index 000000000..93a8309e4
--- /dev/null
+++ b/files/ifc_files/bs_samples/extruded-solid.ifc
@@ -0,0 +1,96 @@
+ISO-10303-21;
+HEADER;
+/* NOTE a valid model view name has to be asserted, replacing 'NotAssigned' ----------------- */
+FILE_DESCRIPTION(
+    ( 'ViewDefinition [NotAssigned]'
+     ,'Comment [manual creation of example file]'
+	)
+	,'2;1');
+/* NOTE standard header information according to ISO 10303-21 ---------------------------------- */
+FILE_NAME(
+	'extruded-solid.ifc',
+	'2012-06-18T18:00:00',
+	('redacted'),
+	('redacted'),
+	'redacted',
+	'redacted - redacted - 3.14159',
+	'reference file created for the IFC4 specification');
+FILE_SCHEMA(('IFC4X3_ADD2'));
+ENDSEC;
+
+DATA;
+/* --------------------------------------------------------------------------------------------- */
+/* general entities required for all IFC data sets, defining the context for the exchange ------ */
+#100= IFCPROJECT('0xScRe4drECQ4DMSqUjd6d',#110,'proxy with swept solid',$,$,$,$,(#201),#301);
+
+/* single owner history sufficient if not otherwise required by the view definition ------------ */
+/* provides the person and application creating the data set, and the time it is created ------- */
+#110= IFCOWNERHISTORY(#111,#115,$,.ADDED.,1320688800,$,$,1320688800);
+#111= IFCPERSONANDORGANIZATION(#112,#113,$);
+#112= IFCPERSON($,'redacted','redacted',$,$,$,$,$);
+#113= IFCORGANIZATION($,'redacted',$,$,$);
+#115= IFCAPPLICATION(#113,'redacted','redacted','redacted');
+
+/* each IFC data set containing geometry has to define a geometric representation context ------ */
+/* the attribute 'ContextType' has to be 'Model' for 3D model geometry ------------------------- */
+#201= IFCGEOMETRICREPRESENTATIONCONTEXT($,'Model',3,1.0E-5,#210,$);
+/* the attribute 'ContextIdentifier' has to be 'Body' for the main 3D shape representation ----- */
+#202= IFCGEOMETRICREPRESENTATIONSUBCONTEXT('Body','Model',*,*,*,*,#201,$,.MODEL_VIEW.,$);
+#210= IFCAXIS2PLACEMENT3D(#901,$,$);
+
+/* each IFC data set containing geometry has to define at absolute minimum length and angle ---- */
+/* here length is milli metre as SI unit, and plane angle is 'degree' as non SI unit ----------- */
+#301= IFCUNITASSIGNMENT((#311,#312));
+#311= IFCSIUNIT(*,.LENGTHUNIT.,.MILLI.,.METRE.);
+#312= IFCCONVERSIONBASEDUNIT(#313,.PLANEANGLEUNIT.,'degree',#314);
+#313= IFCDIMENSIONALEXPONENTS(0,0,0,0,0,0,0);
+#314= IFCMEASUREWITHUNIT(IFCPLANEANGLEMEASURE(0.017453293),#315);
+#315= IFCSIUNIT(*,.PLANEANGLEUNIT.,$,.RADIAN.);
+
+/* each IFC data set containing elements in a building context has to include a building ------- */
+/* at absolute minimum (could have a site and stories as well) --------------------------------- */
+#500= IFCBUILDING('2FCZDorxHDT8NI01kdXi8P',$,'Test Building',$,$,#511,$,$,.ELEMENT.,$,$,$);
+/* if the building is the uppermost spatial structure element it defines the absolut position -- */
+#511= IFCLOCALPLACEMENT($,#512);
+/* no rotation - z and x axes set to '$' are therefore identical to "world coordinate system" -- */ 
+#512= IFCAXIS2PLACEMENT3D(#901,$,$);
+/* if the building is the uppermost spatial structure element it is assigned to the project ---- */
+#519= IFCRELAGGREGATES('2YBqaV_8L15eWJ9DA1sGmT',$,$,$,#100,(#500));
+
+/* shared coordinates - it is permissible to share common instances to reduce file size -------- */
+#901= IFCCARTESIANPOINT((0.,0.,0.));
+#902= IFCDIRECTION((1.,0.,0.));
+#903= IFCDIRECTION((0.,1.,0.));
+#904= IFCDIRECTION((0.,0.,1.)); 
+#905= IFCDIRECTION((-1.,0.,0.));
+#906= IFCDIRECTION((0.,-1.,0.));
+#907= IFCDIRECTION((0.,0.,-1.));
+
+/* --------------------------------------------------------------------------------------------- */
+/* proxy element with swept solid shape representation, assigned to the building --------------- */
+#1000= IFCBUILDINGELEMENTPROXY('1kTvXnbbzCWw8lcMd1dR4o',$,'P-1','sample proxy',$,#1001,#1010,$,$);
+/* proxy element placement relative to the building -------------------------------------------- */
+#1001= IFCLOCALPLACEMENT(#511,#1002);
+/* set local placement to 1 meter on x-axis, and 0 on y, and 0 on z axes ----------------------- */
+/* no rotation - z and x axes set to '$' are therefore identical to those of building ---------- */ 
+#1002= IFCAXIS2PLACEMENT3D(#1003,$,$);
+#1003= IFCCARTESIANPOINT((1000.,0.,0.));
+/* proxy element shape representation ---------------------------------------------------------- */
+#1010= IFCPRODUCTDEFINITIONSHAPE($,$,(#1020));
+/* a single shape representation of type 'SweptSolid' is included ------------------------------ */
+#1020= IFCSHAPEREPRESENTATION(#202,'Body','SweptSolid',(#1021));
+/* based on a profile (or cross section) of 1m by 1m being extruded by 2m ---------------------- */
+#1021= IFCEXTRUDEDAREASOLID(#1022,$,#1034,2000.);
+#1022= IFCRECTANGLEPROFILEDEF(.AREA.,'1m x 1m rectangle',$,1000.,1000.);
+/* extrusion body is placed centric with no rotation inside the object coordinate placement ---- */
+/* extrusion position z = default = (0.,0.,1.), x = default = (1.,0.,0.) ----------------------- */
+/* the default position, i.e. no re-positioning of the results, hence the position is NIL ------ */
+/* the extrusion if perpendicular to the profile - i.e. along the positive z-axis -------------- */
+#1034= IFCDIRECTION((0.,0.,1.)); 
+
+/* proxy element assigned to the building ------------------------------------------------------ */
+#10000=IFCRELCONTAINEDINSPATIALSTRUCTURE('2TnxZkTXT08eDuMuhUUFNy',$,'Physical model',$,(#1000),#500);
+
+
+ENDSEC;
+END-ISO-10303-21;
\ No newline at end of file
diff --git a/files/ifc_files/bs_samples/polygonal-face-tessellation.ifc b/files/ifc_files/bs_samples/polygonal-face-tessellation.ifc
new file mode 100644
index 000000000..d37f7ea01
--- /dev/null
+++ b/files/ifc_files/bs_samples/polygonal-face-tessellation.ifc
@@ -0,0 +1,79 @@
+ISO-10303-21;
+HEADER;
+FILE_DESCRIPTION(('ViewDefinition [ReferenceView]'),'2;1');
+FILE_NAME(
+/* name */ 'polygonal-face-tessellation.ifc',
+/* time_stamp */ '2016-05-26T17:38:29',
+/* author */ ('redacted'),
+/* organization */ ('redacted'),
+/* preprocessor_version */ 'redacted',
+/* originating_system */ 'redacted - redacted - 3.14159',
+/* authorization */ 'None');
+
+FILE_SCHEMA (('IFC4X3_ADD2'));
+ENDSEC;
+
+DATA;
+#1= IFCGEOMETRICREPRESENTATIONCONTEXT($,'Model',3,0.01,#3,$);
+#2= IFCCARTESIANPOINT((0.0,0.0,0.0));
+#3= IFCAXIS2PLACEMENT3D(#3058,#3059,#3060);
+#4= IFCGEOMETRICREPRESENTATIONSUBCONTEXT('Axis','Model',*,*,*,*,#1,$,.MODEL_VIEW.,$);
+#5= IFCGEOMETRICREPRESENTATIONSUBCONTEXT('Body','Model',*,*,*,*,#1,$,.MODEL_VIEW.,$);
+#6= IFCCARTESIANPOINT((0.0,0.0,0.0));
+#7= IFCDIRECTION((1.0,0.0,0.0));
+#8= IFCDIRECTION((0.0,1.0,0.0));
+#9= IFCDIRECTION((0.0,0.0,1.0));
+#10= IFCCARTESIANPOINT((0.0,0.0));
+#11= IFCAXIS2PLACEMENT2D(#10,$);
+#12= IFCSIUNIT(*,.LENGTHUNIT.,$,.METRE.);
+#13= IFCSIUNIT(*,.AREAUNIT.,$,.SQUARE_METRE.);
+#14= IFCSIUNIT(*,.VOLUMEUNIT.,$,.CUBIC_METRE.);
+/* ------------------------------------------------------------------------- */
+/* polygonal face set geometry representation                                */
+#15= IFCCARTESIANPOINTLIST3D(((-10000.0,-10000.0,-10000.0),(10000.0,-10000.0,-10000.0),(10000.0,10000.0,-10000.0),(-10000.0,10000.0,-10000.0),(-10000.0,-10000.0,10000.0),(10000.0,-10000.0,10000.0),(10000.0,10000.0,10000.0),(-10000.0,10000.0,10000.0),(-5000.0,-5000.0,-5000.0),(5000.0,-5000.0,-5000.0),(5000.0,5000.0,-5000.0),(-5000.0,5000.0,-5000.0),(5000.0,-5000.0,10000.0),(-5000.0,-5000.0,10000.0),(5000.0,5000.0,10000.0),(-5000.0,5000.0,10000.0)),$);
+#16= IFCINDEXEDPOLYGONALFACE((2,6,5,1));
+#17= IFCINDEXEDPOLYGONALFACE((3,7,6,2));
+#18= IFCINDEXEDPOLYGONALFACE((4,8,7,3));
+#19= IFCINDEXEDPOLYGONALFACE((1,5,8,4));
+#20= IFCINDEXEDPOLYGONALFACE((4,3,2,1));
+#21= IFCINDEXEDPOLYGONALFACEWITHVOIDS((6,7,8,5),((14,16,15,13)));
+#22= IFCINDEXEDPOLYGONALFACE((13,10,9,14));
+#23= IFCINDEXEDPOLYGONALFACE((15,11,10,13));
+#24= IFCINDEXEDPOLYGONALFACE((16,12,11,15));
+#25= IFCINDEXEDPOLYGONALFACE((14,9,12,16));
+#26= IFCINDEXEDPOLYGONALFACE((9,10,11,12));
+#27= IFCPOLYGONALFACESET(#15,.T.,(#16,#17,#18,#19,#20,#21,#22,#23,#24,#25,#26),$);
+#28= IFCSHAPEREPRESENTATION(#5,'Body','Tessellation',(#27));
+#29= IFCPRODUCTDEFINITIONSHAPE($,$,(#28));
+/* ------------------------------------------------------------------------- */
+/* assigned as shape representation to a proxy                               */
+#30= IFCBUILDINGELEMENTPROXY('1csV6umSb0px7vDxobGEN_',#3054,'NOTDEFINED',$,$,#32,#29,$,.NOTDEFINED.);
+#31= IFCAXIS2PLACEMENT3D(#2,$,$);
+#32= IFCLOCALPLACEMENT(#3047,#31);
+#3047= IFCLOCALPLACEMENT($,#3);
+/* ------------------------------------------------------------------------- */
+/* definition of the minimal building structure, units, owner history        */
+#3048= IFCBUILDING('2tMIBeIVfClPSrbOosOJDI',#3054,'Grasshopper Building','GH Building',$,#3047,$,'GH Building',$,0.0,0.0,$);
+#3049= IFCPERSONANDORGANIZATION(#3050,#3051,$);
+#3050= IFCPERSON('redacted','redacted',$,$,$,$,$,$);
+#3051= IFCORGANIZATION($,'redacted',$,$,$);
+#3052= IFCAPPLICATION(#3053,'redacted','redacted','redacted');
+#3053= IFCORGANIZATION($,'redacted',$,$,$);
+#3054= IFCOWNERHISTORY(#3049,#3052,$,.ADDED.,1464284014,$,$,1464284014);
+#3055= IFCRELCONTAINEDINSPATIALSTRUCTURE('3_FDRX0_zCNwiRAZP_mk8l',#3054,'Building','Building Container for Elements',(#30),#3048);
+#3056= IFCAXIS2PLACEMENT3D(#2,$,$);
+#3058= IFCCARTESIANPOINT((0.0,0.0,0.0));
+#3059= IFCDIRECTION((0.0,0.0,1.0));
+#3060= IFCDIRECTION((1.0,0.0,0.0));
+#3061= IFCPROJECT('37E0t9DhPDuPXM8sgxexaw',#3054,'Grasshopper Project',$,$,$,$,(#1),#3062);
+#3062= IFCUNITASSIGNMENT((#3063,#13,#14,#3064,#3065));
+#3063= IFCSIUNIT(*,.LENGTHUNIT.,.MILLI.,.METRE.);
+#3064= IFCSIUNIT(*,.PLANEANGLEUNIT.,$,.RADIAN.);
+#3065= IFCSIUNIT(*,.TIMEUNIT.,$,.SECOND.);
+#3066= IFCRELAGGREGATES('1jnXpsMarCZQ$Xxt61uMb4',#3054,'Project Container','Project Container for Buildings',#3061,(#3048));
+#3070= IFCAXIS2PLACEMENT3D(#2,$,$);
+ENDSEC;
+
+END-ISO-10303-21;
+
+
diff --git a/files/ifc_files/bs_samples/tessellation-with-image-texture.ifc b/files/ifc_files/bs_samples/tessellation-with-image-texture.ifc
new file mode 100644
index 000000000..8a411b79a
--- /dev/null
+++ b/files/ifc_files/bs_samples/tessellation-with-image-texture.ifc
@@ -0,0 +1,74 @@
+ISO-10303-21;
+HEADER;
+FILE_DESCRIPTION((''),'2;1');
+FILE_NAME('tessellation-with-image-texture.ifc','2016-05-06T03:47:49',(''),(''),'redacted','redacted - redacted - 3.14159','');
+FILE_SCHEMA(('IFC4X3_ADD2'));
+ENDSEC;
+
+DATA;
+
+#1= IFCPROJECT('10kad3X9L7HRl25ZiOK$bx',$,'Project',$,$,$,$,(#2,#3),#4);
+#2= IFCGEOMETRICREPRESENTATIONCONTEXT('3D','Model',3,1.0E-05,#6,$);
+#3= IFCGEOMETRICREPRESENTATIONCONTEXT('2D','Plan',2,1.0E-05,#7,$);
+#4= IFCUNITASSIGNMENT((#8,#9,#10,#11,#12,#13,#14,#15,#16));
+#6= IFCAXIS2PLACEMENT3D(#17,$,$);
+#7= IFCAXIS2PLACEMENT3D(#18,$,$);
+#8= IFCCONVERSIONBASEDUNIT(#19,.AREAUNIT.,'square inch',#20);
+#9= IFCCONVERSIONBASEDUNIT(#21,.FORCEUNIT.,'pound-force',#22);
+#10= IFCCONVERSIONBASEDUNIT(#23,.LENGTHUNIT.,'inch',#24);
+#11= IFCCONVERSIONBASEDUNIT(#25,.MASSUNIT.,'pound',#26);
+#12= IFCCONVERSIONBASEDUNIT(#27,.PLANEANGLEUNIT.,'degree',#28);
+#13= IFCCONVERSIONBASEDUNIT(#29,.PRESSUREUNIT.,'pound-force per square inch',#30);
+#14= IFCCONVERSIONBASEDUNITWITHOFFSET(#31,.THERMODYNAMICTEMPERATUREUNIT.,'Fahrenheit',#32,-459.67);
+#15= IFCCONVERSIONBASEDUNIT(#33,.VOLUMEUNIT.,'cubic inch',#34);
+#16= IFCMONETARYUNIT('USD');
+#17= IFCCARTESIANPOINT((0.,0.,0.));
+#18= IFCCARTESIANPOINT((0.,0.,0.));
+#19= IFCDIMENSIONALEXPONENTS(2,0,0,0,0,0,0);
+#20= IFCMEASUREWITHUNIT(IFCAREAMEASURE(0.0006452),#35);
+#21= IFCDIMENSIONALEXPONENTS(1,1,-2,0,0,0,0);
+#22= IFCMEASUREWITHUNIT(IFCMASSMEASURE(4.44822162),#36);
+#23= IFCDIMENSIONALEXPONENTS(1,0,0,0,0,0,0);
+#24= IFCMEASUREWITHUNIT(IFCLENGTHMEASURE(0.0254),#37);
+#25= IFCDIMENSIONALEXPONENTS(0,1,0,0,0,0,0);
+#26= IFCMEASUREWITHUNIT(IFCMASSMEASURE(0.45359237),#38);
+#27= IFCDIMENSIONALEXPONENTS(0,0,0,0,0,0,0);
+#28= IFCMEASUREWITHUNIT(IFCPLANEANGLEMEASURE(0.0174532925199433),#39);
+#29= IFCDIMENSIONALEXPONENTS(-1,1,-2,0,0,0,0);
+#30= IFCMEASUREWITHUNIT(IFCPRESSUREMEASURE(6894.7572932),#40);
+#31= IFCDIMENSIONALEXPONENTS(0,0,0,0,1,0,0);
+#32= IFCMEASUREWITHUNIT(IFCTHERMODYNAMICTEMPERATUREMEASURE(1.8),#41);
+#33= IFCDIMENSIONALEXPONENTS(3,0,0,0,0,0,0);
+#34= IFCMEASUREWITHUNIT(IFCVOLUMEMEASURE(1.639E-05),#42);
+#35= IFCSIUNIT(*,.AREAUNIT.,$,.SQUARE_METRE.);
+#36= IFCSIUNIT(*,.FORCEUNIT.,$,.NEWTON.);
+#37= IFCSIUNIT(*,.LENGTHUNIT.,$,.METRE.);
+#38= IFCSIUNIT(*,.MASSUNIT.,.KILO.,.GRAM.);
+#39= IFCSIUNIT(*,.PLANEANGLEUNIT.,$,.RADIAN.);
+#40= IFCSIUNIT(*,.PRESSUREUNIT.,$,.PASCAL.);
+#41= IFCSIUNIT(*,.THERMODYNAMICTEMPERATUREUNIT.,$,.KELVIN.);
+#42= IFCSIUNIT(*,.VOLUMEUNIT.,$,.CUBIC_METRE.);
+
+#5= IFCRELDECLARES('3FXPqqCWT9I9Gn7115PFHw',$,$,$,#1,(#43));
+
+#43= IFCBOILERTYPE('2n5ASfQfT84eP9h$zLLJ4A',$,'boiler name',$,$,$,(#44),$,$,.NOTDEFINED.);
+#44= IFCREPRESENTATIONMAP(#45,#46);
+#45= IFCAXIS2PLACEMENT3D(#47,$,$);
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diff --git a/files/ifc_files/reinforcing-assembly.ifc b/files/ifc_files/reinforcing-assembly.ifc
new file mode 100644
index 000000000..86c08cfd2
--- /dev/null
+++ b/files/ifc_files/reinforcing-assembly.ifc
@@ -0,0 +1,456 @@
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+/* name */ 'reinforcing-assembly.ifc',
+/* time_stamp */ '2016-02-04T08:47:55',
+/* author */ ('redacted'),
+/* organization */ ('redacted'),
+/* preprocessor_version */ 'redacted',
+/* originating_system */ 'redacted - redacted - 3.14159',
+/* authorization */ 'None');
+
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+ENDSEC;
+
+END-ISO-10303-21;
+
diff --git a/files/ifc_files/reinforcing-stirrup.ifc b/files/ifc_files/reinforcing-stirrup.ifc
new file mode 100644
index 000000000..a999255b0
--- /dev/null
+++ b/files/ifc_files/reinforcing-stirrup.ifc
@@ -0,0 +1,66 @@
+ISO-10303-21;
+HEADER;
+FILE_DESCRIPTION(('ViewDefinition [NotAssigned]'),'2;1');
+FILE_NAME(
+/* name */ 'reinforcing-stirrup.ifc',
+/* time_stamp */ '2016-02-04T08:47:55',
+/* author */ ('redacted'),
+/* organization */ ('redacted'),
+/* preprocessor_version */ 'redacted',
+/* originating_system */ 'redacted - redacted - 3.14159',
+/* authorization */ 'None');
+
+FILE_SCHEMA (('IFC4X3_ADD2'));
+ENDSEC;
+
+DATA;
+/* general entities required for all IFC data sets, defining the context for the exchange */
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+#2= IFCCARTESIANPOINT((0.0,0.0,0.0));
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+/* defines the default building (as required as the minimum spatial element)  */
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+END-ISO-10303-21;
+
diff --git a/files/ifc_files/sectioned-solid-horizontal.ifc b/files/ifc_files/sectioned-solid-horizontal.ifc
new file mode 100644
index 000000000..34d7a34c0
--- /dev/null
+++ b/files/ifc_files/sectioned-solid-horizontal.ifc
@@ -0,0 +1,190 @@
+ISO-10303-21;
+HEADER;
+FILE_DESCRIPTION (('ViewDefinition [Alignment-basedView]'), '2;1');
+FILE_NAME ('sectioned-solid-horizontal.ifc', '2021-05-31T10:35:59', ('redacted'), ('redacted'), 'redacted', 'redacted - redacted - 3.14159', '');
+FILE_SCHEMA (('IFC4X3_ADD2'));
+ENDSEC;
+
+DATA;
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diff --git a/files/ifc_files/segmented-reference-curve.ifc b/files/ifc_files/segmented-reference-curve.ifc
new file mode 100644
index 000000000..a6ce514ec
--- /dev/null
+++ b/files/ifc_files/segmented-reference-curve.ifc
@@ -0,0 +1,139 @@
+ISO-10303-21;
+HEADER;
+FILE_DESCRIPTION(('ViewDefinition [Alignment-basedView]'),'2;1');
+FILE_NAME('segmented-reference-curve.ifc','2024-11-12T10:00:00',(''),(''),'redacted','redacted - redacted - 3.14159','');
+FILE_SCHEMA(('IFC4X3_ADD2'));
+ENDSEC;
+DATA;
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+#4=IFCPERSON('redacted','redacted',$,$,$,$,$,$);
+#5=IFCORGANIZATION('redacted','redacted',$,$,$);
+#6=IFCPERSONANDORGANIZATION(#4,#5,$);
+#7=IFCSIUNIT(*,.LENGTHUNIT.,$,.METRE.);
+#8=IFCSIUNIT(*,.PLANEANGLEUNIT.,$,.RADIAN.);
+#9=IFCUNITASSIGNMENT((#7,#8));
+#10=IFCCARTESIANPOINT((0.,0.,0.));
+#11=IFCDIRECTION((0.,0.,1.));
+#12=IFCDIRECTION((1.,0.,0.));
+#13=IFCAXIS2PLACEMENT3D(#10,#11,#12);
+#14=IFCLOCALPLACEMENT($,#13);
+#15=IFCRAILWAY('1FNFy9AJeHwuVmwDZHIYIu',#3,$,$,$,#14,$,$,$,$);
+#16=IFCDIRECTION((0.,1.));
+#17=IFCGEOMETRICREPRESENTATIONCONTEXT($,'Model',3,1.E-05,#13,#16);
+#18=IFCRELAGGREGATES('1FNFyAAJeHwu6TwDZHIYIu',#3,$,$,#1,(#15,#20));
+#20=IFCALIGNMENT('1FNFyCAJeHwxedwDZHIYIu',#3,$,$,$,#137,#140,$);
+#21=IFCALIGNMENTHORIZONTAL('1FNFyDAJeHwv87wDZHIYIu',$,$,$,$,#86,$);
+#23=IFCRELNESTS('3BJTAQrjCHwvVKbERtTLTf',$,$,$,#20,(#21,#41,#61,#161));
+#28=IFCCARTESIANPOINT((0.,0.));
+#29=IFCALIGNMENTHORIZONTALSEGMENT($,$,#28,0.,300.,1000.,100.,$,.COSINECURVE.);
+#30=IFCALIGNMENTSEGMENT('1FNFyHAJeHwuDtwDZHIYIu',#3,$,$,$,#67,#70,#29);
+#34=IFCRELNESTS('1FNFyHAJeHwuDtwDZHIYIj',$,$,$,#21,(#30,#145));
+#41=IFCALIGNMENTVERTICAL('1FNFyDAJeHwv87wDZHIYI1',$,$,$,$,#109,$);
+#42=IFCALIGNMENTSEGMENT('1FNFyHAJeHwuDtwDZHIYI2',#3,$,$,$,#91,#94,#44);
+#43=IFCRELNESTS('3CGecNrjCHwxOSbERtTLTf',$,$,$,#41,(#42,#147));
+#44=IFCALIGNMENTVERTICALSEGMENT($,$,0.,100.,0.,0.,0.,$,.CONSTANTGRADIENT.);
+#61=IFCALIGNMENTCANT('1FNFyDAJeHwv87wDZHIYI7',$,$,$,$,#134,$,1.5);
+#62=IFCALIGNMENTSEGMENT('1FNFyHAJeHwuDtwDZHIYI3',#3,$,$,$,#114,#117,#64);
+#63=IFCRELNESTS('2CGecOrjCHww8dbERtTLTf',$,$,$,#61,(#62,#149));
+#64=IFCALIGNMENTCANTSEGMENT($,$,0.,100.,0.,0.,0.16,0.,.COSINECURVE.);
+#65=IFCCOMPOSITECURVE((#66,#78),.F.);
+#66=IFCCURVESEGMENT(.CONTINUOUS.,#72,IFCLENGTHMEASURE(0.),IFCLENGTHMEASURE(100.),#75);
+#67=IFCLOCALPLACEMENT($,#68);
+#68=IFCAXIS2PLACEMENT3D(#69,$,$);
+#69=IFCCARTESIANPOINT((0.,0.,0.));
+#70=IFCPRODUCTDEFINITIONSHAPE($,$,(#71));
+#71=IFCSHAPEREPRESENTATION(#17,'Axis','Segment',(#66));
+#72=IFCAXIS2PLACEMENT2D(#73,#74);
+#73=IFCCARTESIANPOINT((0.,0.));
+#74=IFCDIRECTION((1.,0.));
+#75=IFCCOSINESPIRAL(#76,857.142857142857,461.538461538462);
+#76=IFCAXIS2PLACEMENT2D(#77,$);
+#77=IFCCARTESIANPOINT((0.,0.));
+#78=IFCCURVESEGMENT(.DISCONTINUOUS.,#79,IFCLENGTHMEASURE(0.),IFCLENGTHMEASURE(0.),#82);
+#79=IFCAXIS2PLACEMENT2D(#80,#81);
+#80=IFCCARTESIANPOINT((98.9298874325988,13.1346246945757));
+#81=IFCDIRECTION((1.,0.));
+#82=IFCLINE(#83,#84);
+#83=IFCCARTESIANPOINT((0.,0.));
+#84=IFCVECTOR(#85,1.);
+#85=IFCDIRECTION((1.,0.));
+#86=IFCLOCALPLACEMENT($,#87);
+#87=IFCAXIS2PLACEMENT3D(#88,$,$);
+#88=IFCCARTESIANPOINT((0.,0.,0.));
+#89=IFCGRADIENTCURVE((#90,#153),.F.,#65,#106);
+#90=IFCCURVESEGMENT(.CONTINUOUS.,#96,IFCLENGTHMEASURE(0.),IFCLENGTHMEASURE(100.),#99);
+#91=IFCLOCALPLACEMENT($,#92);
+#92=IFCAXIS2PLACEMENT3D(#93,$,$);
+#93=IFCCARTESIANPOINT((0.,0.,0.));
+#94=IFCPRODUCTDEFINITIONSHAPE($,$,(#95));
+#95=IFCSHAPEREPRESENTATION(#17,'Axis','Segment',(#90));
+#96=IFCAXIS2PLACEMENT2D(#97,#98);
+#97=IFCCARTESIANPOINT((0.,0.));
+#98=IFCDIRECTION((1.,0.));
+#99=IFCLINE(#100,#101);
+#100=IFCCARTESIANPOINT((0.,0.));
+#101=IFCVECTOR(#102,1.);
+#102=IFCDIRECTION((1.,0.));
+#106=IFCAXIS2PLACEMENT2D(#107,#108);
+#107=IFCCARTESIANPOINT((100.,0.));
+#108=IFCDIRECTION((1.,0.));
+#109=IFCLOCALPLACEMENT($,#110);
+#110=IFCAXIS2PLACEMENT3D(#111,$,$);
+#111=IFCCARTESIANPOINT((0.,0.,0.));
+#112=IFCSEGMENTEDREFERENCECURVE((#113,#157),.F.,#89,#130);
+#113=IFCCURVESEGMENT(.CONTINUOUS.,#123,IFCLENGTHMEASURE(0.),IFCLENGTHMEASURE(100.),#127);
+#114=IFCLOCALPLACEMENT($,#115);
+#115=IFCAXIS2PLACEMENT3D(#116,$,$);
+#116=IFCCARTESIANPOINT((0.,0.,0.));
+#117=IFCPRODUCTDEFINITIONSHAPE($,$,(#118));
+#118=IFCSHAPEREPRESENTATION(#17,'Axis','Segment',(#113));
+#123=IFCAXIS2PLACEMENT3D(#124,#125,#126);
+#124=IFCCARTESIANPOINT((0.,0.08,0.));
+#125=IFCDIRECTION((-0.,0.106064981392206,0.994359200551929));
+#126=IFCDIRECTION((1.,0.,0.));
+#127=IFCCOSINESPIRAL(#128,2500.,2500.);
+#128=IFCAXIS2PLACEMENT2D(#129,$);
+#129=IFCCARTESIANPOINT((0.,0.));
+#130=IFCAXIS2PLACEMENT3D(#131,#132,#133);
+#131=IFCCARTESIANPOINT((100.,0.,0.));
+#132=IFCDIRECTION((0.,-0.,1.));
+#133=IFCDIRECTION((1.,0.,0.));
+#134=IFCLOCALPLACEMENT($,#135);
+#135=IFCAXIS2PLACEMENT3D(#136,$,$);
+#136=IFCCARTESIANPOINT((0.,0.,0.));
+#137=IFCLOCALPLACEMENT($,#138);
+#138=IFCAXIS2PLACEMENT3D(#139,$,$);
+#139=IFCCARTESIANPOINT((0.,0.,0.));
+#140=IFCPRODUCTDEFINITIONSHAPE($,$,(#141,#142));
+#141=IFCSHAPEREPRESENTATION(#17,'Axis','Curve3D',(#112));
+#142=IFCSHAPEREPRESENTATION(#17,'FootPrint','Curve2D',(#65));
+#143=IFCCARTESIANPOINT((98.929887264154,13.1346242263917));
+#144=IFCALIGNMENTHORIZONTALSEGMENT($,$,#143,0.216666666666666,0.,0.,0.,$,.LINE.);
+#145=IFCALIGNMENTSEGMENT('0pkgAW6$nFUxI4Rz7nfXqD',$,'H2',$,$,$,$,#144);
+#146=IFCALIGNMENTVERTICALSEGMENT($,$,100.,0.,0.,0.,0.,$,.CONSTANTGRADIENT.);
+#147=IFCALIGNMENTSEGMENT('096DNdiXLAG8XiglQEXS6m',$,'H2',$,$,$,$,#146);
+#148=IFCALIGNMENTCANTSEGMENT($,$,100.,0.,0.,0.,0.,0.,.CONSTANTCANT.);
+#149=IFCALIGNMENTSEGMENT('309BB_YA56aeUKwbrzAQk4',$,'H2',$,$,$,$,#148);
+#150=IFCCARTESIANPOINT((100.,0.));
+#151=IFCDIRECTION((1.,0.));
+#152=IFCAXIS2PLACEMENT2D(#150,#151);
+#153=IFCCURVESEGMENT(.DISCONTINUOUS.,#152,IFCLENGTHMEASURE(0.),IFCLENGTHMEASURE(0.),#99);
+#154=IFCCARTESIANPOINT((100.,0.));
+#155=IFCDIRECTION((1.,0.));
+#156=IFCAXIS2PLACEMENT2D(#154,#155);
+#157=IFCCURVESEGMENT(.DISCONTINUOUS.,#156,IFCLENGTHMEASURE(0.),IFCLENGTHMEASURE(0.),#127);
+#158=IFCPOINTBYDISTANCEEXPRESSION(IFCLENGTHMEASURE(0.),$,$,$,#65);
+#159=IFCAXIS2PLACEMENTLINEAR(#158,$,$);
+#160=IFCLINEARPLACEMENT($,#159,#164);
+#161=IFCREFERENT('0OHVJQIVnCTBfgbzqOY_6p',$,'Start Station',$,$,#160,$,.STATION.);
+#162=IFCGEOMETRICREPRESENTATIONSUBCONTEXT('Body',$,*,*,*,*,#17,$,.MODEL_VIEW.,$);
+#163=IFCCARTESIANPOINT((0.,0.,0.));
+#164=IFCAXIS2PLACEMENT3D(#163,#166,#165);
+#165=IFCDIRECTION((1.,0.,0.));
+#166=IFCDIRECTION((0.,0.,1.));
+#167=IFCPROJECTEDCRS('EPSG:26973',$,$,$,$,$,$);
+#168=IFCMAPCONVERSION(#17,#167,0.,0.,0.,$,$,$);
+ENDSEC;
+END-ISO-10303-21;
diff --git a/files/ifc_files/surface-model.ifc b/files/ifc_files/surface-model.ifc
new file mode 100644
index 000000000..de7de16a3
--- /dev/null
+++ b/files/ifc_files/surface-model.ifc
@@ -0,0 +1,118 @@
+ISO-10303-21;
+HEADER;
+/* NOTE a valid model view name has to be asserted, replacing 'NotAssigned' ----------------- */
+FILE_DESCRIPTION(
+    ( 'ViewDefinition [NotAssigned]'
+     ,'Comment [manual creation of example file]'
+	)
+	,'2;1');
+/* NOTE standard header information according to ISO 10303-21 ---------------------------------- */
+FILE_NAME(
+	'surface-model.ifc',
+	'2011-11-07T18:00:00',
+	('redacted'),
+	('redacted'),
+	'redacted',
+	'redacted - redacted - 3.14159',
+	'reference file created for the IFC4 specification');
+FILE_SCHEMA(('IFC4X3_ADD2'));
+ENDSEC;
+
+DATA;
+/* --------------------------------------------------------------------------------------------- */
+/* general entities required for all IFC data sets, defining the context for the exchange ------ */
+#100= IFCPROJECT('0xScRe4drECQ4DMSqUjd6d',#110,'proxy with surface model',$,$,$,$,(#201),#301);
+
+/* single owner history sufficient if not otherwise required by the view definition ------------ */
+/* provides the person and application creating the data set, and the time it is created ------- */
+#110= IFCOWNERHISTORY(#111,#115,$,.ADDED.,1320688800,$,$,1320688800);
+#111= IFCPERSONANDORGANIZATION(#112,#113,$);
+#112= IFCPERSON($,'redacted','redacted',$,$,$,$,$);
+#113= IFCORGANIZATION($,'redacted',$,$,$);
+#115= IFCAPPLICATION(#113,'redacted','redacted','redacted');
+
+/* each IFC data set containing geometry has to define a geometric representation context ------ */
+/* the attribute 'ContextType' has to be 'Model' for 3D model geometry ------------------------- */
+#201= IFCGEOMETRICREPRESENTATIONCONTEXT($,'Model',3,1.0E-5,#210,$);
+/* the attribute 'ContextIdentifier' has to be 'Body' for the main 3D shape representation ----- */
+#202= IFCGEOMETRICREPRESENTATIONSUBCONTEXT('Body','Model',*,*,*,*,#201,$,.MODEL_VIEW.,$);
+#210= IFCAXIS2PLACEMENT3D(#901,$,$);
+
+/* each IFC data set containing geometry has to define at absolute minimum length and angle ---- */
+/* here length is milli metre as SI unit, and plane angle is 'degree' as non SI unit ----------- */
+#301= IFCUNITASSIGNMENT((#311,#312));
+#311= IFCSIUNIT(*,.LENGTHUNIT.,.MILLI.,.METRE.);
+#312= IFCCONVERSIONBASEDUNIT(#313,.PLANEANGLEUNIT.,'degree',#314);
+#313= IFCDIMENSIONALEXPONENTS(0,0,0,0,0,0,0);
+#314= IFCMEASUREWITHUNIT(IFCPLANEANGLEMEASURE(0.017453293),#315);
+#315= IFCSIUNIT(*,.PLANEANGLEUNIT.,$,.RADIAN.);
+
+/* each IFC data set containing elements in a building context has to include a building ------- */
+/* at absolute minimum (could have a site and stories as well) --------------------------------- */
+#500= IFCBUILDING('2FCZDorxHDT8NI01kdXi8P',$,'Test Building',$,$,#511,$,$,.ELEMENT.,$,$,$);
+/* if the building is the uppermost spatial structure element it defines the absolut position -- */
+#511= IFCLOCALPLACEMENT($,#512);
+/* no rotation - z and x axes set to '$' are therefore identical to "world coordinate system" -- */ 
+#512= IFCAXIS2PLACEMENT3D(#901,$,$);
+/* if the building is the uppermost spatial structure element it is assigned to the project ---- */
+#519= IFCRELAGGREGATES('2YBqaV_8L15eWJ9DA1sGmT',$,$,$,#100,(#500));
+
+/* shared coordinates - it is permissible to share common instances to reduce file size -------- */
+#901= IFCCARTESIANPOINT((0.,0.,0.));
+#902= IFCDIRECTION((1.,0.,0.));
+#903= IFCDIRECTION((0.,1.,0.));
+#904= IFCDIRECTION((0.,0.,1.)); 
+#905= IFCDIRECTION((-1.,0.,0.));
+#906= IFCDIRECTION((0.,-1.,0.));
+#907= IFCDIRECTION((0.,0.,-1.));
+
+/* --------------------------------------------------------------------------------------------- */
+/* proxy element with surface model shape representation, assigned to the building ------------- */
+#1000= IFCBUILDINGELEMENTPROXY('1kTvXnbbzCWw8lcMd1dR4o',$,'P-1','sample proxy',$,#1001,#1010,$,$);
+/* proxy element placement relative to the building -------------------------------------------- */
+#1001= IFCLOCALPLACEMENT(#511,#1002);
+/* set local placement to 1 meter on x-axis, and 0 on y, and 0 on z axes ----------------------- */
+/* no rotation - z and x axes set to '$' are therefore identical to those of building ---------- */ 
+#1002= IFCAXIS2PLACEMENT3D(#1003,$,$);
+#1003= IFCCARTESIANPOINT((1000.,0.,0.));
+/* proxy element shape representation ---------------------------------------------------------- */
+#1010= IFCPRODUCTDEFINITIONSHAPE($,$,(#1020));
+/* a single shape representation of type 'SurfaceModel' is included ---------------------------- */
+#1020= IFCSHAPEREPRESENTATION(#202,'Body','SurfaceModel',(#1021));
+/* face based surface representation ----------------------------------------------------------- */
+/* cube, 1m width, 1m depth, 2m height --------------------------------------------------------- */
+#1021= IFCFACEBASEDSURFACEMODEL ((#1022));
+#1022= IFCCONNECTEDFACESET ((#1110, #1120, #1130, #1140, #1150, #1160));
+#1110= IFCFACE((#1111));
+#1111= IFCFACEOUTERBOUND(#1112,.T.);
+#1112= IFCPOLYLOOP((#1201,#1202,#1206,#1205));
+#1120= IFCFACE((#1121));
+#1121= IFCFACEOUTERBOUND(#1122,.T.);
+#1122= IFCPOLYLOOP((#1206,#1202,#1203,#1207));
+#1130= IFCFACE((#1131));
+#1131= IFCFACEOUTERBOUND(#1132,.T.);
+#1132= IFCPOLYLOOP((#1207,#1203,#1204,#1208));
+#1140= IFCFACE((#1141));
+#1141= IFCFACEOUTERBOUND(#1142,.T.);
+#1142= IFCPOLYLOOP((#1208,#1204,#1201,#1205));
+#1150= IFCFACE((#1151));
+#1151= IFCFACEOUTERBOUND(#1152,.T.);
+#1152= IFCPOLYLOOP((#1201,#1204,#1203,#1202));
+#1160= IFCFACE((#1161));
+#1161= IFCFACEOUTERBOUND(#1162,.T.);
+#1162= IFCPOLYLOOP((#1206,#1207,#1208,#1205));
+/* shared vertices of the faceted boundary representation -------------------------------------- */
+#1201= IFCCARTESIANPOINT((-500.,-500.,0.));
+#1202= IFCCARTESIANPOINT((500.,-500.,0.));
+#1203= IFCCARTESIANPOINT((500.,500.,0.));
+#1204= IFCCARTESIANPOINT((-500.,500.,0.));
+#1205= IFCCARTESIANPOINT((-500.,-500.,2000.));
+#1206= IFCCARTESIANPOINT((500.,-500.,2000.));
+#1207= IFCCARTESIANPOINT((500.,500.,2000.));
+#1208= IFCCARTESIANPOINT((-500.,500.,2000.));
+
+/* proxy element assigned to the building ------------------------------------------------------ */
+#10000=IFCRELCONTAINEDINSPATIALSTRUCTURE('2TnxZkTXT08eDuMuhUUFNy',$,'Physical model',$,(#1000),#500);
+
+ENDSEC;
+END-ISO-10303-21;
\ No newline at end of file
diff --git a/prototypes/ngeom_compare/align_eval.py b/prototypes/ngeom_compare/align_eval.py
new file mode 100644
index 000000000..b37fd42cb
--- /dev/null
+++ b/prototypes/ngeom_compare/align_eval.py
@@ -0,0 +1,245 @@
+"""Python reference evaluator for the IFC4x3 alignment directrix (IfcGradientCurve).
+
+Analytic eval of the horizontal IfcCompositeCurve (line / clothoid / circular arc segments) +
+the vertical gradient, composed into a sampled 3D directrix with per-station frames. Validated
+against the ifcopenshell.geom directrix oracle (align_oracle.py -> directrix_oracle.npy).
+
+This is the SPEC for the adacpp C++ port (ng:: analytic eval). No OCC.
+
+Run: pixi run -e tests-adacpp python prototypes/ngeom_compare/align_eval.py
+"""
+
+from __future__ import annotations
+
+import math
+from dataclasses import dataclass
+
+import numpy as np
+
+SCRATCH = "/tmp/claude-1000/-home-kristoffer-code-dap/d103bfc1-7e2e-4f7e-ba7c-8e213d35e3df/scratchpad"
+
+
+def fresnel(t):
+    """Normalized Fresnel integrals S(t)=int_0^t sin(pi u^2/2) du, C(t)=int_0^t cos(...).
+
+    Power-series sum (converges fast for |t| <~ 2; this fixture's clothoid has t_max ~ 0.31).
+    The adacpp C++ port should swap in a rational/auxiliary-function Fresnel (Boersma) for large
+    arguments; documented as such in the spec.
+    """
+    # C(t) = sum_n (-1)^n (pi/2)^{2n} t^{4n+1} / ((2n)! (4n+1))
+    # S(t) = sum_n (-1)^n (pi/2)^{2n+1} t^{4n+3} / ((2n+1)! (4n+3))
+    hp = math.pi / 2.0
+    C = 0.0
+    S = 0.0
+    # C terms
+    term = t
+    n = 0
+    while True:
+        c = term / (4 * n + 1)
+        C += c
+        # advance term: multiply by -(pi/2)^2 t^4 / ((2n+1)(2n+2))
+        nt = term * (-(hp * hp) * t**4) / ((2 * n + 1) * (2 * n + 2))
+        if abs(c) < 1e-18 and n > 2:
+            break
+        term = nt
+        n += 1
+        if n > 200:
+            break
+    # S terms
+    term = hp * t**3
+    n = 0
+    while True:
+        s = term / (4 * n + 3)
+        S += s
+        nt = term * (-(hp * hp) * t**4) / ((2 * n + 2) * (2 * n + 3))
+        if abs(s) < 1e-18 and n > 2:
+            break
+        term = nt
+        n += 1
+        if n > 200:
+            break
+    return S, C
+
+
+def _rot2d(from_dir, to_dir):
+    """2x2 rotation taking unit vector from_dir -> unit vector to_dir."""
+    fx, fy = from_dir
+    tx, ty = to_dir
+    # angle of to minus angle of from
+    c = fx * tx + fy * ty  # cos
+    s = fx * ty - fy * tx  # sin (cross)
+    return np.array([[c, -s], [s, c]])
+
+
+# ---- parent-curve local eval: param p = arc length -> (point2d, unit tangent2d) ----
+
+
+def _line_eval(p):
+    return np.array([p, 0.0]), np.array([1.0, 0.0])
+
+
+def _circle_eval(p, radius):
+    # IfcCircle in its placement frame: center at origin, start at (R,0), CCW.
+    # arc length p -> angle th = p / R
+    th = p / radius
+    pt = np.array([radius * math.cos(th), radius * math.sin(th)])
+    tg = np.array([-math.sin(th), math.cos(th)])  # d/dp, already unit
+    return pt, tg
+
+
+def _clothoid_eval(p, A):
+    # arc length p along the spiral. x = |A|sqrt(pi) C(t), y = sign(A) |A|sqrt(pi) S(t),
+    # t = p / (|A| sqrt(pi)). scipy.fresnel returns (S, C).
+    aa = abs(A)
+    scale = aa * math.sqrt(math.pi)
+    if scale == 0.0:
+        return np.array([p, 0.0]), np.array([1.0, 0.0])
+    t = p / scale
+    S, C = fresnel(t)
+    pt = np.array([scale * C, math.copysign(1.0, A) * scale * S])
+    # tangent: dx/dp = cos(pi t^2 /2)*... derivative of C is cos(pi t^2/2); chain dt/dp = 1/scale
+    ph = math.pi * t * t / 2.0
+    tg = np.array([math.cos(ph), math.copysign(1.0, A) * math.sin(ph)])
+    n = np.hypot(*tg)
+    return pt, tg / n
+
+
+@dataclass
+class Seg:
+    kind: str  # 'line' | 'circle' | 'clothoid'
+    origin: np.ndarray  # placement origin (2d)
+    refdir: np.ndarray  # placement ref direction (2d, unit)
+    start: float  # SegmentStart (arc length)
+    length: float  # SegmentLength (signed)
+    radius: float = 0.0
+    A: float = 0.0
+
+    def _parent(self, p):
+        if self.kind == "line":
+            return _line_eval(p)
+        if self.kind == "circle":
+            return _circle_eval(p, self.radius)
+        if self.kind == "clothoid":
+            return _clothoid_eval(p, self.A)
+        raise ValueError(self.kind)
+
+    def eval(self, local_len):
+        """local_len in [0, abs(length)] -> global (point2d, unit tangent2d).
+
+        Maps the parent's (point,tangent) at SegmentStart to (origin, refdir) by a rigid 2D
+        transform; advances arc length in the sign of SegmentLength.
+        """
+        sgn = 1.0 if self.length >= 0 else -1.0
+        p = self.start + sgn * local_len
+        P, T = self._parent(p)
+        P0, T0 = self._parent(self.start)
+        if sgn < 0:
+            T = -T  # traversal direction reverses
+            T0 = -T0
+        R = _rot2d(T0, self.refdir)
+        gp = self.origin + R @ (P - P0)
+        gt = R @ T
+        return gp, gt / np.hypot(*gt)
+
+
+# ---- the fixture's two composite curves, hand-transcribed from the IFC ----
+
+
+def horizontal_segs():
+    return [
+        Seg("line", np.array([0.0, 0.0]), np.array([1.0, 0.0]), 0.0, 400.0),
+        Seg("clothoid", np.array([400.0, 0.0]), np.array([1.0, 0.0]), 0.0, 150.0, A=-273.861278752584),
+        Seg(
+            "circle",
+            np.array([549.662851380011, -7.48795505445]),
+            np.array([9.88771077936042e-1, -1.49438132473604e-1]),
+            0.0,
+            -400.0,
+            radius=500.000000000002,
+        ),
+        # #1201 terminator (length 0) omitted
+    ]
+
+
+def vertical_segs():
+    return [
+        Seg(
+            "line", np.array([0.0, 150.0]), np.array([9.99999500000375e-1, -9.99999499995919e-4]), 0.0, 450.000218741065
+        ),
+        Seg(
+            "circle",
+            np.array([449.999993741124, 149.550000006261]),
+            np.array([9.99999500000375e-1, -9.99999499995919e-4]),
+            4.71138898071803,
+            100.00001881,
+            radius=69230.7996321627,
+        ),
+        Seg(
+            "line",
+            np.array([550.0, 149.522222225005]),
+            np.array([9.99999901234583e-1, 4.44444400554072e-4]),
+            0.0,
+            400.000039506171,
+        ),
+        # #2101 terminator omitted
+    ]
+
+
+def _sample_polyline(segs, n_per):
+    """Sample each segment -> stacked global 2D points (no dedup at joins)."""
+    pts = []
+    for s in segs:
+        for i in range(n_per + 1):
+            ll = abs(s.length) * i / n_per
+            gp, _ = s.eval(ll)
+            pts.append(gp)
+    return np.array(pts)
+
+
+def directrix_points(n_per=400):
+    """Compose horizontal (x,y)(s) with vertical z(s) -> sampled 3D directrix.
+
+    The vertical gradient is a curve in (distance, height); we evaluate it, build z(distance)
+    by interpolation on its first coordinate, then lift the horizontal samples.
+    """
+    hsegs = horizontal_segs()
+    # horizontal cumulative arc length at each sample
+    H = []
+    s_acc = 0.0
+    for seg in hsegs:
+        L = abs(seg.length)
+        for i in range(n_per + 1):
+            ll = L * i / n_per
+            gp, _ = seg.eval(ll)
+            H.append((s_acc + ll, gp[0], gp[1]))
+        s_acc += L
+    H = np.array(H)  # (s, x, y)
+
+    # vertical: sample -> (distance, height)
+    V = _sample_polyline(vertical_segs(), n_per)  # columns (distance, height)
+    # build z(distance) via interp on sorted distance
+    order = np.argsort(V[:, 0])
+    vd = V[order, 0]
+    vz = V[order, 1]
+    z = np.interp(H[:, 0], vd, vz)
+    return np.column_stack([H[:, 1], H[:, 2], z])
+
+
+def main():
+    oracle = np.load(f"{SCRATCH}/directrix_oracle.npy")
+    pts = directrix_points(n_per=600)
+    print(f"eval pts: {len(pts)}  oracle pts: {len(oracle)}")
+    print(f"eval first {pts[0]}  last {pts[-1]}")
+    print(f"oracle first {oracle[0]}  last {oracle[-1]}")
+    print(f"eval bbox min {pts.min(0)}  max {pts.max(0)}")
+    print(f"oracle bbox min {oracle.min(0)}  max {oracle.max(0)}")
+
+    # nearest-neighbour max deviation: for each oracle pt, distance to nearest eval pt (brute)
+    d = np.empty(len(oracle))
+    for i, o in enumerate(oracle):
+        d[i] = np.sqrt(((pts - o) ** 2).sum(1).min())
+    print(f"oracle->eval nearest dist: max {d.max():.4f}  mean {d.mean():.5f}  p95 {np.percentile(d,95):.4f}")
+
+
+if __name__ == "__main__":
+    main()
diff --git a/prototypes/ngeom_compare/align_oracle.py b/prototypes/ngeom_compare/align_oracle.py
new file mode 100644
index 000000000..459200968
--- /dev/null
+++ b/prototypes/ngeom_compare/align_oracle.py
@@ -0,0 +1,57 @@
+"""Oracle for the IFC4x3 alignment fixed-reference swept-area solid.
+
+Tessellate files/ifc_files/fixed-reference-swept-area-solid.ifc with ifcopenshell.geom
+(USE_WORLD_COORDS) and report bbox / tri / vertex counts for the AdvancedSweptSolid body
+(#113). This is the parity reference the native ngeom evaluator must match.
+
+Run: pixi run -e tests-adacpp python prototypes/ngeom_compare/align_oracle.py
+"""
+
+from __future__ import annotations
+
+import ifcopenshell
+import ifcopenshell.geom
+import numpy as np
+
+FIXTURE = "files/ifc_files/fixed-reference-swept-area-solid.ifc"
+
+
+def main() -> None:
+    f = ifcopenshell.open(FIXTURE)
+    settings = ifcopenshell.geom.settings()
+    settings.set(settings.USE_WORLD_COORDS, True)
+
+    # The swept solid is the body of the IfcBuiltElement #107 (SimpleProfile).
+    elem = f.by_id(107)
+    shape = ifcopenshell.geom.create_shape(settings, elem)
+    geo = shape.geometry
+    verts = np.asarray(geo.verts, dtype=float).reshape(-1, 3)
+    faces = np.asarray(geo.faces, dtype=int).reshape(-1, 3)
+    print("oracle body (#107 SimpleProfile)")
+    print(f"  verts: {len(verts)}  tris: {len(faces)}")
+    print(f"  bbox min: {verts.min(axis=0)}")
+    print(f"  bbox max: {verts.max(axis=0)}")
+
+    # Sample the directrix (IfcGradientCurve #79) via the Curve3D 'Axis' rep so we have a
+    # ground-truth (x,y,z)(s) to validate the analytic evaluator against.
+    # (IfcShapeRepresentation #106 'Axis' Curve3D contains #79)
+    csettings = ifcopenshell.geom.settings()
+    csettings.set(csettings.USE_WORLD_COORDS, True)
+    try:
+        cshape = ifcopenshell.geom.create_shape(csettings, f.by_id(79))
+        cverts = np.asarray(cshape.verts, dtype=float).reshape(-1, 3)
+        print("\noracle directrix (#79 IfcGradientCurve)")
+        print(f"  sample pts: {len(cverts)}")
+        print(f"  first: {cverts[0]}")
+        print(f"  last:  {cverts[-1]}")
+        print(f"  bbox min: {cverts.min(axis=0)}  max: {cverts.max(axis=0)}")
+        np.save(
+            "/tmp/claude-1000/-home-kristoffer-code-dap/d103bfc1-7e2e-4f7e-ba7c-8e213d35e3df/scratchpad/directrix_oracle.npy",
+            cverts,
+        )
+    except Exception as e:  # noqa: BLE001
+        print(f"directrix sample failed: {e!r}")
+
+
+if __name__ == "__main__":
+    main()
diff --git a/prototypes/ngeom_compare/align_sweep.py b/prototypes/ngeom_compare/align_sweep.py
new file mode 100644
index 000000000..50ece0e72
--- /dev/null
+++ b/prototypes/ngeom_compare/align_sweep.py
@@ -0,0 +1,74 @@
+"""Python reference sweep: profile-along-directrix shell mesh for the alignment fixture.
+
+Builds on align_eval.directrix_points by adding per-station fixed-reference frames and sweeping the
+(baked IfcDerivedProfileDef) 2D profile -> a closed triangle shell. Validated vs the ifcopenshell
+body bbox (align_oracle: x[-0.001,885.72] y[-213.95,5] z[148.515,150.856]).
+
+Spec for the adacpp C++ ng:: sweep. No OCC.
+
+Run: pixi run -e tests-adacpp python prototypes/ngeom_compare/align_sweep.py
+"""
+
+from __future__ import annotations
+
+import align_eval as ae
+import numpy as np
+
+# IfcDerivedProfileDef #114: parent #18 outline points, baked by operator #115 (Axis1=(0,-1)) ->
+# (x,y) -> (y,-x). Hand-applied here (matches piece-1a derived_profile_def).
+_PARENT = np.array([(-4.0, 0.0), (-5.0, -1.0), (5.0, -1.0), (4.0, 0.0)])
+PROFILE = np.column_stack([_PARENT[:, 1], -_PARENT[:, 0]])  # (y, -x)
+
+FIXED_REF = np.array([0.0, 0.0, 1.0])
+
+
+def _frames(pts):
+    """Per-station 3D tangent + fixed-reference in-plane axes (up, lateral)."""
+    T = np.gradient(pts, axis=0)
+    T /= np.linalg.norm(T, axis=1, keepdims=True)
+    F = FIXED_REF
+    lateral = np.cross(T, F)
+    lateral /= np.linalg.norm(lateral, axis=1, keepdims=True)
+    up = np.cross(lateral, T)
+    up /= np.linalg.norm(up, axis=1, keepdims=True)
+    return T, up, lateral
+
+
+def sweep(n_per=600):
+    pts = ae.directrix_points(n_per=n_per)
+    T, up, lateral = _frames(pts)
+    M = len(PROFILE)
+    N = len(pts)
+    # rings[i] = N stations x M profile verts. profile-x -> up, profile-y -> lateral.
+    rings = (
+        pts[:, None, :] + PROFILE[None, :, 0, None] * up[:, None, :] + PROFILE[None, :, 1, None] * lateral[:, None, :]
+    )  # (N, M, 3)
+    verts = rings.reshape(-1, 3)
+
+    faces = []
+    for i in range(N - 1):
+        for j in range(M):
+            a = i * M + j
+            b = i * M + (j + 1) % M
+            c = (i + 1) * M + j
+            d = (i + 1) * M + (j + 1) % M
+            faces.append((a, b, d))
+            faces.append((a, d, c))
+    # end caps (profile is a convex-ish quad -> fan triangulation)
+    for j in range(1, M - 1):
+        faces.append((0, j, j + 1))  # start cap
+        base = (N - 1) * M
+        faces.append((base, base + j + 1, base + j))  # end cap
+    return verts, np.array(faces)
+
+
+def main():
+    verts, faces = sweep(n_per=600)
+    print(f"sweep verts {len(verts)}  tris {len(faces)}")
+    print(f"bbox min {verts.min(0)}")
+    print(f"bbox max {verts.max(0)}")
+    print("oracle body  min [-9.99e-04 -2.139e+02  1.485e+02]  max [885.72 5. 150.856]")
+
+
+if __name__ == "__main__":
+    main()
diff --git a/prototypes/ngeom_compare/align_zdiff.py b/prototypes/ngeom_compare/align_zdiff.py
new file mode 100644
index 000000000..33990da9a
--- /dev/null
+++ b/prototypes/ngeom_compare/align_zdiff.py
@@ -0,0 +1,96 @@
+"""Diagnose the z divergence between our analytic directrix and ifcopenshell's IfcGradientCurve.
+
+Extracts the ORDERED 3D directrix polyline from ifcopenshell (#79) by walking geometry.edges,
+computes cumulative xy-distance s along it, and compares z(s) against our analytic eval. Also
+tessellates each gradient CurveSegment (#80/#88/#96) and base CurveSegment (#55/#63/#71)
+individually to see how ifcopenshell places/orders them.
+
+Run: pixi run -e tests-adacpp python prototypes/ngeom_compare/align_zdiff.py
+"""
+
+from __future__ import annotations
+
+import align_eval as ae
+import ifcopenshell
+import ifcopenshell.geom
+import numpy as np
+
+FIXTURE = "files/ifc_files/fixed-reference-swept-area-solid.ifc"
+
+
+def _settings():
+    s = ifcopenshell.geom.settings()
+    s.set(s.USE_WORLD_COORDS, True)
+    return s
+
+
+def _ordered_polyline(verts, edges):
+    """Walk an edge list (flat pairs) into an ordered vertex-index path from a degree-1 end."""
+    from collections import defaultdict
+
+    adj = defaultdict(list)
+    e = np.asarray(edges, dtype=int).reshape(-1, 2)
+    for a, b in e:
+        adj[a].append(b)
+        adj[b].append(a)
+    ends = [v for v, nb in adj.items() if len(nb) == 1]
+    start = ends[0] if ends else int(e[0, 0])
+    path = [start]
+    prev = None
+    cur = start
+    while True:
+        nxts = [n for n in adj[cur] if n != prev]
+        if not nxts:
+            break
+        prev, cur = cur, nxts[0]
+        path.append(cur)
+        if cur == start or len(path) > len(verts) + 5:
+            break
+    return verts[np.array(path)]
+
+
+def main():
+    f = ifcopenshell.open(FIXTURE)
+    s = _settings()
+
+    # ordered 3D directrix from #79
+    sh = ifcopenshell.geom.create_shape(s, f.by_id(79))
+    v = np.asarray(sh.verts, float).reshape(-1, 3)
+    ed = np.asarray(sh.edges, int)
+    poly = _ordered_polyline(v, ed)
+    # cumulative xy distance along the ordered polyline
+    dxy = np.r_[0.0, np.cumsum(np.linalg.norm(np.diff(poly[:, :2], axis=0), axis=1))]
+    print(f"#79 ordered polyline: {len(poly)} pts, total xy-len {dxy[-1]:.3f}")
+
+    # our analytic z at the same cumulative distance
+    z_ours = []
+    V = ae._sample_polyline(ae.vertical_segs(), 2000)
+    order = np.argsort(V[:, 0])
+    z_ours = np.interp(dxy, V[order, 0], V[order, 1])
+
+    print("\n s(xy)     x        y      z_ifc    z_ours   dz")
+    for k in np.linspace(0, len(poly) - 1, 12).astype(int):
+        print(
+            f"{dxy[k]:7.1f} {poly[k,0]:8.1f} {poly[k,1]:8.1f} {poly[k,2]:8.3f} {z_ours[k]:8.3f} {poly[k,2]-z_ours[k]:+7.3f}"
+        )
+
+    # where does dz cross a threshold? find first index where |dz|>0.01
+    dz = poly[:, 2] - z_ours
+    bad = np.where(np.abs(dz) > 0.01)[0]
+    if len(bad):
+        i = bad[0]
+        print(
+            f"\nfirst divergence at idx {i}: s_xy={dxy[i]:.2f} (x={poly[i,0]:.1f},y={poly[i,1]:.1f}) z_ifc={poly[i,2]:.3f} z_ours={z_ours[i]:.3f}"
+        )
+
+    # segment-3 horizontal starts at distance 550 (x~550), the circle. Print z_ifc vs the
+    # vertical-line z that SHOULD apply there (149.522 + 0.000444*(s-550)).
+    print("\nhorizontal-circle region (s>=550): z_ifc vs expected straight-grade 149.522+4.444e-4*(s-550)")
+    for k in range(len(poly)):
+        if dxy[k] >= 550 and k % max(1, len(poly) // 30) == 0:
+            exp = 149.522222225005 + 4.44444400554072e-4 * (dxy[k] - 550)
+            print(f"  s={dxy[k]:7.1f} z_ifc={poly[k,2]:.4f} z_line={exp:.4f} d={poly[k,2]-exp:+.4f}")
+
+
+if __name__ == "__main__":
+    main()
diff --git a/src/ada/api/beams/geom_beams.py b/src/ada/api/beams/geom_beams.py
index b84c735bf..d5c1128f0 100644
--- a/src/ada/api/beams/geom_beams.py
+++ b/src/ada/api/beams/geom_beams.py
@@ -228,6 +228,28 @@ def parametric_profile_to_arbitrary(area: geo_su.ProfileDef) -> geo_su.Arbitrary
             t_w=area.web_thickness,
             t_ftop=area.flange_thickness,
         )
+    elif isinstance(area, geo_su.RectangleProfileDef):
+        # IFC semantics: the rectangle is centred on the profile position.
+        # adapy's RectangleProfileDef carries no Position (readers only see
+        # the default $), so an explicit centred outline is exact — no
+        # Section detour needed.
+        from ada.geom.curves import Edge, IndexedPolyCurve
+        from ada.geom.points import Point
+
+        dx, dy = area.x_dim / 2.0, area.y_dim / 2.0
+        corners = [
+            Point(-dx, -dy),
+            Point(dx, -dy),
+            Point(dx, dy),
+            Point(-dx, dy),
+        ]
+        segments = [Edge(corners[i], corners[(i + 1) % 4]) for i in range(4)]
+        return geo_su.ArbitraryProfileDef(
+            area.profile_type,
+            IndexedPolyCurve(segments),
+            [],
+            profile_name=getattr(area, "profile_name", None),
+        )
     else:
         raise NotImplementedError(f"Profile def {type(area).__name__} is not implemented")
 
@@ -292,7 +314,11 @@ def profile_disconnected_to_face_geom(beam: Beam) -> Geometry:
         points = np.concatenate([p1, p2, p3, p4]).reshape(-1, 3)
         new_points = np.matmul(rotation_matrix, points.T).T + beam.n1.p
         poly_loop = ada.geom.curves.PolyLoop(polygon=[Point(*p) for p in new_points])
-        connected_faces += [geo_su.ConnectedFaceSet([geo_su.FaceBound(bound=poly_loop, orientation=True)])]
+        # cfs_faces holds Faces (per IfcConnectedFaceSet), each carrying its FaceBound(s) — not a
+        # bare FaceBound. Wrapping keeps this consistent with the IFC face-set reader so the shared
+        # face-set OCC/NGEOM builders handle both.
+        loop_face = geo_su.Face(bounds=[geo_su.FaceBound(bound=poly_loop, orientation=True)])
+        connected_faces += [geo_su.ConnectedFaceSet([loop_face])]
 
     geom = geo_su.FaceBasedSurfaceModel(connected_faces)
     return Geometry(beam.guid, geom, beam.color)
diff --git a/src/ada/api/curves.py b/src/ada/api/curves.py
index 954d95677..fe1821e68 100644
--- a/src/ada/api/curves.py
+++ b/src/ada/api/curves.py
@@ -451,6 +451,73 @@ def from_fem_shell(cls, points3d, tol=1e-3, parent=None) -> CurvePoly2d:
         self._nodes = [Node(p) for p in points3d_pts]
         return self
 
+    @classmethod
+    def from_fem_shells_batch(cls, pts: np.ndarray, parent=None, tol=1e-3) -> list[CurvePoly2d | None]:
+        """Vectorized :meth:`from_fem_shell` for ``m`` same-arity k-gons (m, k, 3).
+
+        The per-element orientation/projection math runs once over arrays
+        (:func:`ada.core.vector_transforms.shell_orientations_bulk` — same
+        floating-point operation order and Decimal rounding as the scalar
+        chain); only the output objects (Point/LineSegment/Node) are built per
+        element. Rows the bulk math can't take (degenerate corners/edges)
+        return ``None`` — the caller runs those through ``from_fem_shell``.
+        """
+        from ada.core.vector_transforms import shell_orientations_bulk
+
+        pts = np.asarray(pts, dtype=float)
+        m, k, _ = pts.shape
+        ok, rot1, rotf = shell_orientations_bulk(pts)
+        origin = pts[:, 0]
+
+        # 3D -> 2D via rot1 (transform_3x3: pos @ rot.T), batched — matmul runs
+        # the same (k,3)@(3,3) product per element as the scalar np.dot.
+        rel = pts - origin[:, None, :]
+        local = np.matmul(rel, np.transpose(rot1, (0, 2, 1)))[:, :, :2]
+
+        # winding: keep first point + reverse the rest when is_clockwise is False.
+        # is_clockwise sums (x2-x1)(y2+y1) over consecutive pairs and closes with
+        # (x[-1]-x[0])(y[-1]+y[0]) — NOT the wrapped shoelace closing edge —
+        # replicated verbatim so the reorder decision matches bit for bit.
+        x, y = local[:, :, 0], local[:, :, 1]
+        psum = ((x[:, 1:] - x[:, :-1]) * (y[:, 1:] + y[:, :-1])).sum(axis=1)
+        psum = psum + (x[:, -1] - x[:, 0]) * (y[:, -1] + y[:, 0])
+        ccw = psum < 0  # is_clockwise returns `not psum < 0`
+        reordered = local.copy()
+        reordered[:, 1:, :] = local[:, :0:-1, :]
+        wound = np.where(ccw[:, None, None], reordered, local)
+
+        # back to 3D via the final frame (transform_3x3 inverse: pos @ rot) + origin
+        wound3 = np.concatenate([wound, np.zeros((m, k, 1))], axis=2)
+        back = np.matmul(wound3, rotf) + origin[:, None, :]
+
+        out: list[CurvePoly2d | None] = []
+        for i in range(m):
+            if not ok[i]:
+                out.append(None)
+                continue
+            points2d = [Point(wound[i, j, 0], wound[i, j, 1]) for j in range(k)]
+            points3d_pts = [Point(back[i, j]) for j in range(k)]
+            segs2d = [LineSegment(points2d[j - 1], points2d[j]) for j in range(k)]
+            segs3d = [LineSegment(points3d_pts[j - 1], points3d_pts[j]) for j in range(k)]
+            seg_global_points, seg_index = segments_to_indexed_lists(segs3d)
+            xf, yf, zf = Direction(rotf[i, 0]), Direction(rotf[i, 1]), Direction(rotf[i, 2])
+
+            self = cls.__new__(cls)
+            self._tol = tol
+            self._parent = parent
+            self._orientation = Placement.from_dirs_precomputed(origin[i], xf, yf, zf)
+            self._placement = Placement()
+            self._radiis = {}
+            self._points2d = points2d
+            self._points3d = points3d_pts
+            self._segments = segs2d
+            self._segments3d = segs3d
+            self._seg_global_points = seg_global_points
+            self._seg_index = seg_index
+            self._nodes = [Node(p) for p in points3d_pts]
+            out.append(self)
+        return out
+
     def get_face_geom(self) -> ArbitraryProfileDef:
         outer_curve = self.curve_geom()
         return ArbitraryProfileDef(ProfileType.AREA, outer_curve, [])
diff --git a/src/ada/api/primitives/base.py b/src/ada/api/primitives/base.py
index e776bfde7..11ae4463c 100644
--- a/src/ada/api/primitives/base.py
+++ b/src/ada/api/primitives/base.py
@@ -20,6 +20,107 @@
     from ada.cadit.ifc.store import IfcStore
 
 
+def _bake_placement_into_geometry(geom_wrapper: Geometry, placement: Placement) -> Geometry | None:
+    """Return a COPY of ``geom_wrapper`` with ``placement`` folded into the underlying solid's
+    ``position``, so a placement-agnostic tessellator renders the shape in world coordinates.
+
+    Only analytic solids (those carrying an ``Axis2Placement3D`` / ``Axis1Placement``
+    ``position`` — Box, Sphere, Cylinder, Cone, Extruded/Revolved/Swept area solids) are
+    supported; anything else (face sets, B-reps) returns ``None`` so the caller keeps the
+    unplaced geometry (a follow-up). Uses the public ``transform_local_points_to_global`` /
+    ``transform_vector`` helpers, which encode the (now self-consistent) Placement rotation
+    convention — ``transform_local_points_to_global(p) == rot_matrix @ p + origin`` — so the
+    location, axis and ref_direction land on the same world frame the tessellator expects.
+    """
+    import copy
+
+    import numpy as np
+
+    from ada import Direction
+    from ada.geom.placement import Axis1Placement, Axis2Placement3D
+
+    abs_p = placement.get_absolute_placement(include_rotations=True)
+
+    def _pt(p):
+        q = abs_p.transform_local_points_to_global(np.asarray([[float(p[0]), float(p[1]), float(p[2])]]))[0]
+        return Point(q[0], q[1], q[2])
+
+    def _vec(v):
+        return abs_p.transform_vector(np.asarray([float(v[0]), float(v[1]), float(v[2])]))
+
+    solid = geom_wrapper.geometry
+    pos = getattr(solid, "position", None)
+    if isinstance(pos, (Axis2Placement3D, Axis1Placement)):
+        new_solid = copy.copy(solid)  # shallow: only ``position`` is replaced
+        loc = _pt(pos.location)
+        axis = _vec(pos.axis)
+        if isinstance(pos, Axis2Placement3D):
+            ref = _vec(pos.ref_direction)
+            new_solid.position = Axis2Placement3D(loc, Direction(*axis), Direction(*ref))
+        else:
+            new_solid.position = Axis1Placement(loc, Direction(*axis))
+        return Geometry(geom_wrapper.id, new_solid, geom_wrapper.color, bool_operations=geom_wrapper.bool_operations)
+
+    # Point-based / face-set geometries (no ``position``): transform their vertices. Covers
+    # tessellated & polygonal face sets and the face-set / surface-model hierarchy
+    # (FaceBasedSurfaceModel -> ConnectedFaceSet -> Face -> FaceBound -> PolyLoop). Anything with a
+    # non-poly-loop bound (EdgeLoop) or a carried surface returns None (unplaced — a follow-up).
+    placed = _bake_placement_into_facelike(solid, _pt)
+    if placed is not None:
+        return Geometry(geom_wrapper.id, placed, geom_wrapper.color, bool_operations=geom_wrapper.bool_operations)
+    return None
+
+
+def _bake_placement_into_facelike(geom, pt):
+    """Return a COPY of a point-based/face-set geometry with every vertex mapped through ``pt``, or
+    None if the geometry carries structure we can't transform by moving vertices alone."""
+    import ada.geom.curves as geo_cu
+    import ada.geom.surfaces as geo_su
+
+    def loop(lp):
+        return geo_cu.PolyLoop([pt(p) for p in lp.polygon]) if isinstance(lp, geo_cu.PolyLoop) else None
+
+    def face(f):
+        if type(f) is not geo_su.Face:  # a FaceSurface carries a surface we'd also have to move
+            return None
+        bounds = []
+        for b in f.bounds:
+            lp = loop(b.bound)
+            if lp is None:
+                return None
+            bounds.append(geo_su.FaceBound(lp, b.orientation))
+        return geo_su.Face(bounds=bounds)
+
+    def faces(fs):
+        out = []
+        for f in fs:
+            nf = face(f)
+            if nf is None:
+                return None
+            out.append(nf)
+        return out
+
+    if isinstance(geom, geo_su.TriangulatedFaceSet):
+        return geo_su.TriangulatedFaceSet([pt(p) for p in geom.coordinates], geom.normals, geom.indices)
+    if isinstance(geom, geo_su.PolygonalFaceSet):
+        return geo_su.PolygonalFaceSet([pt(p) for p in geom.coordinates], geom.faces, geom.closed)
+    if isinstance(geom, geo_su.FaceBasedSurfaceModel):
+        cfs = []
+        for c in geom.fbsm_faces:
+            nf = faces(c.cfs_faces)
+            if nf is None:
+                return None
+            cfs.append(geo_su.ConnectedFaceSet(nf))
+        return geo_su.FaceBasedSurfaceModel(cfs)
+    if isinstance(geom, geo_su.ConnectedFaceSet):
+        nf = faces(geom.cfs_faces)
+        return geo_su.ConnectedFaceSet(nf) if nf is not None else None
+    if isinstance(geom, (geo_su.ClosedShell, geo_su.OpenShell)):
+        nf = faces(geom.cfs_faces)
+        return type(geom)(nf) if nf is not None else None
+    return None
+
+
 class Shape(BackendGeom):
     IFC_CLASSES = ShapeTypes
 
@@ -168,6 +269,15 @@ def solid_geom(self) -> Geometry:
         if self.geom is None:
             raise NotImplementedError(f"solid_geom() not implemented for {self.__class__.__name__}")
 
+        # Carry the Shape's colour onto its Geometry when the wrapper was built
+        # without one (SAT/STEP imports pass ``Geometry(i, geom)`` with no colour,
+        # so the tessellator — which reads ``geom.color`` — otherwise gets None and
+        # renders the body black). ``self.color`` defaults to light-gray, matching
+        # what Plate.solid_geom already injects. A colour the geom already carries
+        # (e.g. an IFC style) is left untouched.
+        if self.geom.color is None and self.color is not None:
+            self.geom.color = self.color
+
         import ada.geom.solids as geo_so
         import ada.geom.surfaces as geo_su
 
@@ -177,7 +287,12 @@ def solid_geom(self) -> Geometry:
                 geo_su.AdvancedFace,
                 geo_su.ClosedShell,
                 geo_su.OpenShell,
+                geo_su.ConnectedFaceSet,  # the native NGEOM reader's B-rep root form
                 geo_su.ShellBasedSurfaceModel,
+                geo_su.FaceBasedSurfaceModel,
+                geo_su.TriangulatedFaceSet,  # pre-tessellated (IfcTriangulatedFaceSet) — direct mesh path
+                geo_su.PolygonalFaceSet,  # IfcPolygonalFaceSet — shared point list + n-gon faces
+                geo_so.FacetedBrep,
                 geo_so.Box,
                 geo_so.Sphere,
                 geo_so.Cylinder,
@@ -186,6 +301,7 @@ def solid_geom(self) -> Geometry:
                 geo_so.ExtrudedAreaSolidTapered,
                 geo_so.RevolvedAreaSolid,
                 geo_so.FixedReferenceSweptAreaSolid,
+                geo_so.SweptDiskSolid,  # pipes/rods (IfcSweptDiskSolid) — OCC + NGEOM builders exist
             ),
         ):
 
@@ -197,6 +313,20 @@ def solid_geom(self) -> Geometry:
                 self.geom.bool_operations = [
                     BooleanOperation(x.primitive.solid_geom(), x.bool_op) for x in self.booleans
                 ]
+
+            # Bake a non-identity placement into the geometry. The tessellator/exporters are
+            # placement-agnostic for generic Shapes (unlike Beam, whose straight_beam_to_geom
+            # bakes it in, and the Prim* subclasses, which override solid_geom) — so an IFC/
+            # native shape read in LOCAL representation coords with its world transform held in
+            # ``self.placement`` would otherwise render unplaced (rotation dropped; translation
+            # only happened to work when it was already baked into the geom). Returns a COPY so
+            # repeat calls don't compound; ``self.geom``/``self.placement`` are never mutated.
+            # Only analytic (positioned) solids are handled today — face-set / B-rep placement
+            # baking is a follow-up (helper returns None → keep the unplaced geom).
+            if not self.placement.is_identity():
+                placed = _bake_placement_into_geometry(self.geom, self.placement)
+                if placed is not None:
+                    return placed
             return self.geom
         else:
             raise NotImplementedError(f"solid_geom() not implemented for {self.geom=}")
diff --git a/src/ada/api/shapes/__init__.py b/src/ada/api/shapes/__init__.py
new file mode 100644
index 000000000..72130502b
--- /dev/null
+++ b/src/ada/api/shapes/__init__.py
@@ -0,0 +1,4 @@
+from .proxies import ShapeProxy
+from .store import ShapeRecord, ShapeStore
+
+__all__ = ["ShapeProxy", "ShapeRecord", "ShapeStore"]
diff --git a/src/ada/api/shapes/proxies.py b/src/ada/api/shapes/proxies.py
new file mode 100644
index 000000000..59712cdbc
--- /dev/null
+++ b/src/ada/api/shapes/proxies.py
@@ -0,0 +1,89 @@
+"""Lazy shape proxies over a :class:`~ada.api.shapes.store.ShapeStore`.
+
+``ShapeProxy`` subclasses ``Shape`` so every ``isinstance`` check, container and
+export path keeps working, but it does not hold an ``ada.geom`` tree: ``.geom``
+hydrates from the store's compact blob on access (weakref-cached there), so a
+7k-solid import costs blobs + small records instead of millions of resident
+dataclass instances. Unlike the FEM ``NodeProxy`` (millions of rows, base init
+skipped), shape counts are ~10k per model, so the proxy runs the normal
+``Shape.__init__`` and keeps material/placement/guid/pickle behaviour intact.
+"""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+from ada.api.primitives.base import Shape
+from ada.base.units import Units
+
+if TYPE_CHECKING:
+    from ada.geom.core import Geometry
+
+    from .store import ShapeStore
+
+
+class ShapeProxy(Shape):
+    def __init__(self, name, store: ShapeStore, index: int, **shape_kwargs):
+        super().__init__(name, geom=None, **shape_kwargs)
+        self._shape_store = store
+        self._store_index = int(index)
+        self._pinned_geom = None
+
+    @property
+    def geom(self) -> Geometry:
+        """The hydrated geometry. Transient unless pinned: edits to the returned tree
+        are lost when the GC reclaims it — call :meth:`pin` (or assign ``.geom``)
+        before mutating."""
+        if self._pinned_geom is not None:
+            return self._pinned_geom
+        return self._shape_store.geometry(self._store_index)
+
+    @geom.setter
+    def geom(self, value: Geometry):
+        # Pin, never re-serialize: the NGEOM encoder silently skips unsupported
+        # kinds, so writing back into the store could lose geometry.
+        self._pinned_geom = value
+
+    def pin(self) -> Geometry:
+        """Hydrate and hold a strong reference so subsequent mutation sticks."""
+        if self._pinned_geom is None:
+            self._pinned_geom = self._shape_store.geometry(self._store_index)
+        return self._pinned_geom
+
+    def ngeom_blob(self):
+        """The stored NGEOM buffer, for consumers that feed adacpp directly
+        (tessellation, stream export) without hydrating. ``None`` when the shape
+        was stored from Python-built geometry (pickle kind)."""
+        return self._shape_store.ngeom_blob(self._store_index)
+
+    def is_bare_curve(self) -> bool:
+        """The stored geometry is a bare curve (wire body) — render as line geometry.
+        Answered from the record, no hydration."""
+        return self._shape_store.record(self._store_index).curve
+
+    @property
+    def units(self):
+        return self._units
+
+    @units.setter
+    def units(self, value):
+        # Mirrors Shape.units but treats the proxy as always-having-geometry: the
+        # base setter keys on ``self._geom is not None``, which is always False
+        # here and would silently skip the scaling.
+        if isinstance(value, str):
+            value = Units.from_str(value)
+        if value != self._units:
+            from ada.occ.utils import transform_shape
+
+            scale_factor = Units.get_scale_factor(self._units, value)
+            # transform_shape returns an OCC body; after a unit conversion the OCC
+            # cache is the source of truth, exactly as on the base class.
+            self._occ_cache = transform_shape(self.solid_occ(), scale_factor)
+
+            if self.metadata.get("ifc_source") is True:
+                raise NotImplementedError()
+
+            self._units = value
+
+    def __repr__(self):
+        return f'{self.__class__.__name__}("{self.name}", store_index={self._store_index})'
diff --git a/src/ada/api/shapes/store.py b/src/ada/api/shapes/store.py
new file mode 100644
index 000000000..49afe13b6
--- /dev/null
+++ b/src/ada/api/shapes/store.py
@@ -0,0 +1,248 @@
+"""Buffer-backed storage for imported shape geometry.
+
+A large STEP/IFC import materialised as ``ada.geom`` object trees costs ~100x its
+compact serialized form in resident memory (millions of small dataclass instances,
+each with a ``__dict__``). ``ShapeStore`` keeps each solid as one compact blob and
+hydrates the ``ada.geom.Geometry`` tree only when a consumer actually asks for it,
+mirroring the FEM array-substrate design (``ada.api.mesh.store.MeshArrays``): flat
+shared storage + transient proxies (``ada.api.shapes.proxies.ShapeProxy``), with a
+``WeakValueDictionary`` cache so repeated access within a live scope is free and
+memory returns to the blob floor when hydrated trees are dropped.
+
+Two blob kinds:
+
+- ``"ngeom"`` — an NGEOM buffer as produced by the adacpp native readers
+  (``StepNgeomStream``). Retained exactly as it arrives (no ``bytes()`` round-trip,
+  no arena append — the buffer crossing the C++ boundary is the stored object, so
+  the transfer stays zero-copy). These blobs double as the tessellation/export
+  fast path: adacpp consumes them directly, skipping hydrate + re-serialize.
+- ``"pickle"`` — Python-built ``ada.geom`` geometry (the IFC reader, API shapes).
+  The NGEOM solid encoders lower parametric solids (Box -> extruded rectangle,
+  parametric profiles -> arbitrary outlines), so round-tripping Python-built
+  geometry through NGEOM would be lossy; pickle keeps profiles, placements and
+  ``bool_operations`` exact at a comparable byte size.
+
+The small per-shape metadata that must stay eagerly queryable (id, color, instance
+transforms/paths) lives in ``ShapeRecord`` next to the blob, not inside it — the
+same split the native stream readers already make (``StepRootMeta``).
+"""
+
+from __future__ import annotations
+
+import pickle
+import weakref
+import zlib
+from collections import OrderedDict
+from dataclasses import dataclass
+from typing import TYPE_CHECKING
+
+from ada.geom.core import Geometry
+
+if TYPE_CHECKING:
+    import numpy as np
+
+    from ada.geom.booleans import BooleanOperation
+    from ada.visit.colors import Color
+
+_NGEOM_MAGIC = b"ADANGEOM"
+
+
+@dataclass(slots=True)
+class ShapeRecord:
+    """Eager per-shape metadata — one small record per stored solid."""
+
+    gid: str
+    kind: str  # "ngeom" | "pickle"
+    color: Color | None = None
+    transforms: list[np.ndarray] | None = None
+    instance_paths: list[tuple] | None = None
+    compressed: bool = False
+    # The stored geometry is a bare curve (SAT wire body / open wireframe round-
+    # tripped through IFC) — consumers render it as line geometry. Recorded at
+    # store time so the tessellator's curve sniff never has to hydrate.
+    curve: bool = False
+
+
+class ShapeStore:
+    """Holds many shapes' geometry as compact blobs; hydrates on demand.
+
+    One store per import (``from_step``/``from_ifc`` call). Proxies keep a strong
+    reference to the store, so a surviving proxy keeps the (compact) blobs alive;
+    hydrated ``Geometry`` trees are only weakly cached and are reclaimed by the GC
+    as soon as no consumer holds them.
+    """
+
+    __slots__ = ("_blobs", "_records", "_geom_cache", "_geom_lru", "hydration_cache_size", "compress", "__weakref__")
+
+    def __init__(self, compress: bool = False, hydration_cache_size: int = 16):
+        self._blobs: list[object] = []
+        self._records: list[ShapeRecord] = []
+        # Mirrors MeshArrays._proxy_cache: same live object for repeated access,
+        # GC'd when the last outside reference drops.
+        self._geom_cache: weakref.WeakValueDictionary[int, Geometry] = weakref.WeakValueDictionary()
+        # Small strong LRU on top of the weak cache. Consumers touch ``.geom``
+        # several times in one call (``solid_geom()`` alone reads it 3-5x) and each
+        # temporary dies between property evaluations, so a purely weak cache
+        # re-decodes the blob per access (~40% slower conversions on the audit).
+        # A bounded strong window keeps the hot shape alive without giving up the
+        # hydrate-all-then-drop memory floor (N x ~0.3 MB, evicted FIFO).
+        self._geom_lru: OrderedDict[int, Geometry] = OrderedDict()
+        self.hydration_cache_size = hydration_cache_size
+        self.compress = compress
+
+    def __len__(self) -> int:
+        return len(self._records)
+
+    # --- ingest -------------------------------------------------------------------------
+
+    def add_blob(
+        self,
+        blob,
+        *,
+        gid: str,
+        color: Color | None = None,
+        transforms: list[np.ndarray] | None = None,
+        instance_paths: list[tuple] | None = None,
+    ) -> int:
+        """Retain an NGEOM buffer (bytes/memoryview/uint8 ndarray) as-arrived.
+
+        The buffer object itself is stored — no copy — unless ``compress`` is on
+        (compression inherently copies; that is the flag's accepted trade-off).
+        """
+        head = bytes(memoryview(blob)[:8])
+        if head != _NGEOM_MAGIC:
+            raise ValueError(f"not an NGEOM buffer (magic={head!r}) for {gid!r}")
+        compressed = False
+        if self.compress:
+            blob = zlib.compress(bytes(blob), 1)
+            compressed = True
+        self._blobs.append(blob)
+        self._records.append(
+            ShapeRecord(
+                gid=gid,
+                kind="ngeom",
+                color=color,
+                transforms=transforms,
+                instance_paths=instance_paths,
+                compressed=compressed,
+            )
+        )
+        return len(self._records) - 1
+
+    def add_geometry(self, geometry: Geometry) -> int:
+        """Store a Python-built ``Geometry`` losslessly (pickle kind) and drop the tree.
+
+        The wrapper's metadata moves to the record; the pickled payload is the inner
+        geometry + ``bool_operations`` (which pickle round-trips exactly, including
+        half-space operands and parametric profiles the NGEOM codec would lower).
+        """
+        from ada.geom.curves import CURVE_GEOM_TUPLE
+
+        payload = pickle.dumps((geometry.geometry, geometry.bool_operations), protocol=pickle.HIGHEST_PROTOCOL)
+        compressed = False
+        if self.compress:
+            payload = zlib.compress(payload, 1)
+            compressed = True
+        self._blobs.append(payload)
+        self._records.append(
+            ShapeRecord(
+                gid=str(geometry.id),
+                kind="pickle",
+                color=geometry.color,
+                transforms=geometry.transforms,
+                instance_paths=geometry.instance_paths,
+                compressed=compressed,
+                curve=isinstance(geometry.geometry, CURVE_GEOM_TUPLE),
+            )
+        )
+        return len(self._records) - 1
+
+    # --- access -------------------------------------------------------------------------
+
+    def record(self, index: int) -> ShapeRecord:
+        return self._records[index]
+
+    def ngeom_blob(self, index: int):
+        """The raw NGEOM buffer for adacpp fast-path consumers (tessellation, stream
+        export) — no hydration. ``None`` for pickle-kind records (those consumers
+        hydrate via :meth:`geometry` and serialize with booleans on the fly)."""
+        rec = self._records[index]
+        if rec.kind != "ngeom":
+            return None
+        blob = self._blobs[index]
+        if rec.compressed:
+            return zlib.decompress(blob)
+        return blob
+
+    def geometry(self, index: int) -> Geometry:
+        """Hydrate the full ``ada.geom.Geometry`` for one shape (weakref-cached, with
+        a small strong LRU window for back-to-back access)."""
+        geom = self._geom_cache.get(index)
+        if geom is not None:
+            self._lru_touch(index, geom)
+            return geom
+        rec = self._records[index]
+        bool_ops: list[BooleanOperation] = []
+        if rec.kind == "ngeom":
+            from ada.cadit.ngeom.deserialize import (
+                deserialize_geometries,
+                promote_closed_shell,
+            )
+
+            roots = deserialize_geometries(self.ngeom_blob(index))
+            if not roots:
+                raise ValueError(f"NGEOM blob for {rec.gid!r} decoded to zero roots")
+            # NGEOM doesn't record shell closedness; restore ClosedShell for manifold
+            # B-rep roots so hydration matches the Python stream reader's form.
+            inner = promote_closed_shell(roots[0][1])
+        else:
+            payload = self._blobs[index]
+            if rec.compressed:
+                payload = zlib.decompress(payload)
+            inner, bool_ops = pickle.loads(payload)
+        hydrated = Geometry(
+            id=rec.gid,
+            geometry=inner,
+            color=rec.color,
+            bool_operations=list(bool_ops),
+            transforms=rec.transforms,
+            instance_paths=rec.instance_paths,
+        )
+        self._geom_cache[index] = hydrated
+        self._lru_touch(index, hydrated)
+        return hydrated
+
+    def _lru_touch(self, index: int, geom: Geometry) -> None:
+        cap = self.hydration_cache_size
+        if cap <= 0:
+            return
+        lru = self._geom_lru
+        lru[index] = geom
+        lru.move_to_end(index)
+        while len(lru) > cap:
+            lru.popitem(last=False)
+
+    # --- diagnostics / pickling -----------------------------------------------------------
+
+    @property
+    def nbytes(self) -> int:
+        """Total stored blob bytes (as-held, i.e. compressed size when compressed)."""
+        return sum(memoryview(b).nbytes for b in self._blobs)
+
+    def __getstate__(self):
+        # Buffer views (e.g. capsule-backed ndarrays from adacpp) coerce to bytes —
+        # the one accepted pickle-time copy. The hydration caches never travel.
+        return {
+            "blobs": [b if isinstance(b, bytes) else bytes(b) for b in self._blobs],
+            "records": self._records,
+            "compress": self.compress,
+            "hydration_cache_size": self.hydration_cache_size,
+        }
+
+    def __setstate__(self, state):
+        self._blobs = state["blobs"]
+        self._records = state["records"]
+        self.compress = state["compress"]
+        self.hydration_cache_size = state.get("hydration_cache_size", 16)
+        self._geom_cache = weakref.WeakValueDictionary()
+        self._geom_lru = OrderedDict()
diff --git a/src/ada/api/spatial/assembly.py b/src/ada/api/spatial/assembly.py
index 0c168902b..5d1330902 100644
--- a/src/ada/api/spatial/assembly.py
+++ b/src/ada/api/spatial/assembly.py
@@ -2,7 +2,7 @@
 
 import os
 import pathlib
-from typing import TYPE_CHECKING, Callable, Union
+from typing import TYPE_CHECKING, Callable, Literal, Union
 
 from ada.api.spatial.part import Part
 from ada.api.user import User
@@ -98,8 +98,29 @@ def __getstate__(self):
     def __setstate__(self, state):
         self.__dict__.update(state)
 
-    def read_ifc(self, ifc_file: str | os.PathLike | ifcopenshell.file, data_only=False, elements2part=None):
-        """Import from IFC file."""
+    def read_ifc(
+        self,
+        ifc_file: str | os.PathLike | ifcopenshell.file,
+        data_only=False,
+        elements2part=None,
+        reader: Literal["ifcopenshell", "native"] | None = None,
+    ):
+        """Import from IFC file.
+
+        ``reader="native"`` uses adacpp's pure-C++ IFC reader (IfcNgeomStream) to build a
+        geometry-shapes Part/ShapeProxy tree (no ifcopenshell/OCC) — colour + spatial hierarchy from
+        the C++ resolver; does NOT reconstruct typed Beam/Plate objects. Default (``ifcopenshell``)
+        is the full typed reader.
+        """
+        if reader == "native":
+            from ada.cadit.ifc.read.native_reader import native_adacpp_ifc_available, native_read_ifc_into
+
+            if not native_adacpp_ifc_available():
+                raise RuntimeError("reader='native' requires adacpp with IfcNgeomStream")
+            native_read_ifc_into(self, ifc_file)
+            if isinstance(ifc_file, (str, os.PathLike)):
+                self.ifc_store.ifc_file_path = pathlib.Path(ifc_file)
+            return
         self.ifc_store.load_ifc_content_from_file(ifc_file, data_only=data_only, elements2part=elements2part)
 
     def read_fem(
@@ -272,6 +293,7 @@ def to_ifc(
         geom_repr_override: dict[str, GeomRepr] = None,
         streaming=False,
         merge_strategy=None,
+        writer: Literal["ifcopenshell", "native"] | None = None,
     ) -> ifcopenshell.file:
         import ifcopenshell.validate
 
@@ -280,6 +302,23 @@ def to_ifc(
         else:
             destination = pathlib.Path(destination).resolve().absolute()
 
+        # Native pure-C++ writer (adacpp blobs_to_ifc): emit analytic IFC solids from each shape's
+        # NGEOM blob — no ifcopenshell/OCC. Needs an on-disk destination + lazy ShapeProxy shapes
+        # (pairs with from_ifc(reader="native")). Raises if no shape carries a blob.
+        if writer == "native":
+            if destination == "object":
+                raise ValueError("to_ifc(writer='native') needs an on-disk destination")
+            from ada.cadit.ifc.write.native_ifc_writer import native_ifc_writer_available, native_write_ifc
+
+            if not native_ifc_writer_available():
+                raise RuntimeError("writer='native' requires adacpp with blobs_to_ifc")
+            os.makedirs(destination.parent, exist_ok=True)
+            native_write_ifc(self, destination)
+            if validate:
+                ifcopenshell.validate.validate(str(destination), logger)
+            logger.info("IFC file creation complete (native)")
+            return None
+
         logger.info(f'Beginning writing to IFC file "{destination}" using IfcOpenShell')
 
         # Memory-bounded path: hand-author Plate solids as SPF text instead of
diff --git a/src/ada/api/spatial/part.py b/src/ada/api/spatial/part.py
index 10ddb97ea..b3b536337 100644
--- a/src/ada/api/spatial/part.py
+++ b/src/ada/api/spatial/part.py
@@ -707,34 +707,114 @@ def _tree_parent(paths) -> Part:
                 parent = p
             return parent
 
-        # "native": adacpp's C++ NGEOM parser hydrated to Geometry (no Python tokenizer); same yield
-        # contract, so the Shape-wrap + product-tree below is identical.
-        if reader == "native":
-            from ada.cadit.step.read.native_reader import (
-                native_adacpp_step_available,
-                native_stream_read_step,
-            )
+        from ada.config import Config
 
-            if not native_adacpp_step_available():
-                raise StepStreamUnsupported("reader='native' requires the adacpp stream_step_to_ngeom entry point")
-            geom_iter = native_stream_read_step(step_path)
-        else:
-            geom_iter = stream_read_step(step_path, local_pool=local_pool, tolerant=tolerant)
+        # Lazy shape store (default on): retain each solid as its compact blob and mint
+        # ShapeProxy objects that hydrate on demand, instead of holding the whole model
+        # as ada.geom trees (~10x resident memory on large assemblies). Opt out via
+        # ADA_CAD_LAZY_SHAPE_STORE=false.
+        store = None
+        if Config().cad_lazy_shape_store:
+            from ada.api.shapes import ShapeProxy, ShapeStore
 
-        new_shapes = []  # (parent_part, shape)
-        try:
-            for i, geometry in enumerate(geom_iter):
-                shp_name = str(geometry.id) if geometry.id not in (None, "") else f"{ada_name}_{i}"
-                shp = Shape(
+            store = ShapeStore(compress=Config().cad_shape_store_compress)
+
+        def _mint_shape(shp_name, geometry) -> Shape:
+            if store is None:
+                return Shape(
                     shp_name, geom=geometry, color=colour or geometry.color, opacity=opacity, units=source_units
                 )
-                parent = _tree_parent(geometry.instance_paths) if product_tree else self
-                new_shapes.append((parent, shp))
-        except StepStreamUnsupported:
-            if reader != "auto":
-                raise
-            logger.info("read_step_file: streaming reader hit an unsupported entity; falling back to OCC reader")
-            return False
+            idx = store.add_geometry(geometry)
+            return ShapeProxy(shp_name, store, idx, color=colour or geometry.color, opacity=opacity, units=source_units)
+
+        new_shapes = []  # (parent_part, shape)
+
+        # "native": adacpp's C++ NGEOM parser. "auto" also probes it first (matching
+        # iter_from_step's read_solids): the native parse is faster and, with the lazy
+        # store, keeps the per-solid NGEOM buffer as-is — no hydration at import at all.
+        # A first-solid hydrate probe guards against files whose buffers the Python
+        # decode path can't handle; those fall back to the pure-Python reader ("auto")
+        # or raise ("native").
+        use_native = False
+        if reader in ("native", "auto"):
+            from ada.cadit.step.read.native_reader import native_adacpp_step_available
+
+            if native_adacpp_step_available():
+                use_native = True
+            elif reader == "native":
+                raise StepStreamUnsupported("reader='native' requires the adacpp stream_step_to_ngeom entry point")
+
+        # The native reader is solid-only; for "auto" a file carrying loose curve/geometric-set
+        # roots (wireframe bodies — SAT wire bodies, evaluated alignment reference curves) would
+        # silently lose them. Route such files to the lossless pure-Python reader instead so
+        # "auto" keeps its no-geometry-left-behind contract. ("native" stays as asked.)
+        if use_native and reader == "auto":
+            from ada.cadit.step.write._solid_source import step_has_curve_set_roots
+
+            if step_has_curve_set_roots(step_path):
+                use_native = False
+                tolerant = True  # the pure-Python fallback must read the curve sets, not raise
+
+        if use_native:
+            from ada.cadit.ngeom.deserialize import (
+                deserialize_geometries,
+                promote_closed_shell,
+            )
+            from ada.cadit.step.read.native_reader import native_stream_read_step_blobs
+            from ada.cadit.step.write._solid_source import NATIVE_DECODE_ERRORS
+            from ada.geom import Geometry
+
+            try:
+                for i, (blob, gid, color, mats, paths) in enumerate(native_stream_read_step_blobs(step_path)):
+                    if i == 0:
+                        deserialize_geometries(blob)  # hydrate-probe (result discarded)
+                    shp_name = gid if gid not in (None, "") else f"{ada_name}_{i}"
+                    if store is not None:
+                        idx = store.add_blob(
+                            blob, gid=shp_name, color=color, transforms=(mats or None), instance_paths=(paths or None)
+                        )
+                        shp = ShapeProxy(
+                            shp_name, store, idx, color=colour or color, opacity=opacity, units=source_units
+                        )
+                    else:
+                        # Eager Shapes get the ClosedShell promotion here (the lazy
+                        # store applies it at hydration) — the streaming reader itself
+                        # yields bare face-sets to keep the exporters' hot loop lean.
+                        geometry = Geometry(
+                            id=shp_name,
+                            geometry=promote_closed_shell(deserialize_geometries(blob)[0][1]),
+                            color=color,
+                            transforms=(mats or None),
+                            instance_paths=(paths or None),
+                        )
+                        shp = _mint_shape(shp_name, geometry)
+                    parent = _tree_parent(paths) if product_tree else self
+                    new_shapes.append((parent, shp))
+            except (*NATIVE_DECODE_ERRORS, RuntimeError) as exc:
+                if reader == "native" or new_shapes:
+                    # native was forced, or solids were already committed (a mid-stream
+                    # failure can't be un-yielded) — fail loudly over silent truncation.
+                    raise
+                logger.info("read_step_file: native STEP reader failed (%s); using the pure-Python reader", exc)
+                use_native = False
+            if use_native and not new_shapes and reader == "auto":
+                # Native recognised no solids; the pure-Python reader supports entity
+                # kinds the native one skips, so give it the file before the OCC fallback.
+                use_native = False
+
+        if not use_native:
+            geom_iter = stream_read_step(step_path, local_pool=local_pool, tolerant=tolerant)
+            try:
+                for i, geometry in enumerate(geom_iter):
+                    shp_name = str(geometry.id) if geometry.id not in (None, "") else f"{ada_name}_{i}"
+                    shp = _mint_shape(shp_name, geometry)
+                    parent = _tree_parent(geometry.instance_paths) if product_tree else self
+                    new_shapes.append((parent, shp))
+            except StepStreamUnsupported:
+                if reader != "auto":
+                    raise
+                logger.info("read_step_file: streaming reader hit an unsupported entity; falling back to OCC reader")
+                return False
 
         # A zero-yield on a non-empty file means the streaming reader didn't
         # recognise the structure — fall back to OCC rather than silently
@@ -934,13 +1014,20 @@ def iter_objects_from_fem(
         else:
             yield from self._iter_merged_plates_from_fem(merge_strategy, detached, mat_cache)
 
-    def _iter_merged_plates_from_fem(self, merge_strategy, detached: bool, mat_cache: dict | None):
-        """Wrap each object-free merged :class:`FaceData` in one transient Plate.
+    def _iter_merged_plates_from_fem(self, merge_strategy, detached: bool, mat_cache: dict | None, chunk: int = 2048):
+        """Wrap the object-free merged :class:`FaceData` records in transient Plates.
+
+        Tri/quad faces are buffered into bounded chunks and built through the
+        vectorized :meth:`CurvePoly2d.from_fem_shells_batch` (bitwise-identical to
+        the per-face ``Plate.from_fem_shell`` — the batch path escapes degenerate
+        rows back to it). ``chunk`` bounds the buffered face count, keeping the
+        streaming exporters' peak memory bounded; yield order matches the face
+        engine's stream order exactly. Merged N-gons use the general
+        ``from_3d_points`` path."""
+        import numpy as np
 
-        Bounded: builds and yields a single Plate at a time. Tri/quad faces take
-        the fast ``Plate.from_fem_shell`` path; merged N-gons use the general
-        ``from_3d_points``."""
         from ada import Plate
+        from ada.api.curves import CurvePoly2d
         from ada.fem.formats.mesh_faces import faces_from_fem
 
         # name -> Material, resolved once from this part's shell sections so the
@@ -951,14 +1038,57 @@ def _iter_merged_plates_from_fem(self, merge_strategy, detached: bool, mat_cache
             if mat is not None and mat.name not in mats:
                 mats[mat.name] = mat
 
+        buf: list = []  # pending tri/quad FaceData, flushed as one vectorized batch
+
+        def _flush():
+            if not buf:
+                return
+            by_k: dict[int, list[int]] = {}
+            for i, f in enumerate(buf):
+                by_k.setdefault(len(f.outline), []).append(i)
+            polys: list = [None] * len(buf)
+            for _k, idxs in by_k.items():
+                pts = np.stack([np.asarray(buf[i].outline, dtype=float) for i in idxs])
+                for i, poly in zip(idxs, CurvePoly2d.from_fem_shells_batch(pts, parent=self)):
+                    polys[i] = poly
+            for f, poly in zip(buf, polys):
+                mat = mats.get(f.material, f.material)
+                if poly is None:
+                    yield Plate.from_fem_shell(f.name, f.outline, f.thickness, mat=mat, parent=self, detached=detached)
+                else:
+                    yield Plate(f.name, poly, f.thickness, mat=mat, parent=self, detached=detached)
+            buf.clear()
+
         for face in faces_from_fem(self.fem, merge_strategy):
-            mat = mats.get(face.material, face.material)
-            if len(face.outline) <= 4:
-                yield Plate.from_fem_shell(
-                    face.name, face.outline, face.thickness, mat=mat, parent=self, detached=detached
+            if face.geom_face is not None:
+                # Analytic patch (SURFACE/PANEL: trimmed cylinder or B-spline
+                # panel) → one curved-plate concept, mirroring the FEM surface
+                # reconstruction path. Flush pending tri/quads first so the
+                # stream order is unchanged.
+                yield from _flush()
+                from ada import PlateCurved
+                from ada.core.guid import create_guid
+                from ada.geom import Geometry
+
+                mat = mats.get(face.material, face.material)
+                yield PlateCurved(
+                    face.name,
+                    Geometry(create_guid(), face.geom_face, None),
+                    float(face.thickness),
+                    mat=mat,
+                    extrude_as_solid=True,
+                    parent=self,
                 )
+            elif len(face.outline) <= 4:
+                buf.append(face)
+                if len(buf) >= chunk:
+                    yield from _flush()
             else:
+                # Flush pending tri/quads first so the stream order is unchanged.
+                yield from _flush()
+                mat = mats.get(face.material, face.material)
                 yield Plate.from_3d_points(face.name, face.outline, face.thickness, mat=mat, parent=self)
+        yield from _flush()
 
     def get_part(self, name: str, search_all_parts_in_assembly=False) -> Part | None:
         """Get part by name."""
@@ -1181,9 +1311,21 @@ def get_all_physical_objects(
             physical_objects.append(all_as_iterable)
 
         if by_type is not None:
+            from ada.api.shapes import ShapeProxy
+
             if not isinstance(by_type, (list, tuple)):
                 by_type = (by_type,)
-            res = filter(lambda x: type(x) in by_type, chain.from_iterable(physical_objects))
+
+            def _match_type(x, _by=tuple(by_type)):
+                # Exact-type filter, but a lazy ShapeProxy counts as its public type
+                # Shape (a proxy is an implementation detail of the import path, not
+                # a distinct kind — Shape subclasses like PrimBox stay excluded).
+                t = type(x)
+                if t is ShapeProxy:
+                    t = Shape
+                return t in _by
+
+            res = filter(_match_type, chain.from_iterable(physical_objects))
         elif by_metadata is not None:
             res = filter(
                 lambda x: all(x.metadata.get(key) == value for key, value in by_metadata.items()),
diff --git a/src/ada/api/transforms.py b/src/ada/api/transforms.py
index 476e8019c..b4a0b6d4f 100644
--- a/src/ada/api/transforms.py
+++ b/src/ada/api/transforms.py
@@ -141,11 +141,17 @@ def from_axis3d(axis: Axis2Placement3D) -> Placement:
 
     @staticmethod
     def from_4x4_matrix(matrix: np.ndarray) -> Placement:
+        # Extract the axes from the matrix ROWS, matching from_axis_angle / from_quaternion /
+        # rotate / get_absolute_placement (all row-based) and ``rot_matrix`` itself. Reading
+        # COLUMNS here (the old behaviour) stored the TRANSPOSE — for a rotation the inverse —
+        # so a rotated IFC ObjectPlacement rendered on the wrong world axis and the round-trip
+        # ``from_4x4_matrix(M).get_matrix4x4() == M`` was broken. See test_placement_convention.
+        matrix = np.asarray(matrix)
         return Placement(
             origin=matrix[:3, 3],
-            xdir=matrix[:3, 0],
-            ydir=matrix[:3, 1],
-            zdir=matrix[:3, 2],
+            xdir=matrix[0, :3],
+            ydir=matrix[1, :3],
+            zdir=matrix[2, :3],
         )
 
     def get_absolute_placement(self, include_rotations=False) -> Placement:
diff --git a/src/ada/cad/__init__.py b/src/ada/cad/__init__.py
index 59894ba48..6972fe0ec 100644
--- a/src/ada/cad/__init__.py
+++ b/src/ada/cad/__init__.py
@@ -28,6 +28,7 @@
 from typing import TYPE_CHECKING, Any, Protocol, runtime_checkable
 
 from ada.cad.registry import (  # noqa: E402 - registry is stdlib-only, no ada.cad cycle
+    DEFAULT_STREAM_TESS_ANGULAR_DEG,
     CadBackendName,
     CadConfig,
     StepReader,
@@ -115,6 +116,9 @@ class BatchMesh:
     indices: Any  # flat uint32,  length = 3 * num_triangles
     groups: "list[MeshGroup]"
     normals: Any = None  # flat float32, len == positions, or None if not supplied
+    mesh_type: int = 4  # glTF primitive mode of ``indices`` — 4=TRIANGLES (default),
+    # 1=LINES for curve-only bodies (alignment axes, trimmed/segmented curves). A single
+    # stream blob is one homogeneous root, so one mode covers the whole BatchMesh.
 
 
 def tessellate_batch_via_loop(backend, shapes, linear_deflection: float = -1.0) -> "BatchMesh":
@@ -243,6 +247,7 @@ def build(self, geometry: "Geometry") -> ShapeHandle:
         # being ported to adacpp C++ incrementally; types not yet ported raise
         # NotImplementedError rather than borrowing pythonocc. End goal: full
         # parity with OccBackend. See dap plan/v3 Phase 7.
+        import ada.geom.curves as gcu
         import ada.geom.solids as so
         import ada.geom.surfaces as su
         from ada.api.beams.geom_beams import parametric_profile_to_arbitrary
@@ -388,20 +393,24 @@ def _arbitrary(area):
 
             polygons = []
             for cfs in g.fbsm_faces:
-                for fb in cfs.cfs_faces:
-                    if not isinstance(fb.bound, cu.PolyLoop):
-                        raise NotImplementedError(
-                            f"AdacppBackend.build: FaceBasedSurfaceModel bound "
-                            f"{type(fb.bound).__name__!r} not yet ported to adacpp."
-                        )
-                    polygons.append([self._xyz(p) for p in fb.bound.polygon])
+                for face in cfs.cfs_faces:  # geo_su.Face, each carrying one or more FaceBound
+                    for fb in face.bounds:
+                        if not isinstance(fb.bound, cu.PolyLoop):
+                            raise NotImplementedError(
+                                f"AdacppBackend.build: FaceBasedSurfaceModel bound "
+                                f"{type(fb.bound).__name__!r} not yet ported to adacpp."
+                            )
+                        polygons.append([self._xyz(p) for p in fb.bound.polygon])
             shape = self._cad.build_face_based_surface_model(polygons)
-        elif isinstance(g, (su.ShellBasedSurfaceModel, su.OpenShell, su.ClosedShell)):
+        elif isinstance(g, (su.ShellBasedSurfaceModel, su.OpenShell, su.ClosedShell, su.ConnectedFaceSet)):
             # Sew the member faces into one shell handle. Each face is built through the
             # AdvancedFace path; open shells (IfcShellBasedSurfaceModel) don't bound a
             # volume, so sew_faces (BRepBuilderAPI_Sewing) is used rather than
             # make_volumes_from_faces. Mirrors OccBackend's make_shell_from_shell_based_
-            # surface_geom / make_open_shell_from_geom.
+            # surface_geom / make_open_shell_from_geom. Bare ConnectedFaceSet is the
+            # native NGEOM reader's B-rep root form (closedness not recorded in the
+            # buffer; hydration promotes verified-closed sets to ClosedShell, the rest
+            # arrive here) — same face-sew as the shells.
             from ada.geom import Geometry as _Geometry
 
             boundary_shells = g.sbsm_boundary if isinstance(g, su.ShellBasedSurfaceModel) else [g]
@@ -409,12 +418,15 @@ def _arbitrary(area):
             if not face_handles:
                 raise NotImplementedError("AdacppBackend.build: shell model has no faces")
             shape = self._cad.sew_faces(face_handles)
-        elif isinstance(g, su.AdvancedFace):
+        elif isinstance(g, (su.AdvancedFace, su.FaceSurface)):
             # B-spline (PlateCurved / loft-derived / SAT) faces. With bounds, the
             # surface is trimmed to the boundary wire(s) — each OrientedEdge with
             # a supplied pcurve drives its edge from surface(pcurve(t)) (the
             # SAT-pcurve path of OccBackend.make_face_from_geom). Without bounds,
             # the natural-UV face. Analytic surfaces aren't ported yet.
+            # FaceSurface is AdvancedFace's structurally-identical sibling (same
+            # face_surface/bounds/same_sense, NOT a subclass) — it is what NGEOM
+            # hydration yields for native-read B-rep faces.
             surf = g.face_surface
             if isinstance(surf, su.Plane) and g.bounds:
                 # Planar AdvancedFace (flat SAT/IFC plates): plane inferred from the boundary
@@ -534,6 +546,15 @@ def _arbitrary(area):
                 self._cad.polygon_face([self._xyz(g.coordinates[i - 1]) for i in face_idx]) for face_idx in g.faces
             ]
             shape = self._cad.sew_faces(faces)
+        elif isinstance(g, su.TriangulatedFaceSet):
+            # Triangle mesh (IfcTriangulatedFaceSet): one planar face per 1-based
+            # index triple, sewn into a shell — same treatment as PolygonalFaceSet.
+            idx = [int(i) for i in g.indices]
+            faces = [
+                self._cad.polygon_face([self._xyz(g.coordinates[i - 1]) for i in idx[k : k + 3]])
+                for k in range(0, len(idx), 3)
+            ]
+            shape = self._cad.sew_faces(faces)
         elif isinstance(g, so.RectangularPyramid):
             # Rectangular base + 4 triangular sides (apex centred above), placed at the frame.
             x, y, z = g.x_length, g.y_length, g.z_length
@@ -570,6 +591,12 @@ def _arbitrary(area):
             if len(edge_list) < 3:
                 raise NotImplementedError("AdacppBackend.build: WireFilledFace needs >=3 boundary edges")
             shape = self._cad.build_filled_face([self._encode_oriented_edge(oe) for oe in edge_list])
+        elif isinstance(g, gcu.CURVE_GEOM_TUPLE):
+            # Bare curve bodies (sectionless SAT wire bodies, construction
+            # wireframes): build the wire so B-rep exports carry them — STEP
+            # writes wires natively (GEOMETRIC_CURVE_SET). Mirrors
+            # geom_to_occ_geom's CURVE_GEOM_TUPLE arm.
+            shape = self._cad.build_wire(self._encode_curve(g))
         else:
             raise NotImplementedError(
                 f"AdacppBackend.build: ada.geom type {type(g).__name__!r} is not yet ported to "
@@ -645,18 +672,88 @@ def _encode_curve(self, curve) -> list[list[float]]:
         if isinstance(curve, cu.Circle):
             axis = self._xyz(curve.position.axis) if curve.position.axis is not None else [0.0, 0.0, 1.0]
             return [[2.0, *self._xyz(curve.position.location), *axis, float(curve.radius)]]
+        if isinstance(curve, cu.Edge) and not isinstance(curve, cu.ArcLine):
+            # Bare line segment (sectionless SAT wire body).
+            return [[0.0, *self._xyz(curve.start), *self._xyz(curve.end)]]
+        if isinstance(curve, cu.ArcLine):
+            return [[1.0, *self._xyz(curve.start), *self._xyz(curve.midpoint), *self._xyz(curve.end)]]
         if isinstance(curve, cu.PolyLine):
             pts = curve.points
             return [[0.0, *self._xyz(a), *self._xyz(b)] for a, b in zip(pts[:-1], pts[1:])]
         if isinstance(curve, cu.TrimmedCurve):
+            import numpy as _np
+
             from ada.geom.points import Point as _Point
 
             b, t1, t2 = curve.basis_curve, curve.trim1, curve.trim2
-            if isinstance(b, cu.Line) and isinstance(t1, _Point) and isinstance(t2, _Point):
-                return [[0.0, *self._xyz(t1), *self._xyz(t2)]]
-            if isinstance(b, cu.Circle) and isinstance(t1, _Point) and isinstance(t2, _Point):
-                mid = self._arc_midpoint(b, t1, t2, curve.sense_agreement)
-                return [[1.0, *self._xyz(t1), *mid, *self._xyz(t2)]]
+            if isinstance(b, cu.Line):
+                # Parameter trims evaluate on P(t) = pnt + t*dir — the reader
+                # keeps the IfcVector magnitude in ``dir`` so t is unscaled.
+                def _line_pt(t):
+                    if isinstance(t, _Point):
+                        return self._xyz(t)
+                    p = _np.asarray(self._xyz(b.pnt), dtype=float)
+                    d = _np.asarray(self._xyz(b.dir), dtype=float)
+                    return [float(v) for v in p + float(t) * d]
+
+                return [[0.0, *_line_pt(t1), *_line_pt(t2)]]
+            if isinstance(b, cu.Circle):
+                # Parameter trims are angles (radians, normalized at read) in
+                # the circle's own x/y frame — the same frame _arc_midpoint
+                # measures in, so sense/wrap handling is shared.
+                def _circle_pt(t):
+                    if isinstance(t, _Point):
+                        return self._xyz(t)
+                    c = _np.asarray(self._xyz(b.position.location), dtype=float)
+                    z = _np.asarray(
+                        self._xyz(b.position.axis) if b.position.axis is not None else [0, 0, 1], dtype=float
+                    )
+                    x = _np.asarray(
+                        self._xyz(b.position.ref_direction) if b.position.ref_direction is not None else [1, 0, 0],
+                        dtype=float,
+                    )
+                    z = z / (_np.linalg.norm(z) or 1.0)
+                    x = x / (_np.linalg.norm(x) or 1.0)
+                    y = _np.cross(z, x)
+                    w = c + float(b.radius) * (_np.cos(float(t)) * x + _np.sin(float(t)) * y)
+                    return [float(v) for v in w]
+
+                p1, p2 = _circle_pt(t1), _circle_pt(t2)
+                mid = self._arc_midpoint(b, p1, p2, curve.sense_agreement)
+                return [[1.0, *p1, *mid, *p2]]
+            if isinstance(b, cu.Ellipse):
+                # adacpp has no ellipse edge record — sample the trimmed arc
+                # (parametric angle; trims normalized to radians at read) into
+                # a fine polyline. Profile use only, so chord error at 64
+                # segments/full-turn is well under tessellation deflection.
+                c = _np.asarray(self._xyz(b.position.location), dtype=float)
+                z = _np.asarray(self._xyz(b.position.axis) if b.position.axis is not None else [0, 0, 1], dtype=float)
+                x = _np.asarray(
+                    self._xyz(b.position.ref_direction) if b.position.ref_direction is not None else [1, 0, 0],
+                    dtype=float,
+                )
+                z = z / (_np.linalg.norm(z) or 1.0)
+                x = x / (_np.linalg.norm(x) or 1.0)
+                y = _np.cross(z, x)
+                sa1, sa2 = float(b.semi_axis1), float(b.semi_axis2)
+
+                def _param_of(t):
+                    if not isinstance(t, _Point):
+                        return float(t)
+                    d = _np.asarray(self._xyz(t), dtype=float) - c
+                    return float(_np.arctan2(float(d @ y) / sa2, float(d @ x) / sa1))
+
+                a0, a1 = _param_of(t1), _param_of(t2)
+                if curve.sense_agreement and a1 <= a0:
+                    a1 += 2.0 * _np.pi
+                elif not curve.sense_agreement and a1 >= a0:
+                    a1 -= 2.0 * _np.pi
+                n = max(8, int(abs(a1 - a0) / (2.0 * _np.pi) * 64))
+                ts = _np.linspace(a0, a1, n + 1)
+                pts = [c + sa1 * _np.cos(t) * x + sa2 * _np.sin(t) * y for t in ts]
+                return [
+                    [0.0, *[float(v) for v in p], *[float(v) for v in q]] for p, q in zip(pts[:-1], pts[1:])
+                ]
             raise NotImplementedError(
                 f"AdacppBackend.build: TrimmedCurve basis {type(b).__name__!r} not yet ported to adacpp."
             )
@@ -665,6 +762,27 @@ def _encode_curve(self, curve) -> list[list[float]]:
             for seg in curve.segments:
                 edges.extend(self._encode_curve(seg.parent_curve))
             return edges
+        if isinstance(curve, cu.GeometricCurveSet):
+            # Loose curve collection (STEP wireframe body) — concatenate the
+            # member encodings; the records stay independent edges.
+            edges = []
+            for element in curve.elements:
+                edges.extend(self._encode_curve(element))
+            return edges
+        if isinstance(curve, cu.GradientCurve):
+            # Alignment directrix (IFC4x3): clothoid segments have no analytic
+            # edge record — encode the sampled polyline (shared with the
+            # NGEOM SweepN tessellation path, which uses the same evaluator).
+            import numpy as _np
+
+            from ada.cadit.ngeom._alignment_sweep import gradient_curve_points
+
+            pts = gradient_curve_points(curve, n_per=100)
+            return [
+                [0.0, *[float(v) for v in a], *[float(v) for v in b]]
+                for a, b in zip(pts[:-1], pts[1:])
+                if float(_np.linalg.norm(b - a)) > 1e-9
+            ]
         raise NotImplementedError(
             f"AdacppBackend.build: profile curve {type(curve).__name__!r} not yet ported to adacpp."
         )
@@ -902,11 +1020,17 @@ def tessellate_batch(self, shapes: "list[ShapeHandle]", linear_deflection: float
             for g in mesh.groups
         ]
         nrm = np.asarray(mesh.normals)
+        # mesh_type: glTF primitive mode (4=TRIANGLES, 1=LINES for curve-only bodies). Older
+        # adacpp builds' Mesh has no mesh_type attr → default TRIANGLES. The binding returns a
+        # MeshType enum whose int value already equals the glTF mode.
+        mt = getattr(mesh, "mesh_type", None)
+        mesh_type = int(getattr(mt, "value", mt)) if mt is not None else 4
         return BatchMesh(
             positions=np.asarray(mesh.positions),
             indices=np.asarray(mesh.indices),
             groups=groups,
             normals=nrm if nrm.size else None,
+            mesh_type=mesh_type,
         )
 
     def ifc_taxonomy_settings(self) -> "list[dict]":
@@ -922,9 +1046,10 @@ def tessellate_stream(
         items: "list[tuple[str, object]]",
         pipeline: str = "libtess2",
         deflection: float = 0.0,
-        angular_deg: float = 20.0,
+        angular_deg: float = DEFAULT_STREAM_TESS_ANGULAR_DEG,
         settings: "dict | None" = None,
         threads: int = 1,
+        model_scale: float = 0.0,
     ) -> "BatchMesh":
         """Tessellate a stream of ``(id, ada.geom geometry)`` via adacpp's NGEOM pipeline.
 
@@ -932,8 +1057,36 @@ def tessellate_stream(
         per-object ``build``/ShapeHandle round-trip) and tessellates it in one C++ call,
         returning a combined ``BatchMesh`` with a group per input id (``node_id`` = the
         item's position). ``pipeline``: ``libtess2`` (OCC-free) | ``occ`` | ``cgal``
-        (ifcopenshell taxonomy kernels). ``geometry`` is an ``ada.geom`` ``FaceSurface`` or
-        ``ConnectedFaceSet`` (unmappable items are skipped by the serializer)."""
+        (ifcopenshell taxonomy kernels). ``geometry`` is an ``ada.geom`` solid/face-set,
+        or a ``core.Geometry`` wrapper — the wrapper's ``bool_operations`` are folded
+        into the buffer as a BOOLEAN_RESULT chain (unmappable items are skipped)."""
+        from ada.cadit.ngeom import serialize_geometries
+
+        return self.tessellate_stream_buffer(
+            serialize_geometries(items),
+            pipeline=pipeline,
+            deflection=deflection,
+            angular_deg=angular_deg,
+            settings=settings,
+            threads=threads,
+            model_scale=model_scale,
+        )
+
+    def tessellate_stream_buffer(
+        self,
+        buffer,
+        *,
+        pipeline: str = "libtess2",
+        deflection: float = 0.0,
+        angular_deg: float = DEFAULT_STREAM_TESS_ANGULAR_DEG,
+        settings: "dict | None" = None,
+        threads: int = 1,
+        model_scale: float = 0.0,
+    ) -> "BatchMesh":
+        """Tessellate a pre-encoded NGEOM buffer — the fast path for blobs already in
+        the neutral form (a lazy ``ShapeStore``'s stored solid, a cached ``.ngeom``
+        file): no hydration and no re-serialization, the buffer goes straight to the
+        C++ kernel."""
         fn = getattr(self._cad, "tessellate_stream", None)
         if fn is None:
             raise NotImplementedError(
@@ -941,16 +1094,26 @@ def tessellate_stream(
             )
         import numpy as np
 
-        from ada.cadit.ngeom import serialize_geometries
-
-        buffer = serialize_geometries(items)
+        if not isinstance(buffer, (bytes, bytearray)):
+            # adacpp's binding currently takes nb::bytes only; drop this coercion once
+            # the buffer-protocol/zero-copy adacpp change lands.
+            buffer = bytes(buffer)
         # ``settings`` overrides the ifcopenshell ConversionSettings for the taxonomy paths
         # (occ/cgal/hybrid); ignored by libtess2. ``threads`` (>1) parallelises a root's faces
         # in the libtess2 path — opt-in, so the STEP->GLB process pool (which parallelises across
         # solids) stays serial per call and doesn't oversubscribe. The signature grew
         # (settings, then threads); try the fullest form and fall back for older adacpp builds.
         try:
-            mesh = fn(buffer, pipeline, deflection, angular_deg, dict(settings or {}), int(threads))
+            # model_scale (>0 => adaptive per-surface density) is the newest param; try it first
+            # and fall back for older adacpp builds (which drop it along with threads/settings).
+            try:
+                mesh = fn(
+                    buffer, pipeline, deflection, angular_deg, dict(settings or {}), int(threads), float(model_scale)
+                )
+            except TypeError:
+                if float(model_scale) > 0.0:
+                    logger.debug("adacpp build has no tessellate_stream model_scale param; fixed angular_deg")
+                mesh = fn(buffer, pipeline, deflection, angular_deg, dict(settings or {}), int(threads))
         except TypeError:
             if int(threads) > 1:
                 logger.debug("adacpp build has no tessellate_stream threads param; running serial")
@@ -967,11 +1130,17 @@ def tessellate_stream(
             for g in mesh.groups
         ]
         nrm = np.asarray(mesh.normals)
+        # mesh_type: glTF primitive mode (4=TRIANGLES, 1=LINES for curve-only bodies). Older
+        # adacpp builds' Mesh has no mesh_type attr → default TRIANGLES. The binding returns a
+        # MeshType enum whose int value already equals the glTF mode.
+        mt = getattr(mesh, "mesh_type", None)
+        mesh_type = int(getattr(mt, "value", mt)) if mt is not None else 4
         return BatchMesh(
             positions=np.asarray(mesh.positions),
             indices=np.asarray(mesh.indices),
             groups=groups,
             normals=nrm if nrm.size else None,
+            mesh_type=mesh_type,
         )
 
     def bbox(
diff --git a/src/ada/cad/registry.py b/src/ada/cad/registry.py
index 421324cb7..67cdd2526 100644
--- a/src/ada/cad/registry.py
+++ b/src/ada/cad/registry.py
@@ -23,6 +23,51 @@
 from enum import Enum
 from functools import lru_cache
 
+# Corpus-wide defaults for the NGEOM stream (libtess2/adacpp) tessellator. angular_deg caps
+# the arc-segment span for any curved geometry (revolves, pipes, cylinders, B-splines) — the
+# linear deflection alone can't keep a large-radius arc smooth because its sag tolerance grows
+# with radius. 10 deg (was 20) keeps a 7 m-radius revolved beam's bulge apex within ~1% of true;
+# it roughly matches the OCC path's 0.2 rad. Override per-run with ADA_STREAM_TESS_ANGULAR /
+# ADA_STREAM_TESS_DEFLECTION or per-model via CadConfig.
+DEFAULT_STREAM_TESS_DEFLECTION = 2.0
+DEFAULT_STREAM_TESS_ANGULAR_DEG = 10.0
+
+# Angular density mode. OFF (default): ``angular_deg`` is a fixed global ceiling for every curved
+# surface (explicit-global-angle mode, backward compatible). ON: the ceiling is applied ADAPTIVELY
+# per surface — a model-relative reference (``model_scale``, the model bbox diagonal) lets tiny
+# curved features (bolts/pins in a large assembly, whose facets are sub-pixel) coarsen while large
+# visible surfaces keep the fine angle. The relaxation itself lives in adacpp (angle_step); adapy
+# only decides the mode and supplies ``model_scale``. Toggle with ADA_STREAM_TESS_ADAPTIVE.
+DEFAULT_STREAM_TESS_ADAPTIVE = False
+
+
+def stream_tess_defaults() -> tuple[float, float]:
+    """(deflection, angular_deg) for the NGEOM stream path: env override else the corpus default."""
+    defl = float(os.environ.get("ADA_STREAM_TESS_DEFLECTION", str(DEFAULT_STREAM_TESS_DEFLECTION)))
+    ang = float(os.environ.get("ADA_STREAM_TESS_ANGULAR", str(DEFAULT_STREAM_TESS_ANGULAR_DEG)))
+    return defl, ang
+
+
+def stream_tess_adaptive() -> bool:
+    """Whether adaptive per-surface angular density is enabled (env override else the default OFF)."""
+    v = os.environ.get("ADA_STREAM_TESS_ADAPTIVE")
+    if v is None:
+        return DEFAULT_STREAM_TESS_ADAPTIVE
+    return v.strip().lower() not in {"0", "false", "no", "off", ""}
+
+
+def stream_tess_model_scale() -> float:
+    """The model reference scale (world units) for adaptive density on the object stream path, or
+    0.0 (off). Adaptive is meaningful only with a model scale, so this returns 0 unless adaptive is
+    enabled AND a scale is supplied via ADA_STREAM_TESS_MODEL_SCALE (the caller sets it once per
+    model — the native STEP->GLB path estimates its own; see ada.cadit.step.model_scale)."""
+    if not stream_tess_adaptive():
+        return 0.0
+    try:
+        return float(os.environ.get("ADA_STREAM_TESS_MODEL_SCALE", "0") or 0.0)
+    except ValueError:
+        return 0.0
+
 
 class CadBackendName(str, Enum):
     OCC = "occ"  # pythonocc-core (native BRepMesh)
@@ -87,12 +132,14 @@ class StepReader(str, Enum):
     for the common case and as robust/complete as OCC for the rest (no geometry skipped). ``STREAM``
     is streaming-only (raises on out-of-scope entities). ``TOLERANT`` streams and *skips* the
     unsupported solids (never OOMs, but drops geometry — avoid as a default). ``OCC`` forces the
-    whole-file OCC reader (needed for scale/transform/rotate-on-import)."""
+    whole-file OCC reader (needed for scale/transform/rotate-on-import). ``NATIVE`` forces
+    adacpp's C++ NGEOM parser (fastest; ``AUTO`` probes it first when adacpp is available)."""
 
     AUTO = "auto"
     STREAM = "stream"
     TOLERANT = "tolerant"
     OCC = "occ"
+    NATIVE = "native"
 
 
 @dataclass
@@ -102,8 +149,8 @@ class CadConfig:
     ``ada.from_step(..., cad_config=cfg)``)."""
 
     path: TessellationPath = TessellationPath.OCC
-    deflection: float = 2.0
-    angular_deg: float = 20.0
+    deflection: float = DEFAULT_STREAM_TESS_DEFLECTION
+    angular_deg: float = DEFAULT_STREAM_TESS_ANGULAR_DEG
     simplify: bool = False  # meshopt cleanup (step2glb merge parity); adacpp paths only
     # The STEP read path the factories default to. AUTO = constant-memory streaming with an OCC
     # fallback for out-of-scope files — the most memory-efficient + robust default. Override per
diff --git a/src/ada/cadit/gxml/write/stream_xml.py b/src/ada/cadit/gxml/write/stream_xml.py
index f0b3da276..7954b7d79 100644
--- a/src/ada/cadit/gxml/write/stream_xml.py
+++ b/src/ada/cadit/gxml/write/stream_xml.py
@@ -233,7 +233,10 @@ def _stream_structures(part, fh, thickness_map, Beam, BeamTapered, Plate, merge_
     else:
         from ada.fem.formats.mesh_faces import iter_faces
 
-        for face in iter_faces(part, merge_strategy):
+        # Genie XML has no curved-surface concept — keep the analytic strategies
+        # polygon-only so cylinder/panel patches merge as their coplanar flats
+        # instead of arriving as unrepresentable geom faces.
+        for face in iter_faces(part, merge_strategy, allow_analytic=False):
             tmp = ET.Element("structures")
             add_plate_polygon_data(
                 face.name, face.outline, face.normal, thickness_map[face.thickness], face.material, tmp
diff --git a/src/ada/cadit/gxml/write/write_beams.py b/src/ada/cadit/gxml/write/write_beams.py
index 7af48768f..fceacfbaa 100644
--- a/src/ada/cadit/gxml/write/write_beams.py
+++ b/src/ada/cadit/gxml/write/write_beams.py
@@ -19,14 +19,25 @@
 
 def add_beams(root: ET.Element, part: Part, sw: SatWriter = None):
     from ada import Beam, BeamTapered
+    from ada.api.beams import BeamRevolve, BeamSweep
 
     iter_beams = part.get_all_physical_objects(by_type=Beam)
     iter_taper = part.get_all_physical_objects(by_type=BeamTapered)
+    # Curved-axis beams: Genie XML's curved_beam element reads back as chord
+    # segments anyway (see read_beams.seg_to_beam), so emit the straight chord
+    # rather than silently dropping the member — mirrors stream_xml.
+    iter_revolve = part.get_all_physical_objects(by_type=BeamRevolve)
+    iter_sweep = part.get_all_physical_objects(by_type=BeamSweep)
 
-    for beam in itertools.chain(iter_beams, iter_taper):
+    for beam in itertools.chain(iter_beams, iter_taper, iter_revolve, iter_sweep):
         parent = beam.parent
         if isinstance(parent, Equipment) and parent.eq_repr != EquipRepr.AS_IS:
             continue
+        if isinstance(beam, (BeamRevolve, BeamSweep)):
+            logger.warning(
+                f"gxml-write: {type(beam).__name__} {beam.name!r} written as a straight chord beam "
+                "(curved axis not supported by the Genie XML writer)"
+            )
         add_straight_beam(beam, root)
 
 
diff --git a/src/ada/cadit/ifc/native_ifc_to_glb.py b/src/ada/cadit/ifc/native_ifc_to_glb.py
new file mode 100644
index 000000000..e055beaa9
--- /dev/null
+++ b/src/ada/cadit/ifc/native_ifc_to_glb.py
@@ -0,0 +1,89 @@
+"""Fully-native IFC->GLB via adacpp (no ifcopenshell, no OCC).
+
+Calls a single adacpp C++ entry (``stream_ifc_to_glb``) that does everything in-process: the pure-C++
+IfcResolver resolves each product's geometry + presentation colour + spatial-structure path, libtess2
+tessellates (welded, crease-angle smooth normals), and the merge-by-colour GLB writer bakes it to
+metres. The GLB carries the same viewer picking contract as the native STEP path — merge-by-colour
+materials + per-material ``draw_ranges_node<matidx>`` and a per-product ``id_hierarchy`` in
+``scenes[0].extras`` — validated field-for-field against ``from_ifc`` -> GLB (geometry + colour +
+hierarchy + names; IFC property sets never live in the GLB, they are fetched on selection).
+
+Single-threaded v1 (IfcResolver's colour/rel maps are built per instance); curve-only bodies
+(alignment axes) are skipped. Honours the same ``ADA_STREAM_TESS_DEFLECTION`` / ``ADA_STREAM_TESS_
+ANGULAR`` env as the STEP native path.
+"""
+
+from __future__ import annotations
+
+import os
+import pathlib
+
+from ada.config import logger
+
+
+def native_ifc_glb_available() -> bool:
+    """True if the adacpp native IFC->GLB entry point is importable."""
+    try:
+        import adacpp  # noqa: F401
+
+        return hasattr(adacpp.cad, "stream_ifc_to_glb")
+    except Exception:
+        return False
+
+
+def native_ifc_to_glb(
+    ifc_path: str | pathlib.Path,
+    glb_path: str | pathlib.Path,
+    deflection: float | None = None,
+    angular_deg: float | None = None,
+    meshopt: bool = True,
+    on_progress=None,
+) -> dict:
+    """Convert ``ifc_path`` to a GLB at ``glb_path`` with the native adacpp IFC pipeline.
+
+    ``deflection`` / ``angular_deg`` default to the ``ADA_STREAM_TESS_DEFLECTION`` (2.0) /
+    ``ADA_STREAM_TESS_ANGULAR`` (20.0) env, matching the streaming path. ``meshopt`` (default on) bakes
+    ``EXT_meshopt_compression`` inline in the C++ writer. Returns ``{solids, total, skipped}``. Raises
+    if adacpp is unavailable or the conversion fails (the converter falls back per its fallback chain).
+    """
+    import adacpp
+
+    if deflection is None:
+        deflection = float(os.environ.get("ADA_STREAM_TESS_DEFLECTION", "2.0"))
+    if angular_deg is None:
+        from ada.cad.registry import DEFAULT_STREAM_TESS_ANGULAR_DEG
+
+        angular_deg = float(os.environ.get("ADA_STREAM_TESS_ANGULAR", str(DEFAULT_STREAM_TESS_ANGULAR_DEG)))
+
+    if on_progress is not None:
+        on_progress("adacpp-native-ifc", 0.1)
+
+    # Same cgroup-aware worker count as the STEP streaming path (cpu quota - 1, capped at 3): bounds
+    # peak RSS and reserves a core for the parent's JetStream heartbeat.
+    try:
+        from ada.visit.scene_handling.scene_from_step_stream import _stream_workers
+
+        num_threads = _stream_workers()
+    except Exception:
+        num_threads = 0  # C++ falls back to cgroup-aware effective_concurrency()
+
+    n = adacpp.cad.stream_ifc_to_glb(
+        str(ifc_path),
+        str(glb_path),
+        deflection=deflection,
+        angular_deg=angular_deg,
+        meshopt=meshopt,
+        num_threads=num_threads,
+    )
+    if n < 0:
+        raise RuntimeError(f"adacpp native stream_ifc_to_glb failed for {ifc_path}")
+
+    logger.info("adacpp-native IFC->GLB: %s products -> %s", n, glb_path)
+    print(
+        f"[adacpp-native-ifc] {n} products -> {glb_path} "
+        f"(deflection={deflection}, angular={angular_deg}, meshopt={meshopt})",
+        flush=True,
+    )
+    if on_progress is not None:
+        on_progress("ready", 1.0)
+    return {"solids": n, "total": n, "skipped": 0}
diff --git a/src/ada/cadit/ifc/read/geom/curves.py b/src/ada/cadit/ifc/read/geom/curves.py
index 9e0b4716c..2988ba57f 100644
--- a/src/ada/cadit/ifc/read/geom/curves.py
+++ b/src/ada/cadit/ifc/read/geom/curves.py
@@ -16,15 +16,24 @@ def get_curve(ifc_entity: ifcopenshell.entity_instance) -> geo_cu.CURVE_GEOM_TYP
         return b_spline_curve_with_knots(ifc_entity)
     elif ifc_entity.is_a("IfcTrimmedCurve"):
         return trimmed_curve(ifc_entity)
+    elif ifc_entity.is_a("IfcSegmentedReferenceCurve"):
+        # Subtype of IfcCompositeCurve (via IfcGradientCurve) — must precede both.
+        return segmented_reference_curve(ifc_entity)
     elif ifc_entity.is_a("IfcGradientCurve"):
         # Subtype of IfcCompositeCurve — must precede it.
         return gradient_curve(ifc_entity)
     elif ifc_entity.is_a("IfcCompositeCurve"):
         return composite_curve(ifc_entity)
+    elif ifc_entity.is_a("IfcCurveSegment"):
+        # A single alignment curve segment used directly as a representation item (an
+        # IfcAlignmentSegment's 'Axis'/'Segment' body).
+        return curve_segment(ifc_entity)
     elif ifc_entity.is_a("IfcLine"):
         return line(ifc_entity)
     elif ifc_entity.is_a("IfcClothoid"):
         return clothoid(ifc_entity)
+    elif ifc_entity.is_a("IfcCosineSpiral"):
+        return cosine_spiral(ifc_entity)
     elif ifc_entity.is_a("IfcCircle"):
         return circle(ifc_entity)
     elif ifc_entity.is_a("IfcEllipse"):
@@ -38,7 +47,15 @@ def get_curve(ifc_entity: ifcopenshell.entity_instance) -> geo_cu.CURVE_GEOM_TYP
 
 
 def line(ifc_entity: ifcopenshell.entity_instance) -> geo_cu.Line:
-    return geo_cu.Line(pnt=Point(ifc_entity.Pnt.Coordinates), dir=Direction(ifc_entity.Dir.Orientation.DirectionRatios))
+    # IfcLine.Dir is an IfcVector — its Magnitude scales the curve's
+    # parameterization (P(t) = Pnt + t*Dir). Fold it into the stored
+    # direction so parameter trims (IfcTrimmedCurve on a line basis)
+    # evaluate correctly; consumers that only need the direction are
+    # magnitude-agnostic.
+    vec = ifc_entity.Dir
+    mag = float(getattr(vec, "Magnitude", 1.0) or 1.0)
+    ratios = tuple(float(x) * mag for x in vec.Orientation.DirectionRatios)
+    return geo_cu.Line(pnt=Point(ifc_entity.Pnt.Coordinates), dir=Direction(ratios))
 
 
 def circle(ifc_entity: ifcopenshell.entity_instance) -> geo_cu.Circle:
@@ -61,6 +78,21 @@ def clothoid(ifc_entity: ifcopenshell.entity_instance) -> geo_cu.Clothoid:
     )
 
 
+def cosine_spiral(ifc_entity: ifcopenshell.entity_instance) -> geo_cu.CosineSpiral:
+    """IfcCosineSpiral — 2D transition spiral about its Position; curvature varies as a cosine.
+    A1 = CosineTerm (required), A0 = ConstantTerm (optional)."""
+    pos = ifc_entity.Position
+    loc = pos.Location.Coordinates
+    rd = pos.RefDirection.DirectionRatios if pos.RefDirection is not None else (1.0, 0.0)
+    ct = ifc_entity.ConstantTerm
+    return geo_cu.CosineSpiral(
+        location=(float(loc[0]), float(loc[1])),
+        ref_direction=(float(rd[0]), float(rd[1])),
+        cosine_term=float(ifc_entity.CosineTerm),
+        constant_term=float(ct) if ct is not None else None,
+    )
+
+
 def _measure(v) -> float:
     return float(v.wrappedValue if hasattr(v, "wrappedValue") else v)
 
@@ -76,6 +108,14 @@ def curve_segment(ifc_entity: ifcopenshell.entity_instance) -> geo_cu.CurveSegme
         rd = pl.RefDirection.DirectionRatios if pl.RefDirection is not None else (1.0, 0.0)
         location = (float(loc[0]), float(loc[1]))
         ref_direction = (float(rd[0]), float(rd[1]))
+    elif pl.is_a("IfcAxis2Placement3D"):
+        # Cant segments of an IfcSegmentedReferenceCurve are placed by a 3D axis placement; the
+        # extra (vertical) component of the location is the superelevation offset. Keep the full
+        # 3D location + ref direction — planar consumers slice [:2].
+        loc = pl.Location.Coordinates
+        rd = pl.RefDirection.DirectionRatios if pl.RefDirection is not None else (1.0, 0.0, 0.0)
+        location = tuple(float(c) for c in loc)
+        ref_direction = tuple(float(c) for c in rd)
     else:  # IfcAxis2PlacementLinear — planar location resolved at evaluation; carry the ref dir
         rd = pl.RefDirection.DirectionRatios if pl.RefDirection is not None else (1.0, 0.0)
         location = (0.0, 0.0)
@@ -99,11 +139,25 @@ def gradient_curve(ifc_entity: ifcopenshell.entity_instance) -> geo_cu.GradientC
     )
 
 
+def segmented_reference_curve(ifc_entity: ifcopenshell.entity_instance) -> geo_cu.SegmentedReferenceCurve:
+    """IfcSegmentedReferenceCurve — cant (superelevation) segments over a BaseCurve (an
+    IfcGradientCurve). The base gives x,y,z; the segments add the vertical cant offset."""
+    return geo_cu.SegmentedReferenceCurve(
+        base_curve=get_curve(ifc_entity.BaseCurve),
+        segments=[curve_segment(s) for s in ifc_entity.Segments],
+        self_intersect=bool(ifc_entity.SelfIntersect),
+    )
+
+
 def ellipse(ifc_entity: ifcopenshell.entity_instance) -> geo_cu.Ellipse:
-    from .placement import axis3d
+    from .placement import axis2d_as_3d, axis3d
 
+    # Profile-plane ellipses (2D placement, no Axis attribute) lift into
+    # the z=0 plane — same treatment as circle() above.
+    pos = ifc_entity.Position
+    position = axis2d_as_3d(pos) if pos.is_a("IfcAxis2Placement2D") else axis3d(pos)
     return geo_cu.Ellipse(
-        position=axis3d(ifc_entity.Position),
+        position=position,
         semi_axis1=ifc_entity.SemiAxis1,
         semi_axis2=ifc_entity.SemiAxis2,
     )
@@ -136,11 +190,34 @@ def composite_curve(ifc_entity: ifcopenshell.entity_instance) -> geo_cu.Composit
     return geo_cu.CompositeCurve(segments=segments, self_intersect=bool(ifc_entity.SelfIntersect))
 
 
+def _plane_angle_scale(f) -> float:
+    """Radians per file plane-angle unit (1.0 for SI radian files; 0.01745…
+    for files declaring a conversion-based DEGREE unit)."""
+    import ifcopenshell.util.unit as uu
+
+    try:
+        return float(uu.calculate_unit_scale(f, unit_type="PLANEANGLEUNIT"))
+    except Exception:  # noqa: BLE001 - missing/odd unit assignment: assume radians
+        return 1.0
+
+
 def trimmed_curve(ifc_entity: ifcopenshell.entity_instance) -> geo_cu.TrimmedCurve:
+    trim1 = _trim_select(ifc_entity.Trim1)
+    trim2 = _trim_select(ifc_entity.Trim2)
+    if ifc_entity.BasisCurve.is_a("IfcConic"):
+        # Parameter trims on conics are angles expressed in the file's
+        # plane-angle unit — normalize to radians at read time so
+        # downstream evaluators need no unit context (the buildingSMART
+        # curve-parameter samples ship one file in degrees, one in radians).
+        scale = _plane_angle_scale(ifc_entity.file)
+        if isinstance(trim1, float):
+            trim1 *= scale
+        if isinstance(trim2, float):
+            trim2 *= scale
     return geo_cu.TrimmedCurve(
         basis_curve=get_curve(ifc_entity.BasisCurve),
-        trim1=_trim_select(ifc_entity.Trim1),
-        trim2=_trim_select(ifc_entity.Trim2),
+        trim1=trim1,
+        trim2=trim2,
         sense_agreement=ifc_entity.SenseAgreement,
         master_representation=ifc_entity.MasterRepresentation,
     )
@@ -204,8 +281,12 @@ def indexed_poly_curve(ifc_entity: ifcopenshell.entity_instance) -> geo_cu.Index
     for segment in ifc_entity.Segments:
         value = [x - 1 for x in segment.wrappedValue]
         if segment.is_a("IfcLineIndex"):
-            segments.append(geo_cu.Edge(pts[value[0]], pts[value[1]]))
-        else:
+            # IfcLineIndex is a POLYLINE through all its points (>=2) — one edge per
+            # consecutive pair. Taking only value[0]/value[1] dropped every intermediate
+            # vertex, collapsing multi-point runs (e.g. an I-section's flange outline).
+            for a, b in zip(value[:-1], value[1:]):
+                segments.append(geo_cu.Edge(pts[a], pts[b]))
+        else:  # IfcArcIndex: exactly (start, mid, end)
             segments.append(geo_cu.ArcLine(pts[value[0]], pts[value[1]], pts[value[2]]))
 
     return geo_cu.IndexedPolyCurve(segments, ifc_entity.SelfIntersect)
diff --git a/src/ada/cadit/ifc/read/geom/geom_reader.py b/src/ada/cadit/ifc/read/geom/geom_reader.py
index 03bdfe16e..8b88ad012 100644
--- a/src/ada/cadit/ifc/read/geom/geom_reader.py
+++ b/src/ada/cadit/ifc/read/geom/geom_reader.py
@@ -20,12 +20,17 @@
     ifc_rectangular_pyramid,
     ifc_sphere,
     revolved_solid_area,
+    sectioned_solid_horizontal,
     swept_disk_solid,
 )
 from .surfaces import advanced_face, curve_bounded_plane
 from .surfaces import face as read_face
 from .surfaces import (
+    closed_shell,
+    connected_face_set,
+    face_based_surface_model,
     half_space_solid,
+    open_shell,
     polygonal_face_set,
     shell_based_surface_model,
     triangulated_face_set,
@@ -55,6 +60,9 @@ def import_geometry_from_ifc_geom(geom_repr: ifcopenshell.entity_instance) -> GE
         return revolved_solid_area(geom_repr)
     elif geom_repr.is_a("IfcFixedReferenceSweptAreaSolid"):
         return fixed_reference_swept_area_solid(geom_repr)
+    elif geom_repr.is_a("IfcSectionedSolidHorizontal"):
+        # Subtype of IfcSectionedSolid — a profile swept along an alignment directrix.
+        return sectioned_solid_horizontal(geom_repr)
     elif geom_repr.is_a("IfcSweptDiskSolid"):
         # Covers the IfcSweptDiskSolidPolygonal subtype too.
         return swept_disk_solid(geom_repr)
@@ -76,6 +84,11 @@ def import_geometry_from_ifc_geom(geom_repr: ifcopenshell.entity_instance) -> GE
         # WithVoids is a sibling of FacetedBrep (both direct IfcManifoldSolidBrep subtypes),
         # so it must be matched explicitly — is_a("IfcFacetedBrep") does not cover it.
         return faceted_brep(geom_repr)
+    elif geom_repr.is_a("IfcAdvancedBrep"):
+        # IfcManifoldSolidBrep subtype: an outer ClosedShell of IfcAdvancedFaces (analytic /
+        # B-spline surfaces). Serialized like any closed shell; the AdvancedFaces carry their
+        # surface + trimming bounds. (Voids on IfcAdvancedBrepWithVoids ignored for now.)
+        return closed_shell(geom_repr.Outer)
     elif geom_repr.is_a("IfcAdvancedFace"):
         return advanced_face(geom_repr)
     elif geom_repr.is_a("IfcFace"):
@@ -84,6 +97,18 @@ def import_geometry_from_ifc_geom(geom_repr: ifcopenshell.entity_instance) -> GE
         return read_face(geom_repr)
     elif geom_repr.is_a("IfcShellBasedSurfaceModel"):
         return shell_based_surface_model(geom_repr)
+    elif geom_repr.is_a("IfcFaceBasedSurfaceModel"):
+        return face_based_surface_model(geom_repr)
+    elif geom_repr.is_a("IfcClosedShell"):
+        # Bare shell as the representation item (write_shapes emits imported
+        # ClosedShell/ConnectedFaceSet bodies this way).
+        return closed_shell(geom_repr)
+    elif geom_repr.is_a("IfcOpenShell"):
+        return open_shell(geom_repr)
+    elif geom_repr.is_a("IfcConnectedFaceSet"):
+        # A bare connected face set (the member type of a face-based surface model). MUST come after
+        # its IfcClosedShell / IfcOpenShell subtypes so those keep their specific readers.
+        return connected_face_set(geom_repr)
     elif geom_repr.is_a("IfcCurveBoundedPlane"):
         return curve_bounded_plane(geom_repr)
     elif geom_repr.is_a("IfcHalfSpaceSolid"):
@@ -97,6 +122,10 @@ def import_geometry_from_ifc_geom(geom_repr: ifcopenshell.entity_instance) -> GE
         # Covers IfcBooleanClippingResult (a subtype). Returns a wrapped Geometry carrying
         # the cut(s) as bool_operations, not a raw geom — callers handle both (read_shapes).
         return boolean_result(geom_repr)
+    elif geom_repr.is_a("IfcMappedItem"):
+        # Instanced reuse of a mapped representation, placed by a transform. Unwrap + read the
+        # underlying geometry natively (no OCC kernel, which otherwise builds the mapped body).
+        return mapped_item(geom_repr)
     elif geom_repr.is_a("IfcCurve"):
         # Curve-only body (Curve3D representation) — e.g. a SAT wire body round-tripped
         # through write_shapes. IfcCurve is the supertype of every concrete curve entity;
@@ -108,6 +137,178 @@ def import_geometry_from_ifc_geom(geom_repr: ifcopenshell.entity_instance) -> GE
         raise NotImplementedError(f"Geometry type {geom_repr.is_a()} not implemented")
 
 
+def mapped_item(geom_repr: ifcopenshell.entity_instance) -> GEOM:
+    """IfcMappedItem — reuse of a MappingSource representation placed by a MappingTarget transform.
+
+    Unwrap the mapped representation item(s), read them natively (recurse), and apply the
+    mapped-item 4x4 (MappingTarget composed with MappingOrigin — via ifcopenshell's pure-Python
+    ``get_mappeditem_transformation``, no OCC kernel). A single-item source bakes the transform
+    into the geometry when it is rigid, else carries it as a mesh-level ``Geometry.transforms``.
+    A *multi-item* mapped representation (e.g. a detailed part exported as several
+    IfcPolygonalFaceSets) merges its faceted items into one geometry and carries the shared 4x4 as a
+    mesh-level transform. Non-faceted multi-item sources raise NotImplementedError so the caller
+    keeps the kernel fallback for that product."""
+    import numpy as np
+    import ifcopenshell.util.placement as _placement
+
+    from ada.geom import Geometry
+
+    items = list(geom_repr.MappingSource.MappedRepresentation.Items)
+    matrix = _placement.get_mappeditem_transformation(geom_repr)
+
+    if len(items) == 1:
+        geom = import_geometry_from_ifc_geom(items[0])
+        try:
+            return _transform_geometry(geom, matrix)
+        except NotImplementedError:
+            # A non-rigid (scale/shear) transform, or an analytic solid whose parameters can't absorb
+            # the 4x4, can't be baked into the geometry. Carry it as a mesh-level world transform
+            # instead (Geometry.transforms) — applied to the tessellated mesh, so it renders natively
+            # without the OCC kernel fallback. Any geom kind + any affine works this way.
+            base = geom if isinstance(geom, Geometry) else Geometry(items[0].id(), geom)
+            base.transforms = [np.asarray(matrix, dtype=float)]
+            return base
+
+    # Several items under one mapping source: merge the faceted items into a single geometry (one
+    # Shape carries one Geometry, so we can't emit them separately) and carry the shared mapped 4x4
+    # as a mesh-level transform. This renders natively instead of the OCC kernel building the mapped
+    # multi-item body. _merge_face_sets raises NotImplementedError for non-face-set items.
+    merged = _merge_face_sets([import_geometry_from_ifc_geom(it) for it in items])
+    base = Geometry(geom_repr.id(), merged)
+    m = np.asarray(matrix, dtype=float)
+    if not np.allclose(m, np.eye(4), atol=1e-12):
+        base.transforms = [m]
+    return base
+
+
+def _merge_face_sets(geoms: list) -> GEOM:
+    """Merge a list of homogeneous face sets into one, concatenating coordinates and offsetting the
+    (1-based) vertex indices. Supports all-PolygonalFaceSet or all-TriangulatedFaceSet inputs; any
+    other/mixed content raises NotImplementedError (the multi-item mapped-item caller then keeps the
+    kernel fallback)."""
+    if geoms and all(isinstance(g, geo_su.PolygonalFaceSet) for g in geoms):
+        coordinates: list = []
+        faces: list[list[int]] = []
+        offset = 0
+        closed = True
+        for g in geoms:
+            faces.extend([[i + offset for i in face] for face in g.faces])
+            coordinates.extend(g.coordinates)
+            offset += len(g.coordinates)
+            closed = closed and g.closed
+        return geo_su.PolygonalFaceSet(coordinates=coordinates, faces=faces, closed=closed)
+    if geoms and all(isinstance(g, geo_su.TriangulatedFaceSet) for g in geoms):
+        coordinates = []
+        normals: list = []
+        indices: list[int] = []
+        offset = 0
+        for g in geoms:
+            indices.extend([i + offset for i in g.indices])
+            coordinates.extend(g.coordinates)
+            normals.extend(g.normals)
+            offset += len(g.coordinates)
+        return geo_su.TriangulatedFaceSet(coordinates=coordinates, normals=normals, indices=indices)
+    kinds = ", ".join(sorted({type(g).__name__ for g in geoms})) or "empty"
+    raise NotImplementedError(f"multi-item mapped representation with non-mergeable items ({kinds})")
+
+
+def mapped_instance_group(prod_def: ifcopenshell.entity_instance):
+    """If a product's Body representation is several IfcMappedItems that all reuse the SAME mapping
+    source (one IfcRepresentationMap instanced N times, e.g. mapped-shape-with-multiple-items), read
+    the source geometry ONCE and return a single Geometry carrying every instance's 4x4 in
+    ``transforms`` — rendered natively via mesh-level instancing instead of the multi-item kernel
+    fallback. Returns None when the pattern doesn't hold (mixed item kinds, differing sources, or a
+    source that isn't itself a single item)."""
+    import numpy as np
+    import ifcopenshell.util.placement as _placement
+
+    from ada.geom import Geometry
+
+    items = []
+    for rep in prod_def.Representation.Representations:
+        if rep.RepresentationIdentifier == "Body":
+            items.extend(rep.Items)
+    if len(items) < 2 or not all(i.is_a("IfcMappedItem") for i in items):
+        return None
+    src = items[0].MappingSource.MappedRepresentation
+    if not all(i.MappingSource.MappedRepresentation == src for i in items):
+        return None
+    src_items = list(src.Items)
+    if len(src_items) != 1:
+        return None
+    base = import_geometry_from_ifc_geom(src_items[0])
+    base = base if isinstance(base, Geometry) else Geometry(src_items[0].id(), base)
+    base.transforms = [np.asarray(_placement.get_mappeditem_transformation(i), dtype=float) for i in items]
+    return base
+
+
+def _transform_curve(curve, xf, r_mat, scale):
+    """Apply a rigid (optionally uniformly-scaled) 4x4 to a curve by transforming its vertices —
+    Edge / ArcLine / IndexedPolyCurve / PolyLine (the swept-solid directrix forms)."""
+    from ada.geom import curves as geo_cu
+
+    if isinstance(curve, geo_cu.Edge):
+        return geo_cu.Edge(xf(curve.start), xf(curve.end))
+    if isinstance(curve, geo_cu.ArcLine):
+        return geo_cu.ArcLine(xf(curve.start), xf(curve.midpoint), xf(curve.end))
+    if isinstance(curve, geo_cu.PolyLine):
+        return geo_cu.PolyLine(points=[xf(p) for p in curve.points])
+    if isinstance(curve, geo_cu.IndexedPolyCurve):
+        return geo_cu.IndexedPolyCurve(
+            [_transform_curve(s, xf, r_mat, scale) for s in curve.segments], curve.self_intersect
+        )
+    raise NotImplementedError(f"mapped-item transform of directrix {type(curve).__name__}")
+
+
+def _transform_geometry(geom: GEOM, matrix) -> GEOM:
+    """Apply a mapped-item 4x4 to a native geometry. Identity returns the geometry unchanged
+    (the common case — the mapped body sits at the source origin and the product's ObjectPlacement
+    does the placing). Otherwise the transform must be rigid (optionally uniform scale): point-set
+    geometries transform their coordinates, an IfcSweptDiskSolid transforms its directrix + scales
+    its radius. Non-rigid transforms and unsupported analytic types raise NotImplementedError."""
+    import numpy as np
+
+    from ada.geom import solids as geo_so
+    from ada.geom import surfaces as geo_su
+    from ada.geom.direction import Direction
+    from ada.geom.points import Point
+
+    m = np.asarray(matrix, dtype=float)
+    if np.allclose(m, np.eye(4), atol=1e-12):
+        return geom
+
+    rot = m[:3, :3]
+    rtr = rot.T @ rot
+    s2 = float(np.trace(rtr)) / 3.0
+    if s2 <= 0 or not np.allclose(rtr, s2 * np.eye(3), atol=1e-6):
+        raise NotImplementedError("non-rigid (shear / non-uniform scale) mapped-item transform")
+    scale = float(np.sqrt(s2))
+
+    def xf(p) -> Point:
+        q = m @ np.array([float(p[0]), float(p[1]), float(p[2]), 1.0])
+        return Point(q[0], q[1], q[2])
+
+    if isinstance(geom, geo_su.PolygonalFaceSet):
+        return geo_su.PolygonalFaceSet(
+            coordinates=[xf(p) for p in geom.coordinates], faces=geom.faces, closed=geom.closed
+        )
+    if isinstance(geom, geo_su.TriangulatedFaceSet):
+        rn = rot / scale  # pure rotation for the normals
+        normals = [Direction(*(rn @ np.asarray([n[0], n[1], n[2]], float))) for n in geom.normals]
+        return geo_su.TriangulatedFaceSet(
+            coordinates=[xf(p) for p in geom.coordinates], normals=normals, indices=geom.indices
+        )
+    if isinstance(geom, geo_so.SweptDiskSolid):
+        return geo_so.SweptDiskSolid(
+            directrix=_transform_curve(geom.directrix, xf, rot / scale, scale),
+            radius=geom.radius * scale,
+            inner_radius=(geom.inner_radius * scale if geom.inner_radius else None),
+            start_param=geom.start_param,
+            end_param=geom.end_param,
+        )
+    raise NotImplementedError(f"mapped-item transform of {type(geom).__name__} (kernel fallback)")
+
+
 def boolean_result(geom_repr: ifcopenshell.entity_instance) -> "Geometry":
     """Read an IfcBooleanResult/IfcBooleanClippingResult into a base Geometry with the cut
     operand(s) attached as bool_operations (applied downstream by apply_geom_booleans).
diff --git a/src/ada/cadit/ifc/read/geom/placement.py b/src/ada/cadit/ifc/read/geom/placement.py
index 5c2853033..50806b700 100644
--- a/src/ada/cadit/ifc/read/geom/placement.py
+++ b/src/ada/cadit/ifc/read/geom/placement.py
@@ -1,7 +1,19 @@
+import numpy as np
+
 from ada import Direction, Point
+from ada.api.transforms import Placement
 from ada.geom.placement import Axis1Placement, Axis2Placement3D
 
 
+def placement_from_ifc_4x4(matrix) -> Placement:
+    """Build a Placement from an IFC world transform (``get_local_placement`` / a standard 4x4
+    ``IfcObjectPlacement``). Now that ``Placement.from_4x4_matrix`` is self-consistent (row-based,
+    ``from_4x4_matrix(M).get_matrix4x4() == M``), this is a plain wrapper — the historic transpose
+    workaround is gone. Kept as a named entry point for the IFC readers (and a home for any
+    future IFC-specific placement handling)."""
+    return Placement.from_4x4_matrix(np.asarray(matrix, dtype=float))
+
+
 def ifc_direction(ifc_entity) -> Direction:
     return Direction(ifc_entity.DirectionRatios)
 
diff --git a/src/ada/cadit/ifc/read/geom/solids.py b/src/ada/cadit/ifc/read/geom/solids.py
index f8fba40c7..4e26d23e0 100644
--- a/src/ada/cadit/ifc/read/geom/solids.py
+++ b/src/ada/cadit/ifc/read/geom/solids.py
@@ -1,6 +1,7 @@
 import ifcopenshell
 
 from ada.geom import solids as geo_so
+from ada.geom import surfaces as geo_su
 from ada.geom.placement import Axis2Placement3D
 from ada.geom.points import Point
 
@@ -9,6 +10,55 @@
 from .surfaces import closed_shell, get_surface
 
 
+def _distance_along(placement: ifcopenshell.entity_instance) -> float:
+    """Arc-length distance of an IfcAxis2PlacementLinear along its base curve — the
+    IfcPointByDistanceExpression.DistanceAlong at its Location."""
+    dist = placement.Location.DistanceAlong
+    return float(dist.wrappedValue if hasattr(dist, "wrappedValue") else dist)
+
+
+def sectioned_solid_horizontal(ifc_entity: ifcopenshell.entity_instance) -> geo_su.TriangulatedFaceSet:
+    """IfcSectionedSolidHorizontal — a profile swept along a (horizontal alignment) directrix, its
+    cross-sections placed at distances along it. For a CONSTANT cross-section (all sections equal)
+    this is a fixed-reference sweep over the directrix range [first, last] cross-section distance;
+    we evaluate it natively to a triangulated shell (no OCC kernel, which otherwise explodes the
+    swept solid into thousands of loose faces). Varying cross-sections aren't handled yet
+    (NotImplementedError -> the caller's kernel fallback)."""
+    import numpy as np
+
+    from ada.cadit.ngeom._alignment_sweep import sectioned_solid_horizontal_mesh
+    from ada.geom import curves as geo_cu
+
+    cross = list(ifc_entity.CrossSections)
+    if any(cs != cross[0] for cs in cross):
+        raise NotImplementedError("IfcSectionedSolidHorizontal with varying cross-sections not yet native")
+
+    profile = get_surface(cross[0])
+    outer = getattr(profile, "outer_curve", None)
+    # The 2D profile outline (the swept cross-section). IndexedPolyCurve/PolyLine expose their
+    # vertices directly; a bare curve type without a vertex list can't seed a swept polygon.
+    if isinstance(outer, geo_cu.IndexedPolyCurve):
+        pts = outer.get_points()
+    elif isinstance(outer, geo_cu.PolyLine):
+        pts = [tuple(p) for p in outer.points]
+    else:
+        raise NotImplementedError(f"sectioned-solid profile outline {type(outer).__name__} not supported")
+    if not pts or len(pts) < 3:
+        raise NotImplementedError("sectioned-solid profile has no polygon outline")
+
+    directrix = get_curve(ifc_entity.Directrix)
+    dists = [_distance_along(p) for p in ifc_entity.CrossSectionPositions]
+    fixed_ref = (0.0, 0.0, 1.0)
+    coords, tris = sectioned_solid_horizontal_mesh(
+        directrix, np.asarray(pts, dtype=float)[:, :2], dists[0], dists[-1], fixed_ref=fixed_ref
+    )
+    return geo_su.TriangulatedFaceSet(
+        coordinates=[Point(float(c[0]), float(c[1]), float(c[2])) for c in coords],
+        normals=[],
+        indices=(tris + 1).reshape(-1).tolist(),  # IFC face indices are 1-based
+    )
+
+
 def faceted_brep(ifc_entity: ifcopenshell.entity_instance) -> geo_so.FacetedBrep:
     # Handles IfcFacetedBrep and the sibling IfcFacetedBrepWithVoids (adds inner void shells).
     voids = [closed_shell(v) for v in ifc_entity.Voids] if ifc_entity.is_a("IfcFacetedBrepWithVoids") else []
diff --git a/src/ada/cadit/ifc/read/geom/surfaces.py b/src/ada/cadit/ifc/read/geom/surfaces.py
index ee489367b..08de2d5fd 100644
--- a/src/ada/cadit/ifc/read/geom/surfaces.py
+++ b/src/ada/cadit/ifc/read/geom/surfaces.py
@@ -36,6 +36,10 @@ def get_surface(ifc_entity: ifcopenshell.entity_instance) -> geo_su.SURFACE_GEOM
         return t_shape_profile_def(ifc_entity)
     elif ifc_entity.is_a("IfcCircleProfileDef"):
         return circle_profile_def(ifc_entity)
+    elif ifc_entity.is_a("IfcRoundedRectangleProfileDef"):
+        # MUST precede IfcRectangleProfileDef — RoundedRectangle is a subtype, so the
+        # rectangle branch would swallow it and drop RoundingRadius (sharp corners).
+        return rounded_rectangle_profile_def(ifc_entity)
     elif ifc_entity.is_a("IfcRectangleProfileDef"):
         return rectangle_profile_def(ifc_entity)
     elif ifc_entity.is_a("IfcDerivedProfileDef"):
@@ -163,7 +167,8 @@ def triangulated_face_set(ifc_entity: ifcopenshell.entity_instance) -> geo_su.Tr
     return geo_su.TriangulatedFaceSet(
         coordinates=[Point(*x) for x in ifc_entity.Coordinates.CoordList],
         indices=flatten(ifc_entity.CoordIndex),
-        normals=[Direction(*x) for x in ifc_entity.Normals],
+        # Normals is OPTIONAL in the schema (flat shading when absent).
+        normals=[Direction(*x) for x in ifc_entity.Normals or []],
     )
 
 
@@ -186,6 +191,45 @@ def rectangle_profile_def(ifc_entity: ifcopenshell.entity_instance) -> geo_su.Re
     )
 
 
+def rounded_rectangle_profile_def(ifc_entity: ifcopenshell.entity_instance) -> geo_su.SURFACE_GEOM_TYPES:
+    """IfcRoundedRectangleProfileDef -> a rectangle (centred on the profile origin) with quarter-circle
+    fillets of RoundingRadius at all four corners, materialised as an ArbitraryProfileDef whose outer
+    curve is an IndexedPolyCurve of 4 Edges + 4 ArcLines. Falls back to a plain rectangle when the
+    radius is ~0 (nothing to round). The dropped rounding was what made the bath-csg void read with
+    sharp interior corners."""
+    x_dim = float(ifc_entity.XDim)
+    y_dim = float(ifc_entity.YDim)
+    hx, hy = x_dim / 2.0, y_dim / 2.0
+    r = float(ifc_entity.RoundingRadius or 0.0)
+    # A valid fillet can't exceed the half-extents; clamp defensively.
+    r = min(r, hx, hy)
+    if r <= 1e-9:
+        return rectangle_profile_def(ifc_entity)
+
+    import math
+
+    def arc(cx, cy, start, end, ang_mid_deg):
+        # midpoint = the on-arc point at 45 deg into the corner (arc spans 90 deg)
+        m = (cx + r * math.cos(math.radians(ang_mid_deg)), cy + r * math.sin(math.radians(ang_mid_deg)))
+        return geo_cu.ArcLine(list(start), list(m), list(end))
+
+    segs = [
+        geo_cu.Edge([-hx + r, -hy], [hx - r, -hy]),  # bottom
+        arc(hx - r, -hy + r, (hx - r, -hy), (hx, -hy + r), -45),  # bottom-right
+        geo_cu.Edge([hx, -hy + r], [hx, hy - r]),  # right
+        arc(hx - r, hy - r, (hx, hy - r), (hx - r, hy), 45),  # top-right
+        geo_cu.Edge([hx - r, hy], [-hx + r, hy]),  # top
+        arc(-hx + r, hy - r, (-hx + r, hy), (-hx, hy - r), 135),  # top-left
+        geo_cu.Edge([-hx, hy - r], [-hx, -hy + r]),  # left
+        arc(-hx + r, -hy + r, (-hx, -hy + r), (-hx + r, -hy), 225),  # bottom-left
+    ]
+    return geo_su.ArbitraryProfileDef(
+        profile_type=geo_su.ProfileType.from_str(ifc_entity.ProfileType),
+        outer_curve=geo_cu.IndexedPolyCurve(segs),
+        profile_name=ifc_entity.ProfileName,
+    )
+
+
 def curve_bounded_plane(ifc_entity: ifcopenshell.entity_instance) -> geo_su.CurveBoundedPlane:
     from .curves import get_curve
 
@@ -339,3 +383,17 @@ def shell_based_surface_model(ifc_entity: ifcopenshell.entity_instance) -> geo_s
             raise NotImplementedError(f"{face} is not yet implemented.")
 
     return geo_su.ShellBasedSurfaceModel(sbsm_boundary=sbsm_boundary)
+
+
+def connected_face_set(ifc_entity: ifcopenshell.entity_instance) -> geo_su.ConnectedFaceSet:
+    """IfcConnectedFaceSet — a set of IfcFace (CfsFaces). Same shape as IfcClosed/OpenShell, but the
+    generic (not necessarily closed) form used inside an IfcFaceBasedSurfaceModel."""
+    from ada.cadit.ifc.read.geom.geom_reader import import_geometry_from_ifc_geom
+
+    return geo_su.ConnectedFaceSet([import_geometry_from_ifc_geom(f) for f in ifc_entity.CfsFaces])
+
+
+def face_based_surface_model(ifc_entity: ifcopenshell.entity_instance) -> geo_su.FaceBasedSurfaceModel:
+    """IfcFaceBasedSurfaceModel — a set of IfcConnectedFaceSet (FbsmFaces). The face-set sibling of
+    IfcShellBasedSurfaceModel; the OCC and NGEOM builders already sew/tessellate its face sets."""
+    return geo_su.FaceBasedSurfaceModel(fbsm_faces=[connected_face_set(cfs) for cfs in ifc_entity.FbsmFaces])
diff --git a/src/ada/cadit/ifc/read/native_reader.py b/src/ada/cadit/ifc/read/native_reader.py
new file mode 100644
index 000000000..d993208d9
--- /dev/null
+++ b/src/ada/cadit/ifc/read/native_reader.py
@@ -0,0 +1,100 @@
+"""Native IFC reader: parse via adacpp's C++ IfcResolver (IfcNgeomStream), no ifcopenshell/OCC.
+
+The geometry-shapes counterpart of ``ada.cadit.step.read.native_reader`` for IFC: iterate the native
+per-product ``IfcNgeomStream`` (blob + meta = guid/color/transforms/instance_paths) and build the
+Assembly's Part/ShapeProxy tree directly — lazy ShapeStore blobs, colour + spatial hierarchy resolved
+in C++. This is a geometry-shapes mode (like the STEP product tree): it does NOT reconstruct typed
+Beam/Plate/Pipe objects — the ifcopenshell reader remains the typed-object path.
+"""
+
+from __future__ import annotations
+
+import pathlib
+from typing import Iterator
+
+
+def native_adacpp_ifc_available() -> bool:
+    """True if adacpp's native per-product IFC->NGEOM stream is importable."""
+    try:
+        import adacpp  # noqa: F401
+
+        return hasattr(adacpp.cad, "IfcNgeomStream")
+    except Exception:
+        return False
+
+
+def native_stream_read_ifc_blobs(ifc_path: str | pathlib.Path) -> Iterator[tuple]:
+    """Yield ``(ngeom_blob, gid, color, world_matrices, instance_paths)`` per IFC product WITHOUT
+    hydrating the geometry — the foundation of the lazy ShapeStore native IFC import. The C++
+    ``StepRootMeta`` is shared with the STEP path, so ``decode_step_root_meta`` decodes it; the IFC
+    GlobalId (``meta.guid``) is preferred as the shape id when present."""
+    import adacpp
+
+    from ada.cadit.step.read.native_reader import decode_step_root_meta
+
+    for nbytes, meta in adacpp.cad.IfcNgeomStream(str(ifc_path)):
+        gid, color, mats, paths = decode_step_root_meta(meta)
+        gid = meta.guid or gid
+        yield nbytes, gid, color, mats, paths
+
+
+def native_read_ifc_into(assembly, ifc_path: str | pathlib.Path, *, product_tree: bool = True) -> int:
+    """Populate ``assembly`` with a Part/ShapeProxy tree from the native IFC reader. Returns the
+    number of shapes added. Lazy ShapeStore by default (``Config().cad_lazy_shape_store``); the eager
+    fallback hydrates each blob to a ``Geometry``."""
+    from ada.api.shapes import ShapeProxy, ShapeStore
+    from ada.api.spatial import Part
+    from ada.config import Config
+
+    # Lazy store retains each product's NGEOM blob (the zero-copy ndarray view the C++ IfcNgeomStream
+    # yields — no memcpy) and, when cad_shape_store_compress is on, zlib-compresses it in place to cut
+    # resident memory — same as the STEP native reader (part.py).
+    store = ShapeStore(compress=Config().cad_shape_store_compress) if Config().cad_lazy_shape_store else None
+    asm_parts: dict[tuple, Part] = {}
+
+    def _tree_parent(paths):
+        # Mirror the STEP reader's _tree_parent: intermediate path levels become nested Parts
+        # (reusing same-name siblings); the last level is the solid's own product (excluded).
+        path = paths[0] if paths else None
+        if not path or len(path) <= 1:
+            return assembly
+        parent = assembly
+        name_path: tuple = ()
+        for level in path[:-1]:
+            pname = (level[1] if level[1] else f"asm_{level[0]}") if isinstance(level, (tuple, list)) else str(level)
+            name_path += (pname,)
+            p = asm_parts.get(name_path)
+            if p is None:
+                existing = parent._parts.get(pname)
+                p = existing if existing is not None else parent.add_part(Part(pname))
+                asm_parts[name_path] = p
+            parent = p
+        return parent
+
+    n = 0
+    for i, (blob, gid, color, mats, paths) in enumerate(native_stream_read_ifc_blobs(ifc_path)):
+        name = gid if gid not in (None, "") else f"{assembly.name}_{i}"
+        if store is not None:
+            idx = store.add_blob(
+                blob, gid=name, color=color, transforms=(mats or None), instance_paths=(paths or None)
+            )
+            shp = ShapeProxy(name, store, idx, color=color)
+        else:
+            from ada.api.primitives import Shape
+            from ada.cadit.ngeom.deserialize import deserialize_geometries
+            from ada.geom import Geometry
+
+            dec = deserialize_geometries(blob)
+            if not dec:
+                continue
+            shp = Shape(
+                name,
+                Geometry(
+                    id=name, geometry=dec[0][1], color=color, transforms=(mats or None), instance_paths=(paths or None)
+                ),
+                color=color,
+            )
+        parent = _tree_parent(paths) if product_tree else assembly
+        parent.add_shape(shp)
+        n += 1
+    return n
diff --git a/src/ada/cadit/ifc/read/read_alignment.py b/src/ada/cadit/ifc/read/read_alignment.py
new file mode 100644
index 000000000..5d18722c7
--- /dev/null
+++ b/src/ada/cadit/ifc/read/read_alignment.py
@@ -0,0 +1,122 @@
+"""Import IFC4x3 alignment-family products (IfcAlignment, IfcAlignmentSegment, IfcReferent, ...)
+whose geometry is curve representations — 'Axis' (Curve3D), 'FootPrint' (Curve2D) or 'Segment'.
+
+These carry no Body/solid, so the generic shape importer skips them and the IfcOpenShell geometry
+kernel can hang on their IfcCurveSegments (a 9000-iter root-find per sample). Instead we read the
+analytic ada.geom curve (IfcSegmentedReferenceCurve / IfcGradientCurve / IfcCompositeCurve /
+IfcCurveSegment with line/arc/clothoid/cosine-spiral parents), evaluate it to a sampled 3D polyline
+with the kernel-free alignment evaluator (validated to ~1e-6 vs the ifcopenshell oracle), and mint a
+Shape carrying that PolyLine — which renders as GL_LINES on every backend (no OCC)."""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+import numpy as np
+
+from ada import Shape
+from ada.cadit.ifc.read.geom.curves import get_curve
+from ada.cadit.ifc.read.read_color import get_product_color
+from ada.cadit.ngeom._alignment_sweep import curve_to_polyline
+from ada.config import logger
+from ada.geom import Geometry
+from ada.geom.curves import PolyLine
+from ada.geom.points import Point
+
+if TYPE_CHECKING:
+    import ifcopenshell
+
+    from ada.cadit.ifc.store import IfcStore
+
+# Representation identifiers we can evaluate, most-preferred first: the 3D reference curve is the
+# primary geometry; the 2D footprint and per-segment bodies are fallbacks.
+_CURVE_REP_PRIORITY = ("Axis", "Segment", "FootPrint", "Curve3D", "Reference")
+
+
+def is_alignment_curve_product(product: ifcopenshell.entity_instance) -> bool:
+    """True if the product carries a curve (Axis/FootPrint/Segment) representation the alignment
+    reader can evaluate — i.e. an alignment-family product with geometry but no Body."""
+    rep = getattr(product, "Representation", None)
+    if rep is None:
+        return False
+    return any(_curve_items(r) for r in rep.Representations)
+
+
+def _dedupe_consecutive(pts, tol: float = 1e-7) -> list[Point]:
+    """Drop consecutive coincident points (zero-length edges) from a sampled polyline — they arise
+    at the boundaries between adjacent curve segments and would make wire-based exporters fail."""
+    out: list[Point] = []
+    for p in pts:
+        q = Point(float(p[0]), float(p[1]), float(p[2]))
+        if not out or float(np.linalg.norm(q - out[-1])) > tol:
+            out.append(q)
+    return out
+
+
+def _curve_items(representation) -> list:
+    """The representation's items if it is a curve representation we handle, else []."""
+    ident = getattr(representation, "RepresentationIdentifier", None)
+    if ident not in _CURVE_REP_PRIORITY:
+        return []
+    return list(representation.Items or [])
+
+
+def import_ifc_alignment(product: ifcopenshell.entity_instance, name, ifc_store: IfcStore) -> Shape | None:
+    """Evaluate the product's preferred curve representation to a Shape carrying a 3D polyline.
+
+    Prefers the 3D 'Axis' reference curve (with cant, for IfcSegmentedReferenceCurve); falls back
+    to a 'Segment' or 'FootPrint' representation. Returns ``None`` if no representation evaluates
+    (logged), so the caller can fall through / skip."""
+    rep = getattr(product, "Representation", None)
+    if rep is None:
+        return None
+
+    # Pick the highest-priority curve representation present.
+    by_ident = {}
+    for r in rep.Representations:
+        if _curve_items(r):
+            by_ident.setdefault(r.RepresentationIdentifier, r)
+    chosen = next((by_ident[i] for i in _CURVE_REP_PRIORITY if i in by_ident), None)
+    if chosen is None:
+        return None
+
+    points: list[Point] = []
+    for item in chosen.Items:
+        try:
+            curve = get_curve(item)
+            pts = curve_to_polyline(curve)
+        except NotImplementedError as exc:
+            logger.debug(f"alignment curve {item.is_a()} on {name!r} not evaluable natively ({exc})")
+            continue
+        except Exception as exc:  # noqa: BLE001 - a single bad item must not drop the whole product
+            logger.warning(f"alignment curve eval failed for {name!r} ({item.is_a()}): {exc}")
+            continue
+        points.extend(_dedupe_consecutive(pts))
+
+    points = _dedupe_consecutive(points)
+    if len(points) < 2:
+        # A curve that collapses to a single point in its own parametric space (e.g. an isolated
+        # constant vertical/cant segment) has no line to draw — skip it. Dropping degenerate
+        # polylines also keeps them out of the wire-based STEP/IFC exporters (which raise on
+        # zero-length edges).
+        logger.info(f'alignment product "{name}" ({product.is_a()}) produced no evaluable curve geometry')
+        return None
+
+    color = get_product_color(product, ifc_store.f)
+    geom = Geometry(product.GlobalId, PolyLine(points=points), color)
+    shape = Shape(
+        name,
+        geom=geom,
+        guid=product.GlobalId,
+        ifc_store=ifc_store,
+        units=ifc_store.assembly.units,
+        color=color,
+        opacity=color.opacity if color is not None else 1.0,
+    )
+    # Alignment products carry no IfcStyledItem, so ``color`` is None; the line-render / GLB
+    # material path reads ``geom.color`` and calls ``.rgb255`` on it. Shape defaults a None color
+    # to light-gray — mirror that onto the geometry so the mesh material is never None (the solid
+    # path does the same sync in Shape.solid_geom).
+    if geom.color is None:
+        geom.color = shape.color
+    return shape
diff --git a/src/ada/cadit/ifc/read/read_beam_section.py b/src/ada/cadit/ifc/read/read_beam_section.py
index c82e1368b..87cb83bff 100644
--- a/src/ada/cadit/ifc/read/read_beam_section.py
+++ b/src/ada/cadit/ifc/read/read_beam_section.py
@@ -36,6 +36,10 @@ def import_section_from_ifc(profile_def, units=Units.M) -> Section:
             t_w=profile_def.WebThickness,
             t_ftop=profile_def.FlangeThickness,
             t_fbtn=profile_def.FlangeThickness,
+            # Flange-root fillet radius (optional in IFC). Stored in the otherwise-unused ``r``
+            # for I-sections so iprofiles() rounds the four web/flange junctions instead of
+            # drawing sharp corners.
+            r=profile_def.FilletRadius,
             units=units,
             sec_str=name,
         )
diff --git a/src/ada/cadit/ifc/read/read_beams.py b/src/ada/cadit/ifc/read/read_beams.py
index 8064ef8e3..002c6c873 100644
--- a/src/ada/cadit/ifc/read/read_beams.py
+++ b/src/ada/cadit/ifc/read/read_beams.py
@@ -12,7 +12,7 @@
 from ada.core.vector_utils import calc_yvec, unit_vector
 
 from .geom.geom_reader import get_product_definitions
-from .geom.placement import axis3d
+from .geom.placement import axis3d, placement_from_ifc_4x4
 from .read_beam_section import import_section_from_ifc
 from .read_materials import read_material
 from .reader_utils import (
@@ -68,21 +68,25 @@ def import_straight_beam(ifc_elem, axis, name, sec, mat, ifc_store: IfcStore) ->
         raise ValueError("Number of body objects attached to element is not 1")
     body = bodies[0]
 
-    rel_place = Placement.from_axis3d(axis3d(ifc_elem.ObjectPlacement.RelativePlacement))
-
-    extrude_dir = unit_vector(rel_place.transform_vector(body.position.axis, inverse=True))
-    ref_dir = unit_vector(rel_place.transform_vector(body.position.ref_direction))
+    extra_opts = {}
+    obj_placement = ifc_elem.ObjectPlacement
+    if obj_placement is not None:
+        # n1/n2 stay in the beam's LOCAL frame (the extrusion's own position/direction — this is
+        # also where the cardinal-point offset lives, baked into ExtrudedAreaSolid.Position by the
+        # authoring tool), and the FULL ObjectPlacement world transform becomes the beam placement.
+        # get_local_placement composes the whole chain, so this covers BOTH a parent chain
+        # (beam-standard-case.ifc) AND a bare RelativePlacement with no parent
+        # (beam-varying-cardinal-points.ifc) — the old no-parent path baked rel_place into the
+        # extrude DIRECTION but left the location + origin untransformed, dropping the placement
+        # entirely and rendering the beam at the wrong spot. placement_from_ifc_4x4 reconciles the
+        # column<->row transpose in Placement.get_matrix4x4 so the scene applies the intended matrix.
+        extra_opts["placement"] = placement_from_ifc_4x4(get_local_placement(obj_placement))
+    extrude_dir = unit_vector(body.position.axis)
+    ref_dir = unit_vector(body.position.ref_direction)
     p1 = body.position.location
     local_y = calc_yvec(ref_dir, extrude_dir)
     p2 = p1 + extrude_dir * body.depth
 
-    extra_opts = {}
-    obj_placement = ifc_elem.ObjectPlacement
-    if obj_placement.PlacementRelTo:
-        local_placement = get_local_placement(obj_placement)
-        place = Placement.from_4x4_matrix(local_placement)
-        extra_opts["placement"] = place
-
     common = dict(
         sec=sec,
         mat=mat,
diff --git a/src/ada/cadit/ifc/read/read_ifc.py b/src/ada/cadit/ifc/read/read_ifc.py
index 7066d8e58..97897d419 100644
--- a/src/ada/cadit/ifc/read/read_ifc.py
+++ b/src/ada/cadit/ifc/read/read_ifc.py
@@ -132,6 +132,7 @@ def load_presentation_layers(self):
         self.ifc_store.assembly.presentation_layers = PresentationLayers(layers)
 
     def load_objects(self, data_only=False, elements2part=None):
+        any_product_imported = False
         for product in self.ifc_store.f.by_type("IfcProduct"):
             if product.Representation is None or data_only is True:
                 logger.info(f'Passing product "{product}"')
@@ -159,5 +160,62 @@ def load_objects(self, data_only=False, elements2part=None):
                 continue
 
             obj.metadata = props
+            any_product_imported = True
 
             add_to_assembly(self.ifc_store.assembly, obj, parent, elements2part)
+
+        # Only when NO placed product carried geometry: a normal model with
+        # uninstantiated type definitions alongside real products must not
+        # grow phantom shapes at the origin.
+        if data_only is False and not any_product_imported:
+            self.load_instanceless_type_products()
+
+    def load_instanceless_type_products(self):
+        """Import geometry from type products in a type-library file.
+
+        Type-library files (e.g. the buildingSMART texture samples: a single
+        IfcBoilerType carrying an IfcTriangulatedFaceSet via a RepresentationMap,
+        with no IfcProduct placed anywhere) hold real geometry that the per-product
+        pass never sees — without this it silently renders as an empty scene.
+        Types WITH occurrences are skipped: their geometry arrives through the
+        placed products."""
+        from ada import Shape
+        from ada.cadit.ifc.read.geom.geom_reader import import_geometry_from_ifc_geom
+        from ada.cadit.ifc.read.read_color import get_product_color
+        from ada.geom import Geometry
+
+        f = self.ifc_store.f
+        for tp in f.by_type("IfcTypeProduct"):
+            if not tp.RepresentationMaps:
+                continue
+            # IFC4 inverse for "occurrences of this type" is Types (IfcRelDefinesByType);
+            # IFC2x3 calls it ObjectTypeOf.
+            rels = getattr(tp, "Types", None) or getattr(tp, "ObjectTypeOf", None) or []
+            if any(rel.RelatedObjects for rel in rels):
+                continue
+            name = tp.Name or tp.GlobalId
+            try:
+                color = get_product_color(tp, f)
+            except Exception:  # noqa: BLE001 - style resolution is best-effort for type maps
+                color = None
+            n_found = 0
+            for rep_map in tp.RepresentationMaps:
+                mapped_rep = rep_map.MappedRepresentation
+                if mapped_rep is None or mapped_rep.RepresentationIdentifier != "Body":
+                    continue
+                for item in mapped_rep.Items:
+                    try:
+                        res = import_geometry_from_ifc_geom(item)
+                    except NotImplementedError as e:
+                        logger.warning(f'Skipping type-product geometry for "{name}" (#{item.id()}): {e}')
+                        continue
+                    geom = res if isinstance(res, Geometry) else Geometry(tp.GlobalId, res, color)
+                    shape_name = name if n_found == 0 else f"{name}_{n_found}"
+                    # guid only on the first shape — one GlobalId can't be shared.
+                    guid = tp.GlobalId if n_found == 0 else None
+                    self.ifc_store.assembly.add_shape(
+                        Shape(shape_name, geom=geom, guid=guid, color=color, ifc_store=self.ifc_store)
+                    )
+                    n_found += 1
+            if n_found > 0:
+                logger.info(f'Imported {n_found} geometry item(s) from instance-less type "{name}"')
diff --git a/src/ada/cadit/ifc/read/read_physical_objects.py b/src/ada/cadit/ifc/read/read_physical_objects.py
index cb780f380..fb6fcdeb1 100644
--- a/src/ada/cadit/ifc/read/read_physical_objects.py
+++ b/src/ada/cadit/ifc/read/read_physical_objects.py
@@ -28,25 +28,33 @@ def _belongs_to_system(product) -> bool:
 def import_physical_ifc_elem(product, name, ifc_store: IfcStore):
     pr_type = product.is_a()
 
+    # Typed imports are best-effort: a product the concept importer can't
+    # express (tessellated body, missing material/axis, unusual profile) must
+    # still land as a generic Shape via the fall-through below — never be
+    # dropped. The named exceptions are the expected downgrades (debug); any
+    # other failure is logged so real importer bugs stay visible.
     if pr_type in ["IfcBeamStandardCase", "IfcBeam"]:
         try:
             return import_ifc_beam(product, name, ifc_store)
         except (NoIfcAxesAttachedError, UnableToConvertBoolResToBeamException) as e:
             logger.debug(e)
-            pass
+        except Exception as e:  # noqa: BLE001
+            logger.warning(f'Beam import of "{name}" failed ("{e}"); importing as a generic shape')
     if pr_type in ["IfcPlateStandardCase", "IfcPlate"]:
         try:
             return import_ifc_plate(product, name, ifc_store)
         except NoIfcAxesAttachedError as e:
             logger.debug(e)
-            pass
+        except Exception as e:  # noqa: BLE001
+            logger.warning(f'Plate import of "{name}" failed ("{e}"); importing as a generic shape')
 
     if pr_type in ["IfcWall", "IfcWallStandardCase"]:
         try:
             return import_ifc_wall(product, name, ifc_store)
         except NoIfcAxesAttachedError as e:
             logger.debug(e)
-            pass
+        except Exception as e:  # noqa: BLE001
+            logger.warning(f'Wall import of "{name}" failed ("{e}"); importing as a generic shape')
 
     if product.is_a("IfcFastener"):
         return import_ifc_fastener(product, name, ifc_store)
@@ -63,12 +71,20 @@ def import_physical_ifc_elem(product, name, ifc_store: IfcStore):
         return import_pipe_segment(product, name, ifc_store)
 
     # Non-physical products (alignment, annotation, grid, positioning) carry only
-    # curve/axis representations, never body geometry. Importing them as empty Shapes
-    # pollutes the model and makes downstream exporters choke on a geometry-less shape
-    # (solid_geom() raises) — and feeding their curves to the IfcOpenShell geometry kernel
-    # can hang (IfcCurveSegment runs a 9000-iter root find per sample). Skip any product
-    # that is neither a physical IfcElement nor carries a Body representation.
+    # curve/axis representations, never body geometry. Feeding their IfcCurveSegments to the
+    # IfcOpenShell geometry kernel can hang (a 9000-iter root find per sample), so we never do —
+    # instead the alignment reader evaluates the analytic curve to a polyline natively (no OCC)
+    # and renders it as GL_LINES.
     if not product.is_a("IfcElement") and not _has_body_representation(product):
+        from .read_alignment import import_ifc_alignment, is_alignment_curve_product
+
+        if is_alignment_curve_product(product):
+            alignment = import_ifc_alignment(product, name, ifc_store)
+            if alignment is not None:
+                return alignment
+        # No evaluable curve geometry (a geometry-less positioning product, an annotation, …):
+        # importing it as an empty Shape pollutes the model and makes exporters choke
+        # (solid_geom() raises), so skip it.
         logger.info(f'skipping non-physical product "{name}" ({product.is_a()})')
         return None
 
diff --git a/src/ada/cadit/ifc/read/read_shapes.py b/src/ada/cadit/ifc/read/read_shapes.py
index 01e580935..b7f9f3a62 100644
--- a/src/ada/cadit/ifc/read/read_shapes.py
+++ b/src/ada/cadit/ifc/read/read_shapes.py
@@ -7,8 +7,8 @@
 from ifcopenshell.util.placement import get_local_placement
 
 from ada import Shape
-from ada.api.transforms import Placement
 from ada.cadit.ifc.read.geom.geom_reader import get_product_definitions
+from ada.cadit.ifc.read.geom.placement import placement_from_ifc_4x4
 from ada.cadit.ifc.read.read_color import get_product_color
 from ada.config import Config, logger
 from ada.geom import Geometry
@@ -24,23 +24,25 @@ def import_ifc_shape(product: ifcopenshell.entity_instance, name, ifc_store: Ifc
 
     geom = None
     occ_body = None
+    blob_rec = None
     if Config().ifc_import_shape_geom or force_geom:
-        geom, occ_body = _read_shape_geometry(product, color)
+        geom, occ_body, blob_rec = _read_shape_geometry(product, color, ifc_store)
 
     extra_opts = {}
-    # Only apply the IFC local placement when we keep the native (parametric) geometry,
-    # which is expressed in the product's local coordinates. The kernel fallback below
-    # bakes world coordinates into the OCC body (``USE_WORLD_COORDS``), so re-applying
-    # the placement there would double-transform it.
+    # Only apply the IFC local placement when we keep the native (parametric) geometry, which is
+    # expressed in the product's local coordinates. The kernel fallback below bakes world
+    # coordinates into the OCC body (``USE_WORLD_COORDS``), so re-applying the placement there would
+    # double-transform it. ``get_local_placement`` returns the full world 4x4 regardless of whether
+    # the ObjectPlacement is relative (PlacementRelTo chain) or ABSOLUTE — an absolute placement can
+    # still carry a non-identity rotation (e.g. an IfcBeam that fell through to the shape importer,
+    # with its extrusion axis rotated into the world frame), so it must be applied too. Gating on
+    # PlacementRelTo dropped those rotations and rendered the product on the wrong world axis.
     if occ_body is None:
         obj_placement = product.ObjectPlacement
-        if obj_placement is not None and obj_placement.PlacementRelTo:
-            local_placement = get_local_placement(obj_placement)
-            extra_opts["placement"] = Placement.from_4x4_matrix(local_placement)
+        if obj_placement is not None:
+            extra_opts["placement"] = placement_from_ifc_4x4(get_local_placement(obj_placement))
 
-    shape = Shape(
-        name,
-        geom=geom,
+    common = dict(
         guid=product.GlobalId,
         ifc_store=ifc_store,
         units=ifc_store.assembly.units,
@@ -49,6 +51,39 @@ def import_ifc_shape(product: ifcopenshell.entity_instance, name, ifc_store: Ifc
         **extra_opts,
     )
 
+    if (geom is not None or blob_rec is not None) and Config().cad_lazy_shape_store:
+        # Lazy shape store (default on): keep the geometry as one compact blob and
+        # mint a ShapeProxy that hydrates on demand — large IFC imports stop holding
+        # every product's ada.geom tree. Python-native geometry pickles losslessly
+        # (bool_operations, half-space operands, parametric profiles); products the
+        # Python readers can't resolve keep the adacpp IfcNgeomStream NGEOM buffer
+        # as-arrived (zero-copy, tessellation fast-path capable). Kernel-fallback
+        # products (occ_body) stay eager Shapes: their geometry is the transient
+        # OCC body, and there is nothing heavy retained to avoid.
+        from ada.api.shapes import ShapeProxy, ShapeStore
+
+        store = getattr(ifc_store, "_lazy_shape_store", None)
+        if store is None:
+            store = ShapeStore(compress=Config().cad_shape_store_compress)
+            ifc_store._lazy_shape_store = store
+        if geom is not None:
+            idx = store.add_geometry(geom)
+        else:
+            blob, meta = blob_rec
+            # meta.transforms is the composed world placement (column-major 16-float,
+            # like the STEP path); a single instance becomes the Shape placement so
+            # downstream behaves exactly like the eager IFC path (local geometry +
+            # Placement). Multi-instance products were filtered out at lookup time.
+            if len(meta.transforms) == 1:
+                import numpy as np
+
+                mat = np.asarray(meta.transforms[0], dtype=float).reshape(4, 4, order="F")
+                common["placement"] = placement_from_ifc_4x4(mat)
+            idx = store.add_blob(blob, gid=product.GlobalId, color=color)
+        return ShapeProxy(name, store, idx, **common)
+
+    shape = Shape(name, geom=geom, **common)
+
     # Assign the kernel-built OCC body to the transient cache explicitly rather than via
     # the constructor: the constructor only routes ``geom`` to ``_occ_cache`` when the
     # *active* backend recognises it as a shape handle, which is false under adacpp (the
@@ -60,18 +95,19 @@ def import_ifc_shape(product: ifcopenshell.entity_instance, name, ifc_store: Ifc
     return shape
 
 
-def _read_shape_geometry(product: ifcopenshell.entity_instance, color):
+def _read_shape_geometry(product: ifcopenshell.entity_instance, color, ifc_store: IfcStore = None):
     """Resolve a product's body geometry, preferring adapy's native (parametric) reader.
 
-    Returns ``(geom, occ_body)``: a native :class:`~ada.geom.Geometry` when every body
-    item is a type adapy reads natively, else ``(None, occ_body)`` where ``occ_body`` is a
-    world-placed OCC ``TopoDS`` built by the IfcOpenShell geometry kernel. The kernel
+    Returns ``(geom, occ_body, blob_rec)``: a native :class:`~ada.geom.Geometry` when
+    every body item is a type adapy reads natively; else ``blob_rec = (ngeom_buffer,
+    meta)`` from adacpp's dep-free ``IfcNgeomStream`` when it resolved the product
+    (B-reps and analytic solids, kernel-free and lazily storable); else ``occ_body``,
+    a world-placed OCC ``TopoDS`` built by the IfcOpenShell geometry kernel. The kernel
     fallback is what lets ``ifc.import_shape_geom`` be on by default: any IFC geometry
-    representation (swept/half-space/mapped/b-spline/...) still imports, just as a faceted
-    B-rep rather than a parametric one. Returns ``(None, None)`` only when no geometry can
-    be produced at all (logged)."""
+    representation still imports, just as a faceted B-rep rather than a parametric one.
+    ``(None, None, None)`` only when no geometry can be produced at all (logged)."""
     if product.Representation is None:
-        return None, None
+        return None, None, None
 
     try:
         geometries = get_product_definitions(product)
@@ -79,17 +115,30 @@ def _read_shape_geometry(product: ifcopenshell.entity_instance, color):
         logger.debug(f"native IFC geom reader unsupported for {product.is_a()}; using kernel fallback ({e})")
         geometries = []
 
+    if len(geometries) > 1:
+        # A product with several Body items (e.g. multiple IfcMappedItem instances) needs ALL of
+        # them — one Shape carries one geometry, so taking geometries[0] would silently drop the
+        # rest. When they're all instances of one shared mapping source, fold them into a single
+        # mesh-instanced Geometry (renders natively); otherwise keep the kernel fallback (the OCC
+        # kernel builds every item into one compound).
+        from ada.cadit.ifc.read.geom.geom_reader import mapped_instance_group
+
+        folded = mapped_instance_group(product)
+        if folded is not None:
+            geometries = [folded]
+        else:
+            logger.debug(f"product {product.is_a()} has {len(geometries)} Body geometries; kernel fallback")
+            geometries = []
+
     if geometries:
-        if len(geometries) > 1:
-            logger.warning(f"Multiple geometries on product {product}. Choosing geometry @ index=0")
         geometry = geometries[0]
         # A boolean result (e.g. IfcBooleanClippingResult) already comes back as a Geometry
         # carrying its bool_operations — adopt the product's guid/color rather than re-wrap.
         if isinstance(geometry, Geometry):
             geometry.id = product.GlobalId
             geometry.color = color
-            return geometry, None
-        return Geometry(product.GlobalId, geometry, color), None
+            return geometry, None, None
+        return Geometry(product.GlobalId, geometry, color), None, None
 
     # Only fall back to the kernel for products that carry a *Body* representation, i.e. an
     # actual solid/surface to render. Curve-only products (e.g. IfcAlignmentSegment, whose
@@ -99,12 +148,47 @@ def _read_shape_geometry(product: ifcopenshell.entity_instance, color):
     # break. The native reader already restricts itself to "Body" items, so this keeps the
     # fallback aligned with it.
     if not _has_body_representation(product):
-        return None, None
+        return None, None, None
+
+    # Between the Python-native readers and the OCC kernel: adacpp's dep-free native IFC
+    # resolver (advanced/faceted B-reps + analytic solids the Python readers don't cover).
+    blob_rec = _native_geom_blob(product, ifc_store)
+    if blob_rec is not None:
+        return None, None, blob_rec
 
     occ_body = _kernel_occ_shape(product)
     if occ_body is None:
         logger.warning(f"No geometry could be produced for product {product}")
-    return None, occ_body
+    return None, occ_body, None
+
+
+def _native_geom_blob(product: ifcopenshell.entity_instance, ifc_store: IfcStore):
+    """``(ngeom_buffer, meta)`` for a product from adacpp's ``IfcNgeomStream``, or
+    ``None``. The whole file is scanned ONCE per store on first need (guid-keyed map;
+    buffers retained zero-copy as they arrive). Multi-instance (mapped-item) products
+    are excluded — the lazy Shape path models one placement per Shape."""
+    if ifc_store is None or not Config().cad_lazy_shape_store:
+        return None
+    path = getattr(ifc_store, "ifc_file_path", None)
+    if path is None:
+        return None
+    cache = getattr(ifc_store, "_native_geom_blobs", None)
+    if cache is None:
+        cache = {}
+        try:
+            import adacpp
+
+            stream = adacpp.cad.IfcNgeomStream(str(path))
+            for blob, meta in stream:
+                if meta.guid and len(meta.transforms) <= 1:
+                    cache[meta.guid] = (blob, meta)
+        except (ImportError, AttributeError):
+            pass  # no adacpp / build predates IfcNgeomStream
+        except Exception as exc:  # noqa: BLE001 - a native scan failure must not break the import
+            logger.warning("native IFC NGEOM scan failed (%s); using the kernel fallback", exc)
+            cache = {}
+        ifc_store._native_geom_blobs = cache
+    return cache.get(product.GlobalId)
 
 
 def _has_body_representation(product: ifcopenshell.entity_instance) -> bool:
@@ -172,7 +256,7 @@ def import_ifc_sphere(product: ifcopenshell.entity_instance, name, ifc_store: If
     extra_opts = {}
     obj_placement = product.ObjectPlacement
     if obj_placement is not None and obj_placement.PlacementRelTo:
-        extra_opts["placement"] = Placement.from_4x4_matrix(get_local_placement(obj_placement))
+        extra_opts["placement"] = placement_from_ifc_4x4(get_local_placement(obj_placement))
 
     # A sphere-bodied product marked MassPoint reads back as MassPoint (mass from properties).
     if product.ObjectType == "MassPoint":
diff --git a/src/ada/cadit/ifc/read/reader_utils.py b/src/ada/cadit/ifc/read/reader_utils.py
index f69590f02..f92abe19e 100644
--- a/src/ada/cadit/ifc/read/reader_utils.py
+++ b/src/ada/cadit/ifc/read/reader_utils.py
@@ -18,7 +18,11 @@
 def open_ifc(ifc_file_path: Union[str, pathlib.Path, StringIO]):
     if type(ifc_file_path) is StringIO:
         return ifcopenshell.file.from_string(str(ifc_file_path.read()))
-    return ifcopenshell.open(str(ifc_file_path))
+    # Transparently inflate a gzip-compressed IFC shipped under a plain .ifc name (see
+    # ada.cadit.ifc.store.open_ifc_file).
+    from ada.cadit.ifc.store import open_ifc_file
+
+    return open_ifc_file(ifc_file_path)
 
 
 def get_ifc_property_sets(ifc_elem) -> dict:
@@ -141,6 +145,14 @@ def get_org(f, org_id):
 def add_to_assembly(assembly: Assembly, obj, ifc_parent, elements2part):
     from ada import Pipe
 
+    if ifc_parent is None:
+        # IFC4x3 alignment-hosted products (e.g. a signal on an
+        # IfcLinearPlacement) may have no spatial containment relation
+        # at all — attach to the assembly root instead of crashing.
+        logger.info(f'No spatial parent for {type(obj)} "{obj.name}". Adding to Assembly root')
+        assembly.add_shape(obj)
+        return
+
     pp_name = ifc_parent.Name
 
     if pp_name is None:
diff --git a/src/ada/cadit/ifc/store.py b/src/ada/cadit/ifc/store.py
index 948918127..827f60769 100644
--- a/src/ada/cadit/ifc/store.py
+++ b/src/ada/cadit/ifc/store.py
@@ -10,8 +10,9 @@
 
 from ada.base.changes import ChangeAction
 from ada.base.types import GeomRepr
+from ada.base.units import Units
 from ada.cadit.ifc.units_conversion import convert_file_length_units
-from ada.cadit.ifc.utils import assembly_to_ifc_file, default_settings, get_unit_type
+from ada.cadit.ifc.utils import assembly_to_ifc_file, calculate_unit_scale, default_settings
 from ada.cadit.ifc.write.write_user import create_owner_history_from_user
 from ada.config import Config, logger
 
@@ -19,6 +20,22 @@
 
     from ada import Assembly, Section, User
     from ada.cadit.ifc.read.read_ifc import IfcReader
+
+
+def open_ifc_file(ifc_file_path: str | os.PathLike) -> ifcopenshell.file:
+    """Open an IFC file, transparently decompressing a gzip-compressed model. Some exporters and
+    servers ship a gzip'd IFC under a plain ``.ifc`` name; ``ifcopenshell.open`` then fails with
+    'Unable to parse IFC SPF header'. Detect the gzip magic (0x1f 0x8b) and load the inflated SPF
+    text via ``from_string`` instead."""
+    import gzip
+
+    path = str(ifc_file_path)
+    with open(path, "rb") as fh:
+        is_gzip = fh.read(2) == b"\x1f\x8b"
+    if is_gzip:
+        with gzip.open(path, "rt", encoding="utf-8", errors="replace") as fh:
+            return ifcopenshell.file.from_string(fh.read())
+    return ifcopenshell.open(path)
     from ada.cadit.ifc.write.write_ifc import IfcWriter
 
 
@@ -67,7 +84,7 @@ def __post_init__(self):
             if self.ifc_file_path is not None:
                 self.ifc_file_path = pathlib.Path(self.ifc_file_path)
                 if self.ifc_file_path.exists():
-                    self.f = ifcopenshell.open(str(self.ifc_file_path))
+                    self.f = open_ifc_file(self.ifc_file_path)
             elif self.assembly is not None:
                 self.f = assembly_to_ifc_file(self.assembly)
                 self.add_standard_contexts()
@@ -148,7 +165,28 @@ def get_context(self, context_id):
 
         matches = [x for x in contexts if x.ContextIdentifier == context_id and x.ContextType == "Model"]
         if len(matches) == 0:
-            raise ValueError(f'0 IfcGeometry Subcontexts found with "{context_id=}"')
+            # Imported files don't always carry the standard subcontexts (e.g.
+            # the buildingSMART type-library samples have '3D'/'2D' model+plan
+            # contexts and nothing else). Writing into such a store must not
+            # fail — create the missing subcontext under the model context,
+            # exactly as add_standard_contexts would for a fresh file.
+            model_ctxs = [
+                x
+                for x in contexts
+                if not x.is_a("IfcGeometricRepresentationSubContext") and (x.ContextType or "").upper() == "MODEL"
+            ]
+            if not model_ctxs:
+                raise ValueError(f'0 IfcGeometry Subcontexts found with "{context_id=}"')
+            target_view = {"Axis": "GRAPH_VIEW"}.get(context_id, "MODEL_VIEW")
+            sub = self.f.create_entity(
+                "IfcGeometricRepresentationSubContext",
+                ContextIdentifier=context_id,
+                ContextType="Model",
+                ParentContext=model_ctxs[0],
+                TargetView=target_view,
+            )
+            self._context_cache[context_id] = sub
+            return sub
         if len(matches) > 1:
             raise ValueError(f'Multiple Subcontexts found with "{context_id=}"')
 
@@ -251,9 +289,14 @@ def load_ifc_content_from_file(
         if projects and getattr(projects[0], "GlobalId", None):
             self.assembly._guid = projects[0].GlobalId
 
-        unit_type = get_unit_type(self.f)
-
-        if unit_type != self.assembly.units:
+        # Compare raw length scales rather than mapping to the Units
+        # enum — files in inches/feet (conversion-based units, e.g. the
+        # buildingSMART samples at scale 0.0254) have no enum member but
+        # convert_file_length_units handles them fine via ifcopenshell's
+        # unit entities.
+        unit_scale = calculate_unit_scale(self.f)  # meters per file length unit
+        target_scale = 0.001 if self.assembly.units == Units.MM else 1.0
+        if abs(unit_scale - target_scale) > 1e-9 * target_scale:
             self.f = convert_file_length_units(self.f, self.assembly.units)
 
         if elements2part is None:
@@ -431,7 +474,7 @@ def ifc_obj_from_ifc_file(ifc_file: str | os.PathLike) -> ifcopenshell.file:
         ifc_file = pathlib.Path(ifc_file).resolve().absolute()
         if ifc_file.exists() is False:
             raise FileNotFoundError(f'Unable to find "{ifc_file}"')
-        return ifcopenshell.open(str(ifc_file))
+        return open_ifc_file(ifc_file)
 
     @staticmethod
     def copy_ifc_obj(ifc_file: ifcopenshell.file) -> ifcopenshell.file:
diff --git a/src/ada/cadit/ifc/write/geom/surfaces.py b/src/ada/cadit/ifc/write/geom/surfaces.py
index 855d0c16a..c2a7ea979 100644
--- a/src/ada/cadit/ifc/write/geom/surfaces.py
+++ b/src/ada/cadit/ifc/write/geom/surfaces.py
@@ -179,6 +179,27 @@ def polygonal_face_set(pfs: geo_su.PolygonalFaceSet, f: ifcopenshell.file) -> if
     )
 
 
+def triangulated_face_set(tfs: geo_su.TriangulatedFaceSet, f: ifcopenshell.file) -> ifcopenshell.entity_instance:
+    """Converts a TriangulatedFaceSet back to an IfcTriangulatedFaceSet.
+
+    ``indices`` is stored flat and 1-based (the reader flattens CoordIndex);
+    IFC wants triples. A kernel build would be both lossy and unsupported for
+    a bare triangle mesh — this is the 1:1 emit."""
+    coordinates = f.create_entity(
+        "IfcCartesianPointList3D",
+        CoordList=[(float(p.x), float(p.y), float(p.z)) for p in tfs.coordinates],
+    )
+    idx = [int(i) for i in tfs.indices]
+    coord_index = [tuple(idx[i : i + 3]) for i in range(0, len(idx), 3)]
+    normals = [(float(n.x), float(n.y), float(n.z)) for n in tfs.normals] or None
+    return f.create_entity(
+        "IfcTriangulatedFaceSet",
+        Coordinates=coordinates,
+        Normals=normals,
+        CoordIndex=coord_index,
+    )
+
+
 def create_closed_shell(cs: geo_su.ClosedShell, f: ifcopenshell.file) -> ifcopenshell.entity_instance:
     """Converts a ClosedShell to an IFC representation.
 
diff --git a/src/ada/cadit/ifc/write/native_ifc_writer.py b/src/ada/cadit/ifc/write/native_ifc_writer.py
new file mode 100644
index 000000000..5b7453a10
--- /dev/null
+++ b/src/ada/cadit/ifc/write/native_ifc_writer.py
@@ -0,0 +1,61 @@
+"""Native IFC writer: emit via adacpp's ``blobs_to_ifc`` (C++ ifc_emit), no ifcopenshell/OCC.
+
+Feeds each shape's NGEOM blob + out-of-band record (colour, world transforms, spatial paths) to the
+native emitter, which decodes the blob and writes the analytic IFC solid (IfcExtrudedAreaSolid /
+IfcSweptDiskSolid / IfcBooleanResult / IfcAdvancedBrep / ...) + IfcStyledItem + the spatial tree — the
+inverse of the native IFC reader, so a native round-trip keeps the CSG analytic (never tessellated).
+
+Only shapes that carry an NGEOM blob (lazy ShapeProxy) are emittable; others are skipped (the caller
+falls back to the ifcopenshell writer). Best paired with ``from_ifc(reader="native")``.
+"""
+
+from __future__ import annotations
+
+import pathlib
+
+
+def native_ifc_writer_available() -> bool:
+    """True if adacpp's native NGEOM-blobs->IFC emitter is importable."""
+    try:
+        import adacpp  # noqa: F401
+
+        return hasattr(adacpp.cad, "blobs_to_ifc")
+    except Exception:
+        return False
+
+
+def native_write_ifc(assembly, out_path: str | pathlib.Path, schema: str = "IFC4X3_ADD2") -> dict:
+    """Write ``assembly`` to an IFC file natively. Returns the losslessness audit dict
+    (solids_in/out, faces_in/out/dropped, drop_reasons). Raises if no shape carries an NGEOM blob."""
+    import adacpp
+    import numpy as np
+
+    from ada.api.shapes import ShapeProxy
+    from ada.base.units import Units
+
+    blobs: list[bytes] = []
+    colors: list[list[float]] = []
+    transforms: list[list[list[float]]] = []
+    paths: list[list[list[tuple]]] = []
+
+    for shp in assembly.get_all_physical_objects():
+        if not isinstance(shp, ShapeProxy):
+            continue  # native writer needs the raw NGEOM blob (lazy store)
+        blob = shp.ngeom_blob()
+        if blob is None:
+            continue
+        rec = shp._shape_store.record(shp._store_index)
+        blobs.append(bytes(blob))
+        col = rec.color if rec.color is not None else shp.color
+        colors.append([float(c) for c in col][:4] if col is not None else [0.0, 0.0, 0.0, -1.0])
+        # ShapeRecord transforms are 4x4 (column-major-decoded); flatten back to 16-float column-major.
+        mats = rec.transforms or []
+        transforms.append([list(np.asarray(m, dtype="float32").flatten(order="F")) for m in mats])
+        ip = rec.instance_paths or []
+        paths.append([[(int(r), str(nm)) for (r, nm) in lvl] for lvl in ip])
+
+    if not blobs:
+        raise RuntimeError("native IFC writer: no shape carries an NGEOM blob (need lazy ShapeProxy shapes)")
+
+    unit_scale = 0.001 if assembly.units == Units.MM else 1.0
+    return adacpp.cad.blobs_to_ifc(blobs, colors, transforms, paths, str(out_path), schema, unit_scale)
diff --git a/src/ada/cadit/ifc/write/stream_ifc.py b/src/ada/cadit/ifc/write/stream_ifc.py
index 7ea6ce87d..c60d18b87 100644
--- a/src/ada/cadit/ifc/write/stream_ifc.py
+++ b/src/ada/cadit/ifc/write/stream_ifc.py
@@ -377,12 +377,22 @@ def _emit(pl) -> None:
         else:
             # Part.iter_objects_from_fem builds one element's plate(s) at a time; being
             # ``detached`` they carry no material back-ref and free as soon as _emit drops
-            # them, so peak memory stays bounded.
+            # them, so peak memory stays bounded. Curved plates (the SURFACE/PANEL
+            # strategies' analytic cylinder/B-spline patches) can't be expressed by the
+            # hand-authored flat-plate text — they buffer (tens of objects by construction)
+            # and emit as B-rep products after the flat stream, since the B-rep emitter
+            # must own the id counter while it runs.
+            from ada import PlateCurved
+
+            curved_pending: list = []  # (owning part guid, PlateCurved)
             for part, n_shells in fused:
                 cnt = 0
                 for pl in part.iter_objects_from_fem(
                     beams=False, plates=True, detached=True, mat_cache=mat_cache, merge_strategy=merge_strategy
                 ):
+                    if isinstance(pl, PlateCurved):
+                        curved_pending.append((part.guid, pl))
+                        continue
                     _emit(pl)
                     cnt += 1
                     if cnt % 2000 == 0:
@@ -396,6 +406,42 @@ def _emit(pl) -> None:
                 if progress_callback is not None:
                     progress_callback(n_shells, n_shells)
 
+            if curved_pending:
+                from ada.cadit.step.write.stream_step_to_ifc import _IfcBrepEmitter
+                from ada.geom.surfaces import OpenShell, ShellBasedSurfaceModel
+
+                be = _IfcBrepEmitter(emitter.nid - 1)
+                be._flush = lambda buf: (out.write("\n".join(buf) + "\n"), buf.clear())
+                ident_place = be._emit(
+                    lines, f"IfcLocalPlacement($,#{be._axis2(lines, (0, 0, 0), (0, 0, 1), (1, 0, 0))})"
+                )
+                for part_guid, pl in curved_pending:
+                    try:
+                        shell = ShellBasedSurfaceModel(sbsm_boundary=[OpenShell(cfs_faces=[pl.geom.geometry])])
+                        brep, rep_type = be.solid(lines, shell)
+                        if brep is None:
+                            skipped += 1
+                            continue
+                        rep = be._emit(lines, f"IfcShapeRepresentation(#{body_ctx_id},'Body','{rep_type}',(#{brep}))")
+                        pds = be._emit(lines, f"IfcProductDefinitionShape($,$,(#{rep}))")
+                        pid = be._emit(
+                            lines,
+                            f"IfcPlate('{create_guid()}',#{owner_id},{_spf_str(pl.name)},$,$,"
+                            f"#{ident_place},#{pds},$,$)",
+                        )
+                        total += 1
+                        _record_spatial(part_guid, pid)
+                        mat = getattr(pl, "material", None)
+                        if mat is not None:
+                            _record_material(mat.guid, pid)
+                    except Exception as exc:  # noqa: BLE001 — one bad plate shouldn't sink the file
+                        skipped += 1
+                        logger.warning(f"streaming IFC: skipped curved plate {getattr(pl, 'name', '?')!r}: {exc}")
+                if lines:
+                    out.write("\n".join(lines) + "\n")
+                    lines.clear()
+                emitter.nid = be.nid + 1  # continue the trailing-relationship ids past the B-rep entities
+
         # ── trailing relationships (hand-emitted from recorded ids) ──
         nid = emitter.nid
 
diff --git a/src/ada/cadit/ifc/write/write_shapes.py b/src/ada/cadit/ifc/write/write_shapes.py
index 2f4178df6..19172b063 100644
--- a/src/ada/cadit/ifc/write/write_shapes.py
+++ b/src/ada/cadit/ifc/write/write_shapes.py
@@ -3,6 +3,7 @@
 from typing import TYPE_CHECKING
 
 import ada.geom.curves as geo_cu
+import ada.geom.solids as geo_so
 import ada.geom.surfaces as geo_su
 from ada import (
     Boolean,
@@ -19,11 +20,13 @@
 from ada.base.units import Units
 from ada.cadit.ifc.utils import add_colour, create_local_placement, tesselate_shape
 from ada.cadit.ifc.write.geom.curves import indexed_poly_curve, poly_line
+from ada.cadit.ifc.write.geom.solids import faceted_brep
 from ada.cadit.ifc.write.geom.surfaces import (
     advanced_face,
     create_closed_shell,
     create_half_space_geom,
     curve_bounded_plane,
+    triangulated_face_set,
 )
 from ada.cadit.ifc.write.shapes.box import generate_ifc_box_geom
 from ada.cadit.ifc.write.shapes.cone import generate_ifc_cone_geom
@@ -195,6 +198,14 @@ def generate_parametric_solid(shape: Shape | PrimSphere, f):
         geo_su.AdvancedFace: advanced_face,
         geo_su.CurveBoundedPlane: curve_bounded_plane,
         geo_su.ClosedShell: create_closed_shell,
+        # Bare CONNECTED_FACE_SET: the native NGEOM reader's B-rep root form when the
+        # closedness promotion couldn't verify the shell (e.g. edges split differently
+        # across adjacent faces). Same face-set emit as ClosedShell.
+        geo_su.ConnectedFaceSet: create_closed_shell,
+        # Mesh-native bodies (IFC tessellated imports): 1:1 emit — the
+        # tessellation fallback would need a kernel build these kinds don't have.
+        geo_su.TriangulatedFaceSet: triangulated_face_set,
+        geo_so.FacetedBrep: faceted_brep,
         # Curve-only bodies (SAT wire bodies import as bare curve geometry):
         # emitted as a Curve3D representation instead of failing solid_occ().
         geo_cu.Edge: _edge_as_polyline,
@@ -204,7 +215,9 @@ def generate_parametric_solid(shape: Shape | PrimSphere, f):
         BoolHalfSpace: create_half_space_geom,
     }
 
-    if type(shape) is Shape:
+    from ada.api.shapes import ShapeProxy
+
+    if type(shape) in (Shape, ShapeProxy):
         param_geo = shape.geom.geometry
     else:
         param_geo = shape
@@ -226,6 +239,8 @@ def generate_parametric_solid(shape: Shape | PrimSphere, f):
         geo_su.AdvancedFace: "AdvancedSurface",
         geo_su.CurveBoundedPlane: "AdvancedSurface",
         geo_su.ClosedShell: "AdvancedSurface",
+        geo_su.TriangulatedFaceSet: "Tessellation",
+        geo_so.FacetedBrep: "Brep",
         geo_cu.Edge: "Curve3D",
         geo_cu.IndexedPolyCurve: "Curve3D",
         geo_cu.PolyLine: "Curve3D",
diff --git a/src/ada/cadit/ngeom/_alignment_sweep.py b/src/ada/cadit/ngeom/_alignment_sweep.py
index 012f60b4b..aa669947f 100644
--- a/src/ada/cadit/ngeom/_alignment_sweep.py
+++ b/src/ada/cadit/ngeom/_alignment_sweep.py
@@ -54,8 +54,26 @@ def _fresnel(t: float) -> tuple[float, float]:
     return S, C
 
 
-def _parent_eval(curve, p: float) -> tuple[np.ndarray, np.ndarray]:
-    """Parent curve at arc length ``p`` (its own frame) -> (point2d, unit tangent2d)."""
+def _cosine_spiral_theta(curve: geo_cu.CosineSpiral, L: float, s: np.ndarray) -> np.ndarray:
+    """Heading angle theta(s) = s/A0 + (L/(pi*A1))*sin(pi*s/L) for an IfcCosineSpiral (A1 =
+    CosineTerm, A0 = ConstantTerm, L = the containing segment length). Validated to ~1e-7 vs the
+    ifcopenshell oracle on the segmented-reference-curve fixture."""
+    A1 = float(curve.cosine_term)
+    A0 = float(curve.constant_term) if curve.constant_term else None
+    th = np.zeros_like(s, dtype=float)
+    if A0:
+        th = th + s / A0
+    if L > 0.0 and A1 != 0.0:
+        th = th + (L / (math.pi * A1)) * np.sin(math.pi * s / L)
+    return th
+
+
+def _parent_eval(curve, p: float, seg_length: float | None = None) -> tuple[np.ndarray, np.ndarray]:
+    """Parent curve at arc length ``p`` (its own frame) -> (point2d, unit tangent2d).
+
+    ``seg_length`` is the length of the containing CurveSegment — required by transcendental
+    spirals (IfcCosineSpiral) whose heading uses the total length L; ignored by the closed-form
+    parents (line/arc/clothoid)."""
     if isinstance(curve, geo_cu.Line):
         # IfcLine parents in alignments are unit-magnitude direction at the origin.
         return np.array([p, 0.0]), np.array([1.0, 0.0])
@@ -74,6 +92,18 @@ def _parent_eval(curve, p: float) -> tuple[np.ndarray, np.ndarray]:
         ph = math.pi * t * t / 2.0
         tg = np.array([math.cos(ph), sgn * math.sin(ph)])
         return (np.array([scale * C, sgn * scale * S]), tg / np.hypot(*tg))
+    if isinstance(curve, geo_cu.CosineSpiral):
+        # No closed form: integrate (cos theta, sin theta) from 0 to p (theta closed-form).
+        L = abs(float(seg_length)) if seg_length else 0.0
+        n = max(32, int(abs(p) / 0.1) + 1)
+        xs = np.linspace(0.0, p, n)
+        th = _cosine_spiral_theta(curve, L, xs)
+        dx = np.diff(xs)
+        cx, cy = np.cos(th), np.sin(th)
+        px = float(np.sum((cx[:-1] + cx[1:]) * 0.5 * dx))
+        py = float(np.sum((cy[:-1] + cy[1:]) * 0.5 * dx))
+        thp = float(_cosine_spiral_theta(curve, L, np.array([p]))[0])
+        return np.array([px, py]), np.array([math.cos(thp), math.sin(thp)])
     raise NotImplementedError(f"alignment parent curve {type(curve).__name__}")
 
 
@@ -93,8 +123,8 @@ def _seg_eval(seg: geo_cu.CurveSegment, local_len: float) -> tuple[np.ndarray, n
     length = float(seg.segment_length)
     sgn = 1.0 if length >= 0 else -1.0
     p = float(seg.segment_start) + sgn * local_len
-    P, T = _parent_eval(seg.parent_curve, p)
-    P0, T0 = _parent_eval(seg.parent_curve, float(seg.segment_start))
+    P, T = _parent_eval(seg.parent_curve, p, seg_length=length)
+    P0, T0 = _parent_eval(seg.parent_curve, float(seg.segment_start), seg_length=length)
     if sgn < 0:
         T, T0 = -T, -T0
     origin = np.asarray(seg.location, dtype=float)[:2]
@@ -108,7 +138,11 @@ def _seg_eval(seg: geo_cu.CurveSegment, local_len: float) -> tuple[np.ndarray, n
 
 def _curve_segments(curve) -> list[geo_cu.CurveSegment]:
     """The CurveSegment list of a CompositeCurve / GradientCurve base (skip zero-length terminators)."""
-    segs = curve.segments if isinstance(curve, (geo_cu.CompositeCurve, geo_cu.GradientCurve)) else curve
+    segs = (
+        curve.segments
+        if isinstance(curve, (geo_cu.CompositeCurve, geo_cu.GradientCurve, geo_cu.SegmentedReferenceCurve))
+        else curve
+    )
     return [s for s in segs if isinstance(s, geo_cu.CurveSegment) and abs(float(s.segment_length)) > 1e-9]
 
 
@@ -127,6 +161,177 @@ def _sample_planar(segs: list[geo_cu.CurveSegment], n_per: int) -> tuple[np.ndar
     return np.array(s_vals), np.array(pts)
 
 
+def gradient_curve_points_with_s(directrix: geo_cu.GradientCurve, n_per: int = 300) -> tuple[np.ndarray, np.ndarray]:
+    """(arc length s, 3D polyline) of a GradientCurve: horizontal alignment (base_curve, sampled
+    per segment) with the vertical gradient's height interpolated over arc length."""
+    hsegs = _curve_segments(directrix.base_curve)
+    s, hxy = _sample_planar(hsegs, n_per)  # (s,), (s,2)
+
+    # vertical gradient -> z(s) by interpolation on its (distance, height) samples
+    vsegs = _curve_segments(directrix)
+    if vsegs:
+        _, vdh = _sample_planar(vsegs, max(n_per, 50))
+        order = np.argsort(vdh[:, 0])
+        z = np.interp(s, vdh[order, 0], vdh[order, 1])
+    else:
+        z = np.zeros_like(s)
+
+    return s, np.column_stack([hxy[:, 0], hxy[:, 1], z])
+
+
+def gradient_curve_points(directrix: geo_cu.GradientCurve, n_per: int = 300) -> np.ndarray:
+    """Sampled 3D polyline of a GradientCurve (see gradient_curve_points_with_s). Clothoid
+    segments have no analytic B-rep form, so exports/sweeps consume this sampling."""
+    return gradient_curve_points_with_s(directrix, n_per)[1]
+
+
+def composite_curve_points(curve: geo_cu.CompositeCurve, n_per: int = 300) -> np.ndarray:
+    """Sampled 3D polyline of a horizontal CompositeCurve (z = 0)."""
+    _, xy = _sample_planar(_curve_segments(curve), n_per)
+    return np.column_stack([xy[:, 0], xy[:, 1], np.zeros(len(xy))])
+
+
+def _cant_offset(seg: geo_cu.CurveSegment, s_rel: np.ndarray) -> np.ndarray | None:
+    """Vertical superelevation offset of one IfcSegmentedReferenceCurve cant segment at base-curve
+    arc lengths ``s_rel`` measured from the segment start. For a cosine-spiral cant this is the
+    closed form ``e0 + (L^2/CosineTerm)*(cos(pi*s/L) - 1)`` where e0 is the vertical component of
+    the 3D segment placement (validated to machine precision vs the ifcopenshell oracle). Returns
+    ``None`` for parent kinds not handled analytically (caller keeps the base-curve z)."""
+    L = abs(float(seg.segment_length))
+    loc = np.asarray(seg.location, dtype=float)
+    e0 = float(loc[1]) if loc.size >= 2 else 0.0  # local-y of the 3D placement -> vertical offset
+    parent = seg.parent_curve
+    if isinstance(parent, geo_cu.CosineSpiral) and L > 0.0 and float(parent.cosine_term) != 0.0:
+        amp = L * L / float(parent.cosine_term)
+        return e0 + amp * (np.cos(math.pi * s_rel / L) - 1.0)
+    if isinstance(parent, geo_cu.Line):
+        # A line-parent cant segment is a constant superelevation (no transition).
+        return np.full_like(s_rel, e0)
+    return None
+
+
+def segmented_reference_curve_points(curve: geo_cu.SegmentedReferenceCurve, n_per: int = 300) -> np.ndarray:
+    """Sampled 3D polyline of an IfcSegmentedReferenceCurve: the base GradientCurve's (x,y,z) with
+    the cant segments' vertical offset added. The horizontal geometry is the base curve's; only z
+    is displaced by the superelevation."""
+    base = curve.base_curve
+    if isinstance(base, geo_cu.GradientCurve):
+        s, pts = gradient_curve_points_with_s(base, n_per)
+    elif isinstance(base, geo_cu.CompositeCurve):
+        pts = composite_curve_points(base, n_per)
+        s, _ = _sample_planar(_curve_segments(base), n_per)
+    else:
+        raise NotImplementedError(f"segmented-reference base {type(base).__name__}")
+
+    dz = np.zeros(len(s))
+    for seg in _curve_segments(curve):
+        s0 = float(seg.segment_start)
+        L = abs(float(seg.segment_length))
+        mask = (s >= s0 - 1e-9) & (s <= s0 + L + 1e-9)
+        off = _cant_offset(seg, s[mask] - s0)
+        if off is not None:
+            dz[mask] = off
+    pts = pts.copy()
+    pts[:, 2] += dz
+    return pts
+
+
+def curve_to_polyline(curve, n_per: int = 300) -> np.ndarray:
+    """Sample any supported alignment curve container to a 3D polyline (N,3). Dispatches over
+    SegmentedReferenceCurve / GradientCurve / CompositeCurve / a bare CurveSegment."""
+    if isinstance(curve, geo_cu.SegmentedReferenceCurve):
+        return segmented_reference_curve_points(curve, n_per)
+    if isinstance(curve, geo_cu.GradientCurve):
+        return gradient_curve_points(curve, n_per)
+    if isinstance(curve, geo_cu.CompositeCurve):
+        return composite_curve_points(curve, n_per)
+    if isinstance(curve, geo_cu.CurveSegment):
+        _, xy = _sample_planar([curve], n_per)
+        return np.column_stack([xy[:, 0], xy[:, 1], np.zeros(len(xy))])
+    raise NotImplementedError(f"alignment curve container {type(curve).__name__}")
+
+
+def _directrix_points_with_s(curve, n_per: int) -> tuple[np.ndarray, np.ndarray]:
+    """(arc length s, 3D points) for a sweep directrix — GradientCurve / SegmentedReferenceCurve
+    (via its base) / CompositeCurve. ``s`` is measured along the base curve, matching the distance
+    coordinate the IfcSectionedSolidHorizontal cross-section positions are given in."""
+    if isinstance(curve, geo_cu.SegmentedReferenceCurve):
+        curve = curve.base_curve
+    if isinstance(curve, geo_cu.GradientCurve):
+        return gradient_curve_points_with_s(curve, n_per)
+    if isinstance(curve, geo_cu.CompositeCurve):
+        s, xy = _sample_planar(_curve_segments(curve), n_per)
+        return s, np.column_stack([xy[:, 0], xy[:, 1], np.zeros(len(xy))])
+    raise NotImplementedError(f"sweep directrix {type(curve).__name__}")
+
+
+def sectioned_solid_horizontal_mesh(
+    directrix,
+    profile_xy,
+    start_dist: float,
+    end_dist: float,
+    fixed_ref=(0.0, 0.0, 1.0),
+    n_stations: int = 400,
+) -> tuple[np.ndarray, np.ndarray]:
+    """Triangulated swept solid for an IfcSectionedSolidHorizontal with a CONSTANT cross-section.
+
+    ``profile_xy`` is the (M,2) closed outline (no repeated closing vertex). The profile is swept
+    along ``directrix`` over arc length ``[start_dist, end_dist]`` with fixed-reference framing
+    (no Frenet roll): at each station the profile's local x maps to the lateral axis and local y to
+    the fixed-reference "up" (validated exact against the ifcopenshell oracle bbox). Returns
+    ``(coords (K,3), tri_indices (T,3) 0-based)`` — a closed shell (side quads + fan end caps),
+    wound outward (signed-volume checked)."""
+    prof = np.asarray(profile_xy, dtype=float)[:, :2]
+    if len(prof) >= 2 and np.allclose(prof[0], prof[-1]):
+        prof = prof[:-1]  # drop the repeated closing vertex
+    m = len(prof)
+    if m < 3:
+        raise NotImplementedError("sectioned solid profile has < 3 outline vertices")
+
+    s, pts = _directrix_points_with_s(directrix, n_per=max(200, n_stations // 2))
+    lo, hi = min(start_dist, end_dist), max(start_dist, end_dist)
+    stations = np.linspace(lo, hi, n_stations)
+    centers = np.column_stack([np.interp(stations, s, pts[:, k]) for k in range(3)])
+
+    F = np.asarray(fixed_ref, dtype=float)
+    F = F / np.linalg.norm(F)
+    tangent = np.gradient(centers, axis=0)
+    tangent /= np.linalg.norm(tangent, axis=1, keepdims=True)
+    lateral = np.cross(tangent, F)
+    lateral /= np.linalg.norm(lateral, axis=1, keepdims=True)
+    up = np.cross(lateral, tangent)
+    up /= np.linalg.norm(up, axis=1, keepdims=True)
+
+    n = len(centers)
+    rings = (
+        centers[:, None, :]
+        + prof[None, :, 0, None] * lateral[:, None, :]  # profile x -> lateral
+        + prof[None, :, 1, None] * up[:, None, :]  # profile y -> fixed-reference up
+    )  # (n, m, 3)
+    coords = rings.reshape(-1, 3)
+
+    faces = []
+    for i in range(n - 1):
+        for j in range(m):
+            a, b = i * m + j, i * m + (j + 1) % m
+            c, d = (i + 1) * m + j, (i + 1) * m + (j + 1) % m
+            faces.append((a, b, d))
+            faces.append((a, d, c))
+    base = (n - 1) * m
+    for j in range(1, m - 1):  # convex fan end caps
+        faces.append((0, j + 1, j))
+        faces.append((base, base + j, base + j + 1))
+    tris = np.asarray(faces, dtype=np.int64)
+
+    # Orient outward: a closed shell with inward winding tessellates dark. Flip all triangles when
+    # the signed volume (divergence theorem over the triangles) is negative.
+    v0, v1, v2 = coords[tris[:, 0]], coords[tris[:, 1]], coords[tris[:, 2]]
+    signed_vol = float(np.einsum("ij,ij->i", v0, np.cross(v1, v2)).sum()) / 6.0
+    if signed_vol < 0.0:
+        tris = tris[:, ::-1]
+    return coords, tris
+
+
 def directrix_frames(
     solid: geo_so.FixedReferenceSweptAreaSolid, n_per: int = 300
 ) -> tuple[np.ndarray, np.ndarray, np.ndarray]:
@@ -137,16 +342,7 @@ def directrix_frames(
     if not isinstance(directrix, geo_cu.GradientCurve):
         raise NotImplementedError(f"directrix {type(directrix).__name__} (only GradientCurve supported)")
 
-    hsegs = _curve_segments(directrix.base_curve)
-    s, hxy = _sample_planar(hsegs, n_per)  # (s,), (s,2)
-
-    # vertical gradient -> z(s) by interpolation on its (distance, height) samples
-    vsegs = _curve_segments(directrix)
-    _, vdh = _sample_planar(vsegs, max(n_per, 50))
-    order = np.argsort(vdh[:, 0])
-    z = np.interp(s, vdh[order, 0], vdh[order, 1])
-
-    pts = np.column_stack([hxy[:, 0], hxy[:, 1], z])
+    pts = gradient_curve_points(directrix, n_per)
 
     F = np.asarray(solid.fixed_reference, dtype=float)
     F = F / np.linalg.norm(F)
diff --git a/src/ada/cadit/ngeom/deserialize.py b/src/ada/cadit/ngeom/deserialize.py
index 34f12a955..6cb7a5264 100644
--- a/src/ada/cadit/ngeom/deserialize.py
+++ b/src/ada/cadit/ngeom/deserialize.py
@@ -10,8 +10,10 @@
 emits one NGEOM root per solid (a B-rep ``ConnectedFaceSet``), and this rebuilds each as an
 ``ada.geom`` geometry. Also the round-trip oracle for ``serialize_geometries``.
 
-Swept/CSG solids (extruded/revolved/boolean/sphere primitives) are serialized as synthesized profile
-faces; the native STEP path never emits them (STEP solids are explicit B-reps), so those tags raise.
+Swept/CSG solids (extruded/revolved/boolean/sphere — tags 50-53) are serialized with a synthesized
+profile FACE; they decode back to the ada.geom solid (the profile is rebuilt from the face's local-XY
+boundary loops). Only the baked-frame FixedReferenceSweptAreaSolid (tag 54) can't be inverted — its
+directrix is gone — so it raises (hydrate that via the adacpp tessellator instead).
 """
 
 from __future__ import annotations
@@ -35,6 +37,13 @@
 _CIRCLE, _ELLIPSE, _BSPLINE_CURVE, _TRIMMED_CURVE = 20, 21, 22, 24
 _PLANE, _CYLINDER, _CONE, _SPHERE, _TORUS, _BSPLINE_SURFACE = 40, 41, 42, 43, 44, 45
 _SURF_LIN_EXTRUSION, _SURF_REVOLUTION = 46, 47
+_EXTRUDED_AREA_SOLID, _REVOLVED_AREA_SOLID, _BOOLEAN_RESULT, _SPHERE_SOLID, _FIXED_REF_SWEPT_SOLID = (
+    50,
+    51,
+    52,
+    53,
+    54,
+)
 _EDGE_CURVE, _ORIENTED_EDGE, _EDGE_LOOP, _POLY_LOOP, _FACE_BOUND, _FACE_SURFACE, _CONNECTED_FACE_SET = (
     60,
     61,
@@ -275,6 +284,110 @@ def _connected_face_set(self, c: _Cur):
         n = c.i32()
         return su.ConnectedFaceSet([self.get(i) for i in c.i32a(n)])
 
+    # --- swept / CSG solids (tags 50-54) ---
+    @staticmethod
+    def _loop_to_curve(loop) -> cu.IndexedPolyCurve:
+        """One profile boundary loop (in the profile's local XY plane, z=0) → a closed 2D
+        IndexedPolyCurve. A ``PolyLoop`` is a straight-edge polygon; an ``EdgeLoop`` restores a
+        Circle-backed oriented edge as an ``ArcLine`` (fillet round-trip), else a straight ``Edge``."""
+
+        def p2d(p) -> Point:
+            return Point(float(p[0]), float(p[1]))
+
+        if isinstance(loop, cu.PolyLoop):
+            pts = [p2d(p) for p in loop.polygon]
+            return cu.IndexedPolyCurve([cu.Edge(pts[i], pts[(i + 1) % len(pts)]) for i in range(len(pts))])
+
+        segs: list = []
+        for oe in loop.edge_list:
+            s, e = p2d(oe.start), p2d(oe.end)
+            geom = getattr(oe.edge_element, "edge_geometry", None)
+            if isinstance(geom, cu.Circle):
+                ctr = np.asarray(geom.position.location, dtype=float)[:2]
+                a = np.asarray(s, dtype=float) - ctr
+                b = np.asarray(e, dtype=float) - ctr
+                bis = a + b  # minor-arc midpoint direction (profile fillets are minor arcs)
+                if np.linalg.norm(bis) < 1e-12:  # half-circle: rotate `a` 90°
+                    bis = np.array([-a[1], a[0]])
+                mid = ctr + float(geom.radius) * bis / (np.linalg.norm(bis) or 1.0)
+                segs.append(cu.ArcLine(s, Point(float(mid[0]), float(mid[1])), e))
+            else:
+                segs.append(cu.Edge(s, e))
+        return cu.IndexedPolyCurve(segs)
+
+    def _profile_from_face(self, face) -> su.ArbitraryProfileDef:
+        """Rebuild the swept-area ProfileDef the encoder flattened into a planar FACE — outer bound
+        first, then any inner (void) bounds."""
+        bounds = list(getattr(face, "bounds", None) or [])
+        if not bounds:
+            raise NgeomDecodeError("swept solid profile face has no bounds")
+        return su.ArbitraryProfileDef(
+            profile_type=su.ProfileType.AREA,
+            outer_curve=self._loop_to_curve(bounds[0].bound),
+            inner_curves=[self._loop_to_curve(b.bound) for b in bounds[1:]],
+        )
+
+    def _extruded_area_solid(self, c: _Cur):
+        import ada.geom.solids as so
+
+        profile = self._profile_from_face(self.get(c.i32()))
+        position = self.get(c.i32())
+        direction = Direction(*c.v3())
+        depth = c.f64()
+        return so.ExtrudedAreaSolid(
+            swept_area=profile, position=position, depth=depth, extruded_direction=direction
+        )
+
+    def _revolved_area_solid(self, c: _Cur):
+        import math
+
+        import ada.geom.solids as so
+
+        profile = self._profile_from_face(self.get(c.i32()))
+        position = self.get(c.i32())
+        axis_local = self.get(c.i32())  # Axis1Placement in the position-LOCAL frame (encoder transform)
+        angle_rad = c.f64()
+        # Invert the encoder's world→local axis transform (serialize.revolved_area_solid): rebuild the
+        # position frame's rotation and map the local axis back to world. angle is stored in RADIANS;
+        # RevolvedAreaSolid.angle is DEGREES.
+        xdir = np.asarray(position.ref_direction if position.ref_direction is not None else (1, 0, 0), float)
+        zdir = np.asarray(position.axis if position.axis is not None else (0, 0, 1), float)
+        xdir = xdir / (np.linalg.norm(xdir) or 1.0)
+        zdir = zdir / (np.linalg.norm(zdir) or 1.0)
+        rot = np.column_stack([xdir, np.cross(zdir, xdir), zdir])  # local→world
+        origin = np.asarray(position.location, float)
+        loc_w = rot @ np.asarray(axis_local.location, float) + origin
+        dir_w = rot @ np.asarray(axis_local.axis, float)
+        axis = Axis1Placement(Point(*loc_w), Direction(*dir_w))
+        return so.RevolvedAreaSolid(
+            swept_area=profile, position=position, axis=axis, angle=math.degrees(angle_rad)
+        )
+
+    def _sphere_solid(self, c: _Cur):
+        import ada.geom.solids as so
+
+        pos = self.get(c.i32())
+        radius = c.f64()
+        return so.Sphere(center=Point(*pos.location), radius=radius)
+
+    def _boolean_result(self, c: _Cur):
+        from ada.geom.booleans import BooleanResult, BoolOpEnum
+
+        op = {0: BoolOpEnum.DIFFERENCE, 1: BoolOpEnum.UNION, 2: BoolOpEnum.INTERSECTION}[c.i32()]
+        first = self.get(c.i32())
+        second = self.get(c.i32())
+        return BooleanResult(first_operand=first, second_operand=second, operator=op)
+
+    def _fixed_ref_swept(self, c: _Cur):
+        # tag 54 bakes an alignment sweep into per-station (origin, dir_x, dir_y) frames — the
+        # analytic directrix is gone, so it cannot be rebuilt as an ada.geom
+        # FixedReferenceSweptAreaSolid. Consumers that need this must decode via adacpp (which
+        # tessellates the frames directly); flag it rather than return a wrong solid.
+        raise NgeomDecodeError(
+            "FIXED_REF_SWEPT_SOLID (tag 54) is a baked per-station frame field with no invertible "
+            "directrix — hydrate via the adacpp tessellator, not the Python deserializer"
+        )
+
 
 _DISPATCH = {
     _PLACEMENT3: _Decoder._placement3,
@@ -303,6 +416,11 @@ def _connected_face_set(self, c: _Cur):
     _FACE_BOUND: _Decoder._face_bound,
     _FACE_SURFACE: _Decoder._face_surface,
     _CONNECTED_FACE_SET: _Decoder._connected_face_set,
+    _EXTRUDED_AREA_SOLID: _Decoder._extruded_area_solid,
+    _REVOLVED_AREA_SOLID: _Decoder._revolved_area_solid,
+    _BOOLEAN_RESULT: _Decoder._boolean_result,
+    _SPHERE_SOLID: _Decoder._sphere_solid,
+    _FIXED_REF_SWEPT_SOLID: _Decoder._fixed_ref_swept,
 }
 
 
@@ -341,6 +459,81 @@ def deserialize_geometries(buffer: bytes) -> list[tuple[str, object]]:
     return out
 
 
+def connected_face_set_is_closed(cfs) -> bool:
+    """Topological closedness of a decoded ``ConnectedFaceSet``: every (undirected)
+    edge is used exactly twice across the faces' bounds — the manifold-closed-shell
+    condition. NGEOM tag 66 does not record whether the source shell was closed
+    (MANIFOLD_SOLID_BREP) or open (SHELL_BASED_SURFACE_MODEL), so the native read
+    paths use this to restore ``ClosedShell`` parity with the Python stream reader.
+
+    Edges are keyed by VALUE, not object identity — the C++ emitter re-encodes an
+    edge record per referencing face. Endpoints alone are ambiguous for arcs (two
+    halves of one circle share both endpoints), so the key adds the underlying
+    curve's signature and the oriented edge's parameter range. Two uses of the same
+    key = the edge is interior; any other count = a free or non-manifold edge. A
+    model whose adjacent faces don't encode identical edge values conservatively
+    reads as open."""
+    from collections import Counter
+
+    edge_use: Counter = Counter()
+    for f in getattr(cfs, "cfs_faces", []) or []:
+        for b in getattr(f, "bounds", []) or []:
+            loop = getattr(b, "bound", None)
+            edge_list = getattr(loop, "edge_list", None)
+            if edge_list is not None:
+                for oe in edge_list:
+                    e = oe.edge_element
+                    a, z = tuple(map(float, e.start)), tuple(map(float, e.end))
+                    ts, te = getattr(oe, "t_start", None), getattr(oe, "t_end", None)
+                    trange = None if ts is None else (min(ts, te), max(ts, te))
+                    key = ((a, z) if a <= z else (z, a), _edge_curve_sig(e.edge_geometry), trange)
+                    edge_use[key] += 1
+                continue
+            polygon = getattr(loop, "polygon", None)
+            if polygon is not None:
+                pts = [tuple(map(float, p)) for p in polygon]
+                for i, a in enumerate(pts):
+                    z = pts[(i + 1) % len(pts)]
+                    if a == z:
+                        continue
+                    edge_use[((a, z) if a <= z else (z, a), None, None)] += 1
+    if not edge_use:
+        return False
+    return all(n == 2 for n in edge_use.values())
+
+
+def _edge_curve_sig(geom):
+    """A value signature of an edge's underlying curve, discriminating edges whose
+    endpoints coincide (arcs of one circle, seam edges). Decoded floats from equal
+    source records are bit-identical, so exact tuples work as keys."""
+    if geom is None:
+        return None
+    tname = type(geom).__name__
+    pos = getattr(geom, "position", None)
+    loc = tuple(map(float, pos.location)) if pos is not None else None
+    if hasattr(geom, "radius"):  # Circle / cylinder-ish
+        return (tname, loc, float(geom.radius))
+    if hasattr(geom, "semi_axis1"):  # Ellipse
+        return (tname, loc, float(geom.semi_axis1), float(geom.semi_axis2))
+    cps = getattr(geom, "control_points_list", None)
+    if cps is not None:  # B-spline
+        return (tname, tuple(tuple(map(float, p)) for p in cps))
+    pnt = getattr(geom, "pnt", None)
+    if pnt is not None:  # Line
+        return (tname,)
+    return (tname, loc)
+
+
+def promote_closed_shell(geometry):
+    """Return ``ClosedShell(cfs_faces)`` when ``geometry`` is a bare, topologically
+    closed ``ConnectedFaceSet`` root; otherwise return it unchanged. Restores the
+    Python stream reader's root form (solid_geom / OCC build / STEP re-emit all key
+    on ClosedShell vs open shells) for natively-parsed B-reps."""
+    if type(geometry) is su.ConnectedFaceSet and connected_face_set_is_closed(geometry):
+        return su.ClosedShell(cfs_faces=geometry.cfs_faces)
+    return geometry
+
+
 def iter_connected_face_set_faces(buffer: bytes):
     """If the NGEOM buffer's single root is a ``ConnectedFaceSet`` (a B-rep solid's
     shell), return ``(rid, n_faces, face_gen)`` where ``face_gen`` yields each
diff --git a/src/ada/cadit/ngeom/serialize.py b/src/ada/cadit/ngeom/serialize.py
index 419d2a17e..a045de327 100644
--- a/src/ada/cadit/ngeom/serialize.py
+++ b/src/ada/cadit/ngeom/serialize.py
@@ -24,7 +24,17 @@
 def _sample_arc(start, mid, end, n: int = 24) -> list:
     """Sample a 3-point circular arc (IFC ArcLine) into an ordered polyline start->mid->end.
     Falls back to the 3 raw points if the points are (near-)collinear."""
-    p0, p1, p2 = np.asarray(start, float), np.asarray(mid, float), np.asarray(end, float)
+
+    # A profile's ArcLine (I/T/... section fillet) carries 2D points; np.cross of two 2D vectors is
+    # a SCALAR, and the circumcenter math below then does np.cross(vec, scalar) -> "array has zero
+    # dimension". Lift to 3D (z=0) so the cross products stay vector-valued.
+    def _v3(p):
+        p = np.asarray(p, float).ravel()
+        return p if p.shape[0] == 3 else np.array([p[0] if p.shape[0] > 0 else 0.0,
+                                                   p[1] if p.shape[0] > 1 else 0.0, 0.0])
+
+    start, mid, end = _v3(start), _v3(mid), _v3(end)
+    p0, p1, p2 = start, mid, end
     a, b = p1 - p0, p2 - p0
     n_vec = np.cross(a, b)
     nn = np.linalg.norm(n_vec)
@@ -60,6 +70,80 @@ def ang(p):
     return pts
 
 
+def _sample_trimmed_curve(tc, n: int = 24) -> list:
+    """Sample a TrimmedCurve — a conic arc (circle/ellipse) or a line segment — start->end into an
+    ordered point list. Conic trims are angles in radians (the reader normalized the file's plane
+    -angle unit); a Cartesian-point trim is projected back to its angle."""
+    import ada.geom.curves as _cu
+
+    basis = tc.basis_curve
+    if isinstance(basis, (_cu.Circle, _cu.Ellipse)):
+        pos = basis.position
+        loc = np.asarray(pos.location, float)
+        ref = np.asarray(pos.ref_direction, float)
+        ref = ref / (np.linalg.norm(ref) or 1.0)
+        axis = np.asarray(pos.axis, float)
+        axis = axis / (np.linalg.norm(axis) or 1.0)
+        y = np.cross(axis, ref)
+        a = float(getattr(basis, "radius", None) or basis.semi_axis1)
+        b = float(getattr(basis, "radius", None) or basis.semi_axis2)
+
+        def _angle(trim):
+            if isinstance(trim, (int, float)):
+                return float(trim)
+            d = np.asarray(trim, float) - loc  # Cartesian point -> its parametric angle
+            return float(np.arctan2((d @ y) / (b or 1.0), (d @ ref) / (a or 1.0)))
+
+        t1, t2 = _angle(tc.trim1), _angle(tc.trim2)
+        if tc.sense_agreement:
+            if t2 <= t1:
+                t2 += 2.0 * np.pi
+        elif t2 >= t1:
+            t2 -= 2.0 * np.pi
+        return [loc + a * np.cos(t) * ref + b * np.sin(t) * y for t in np.linspace(t1, t2, n + 1)]
+    if isinstance(basis, _cu.Line):
+        p0 = np.asarray(basis.pnt, float)
+        d = np.asarray(basis.dir, float)
+
+        def _pt(trim):
+            return (p0 + float(trim) * d) if isinstance(trim, (int, float)) else np.asarray(trim, float)
+
+        endpoints = [_pt(tc.trim1), _pt(tc.trim2)]
+        return endpoints if tc.sense_agreement else endpoints[::-1]  # False = reversed trim direction
+    raise _Unsupported(f"trimmed-curve basis {type(basis).__name__}")
+
+
+def _composite_curve_loop_points(cc) -> list:
+    """Ordered boundary points of an IfcCompositeCurve profile boundary — sample each segment's
+    parent curve (trimmed conic / line / polyline), honour ``same_sense``, and chain, dropping the
+    shared join point so the POLY_LOOP closes cleanly."""
+    import ada.geom.curves as _cu
+
+    def _p3(x):
+        x = np.asarray(x, float).ravel()
+        return np.array([x[0], x[1], x[2] if x.shape[0] > 2 else 0.0])
+
+    pts: list = []
+    for seg in cc.segments:
+        p = seg.parent_curve
+        if isinstance(p, _cu.TrimmedCurve):
+            spts = [_p3(x) for x in _sample_trimmed_curve(p)]
+        elif isinstance(p, _cu.PolyLine):
+            spts = [_p3(x) for x in p.points]
+        elif isinstance(p, _cu.ArcLine):
+            spts = [_p3(x) for x in _sample_arc(p.start, p.midpoint, p.end)]
+        else:
+            raise _Unsupported(f"composite-curve segment {type(p).__name__}")
+        if not getattr(seg, "same_sense", True):
+            spts = spts[::-1]
+        if pts and np.linalg.norm(pts[-1] - spts[0]) < 1e-7:
+            spts = spts[1:]
+        pts.extend(spts)
+    if len(pts) > 1 and np.linalg.norm(pts[0] - pts[-1]) < 1e-7:
+        pts.pop()
+    return [(float(p[0]), float(p[1]), float(p[2]) if len(p) > 2 else 0.0) for p in pts]
+
+
 # tag catalog (spec §3)
 _PLACEMENT3 = 1
 _PLACEMENT1 = 2
@@ -110,6 +194,7 @@ class _Encoder:
     def __init__(self):
         self._records: list[tuple[int, bytes]] = []
         self._memo: dict[int, int] = {}  # id(obj) -> record index
+        self._pinned_inferred: list = []  # keep transient inferred planes alive (id()-memo safety)
 
     def _add(self, tag: int, payload: bytes) -> int:
         idx = len(self._records)
@@ -352,10 +437,37 @@ def face_bound(self, fb: su.FaceBound) -> int:
         lp = self.loop(fb.bound)
         return self._add(_FACE_BOUND, self.i32(lp) + self.i32(1 if fb.orientation else 0))
 
-    def face_surface(self, f: su.FaceSurface) -> int:
-        surf = self.surface(f.face_surface)
+    def _infer_plane(self, loop) -> su.Plane:
+        from ada.geom.placement import Axis2Placement3D
+
+        pts = np.asarray([list(p)[:3] for p in loop.polygon], float)
+        nrm = np.zeros(3)
+        for i in range(len(pts)):
+            nrm += np.cross(pts[i], pts[(i + 1) % len(pts)])
+        ln = float(np.linalg.norm(nrm))
+        if ln < 1e-12:
+            raise _Unsupported("degenerate planar face")
+        axis = nrm / ln
+        ref = pts[1] - pts[0]
+        ref = ref - float(np.dot(ref, axis)) * axis
+        rn = float(np.linalg.norm(ref))
+        if rn < 1e-9:
+            alt = np.array([1.0, 0.0, 0.0]) if abs(axis[0]) < 0.9 else np.array([0.0, 1.0, 0.0])
+            ref = np.cross(axis, alt)
+            rn = float(np.linalg.norm(ref))
+        ref = ref / rn
+        plane = su.Plane(position=Axis2Placement3D(location=pts[0].tolist(), axis=axis.tolist(), ref_direction=ref.tolist()))
+        # Pin it: surface() memoizes by id(), and a transient inferred plane would be GC'd right
+        # after — the next face's plane reusing the freed id() then collides in the memo and gets
+        # the previous plane's record, mis-placing the face. Keep every inferred plane alive.
+        self._pinned_inferred.append(plane)
+        return plane
+
+    def face_surface(self, f: su.Face) -> int:
+        fs = getattr(f, "face_surface", None)
+        surf = self.surface(fs if fs is not None else self._infer_plane(f.bounds[0].bound))
         bounds = [self.face_bound(b) for b in f.bounds]
-        body = self.i32(surf) + self.i32(1 if f.same_sense else 0) + self.i32(len(bounds))
+        body = self.i32(surf) + self.i32(1 if getattr(f, "same_sense", True) else 0) + self.i32(len(bounds))
         body += b"".join(self.i32(b) for b in bounds)  # 1-2 bounds/face: inline (per-face hot path)
         return self._add(_FACE_SURFACE, body)
 
@@ -374,16 +486,39 @@ def connected_face_set(self, cfs) -> int:
     @staticmethod
     def _loop_points_3d(curve) -> list[tuple[float, float, float]]:
         """Ordered boundary points of a closed profile curve, lifted to z=0
-        (the profile lives in its local XY plane). IndexedPolyCurve / Polyline
-        expose ``get_points()``; fall back to ``.points``."""
+        (the profile lives in its local XY plane).
+
+        For an IndexedPolyCurve, walk the SEGMENTS so ``ArcLine`` fillets are sampled into
+        arc polylines — ``get_points()`` returns only each segment's start/end, chording every
+        arc. Chording a concave web/flange fillet fills the whole corner triangle instead of
+        the smaller arc region, so an IPE profile came out ~4% over-area with straight
+        chamfers instead of rounded fillets. Polyline / everything else falls back to
+        ``get_points()`` / ``.points``."""
+        import ada.geom.curves as cu
+
+        def _to3(p):
+            p = list(p)
+            return (float(p[0]), float(p[1]), float(p[2]) if len(p) > 2 else 0.0)
+
+        if isinstance(curve, cu.CompositeCurve):  # trimmed-conic / line segments -> sampled loop
+            return _composite_curve_loop_points(curve)
+
+        segs = getattr(curve, "segments", None)
+        if segs and any(isinstance(s, cu.ArcLine) for s in segs):
+            pts: list[tuple[float, float, float]] = []
+            for s in segs:
+                if isinstance(s, cu.ArcLine):
+                    arc = _sample_arc(s.start, s.midpoint, s.end)
+                    pts.extend(_to3(p) for p in arc[:-1])  # end repeats the next segment's start
+                else:  # Edge / straight segment
+                    pts.append(_to3(s.start))
+            return pts
+
         getp = getattr(curve, "get_points", None)
         raw = getp() if callable(getp) else getattr(curve, "points", None)
         if raw is None:
             raise _Unsupported(f"profile curve {type(curve).__name__}")
-        pts: list[tuple[float, float, float]] = []
-        for p in raw:
-            p = list(p)
-            pts.append((float(p[0]), float(p[1]), float(p[2]) if len(p) > 2 else 0.0))
+        pts = [_to3(p) for p in raw]
         if len(pts) > 1 and pts[0] == pts[-1]:  # POLY_LOOP closes implicitly
             pts.pop()
         return pts
@@ -485,13 +620,48 @@ def box_solid(self, box) -> int:
 
     def revolved_area_solid(self, ras) -> int:
         """RevolvedAreaSolid -> profile FACE + revolution axis (placement1) +
-        angle + placement. Decoded by adacpp into a BRepPrimAPI_MakeRevol."""
+        angle + placement. Decoded by adacpp into a BRepPrimAPI_MakeRevol.
+
+        Two frame/unit conventions must be reconciled with the NGEOM tessellator:
+
+        * ``RevolvedAreaSolid.angle`` is in DEGREES (the OCC build path converts it
+          ``angle_deg * pi/180``); the NGEOM field is RADIANS (``_revolve_z`` writes
+          ``2*pi`` for a full turn). Without the conversion a 87.2deg beam revolve
+          tessellated as 87.2 RADIANS (~14 turns), splattering the profile.
+
+        * ``tessellate_revolve`` rotates the (local) profile ring about the axis and
+          THEN transforms by the position frame (``F.to_world(rotate(ring, axo, axd))``)
+          — i.e. it expects the axis in the POSITION-LOCAL frame (as cylinders/cones
+          emit it: local +Z at the origin). But ``ras.axis`` is in GLOBAL coordinates
+          (the convention the OCC build path consumes). Left global, the axis and the
+          profile's own normal ended up parallel and the sweep collapsed flat. Rotation
+          commutes with the rigid position transform when the axis is expressed in that
+          frame, so transform the global axis into position-local here."""
+        import math
+
+        import numpy as np
+
+        pos = ras.position
+        xdir = np.asarray(pos.ref_direction if pos.ref_direction is not None else (1.0, 0.0, 0.0), dtype=float)
+        zdir = np.asarray(pos.axis if pos.axis is not None else (0.0, 0.0, 1.0), dtype=float)
+        xdir = xdir / (np.linalg.norm(xdir) or 1.0)
+        zdir = zdir / (np.linalg.norm(zdir) or 1.0)
+        ydir = np.cross(zdir, xdir)
+        rot = np.column_stack([xdir, ydir, zdir])  # local->world; rot.T is world->local
+        origin = np.asarray(pos.location, dtype=float)
+
+        ax_loc_world = np.asarray(ras.axis.location, dtype=float)
+        ax_dir_world = np.asarray(ras.axis.axis, dtype=float)
+        local_loc = rot.T @ (ax_loc_world - origin)
+        local_dir = rot.T @ ax_dir_world
+
         face = self._profile_face(ras.swept_area)
+        axis_rec = self._add(_PLACEMENT1, self.v3(tuple(local_loc)) + self.v3(tuple(local_dir)))
         body = (
             self.i32(face)
-            + self.i32(self.placement3(ras.position))
-            + self.i32(self.placement1(ras.axis))
-            + self.f64(ras.angle)
+            + self.i32(self.placement3(pos))
+            + self.i32(axis_rec)
+            + self.f64(math.radians(ras.angle))
         )
         return self._add(_REVOLVED_AREA_SOLID, body)
 
@@ -515,6 +685,62 @@ def fixed_reference_swept_area_solid(self, frs) -> int:
         )
         return self._add(_FIXED_REF_SWEPT_SOLID, body)
 
+    def _sweep_frames(self, directrix):
+        """Per-station (origin, profile-x, profile-y) frames along a general 3D directrix, using a
+        rotation-minimising (parallel-transport) frame so the swept profile doesn't twist. profile-x
+        and profile-y are both perpendicular to the tangent; profile-x x profile-y = tangent."""
+        pts = np.asarray(self._loop_points_3d(directrix), float)
+        if len(pts) < 2:
+            return pts, np.zeros((0, 3)), np.zeros((0, 3))
+        t = np.gradient(pts, axis=0)
+        tn = np.linalg.norm(t, axis=1, keepdims=True)
+        t = t / np.where(tn < 1e-12, 1.0, tn)
+        ref = np.array([0.0, 0.0, 1.0]) if abs(t[0, 2]) < 0.9 else np.array([1.0, 0.0, 0.0])
+        dir_x = np.zeros((len(pts), 3))
+        x0 = np.cross(ref, t[0])
+        dir_x[0] = x0 / (np.linalg.norm(x0) or 1.0)
+        for i in range(1, len(pts)):
+            v1, v2 = t[i - 1], t[i]
+            ax = np.cross(v1, v2)
+            s = float(np.linalg.norm(ax))
+            xp = dir_x[i - 1]
+            if s < 1e-9:  # no bend -> carry the frame
+                dir_x[i] = xp
+            else:  # Rodrigues-rotate the frame by the tangent turn
+                ax /= s
+                ang = np.arctan2(s, float(np.dot(v1, v2)))
+                dir_x[i] = xp * np.cos(ang) + np.cross(ax, xp) * np.sin(ang) + ax * float(np.dot(ax, xp)) * (1 - np.cos(ang))
+            dir_x[i] -= float(np.dot(dir_x[i], t[i])) * t[i]  # re-orthogonalise against the tangent
+            dir_x[i] /= np.linalg.norm(dir_x[i]) or 1.0
+        return pts, dir_x, np.cross(t, dir_x)
+
+    def swept_disk_solid(self, sds) -> int:
+        """IfcSweptDiskSolid (rebar/pipe) -> a circular/annular profile swept along the directrix,
+        encoded like a FixedReferenceSweptAreaSolid (profile FACE + per-station frames). The
+        directrix is sampled + parallel-transport-framed here, so any directrix (polyline, arc,
+        composite) works — not just alignment GradientCurves."""
+        from ada.geom.placement import Axis2Placement3D
+
+        o = Axis2Placement3D(location=(0.0, 0.0, 0.0))
+        inner = [cu.Circle(position=o, radius=float(sds.inner_radius))] if sds.inner_radius else []
+        prof = su.ArbitraryProfileDef(
+            profile_type=su.ProfileType.AREA, outer_curve=cu.Circle(position=o, radius=float(sds.radius)),
+            inner_curves=inner,
+        )
+        face = self._profile_face(prof)
+        origins, dir_x, dir_y = self._sweep_frames(sds.directrix)
+        if len(origins) < 2:
+            raise _Unsupported("swept-disk directrix has < 2 stations")
+        body = (
+            self.i32(face)
+            + self.i32(self.placement3(o))
+            + self.i32(len(origins))
+            + self._f64_raw(origins.ravel())
+            + self._f64_raw(dir_x.ravel())
+            + self._f64_raw(dir_y.ravel())
+        )
+        return self._add(_FIXED_REF_SWEPT_SOLID, body)
+
     def _xz_planar_face(self, pts3d) -> int:
         """Planar FACE_SURFACE in the local XZ plane (y=0; normal=+Y, ref=+X)."""
         place = self._add(_PLACEMENT3, self.v3((0.0, 0.0, 0.0)) + self.v3((0.0, 1.0, 0.0)) + self.v3((1.0, 0.0, 0.0)))
@@ -608,9 +834,11 @@ def _planar_face_from_loop(self, bound) -> int:
         return self._add(_FACE_SURFACE, self.i32(plane) + self.i32(1) + self.i32(1) + self.i32(bnd))
 
     def _any_face(self, f) -> int:
-        # FaceSurface / AdvancedFace -> normal path; bare FaceBound (planar loop,
-        # no surface — Beam.shell_geom) -> synthesize a planar face.
-        if hasattr(f, "face_surface") and hasattr(f, "bounds"):
+        # FaceSurface / AdvancedFace / a plain IfcFace (bounds, but no surface attribute — e.g. an
+        # IfcFaceBasedSurfaceModel's polyloop faces) all go through face_surface, which infers a
+        # plane when no surface is carried. A bare FaceBound (planar loop — Beam.shell_geom) ->
+        # synthesize a planar face.
+        if hasattr(f, "bounds"):
             return self.face_surface(f)
         bound = getattr(f, "bound", None)
         if bound is not None:
@@ -652,6 +880,65 @@ def boolean_result(self, br) -> int:
         b = self._dispatch(br.second_operand)
         return self._add(_BOOLEAN_RESULT, self.i32(op) + self.i32(a) + self.i32(b))
 
+    def half_space_box(self, hs, ref_min, ref_max) -> int:
+        """HalfSpaceSolid -> a finite box (EXTRUDED_AREA_SOLID) on the material side
+        of the plane, sized to cover the reference bbox — the same lowering adacpp's
+        native STEP/IFC readers apply (``mk_halfspace``), so the neutral buffer needs
+        no half-space entity and the boolean evaluates identically everywhere.
+        ``agreement_flag=True`` keeps the material BELOW the plane (-normal side)."""
+        import math
+
+        pos = hs.base_surface.position
+        o, z, x_ref = _frame_vectors(pos)
+        agree = bool(getattr(hs, "agreement_flag", True))
+        hd = tuple(-c for c in z) if agree else z
+
+        c = tuple((mn + mx) / 2.0 for mn, mx in zip(ref_min, ref_max))
+        diag = math.sqrt(sum((mx - mn) ** 2 for mn, mx in zip(ref_min, ref_max)))
+        s = diag * 1.5 + 1e-6
+        # project the bbox centre onto the cutting plane -> box origin ON the plane
+        d = sum(zc * (cc - oc) for zc, cc, oc in zip(z, c, o))
+        cp = tuple(cc - zc * d for cc, zc in zip(c, z))
+        # frame: local Z = material side; X from the plane frame, orthonormalised
+        t = x_ref if abs(sum(a * b for a, b in zip(hd, x_ref))) < 0.9 else _perp_of(z, x_ref)
+        dt = sum(a * b for a, b in zip(hd, t))
+        fx = tuple(tc - hc * dt for tc, hc in zip(t, hd))
+        n = math.sqrt(sum(v * v for v in fx)) or 1.0
+        fx = tuple(v / n for v in fx)
+
+        pts = [(-s, -s, 0.0), (s, -s, 0.0), (s, s, 0.0), (-s, s, 0.0)]
+        loop = self._add(_POLY_LOOP, self.i32(4) + self._v3_raw(pts))
+        bound = self._add(_FACE_BOUND, self.i32(loop) + self.i32(1))
+        face = self._planar_face([bound])
+        place = self._add(_PLACEMENT3, self.v3(cp) + self.v3(hd) + self.v3(fx))
+        body = self.i32(face) + self.i32(place) + self.v3((0.0, 0.0, 1.0)) + self.f64(s)
+        return self._add(_EXTRUDED_AREA_SOLID, body)
+
+    def _fold_bool_ops(self, base_idx: int, base_geom, bool_ops) -> int:
+        """Chain a base solid's ``Geometry.bool_operations`` into nested
+        BOOLEAN_RESULT records (base as first operand, applied in order) so cuts
+        reach the neutral kernel instead of being dropped with the wrapper."""
+        idx = base_idx
+        bbox = None
+        for op in bool_ops:
+            og = op.second_operand
+            while hasattr(og, "geometry") and hasattr(og, "bool_operations"):
+                og = og.geometry  # unwrap core.Geometry
+            import ada.geom.surfaces as _su
+
+            if isinstance(og, _su.HalfSpaceSolid):
+                if bbox is None:
+                    bbox = _loose_bbox(base_geom)
+                if bbox is None:
+                    raise _Unsupported("HalfSpaceSolid operand without a boundable base solid")
+                op_idx = self.half_space_box(og, bbox[0], bbox[1])
+            else:
+                op_idx = self._dispatch(og)
+            op_name = getattr(op.operator, "value", op.operator)
+            opi = {"DIFFERENCE": 0, "UNION": 1, "INTERSECTION": 2}.get(str(op_name).upper(), 0)
+            idx = self._add(_BOOLEAN_RESULT, self.i32(opi) + self.i32(idx) + self.i32(op_idx))
+        return idx
+
     # --- root + finish -----------------------------------------------------------------
     def _dispatch(self, geom) -> int:
         """Serialize one geometry instance to its record index (used for both
@@ -667,6 +954,8 @@ def _dispatch(self, geom) -> int:
             return self.revolved_area_solid(geom)
         if isinstance(geom, _so.FixedReferenceSweptAreaSolid):
             return self.fixed_reference_swept_area_solid(geom)
+        if isinstance(geom, _so.SweptDiskSolid):
+            return self.swept_disk_solid(geom)
         if isinstance(geom, _so.Box):
             return self.box_solid(geom)
         if isinstance(geom, _so.Cylinder):
@@ -687,11 +976,28 @@ def _dispatch(self, geom) -> int:
             return self.face_surface(geom)
         if isinstance(geom, (su.ConnectedFaceSet, su.ClosedShell, su.OpenShell)):
             return self.connected_face_set(geom)
+        if isinstance(geom, _so.FacetedBrep):
+            # Render the outer shell's faces natively (each plain planar Face gets an inferred
+            # plane in face_surface). Voids (FacetedBrepWithVoids) need a boolean cut not yet in
+            # the stream path — the outer surface still renders, cavities simply not carved.
+            return self.connected_face_set(geom.outer)
         raise _Unsupported(f"geometry {type(geom).__name__}")
 
     def root(self, geom) -> int:
-        """Serialize a top-level geometry instance, returning its record index."""
-        return self._dispatch(geom)
+        """Serialize a top-level geometry instance, returning its record index.
+
+        Accepts a raw ``ada.geom`` type or a ``core.Geometry`` wrapper — the wrapper's
+        ``bool_operations`` are folded into a BOOLEAN_RESULT chain (previously every
+        caller stripped the wrapper, silently dropping IFC clipping cuts and API
+        booleans from the stream-tessellation/export paths)."""
+        ops = []
+        while hasattr(geom, "geometry") and hasattr(geom, "bool_operations"):
+            ops.extend(geom.bool_operations or [])
+            geom = geom.geometry
+        idx = self._dispatch(geom)
+        if ops:
+            idx = self._fold_bool_ops(idx, geom, ops)
+        return idx
 
     def finish(self, roots: list[tuple[int, str]]) -> bytes:
         out = bytearray(b"ADANGEOM")
@@ -709,6 +1015,131 @@ class _Unsupported(Exception):
     pass
 
 
+def _frame_vectors(pos) -> tuple[tuple, tuple, tuple]:
+    """(origin, z, x) of an Axis2Placement3D with the usual defaults, as plain tuples."""
+    import math
+
+    o = tuple(float(v) for v in pos.location) if pos is not None else (0.0, 0.0, 0.0)
+    z = tuple(float(v) for v in pos.axis) if pos is not None and pos.axis is not None else (0.0, 0.0, 1.0)
+    n = math.sqrt(sum(v * v for v in z)) or 1.0
+    z = tuple(v / n for v in z)
+    if pos is not None and getattr(pos, "ref_direction", None) is not None:
+        x = tuple(float(v) for v in pos.ref_direction)
+    else:
+        x = _perp_of(z, (1.0, 0.0, 0.0))
+    return o, z, x
+
+
+def _perp_of(z, seed) -> tuple:
+    """A unit vector perpendicular to ``z``, seeded by ``seed`` (world X/Y fallback)."""
+    import math
+
+    d = sum(a * b for a, b in zip(z, seed))
+    if abs(d) > 0.9:
+        seed = (0.0, 1.0, 0.0)
+        d = sum(a * b for a, b in zip(z, seed))
+    v = tuple(s - zc * d for s, zc in zip(seed, z))
+    n = math.sqrt(sum(c * c for c in v)) or 1.0
+    return tuple(c / n for c in v)
+
+
+def _loose_bbox(geom) -> tuple[tuple, tuple] | None:
+    """Loose world-frame bbox of an ada.geom solid — over-estimate is fine, it only
+    sizes the finite box a HalfSpaceSolid operand is lowered to (mirrors adacpp's
+    ``solid_item_bbox``). Pure Python/ada.geom — the neutral path stays OCC-free.
+    Returns ``((minx,miny,minz), (maxx,maxy,maxz))`` or ``None``."""
+    import ada.geom.booleans as _bo
+    import ada.geom.solids as _so
+    import ada.geom.surfaces as _su
+
+    while hasattr(geom, "geometry") and hasattr(geom, "bool_operations"):
+        geom = geom.geometry
+
+    def frame_pts(pos, local_pts):
+        o, z, x = _frame_vectors(pos)
+        y = (
+            z[1] * x[2] - z[2] * x[1],
+            z[2] * x[0] - z[0] * x[2],
+            z[0] * x[1] - z[1] * x[0],
+        )
+        return [tuple(o[i] + x[i] * p[0] + y[i] * p[1] + z[i] * p[2] for i in range(3)) for p in local_pts]
+
+    pts: list[tuple] = []
+    if isinstance(geom, _bo.BooleanResult):
+        return _loose_bbox(geom.first_operand)  # the result is contained in operand a
+    if isinstance(geom, _so.ExtrudedAreaSolid):
+        profile = geom.swept_area
+        outer = getattr(profile, "outer_curve", None)
+        if outer is None:
+            try:
+                from ada.api.beams.geom_beams import parametric_profile_to_arbitrary
+
+                outer = parametric_profile_to_arbitrary(profile).outer_curve
+            except Exception:  # noqa: BLE001
+                return None
+        base = _profile_curve_pts(outer)
+        if base is None:
+            return None
+        d = tuple(float(v) * float(geom.depth) for v in geom.extruded_direction)
+        local = base + [(p[0] + d[0], p[1] + d[1], p[2] + d[2]) for p in base]
+        pts = frame_pts(geom.position, local)
+    elif isinstance(geom, _so.RevolvedAreaSolid):
+        base = _profile_curve_pts(getattr(geom.swept_area, "outer_curve", None))
+        if base is None:
+            return None
+        r = max((p[0] ** 2 + p[1] ** 2 + p[2] ** 2) ** 0.5 for p in base)
+        world = frame_pts(geom.position, base)
+        pts = [tuple(c + s * r for c in p) for p in world for s in (-1.0, 1.0)]
+    elif isinstance(geom, _so.Box):
+        x, y, z = float(geom.x_length), float(geom.y_length), float(geom.z_length)
+        pts = frame_pts(geom.position, [(0, 0, 0), (x, 0, 0), (x, y, 0), (0, y, 0), (0, 0, z), (x, y, z)])
+    elif isinstance(geom, _so.Cylinder) or isinstance(geom, _so.Cone):
+        r = float(getattr(geom, "radius", 0.0) or getattr(geom, "bottom_radius", 0.0))
+        h = float(geom.height)
+        pts = frame_pts(geom.position, [(-r, -r, 0), (r, r, 0), (-r, -r, h), (r, r, h)])
+    elif isinstance(geom, _so.Sphere):
+        c, r = geom.center, float(geom.radius)
+        pts = [tuple(float(cc) + s * r for cc in c) for s in (-1.0, 1.0)]
+    else:
+        faces = getattr(geom, "cfs_faces", None)
+        if faces is None and hasattr(geom, "outer"):  # AdvancedBrep / FacetedBrep
+            faces = getattr(geom.outer, "cfs_faces", None)
+        if faces is None and hasattr(geom, "bounds"):  # a single face
+            faces = [geom]
+        if faces is None:
+            return None
+        for f in faces:
+            for b in getattr(f, "bounds", []) or []:
+                loop = getattr(b, "bound", None)
+                for oe in getattr(loop, "edge_list", None) or []:
+                    e = getattr(oe, "edge_element", oe)
+                    pts.append(tuple(float(v) for v in e.start))
+                    pts.append(tuple(float(v) for v in e.end))
+                for p in getattr(loop, "polygon", None) or []:
+                    pts.append(tuple(float(v) for v in p))
+    if not pts:
+        return None
+    mn = tuple(min(p[i] for p in pts) for i in range(3))
+    mx = tuple(max(p[i] for p in pts) for i in range(3))
+    return mn, mx
+
+
+def _profile_curve_pts(curve) -> list[tuple[float, float, float]] | None:
+    """Boundary points of a profile curve (shared with the encoder's poly path);
+    conics fall back to their bounding square."""
+    if curve is None:
+        return None
+    r = float(getattr(curve, "radius", 0.0) or getattr(curve, "semi_axis1", 0.0) or 0.0)
+    if r > 0.0:
+        pos = getattr(curve, "position", None)
+        o = tuple(float(v) for v in pos.location) if pos is not None else (0.0, 0.0, 0.0)
+        return [(o[0] + sx * r, o[1] + sy * r, o[2]) for sx in (-1, 1) for sy in (-1, 1)]
+    try:
+        return _Encoder._loop_points_3d(curve)
+    except _Unsupported:
+        return None
+
+
 def serialize_geometries(items: Iterable[tuple[str, object]]) -> bytes:
     """Serialize ``(id, geometry)`` pairs into one NGEOM buffer.
 
diff --git a/src/ada/cadit/sat/parser/parser.py b/src/ada/cadit/sat/parser/parser.py
index 36c675ef6..45669fd09 100644
--- a/src/ada/cadit/sat/parser/parser.py
+++ b/src/ada/cadit/sat/parser/parser.py
@@ -51,6 +51,41 @@
 )
 from ada.config import logger
 
+# Non-numeric trailing flag tokens found in ACIS surface/curve records.
+_SAT_FLAG_TOKENS = frozenset(
+    {"I", "F", "#", "forward", "reversed", "both", "in", "out", "double", "single", "reverse_v", "forward_v"}
+)
+
+
+def _numeric_after_header(parts: list[str]) -> list[float]:
+    """Numeric geometry fields of an ACIS surface/curve record, past the entity header.
+
+    The header is ``$owner <int> <int> $attrib`` — those two bare integers are numeric, so a plain
+    float-filter over the whole record swallows them and shifts every coordinate by two (a plane then
+    gets a garbage frame and its face tessellates to a single triangle). Skip up to and including the
+    2nd ``$``-reference, then collect floats (dropping trailing flag words). Falls back to the whole
+    record if the expected two references aren't present.
+    """
+    start = 0
+    dollars = 0
+    for i, p in enumerate(parts):
+        if p.startswith("$"):
+            dollars += 1
+            if dollars == 2:
+                start = i + 1
+                break
+    if dollars < 2:
+        start = 0
+    out: list[float] = []
+    for p in parts[start:]:
+        if p in _SAT_FLAG_TOKENS:
+            continue
+        try:
+            out.append(float(p))
+        except ValueError:
+            continue
+    return out
+
 
 class AcisSatParser:
     """
@@ -555,16 +590,8 @@ def _parse_point(self, index: int, data: str) -> AcisPoint:
     def _parse_straight_curve(self, index: int, data: str) -> AcisStraightCurve:
         """Parse straight-curve entity."""
         parts = data.split()
-        # straight-curve format: $attrib origin(x,y,z) direction(x,y,z) I I #
-        # Skip reference tokens (starting with $) and find numeric values
-        numeric_values = []
-        for part in parts:
-            if part.startswith("$") or part in ["I", "F", "#"]:
-                continue
-            try:
-                numeric_values.append(float(part))
-            except ValueError:
-                continue
+        # straight-curve format: <header> origin(x,y,z) direction(x,y,z) I I #
+        numeric_values = _numeric_after_header(parts)
 
         origin = numeric_values[0:3] if len(numeric_values) >= 3 else [0, 0, 0]
         direction = numeric_values[3:6] if len(numeric_values) >= 6 else [0, 0, 1]
@@ -630,27 +657,12 @@ def _parse_spline_curve_data(self, spline_str: str) -> Optional[AcisSplineCurveD
     def _parse_plane_surface(self, index: int, data: str) -> AcisPlaneSurface:
         """Parse plane-surface entity."""
         parts = data.split()
-        # plane-surface format: $attrib origin(x,y,z) normal(x,y,z) u_direction(x,y,z) sense I I I I #
-        # Skip reference tokens (starting with $) and non-numeric flags
-        numeric_values = []
-        for part in parts:
-            if part.startswith("$") or part in [
-                "I",
-                "F",
-                "#",
-                "forward",
-                "reversed",
-                "both",
-                "in",
-                "out",
-                "double",
-                "single",
-            ]:
-                continue
-            try:
-                numeric_values.append(float(part))
-            except ValueError:
-                continue
+        # plane-surface format: <header> origin(x,y,z) normal(x,y,z) u_direction(x,y,z) sense I I I I #
+        # The ACIS record header is `$owner -1 -1 $attrib` — those two bare `-1` integers are numeric,
+        # so a plain float-filter swallowed them into the geometry and shifted origin/normal/u_dir by
+        # two (planes came out with a garbage frame → the face tessellated to a single triangle). Skip
+        # past the header (up to and including the 2nd $-reference) before reading the coordinates.
+        numeric_values = _numeric_after_header(parts)
 
         origin = numeric_values[0:3] if len(numeric_values) >= 3 else [0, 0, 0]
         normal = numeric_values[3:6] if len(numeric_values) >= 6 else [0, 0, 1]
diff --git a/src/ada/cadit/step/model_scale.py b/src/ada/cadit/step/model_scale.py
new file mode 100644
index 000000000..b11b9dbf9
--- /dev/null
+++ b/src/ada/cadit/step/model_scale.py
@@ -0,0 +1,61 @@
+"""Estimate a model reference scale (bbox diagonal, world units) for adaptive tessellation.
+
+The adaptive angular density (see ``ada.cad.registry.stream_tess_adaptive``) relaxes the fine
+angular ceiling for curved surfaces small *relative to the model*. That needs a model length
+scale. A raw min/max bounding box is unusable: CAD STEP files routinely carry a handful of
+far-flung reference/construction points (the crane spans ±500 m of stray points yet its real
+geometry is ~13-45 m), which inflate the diagonal ~30x and would coarsen every surface.
+
+So we use an OUTLIER-ROBUST estimate: sample CARTESIAN_POINT coordinates and take ~2x the 99th
+percentile of point magnitude. The scan is bounded (a prefix of the file is enough to capture the
+bulk distribution; the rare outliers are exactly what we want the percentile to reject), so this
+adds only a short read even on a multi-GB STEP.
+"""
+
+from __future__ import annotations
+
+import pathlib
+import re
+
+_COORD_RE = re.compile(rb"CARTESIAN_POINT\([^(]*\(\s*([-0-9.eE]+)\s*,\s*([-0-9.eE]+)\s*,\s*([-0-9.eE]+)")
+
+
+def estimate_step_model_scale(
+    path: str | pathlib.Path, *, budget_bytes: int = 96_000_000, chunks: int = 24, max_samples: int = 600_000
+) -> float:
+    """Robust model bbox-diagonal estimate for a STEP file, or 0.0 if it can't be determined.
+
+    Samples ``chunks`` evenly-spaced windows across the whole file (CARTESIAN_POINT entities may sit
+    anywhere — some exporters emit them only in the last ~40% of the file, so a prefix scan misses
+    them), collecting up to ``max_samples`` point magnitudes within ``budget_bytes`` of total reads.
+    Returns ``2 * p99(|point|)`` — the p99 rejects stray reference points, doubling turns a radius
+    into a diameter-like span. 0.0 (adaptive disabled for this file) when too few points are found.
+    """
+    try:
+        import numpy as np
+
+        p = pathlib.Path(path)
+        size = p.stat().st_size
+    except OSError:
+        return 0.0
+
+    n_chunks = max(1, chunks)
+    win = max(1, budget_bytes // n_chunks)
+    mags: list[float] = []
+    with open(p, "rb") as f:
+        for i in range(n_chunks):
+            off = 0 if n_chunks == 1 else int((size - win) * i / (n_chunks - 1))
+            f.seek(max(0, off))
+            data = f.read(win)
+            for m in _COORD_RE.finditer(data):
+                try:
+                    x, y, z = float(m.group(1)), float(m.group(2)), float(m.group(3))
+                except ValueError:
+                    continue
+                mags.append((x * x + y * y + z * z) ** 0.5)
+            if len(mags) >= max_samples:
+                break
+
+    if len(mags) < 100:
+        return 0.0
+    return float(2.0 * np.percentile(np.asarray(mags), 99.0))
diff --git a/src/ada/cadit/step/native_ifc_to_step.py b/src/ada/cadit/step/native_ifc_to_step.py
index 8f9e2ffe3..d1a58f42b 100644
--- a/src/ada/cadit/step/native_ifc_to_step.py
+++ b/src/ada/cadit/step/native_ifc_to_step.py
@@ -39,7 +39,8 @@ def native_ifc_to_step(
     if deflection is None:
         deflection = float(os.environ.get("ADA_STREAM_TESS_DEFLECTION", "2.0"))
     if angular_deg is None:
-        angular_deg = float(os.environ.get("ADA_STREAM_TESS_ANGULAR", "20.0"))
+        from ada.cad.registry import DEFAULT_STREAM_TESS_ANGULAR_DEG
+        angular_deg = float(os.environ.get("ADA_STREAM_TESS_ANGULAR", str(DEFAULT_STREAM_TESS_ANGULAR_DEG)))
     if on_progress is not None:
         on_progress("adacpp-native-ifc2step", 0.1)
     stats = adacpp.cad.stream_ifc_to_step(str(ifc_path), str(out_path), deflection=deflection, angular_deg=angular_deg)
diff --git a/src/ada/cadit/step/native_step_to_glb.py b/src/ada/cadit/step/native_step_to_glb.py
index 5c63a375d..270f352e9 100644
--- a/src/ada/cadit/step/native_step_to_glb.py
+++ b/src/ada/cadit/step/native_step_to_glb.py
@@ -59,7 +59,21 @@ def native_step_to_glb(
     if deflection is None:
         deflection = float(os.environ.get("ADA_STREAM_TESS_DEFLECTION", "2.0"))
     if angular_deg is None:
-        angular_deg = float(os.environ.get("ADA_STREAM_TESS_ANGULAR", "20.0"))
+        from ada.cad.registry import DEFAULT_STREAM_TESS_ANGULAR_DEG
+        angular_deg = float(os.environ.get("ADA_STREAM_TESS_ANGULAR", str(DEFAULT_STREAM_TESS_ANGULAR_DEG)))
+
+    # Adaptive per-surface angular density is ON BY DEFAULT for STEP->GLB: large curved CAD
+    # assemblies (crane: 7291 solids, thousands of sub-cm bolts/pins) over-tessellate at a fixed
+    # fine angle, and the GLB is the transfer-size-sensitive product. We estimate a model reference
+    # scale so adacpp coarsens tiny features while keeping large surfaces fine. ADA_STREAM_TESS_
+    # ADAPTIVE=0/false forces the fixed-angle path (model_scale 0 => angular_deg governs everything).
+    adaptive_env = os.environ.get("ADA_STREAM_TESS_ADAPTIVE")
+    adaptive = True if adaptive_env is None else adaptive_env.strip().lower() not in {"0", "false", "no", "off", ""}
+    model_scale = 0.0
+    if adaptive:
+        from ada.cadit.step.model_scale import estimate_step_model_scale
+
+        model_scale = estimate_step_model_scale(step_path)
 
     if num_threads <= 0:
         # ``num_threads=0`` lets the C++ pick std::thread::hardware_concurrency(), which reports the
@@ -79,14 +93,23 @@ def native_step_to_glb(
     if on_progress is not None:
         on_progress("adacpp-native", 0.1)
 
-    n = adacpp.cad.stream_step_to_glb(
-        str(step_path),
-        str(glb_path),
-        deflection=deflection,
-        angular_deg=angular_deg,
-        num_threads=num_threads,
-        meshopt=meshopt,
+    glb_kwargs = dict(
+        deflection=deflection, angular_deg=angular_deg, num_threads=num_threads, meshopt=meshopt
     )
+    # Only forward model_scale to an adacpp build that accepts it (nanobind embeds the signature in
+    # __doc__); an older extension would raise on the unknown kwarg. Off (0.0) behaves as before.
+    if "model_scale" in (adacpp.cad.stream_step_to_glb.__doc__ or ""):
+        glb_kwargs["model_scale"] = model_scale
+    elif model_scale > 0.0:
+        logger.warning("adacpp build predates adaptive tessellation (no model_scale); using fixed angular_deg")
+    # Opt-in per-face clickable regions (scenes[0].extras face_ranges_node<m>): ADA_STREAM_TESS_FACE_REGIONS=1.
+    # Off by default — it bloats the GLB and forces serial face tessellation. Only forward to an adacpp
+    # build whose binding accepts it (older extensions would raise on the unknown kwarg).
+    fr_env = os.environ.get("ADA_STREAM_TESS_FACE_REGIONS")
+    face_regions = fr_env is not None and fr_env.strip().lower() not in {"0", "false", "no", "off", ""}
+    if face_regions and "face_regions" in (adacpp.cad.stream_step_to_glb.__doc__ or ""):
+        glb_kwargs["face_regions"] = True
+    n = adacpp.cad.stream_step_to_glb(str(step_path), str(glb_path), **glb_kwargs)
     if n < 0:
         raise RuntimeError(f"adacpp native stream_step_to_glb failed for {step_path}")
 
@@ -96,7 +119,8 @@ def native_step_to_glb(
     # capture (the worker adds wall-time + peak RSS to the row's metrics separately).
     print(
         f"[adacpp-native] {n} solids -> {glb_path} "
-        f"(threads={num_threads}, deflection={deflection}, angular={angular_deg}, meshopt={meshopt})",
+        f"(threads={num_threads}, deflection={deflection}, angular={angular_deg}, meshopt={meshopt}, "
+        f"adaptive={'off' if model_scale <= 0 else f'model_scale={model_scale:.0f}'})",
         flush=True,
     )
     if on_progress is not None:
diff --git a/src/ada/cadit/step/native_step_to_ifc.py b/src/ada/cadit/step/native_step_to_ifc.py
index 32326cb49..349b8c82b 100644
--- a/src/ada/cadit/step/native_step_to_ifc.py
+++ b/src/ada/cadit/step/native_step_to_ifc.py
@@ -55,7 +55,8 @@ def native_step_to_ifc(
     if deflection is None:
         deflection = float(os.environ.get("ADA_STREAM_TESS_DEFLECTION", "2.0"))
     if angular_deg is None:
-        angular_deg = float(os.environ.get("ADA_STREAM_TESS_ANGULAR", "20.0"))
+        from ada.cad.registry import DEFAULT_STREAM_TESS_ANGULAR_DEG
+        angular_deg = float(os.environ.get("ADA_STREAM_TESS_ANGULAR", str(DEFAULT_STREAM_TESS_ANGULAR_DEG)))
     if num_threads <= 0:
         # Bound to the cgroup-aware allotment (not the node's core count) so we don't oversubscribe a
         # CPU-capped pod — same rule as the native GLB/mesh paths.
diff --git a/src/ada/cadit/step/native_step_to_mesh.py b/src/ada/cadit/step/native_step_to_mesh.py
index d2dda891d..54110e5c2 100644
--- a/src/ada/cadit/step/native_step_to_mesh.py
+++ b/src/ada/cadit/step/native_step_to_mesh.py
@@ -53,7 +53,8 @@ def native_step_to_mesh(
     if deflection is None:
         deflection = float(os.environ.get("ADA_STREAM_TESS_DEFLECTION", "2.0"))
     if angular_deg is None:
-        angular_deg = float(os.environ.get("ADA_STREAM_TESS_ANGULAR", "20.0"))
+        from ada.cad.registry import DEFAULT_STREAM_TESS_ANGULAR_DEG
+        angular_deg = float(os.environ.get("ADA_STREAM_TESS_ANGULAR", str(DEFAULT_STREAM_TESS_ANGULAR_DEG)))
     if num_threads <= 0:
         # Mirror the native GLB path: bound threads to the cgroup-aware allotment, not the node's
         # core count, so we don't oversubscribe a CPU-capped pod or bloat per-thread malloc arenas.
@@ -64,13 +65,33 @@ def native_step_to_mesh(
         except Exception:  # noqa: BLE001
             num_threads = 0
 
+    # Adaptive per-surface density is ON BY DEFAULT for STEP->OBJ/STL too (same rationale as
+    # STEP->GLB: dense curved assemblies over-tessellate, and the text OBJ/STL are the largest,
+    # slowest products — the crane's 107M-tri OBJ/STL blew the 5-min timeout). ADA_STREAM_TESS_
+    # ADAPTIVE=0/false forces the fixed-angle path.
+    adaptive_env = os.environ.get("ADA_STREAM_TESS_ADAPTIVE")
+    adaptive = True if adaptive_env is None else adaptive_env.strip().lower() not in {"0", "false", "no", "off", ""}
+    model_scale = 0.0
+    if adaptive:
+        from ada.cadit.step.model_scale import estimate_step_model_scale
+
+        model_scale = estimate_step_model_scale(step_path)
+
     if on_progress is not None:
         on_progress("adacpp-native-mesh", 0.1)
-    n = adacpp.cad.stream_step_to_mesh(
-        str(step_path), str(out_path), fmt, deflection=deflection, angular_deg=angular_deg, num_threads=num_threads
-    )
+    mesh_kwargs = dict(deflection=deflection, angular_deg=angular_deg, num_threads=num_threads)
+    if "model_scale" in (adacpp.cad.stream_step_to_mesh.__doc__ or ""):
+        mesh_kwargs["model_scale"] = model_scale
+    elif model_scale > 0.0:
+        logger.warning("adacpp build predates adaptive tessellation (no model_scale); using fixed angular_deg")
+    n = adacpp.cad.stream_step_to_mesh(str(step_path), str(out_path), fmt, **mesh_kwargs)
     if n < 0:
         raise RuntimeError(f"adacpp native stream_step_to_mesh failed for {step_path}")
+    # Record the triangle tally for the audit (convert_meta["tri_stats"]) so a tessellation-output
+    # change (density drift, the adaptive thread bug, a dropped solid) is caught run-to-run.
+    from ada.cadit.step.tess_stats import record_tri_stats
+
+    record_tri_stats(n_tris=n, engine="adacpp:libtess2")
     logger.info("adacpp-native STEP->%s: %s triangles -> %s", fmt.upper(), n, out_path)
     print(
         f"[adacpp-native] {n} triangles -> {out_path} (fmt={fmt}, threads={num_threads}, "
diff --git a/src/ada/cadit/step/native_step_to_step.py b/src/ada/cadit/step/native_step_to_step.py
index 4c5ce22c4..5f6a6252d 100644
--- a/src/ada/cadit/step/native_step_to_step.py
+++ b/src/ada/cadit/step/native_step_to_step.py
@@ -40,7 +40,8 @@ def native_step_to_step(
     if deflection is None:
         deflection = float(os.environ.get("ADA_STREAM_TESS_DEFLECTION", "2.0"))
     if angular_deg is None:
-        angular_deg = float(os.environ.get("ADA_STREAM_TESS_ANGULAR", "20.0"))
+        from ada.cad.registry import DEFAULT_STREAM_TESS_ANGULAR_DEG
+        angular_deg = float(os.environ.get("ADA_STREAM_TESS_ANGULAR", str(DEFAULT_STREAM_TESS_ANGULAR_DEG)))
     if num_threads <= 0:
         try:
             from ada.visit.scene_handling.scene_from_step_stream import _stream_workers
diff --git a/src/ada/cadit/step/read/native_reader.py b/src/ada/cadit/step/read/native_reader.py
index e9454ebe1..4bc4de9ae 100644
--- a/src/ada/cadit/step/read/native_reader.py
+++ b/src/ada/cadit/step/read/native_reader.py
@@ -30,21 +30,38 @@ def native_adacpp_step_available() -> bool:
         return False
 
 
+def native_stream_read_step_blobs(step_path: str | pathlib.Path) -> Iterator[tuple]:
+    """Yield ``(ngeom_blob, gid, color, world_matrices, instance_paths)`` per solid WITHOUT
+    hydrating the geometry — the foundation of the lazy ``ShapeStore`` import path.
+
+    The blob is yielded exactly as it crosses the adacpp boundary (today ``bytes``; a
+    buffer view once the zero-copy binding lands) so the consumer can retain it with
+    no further copies. Hydration, when a consumer eventually wants the ``ada.geom``
+    tree, is ``deserialize_geometries(blob)``."""
+    import adacpp
+
+    for nbytes, meta in adacpp.cad.StepNgeomStream(str(step_path)):
+        gid, color, mats, paths = decode_step_root_meta(meta)
+        yield nbytes, gid, color, mats, paths
+
+
 def native_stream_read_step(step_path: str | pathlib.Path) -> Iterator[Geometry]:
     """Yield one ``ada.geom.Geometry`` per solid, parsed natively — the inverse-serialized B-rep plus
     its colour, world-placement matrices and assembly paths. A drop-in for ``stream_read_step``.
 
     Uses the streaming ``StepNgeomStream`` iterator (one solid's NGEOM buffer at a time, bounded
     memory), so it scales to large assemblies instead of materialising the whole parsed model."""
-    import adacpp
-
     from ada.cadit.ngeom.deserialize import deserialize_geometries
 
-    for nbytes, meta in adacpp.cad.StepNgeomStream(str(step_path)):
+    for nbytes, gid, color, mats, paths in native_stream_read_step_blobs(step_path):
         decoded = deserialize_geometries(nbytes)  # exactly one root per streamed buffer
         if not decoded:
             continue
-        gid, color, mats, paths = decode_step_root_meta(meta)
+        # Roots are yielded as decoded (bare ConnectedFaceSet). The ClosedShell
+        # promotion (edge-pairing closedness check) costs ~17% of this loop on a
+        # large B-rep assembly and only matters where shells are re-exported or
+        # solid-built — the Assembly import paths apply promote_closed_shell at
+        # wrap/hydration; the streaming exporters (obj/stl/step emit) don't need it.
         yield Geometry(
             id=gid, geometry=decoded[0][1], color=color, transforms=(mats or None), instance_paths=(paths or None)
         )
diff --git a/src/ada/cadit/step/read/stream_reader.py b/src/ada/cadit/step/read/stream_reader.py
index 374d21bac..444a1af52 100644
--- a/src/ada/cadit/step/read/stream_reader.py
+++ b/src/ada/cadit/step/read/stream_reader.py
@@ -1776,6 +1776,12 @@ def _b_brep_with_voids(r: _Resolver, a: list) -> ClosedShell:
     "COMPLEX_TRIANGULATED_FACE_SET": _b_triangulated_face_set,
     "TESSELLATED_SHELL": _b_tessellated_shell,
     "TESSELLATED_SOLID": _b_tessellated_shell,
+    # Wireframe bodies (GEOMETRICALLY_BOUNDED_WIREFRAME_SHAPE_REPRESENTATION
+    # items): loose curves are renderable line geometry — without these entries
+    # a wire-only STEP (e.g. adapy's own GEOMETRIC_CURVE_SET export of a
+    # sectionless SAT wire body) reads back as zero roots.
+    "GEOMETRIC_CURVE_SET": _b_geometric_set,
+    "GEOMETRIC_SET": _b_geometric_set,
 }
 
 
diff --git a/src/ada/cadit/step/tess_stats.py b/src/ada/cadit/step/tess_stats.py
new file mode 100644
index 000000000..b5e0f18dc
--- /dev/null
+++ b/src/ada/cadit/step/tess_stats.py
@@ -0,0 +1,109 @@
+"""Per-conversion triangle tallies, folded into the audit ``convert_meta`` so a
+run-to-run change in tessellation output (a regression, a density-toggle drift, a
+silently-dropped solid) is visible without re-downloading and re-parsing the artefact.
+
+Same mechanism as the OCC mesh-health / tess-fallback tallies (``ada.occ.tessellating``):
+the conversion records a compact stats dict here; ``subprocess_convert`` consumes it at
+job completion and emits a ``[TRISTATS-JSON]`` marker line the worker parent folds into
+``audit_log.convert_meta["tri_stats"]``.
+
+Schema (all keys optional except ``n_tris``):
+    {
+      "n_tris": <int>,                # total output triangles
+      "engine": "adacpp:libtess2" | "adacpp:occ" | ...,
+      "n_primitives": <int>,          # GLB: draw primitives (material-merged, not solids)
+      "n_solids": <int>,              # mesh/GLB: source solids/products when known
+      "max_tris_per_solid": <int>,    # heaviest single solid, when known
+    }
+The primary regression signal is ``n_tris`` (e.g. the adaptive-density thread bug that
+doubled a monster solid's triangles would show up here immediately); ``n_solids`` catches
+"no geometry left behind" drops.
+"""
+
+from __future__ import annotations
+
+import json
+import struct
+import threading
+
+_LOCK = threading.Lock()
+_STATS: dict = {}
+
+
+def record_tri_stats(
+    *,
+    n_tris: int,
+    engine: str | None = None,
+    n_solids: int | None = None,
+    n_primitives: int | None = None,
+    max_tris_per_solid: int | None = None,
+) -> None:
+    """Record this conversion's triangle tally (last writer wins — one conversion per child)."""
+    with _LOCK:
+        _STATS.clear()
+        _STATS["n_tris"] = int(n_tris)
+        if engine:
+            _STATS["engine"] = str(engine)
+        if n_solids is not None:
+            _STATS["n_solids"] = int(n_solids)
+        if n_primitives is not None:
+            _STATS["n_primitives"] = int(n_primitives)
+        if max_tris_per_solid is not None:
+            _STATS["max_tris_per_solid"] = int(max_tris_per_solid)
+
+
+def consume_tri_stats() -> dict:
+    """Return and clear the recorded stats (empty dict if none recorded)."""
+    with _LOCK:
+        s = dict(_STATS)
+        _STATS.clear()
+        return s
+
+
+# Triangle-primitive modes in glTF (4=TRIANGLES, 5=TRIANGLE_STRIP, 6=TRIANGLE_FAN). Default is 4.
+_TRI_MODES = {4, 5, 6}
+
+
+def count_glb_tri_stats(path) -> dict:
+    """Total triangles + primitive count of a .glb, parsing ONLY the JSON chunk (no vertex data).
+
+    adacpp merges solids by material, so a GLB primitive is a material batch, not a source solid —
+    hence ``n_primitives`` (not ``n_solids``). Returns ``{}`` on any parse failure (best-effort).
+    """
+    try:
+        with open(path, "rb") as f:
+            head = f.read(12)
+            if len(head) < 12 or head[:4] != b"glTF":
+                return {}
+            # First chunk after the 12-byte header must be the JSON chunk.
+            chunk_hdr = f.read(8)
+            if len(chunk_hdr) < 8:
+                return {}
+            clen, ctype = struct.unpack("<II", chunk_hdr)
+            if ctype != 0x4E4F534A:  # 'JSON'
+                return {}
+            gltf = json.loads(f.read(clen).decode("utf-8", "replace"))
+    except (OSError, ValueError):
+        return {}
+
+    accessors = gltf.get("accessors") or []
+    n_tris = 0
+    n_prims = 0
+    for mesh in gltf.get("meshes") or []:
+        for prim in mesh.get("primitives") or []:
+            if prim.get("mode", 4) not in _TRI_MODES:
+                continue
+            idx = prim.get("indices")
+            attrs = prim.get("attributes") or {}
+            acc = None
+            if idx is not None and 0 <= idx < len(accessors):
+                acc = accessors[idx]
+            elif "POSITION" in attrs and 0 <= attrs["POSITION"] < len(accessors):
+                acc = accessors[attrs["POSITION"]]
+            if acc is None:
+                continue
+            n_prims += 1
+            n_tris += int(acc.get("count", 0)) // 3
+    if n_tris <= 0:
+        return {}
+    return {"n_tris": n_tris, "n_primitives": n_prims}
diff --git a/src/ada/cadit/step/write/_solid_source.py b/src/ada/cadit/step/write/_solid_source.py
index 29fd487dc..b57c8ea04 100644
--- a/src/ada/cadit/step/write/_solid_source.py
+++ b/src/ada/cadit/step/write/_solid_source.py
@@ -28,6 +28,27 @@ def native_available() -> bool:
     return native_adacpp_step_available()
 
 
+# Loose curve/geometric-set roots (wireframe bodies — SAT wire bodies, evaluated alignment
+# reference curves) that the native adacpp reader (solid-only) silently drops. "auto" must stay
+# lossless, so a file carrying these routes to the pure-Python reader instead.
+_CURVE_SET_MARKERS = (b"GEOMETRIC_CURVE_SET", b"GEOMETRIC_SET")
+
+
+def step_has_curve_set_roots(src_path: str | pathlib.Path, size_limit: int = 64_000_000) -> bool:
+    """Cheap check: does the STEP file contain loose curve/geometric-set roots that the native
+    (solid-only) reader would drop? Bounded to files under ``size_limit`` — such wireframe bodies
+    are small, and a multi-GB solid assembly is not worth a full extra scan (kept on the fast
+    native path)."""
+    try:
+        p = pathlib.Path(src_path)
+        if p.stat().st_size > size_limit:
+            return False
+        data = p.read_bytes()
+    except OSError:
+        return False
+    return any(m in data for m in _CURVE_SET_MARKERS)
+
+
 def _python_solids(src_path) -> Iterator[Geometry]:
     # local_pool=False: random-access two-pass index (valid for any reference order);
     # tolerant skips unsupported solids rather than raising.
@@ -43,6 +64,12 @@ def read_solids(src_path: str | pathlib.Path) -> Iterator[Geometry]:
         yield from _python_solids(src_path)
         return
 
+    # The native reader is solid-only; a file with loose curve/geometric-set roots (wireframe
+    # bodies) would silently lose them, so route it to the lossless pure-Python reader.
+    if step_has_curve_set_roots(src_path):
+        yield from _python_solids(src_path)
+        return
+
     from ada.cadit.step.read.native_reader import native_stream_read_step
 
     gen = native_stream_read_step(src_path)
diff --git a/src/ada/cadit/step/write/ap242_stream.py b/src/ada/cadit/step/write/ap242_stream.py
index 4f7c0fa7d..d2835b70e 100644
--- a/src/ada/cadit/step/write/ap242_stream.py
+++ b/src/ada/cadit/step/write/ap242_stream.py
@@ -739,7 +739,8 @@ def _tessellate_solid(self, g):
         if fn is None:
             return None, None
         defl = float(os.environ.get("ADA_STREAM_TESS_DEFLECTION", "2.0"))
-        ang = float(os.environ.get("ADA_STREAM_TESS_ANGULAR", "20.0"))
+        from ada.cad.registry import DEFAULT_STREAM_TESS_ANGULAR_DEG
+        ang = float(os.environ.get("ADA_STREAM_TESS_ANGULAR", str(DEFAULT_STREAM_TESS_ANGULAR_DEG)))
         try:
             mesh = fn([("0", g)], pipeline="libtess2", deflection=defl, angular_deg=ang)
         except Exception as exc:  # noqa: BLE001 - tessellation can't cover this solid
@@ -859,6 +860,38 @@ def add_solid_instances(self, g, *, name="shape", color=None, instances=()):
             self._instances.append((pd, sr, nm, parent_rep, tuple(tf) if tf is not None else None))
         return len(instances)
 
+    def add_baked_instances(self, g, *, name="shape", color=None, transforms=()) -> int:
+        """Emit one component per world 4x4 in ``transforms``, each BAKED into a faceted
+        MANIFOLD_SOLID_BREP whose planar faces are recomputed from the transformed points — so
+        ANY affine (including the non-uniform-scale mapped-item transforms an IfcMappedItem carries)
+        is represented losslessly. This mirrors adacpp's step_emit "bake per-instance geometry"
+        (a scale/shear can't ride a rotation-only STEP placement, and NAUO/AXIS2_PLACEMENT is
+        rigid-only), so it is the transform-preserving path for mapped/instanced shapes that the
+        analytic ``add_extrusion``/``add_brep`` writers can't place. Returns the number emitted.
+
+        ``transforms`` is a list of row-major flat-16 4x4 world matrices (``None`` = identity)."""
+        nm = (name or "shape").replace("'", "''")
+        saved_tf, saved_t = getattr(self, "_tf", None), getattr(self, "_t", (0.0, 0.0, 0.0))
+        emitted = 0
+        for m in transforms:
+            self._tf = tuple(float(x) for x in m) if m is not None else None
+            self._t = (0.0, 0.0, 0.0)
+            try:
+                item = self._emit_faceted_brep(g, nm, color)  # bakes self._tf into world points
+            except Exception as exc:  # noqa: BLE001 - one bad instance shouldn't sink the file
+                logger.warning("ap242 add_baked_instances skipped %r: %s", name, exc)
+                item = None
+            finally:
+                self._tf, self._t = saved_tf, saved_t
+            if item is None:
+                continue
+            if self.assembly:
+                self._emit_component(item, nm)
+            else:
+                self._solids.append(item)
+            emitted += 1
+        return emitted
+
     def _register_asm_path(self, parent_path) -> int | None:
         """Register the intermediate assembly nodes of ``parent_path`` (root-first
         ``(rep_id, name)`` levels) and their parent edges; return the rep_id of the
@@ -1041,12 +1074,25 @@ def emit(v0, p0, v1, p1):
         else:
             return None  # unsupported edge geometry
 
-        # Key by the EdgeCurve OBJECT identity: a truly-shared edge resolves to the
-        # same ec object in both adjacent faces (reader memoisation), while the two
-        # semicircle arcs of one circle are distinct objects — so they are NOT merged
-        # (a geometric vertex-pair key collides them and corrupts the topology).
+        # Key by the EDGE_CURVE's VALUE, not the ec object's identity: the Python
+        # reader memoises shared edges into one object, but NGEOM-hydrated trees
+        # (native reader / lazy ShapeStore) re-decode one EdgeCurve object per
+        # referencing face — identity keying would emit duplicate EDGE_CURVEs and
+        # the shell would read back with free edges (no solid). The value key is the
+        # raw emit direction (unnormalised — two complementary arcs of one circle
+        # run opposite ways), the underlying curve's signature (arcs of one circle
+        # share endpoints; the signature alone doesn't split them, direction and
+        # t-range do), the trim range, and same_sense.
+        ts, te = getattr(oe, "t_start", None), getattr(oe, "t_end", None)
+        key = (
+            self._vfor(ec.start),
+            self._vfor(ec.end),
+            _edge_curve_value_sig(g),
+            bool(ec.same_sense),
+            None if ts is None else (min(ts, te), max(ts, te)),
+        )
         return self._shared_oriented(
-            id(ec),
+            key,
             self._vfor(oe.start),
             self._vfor(oe.end),  # loop traversal direction
             self._vfor(ec.start),
@@ -1270,6 +1316,82 @@ def _curve_to_segs(curve, *, is_outer):
     return None
 
 
+def _transform_extrusion(ext, W):
+    """Apply a world affine 4x4 ``W`` to an :class:`Extrusion`, returning a NEW analytic Extrusion
+    (exact planar faces + line/arc edges — no tessellation), or None when the transform can't be
+    carried analytically (an oblique extrude vector under shear, or a circular arc that a
+    non-uniform in-plane scale would turn elliptic). The caller then facet-bakes that instance.
+
+    The profile's own 2D coordinates absorb the linear map: each 2D point is lifted to 3D in the
+    source frame, mapped by ``W``'s rotation/scale, and re-projected into a fresh orthonormal frame
+    fitted to the transformed profile plane — so a rotation, a uniform, or an axis-aligned
+    non-uniform scale (the common mapped-instance case) all stay a valid ExtrudedAreaSolid."""
+    import numpy as np
+
+    Wm = np.asarray(W, dtype=float)
+    R = Wm[:3, :3]
+    o = np.asarray(ext.origin, dtype=float)
+    xd = np.asarray(ext.xdir, dtype=float)
+    nd = np.asarray(ext.normal, dtype=float)
+    yd = np.cross(nd, xd)
+
+    # The transformed profile plane's normal is cross(R@xd, R@yd) — NOT R@nd (that only coincides
+    # for axis-aligned scale/rotation; a shear tilts the plane while leaving R@nd unchanged).
+    tx, ty = R @ xd, R @ yd
+    n2 = np.cross(tx, ty)
+    if np.linalg.norm(n2) < 1e-12:
+        return None
+    n_hat = n2 / np.linalg.norm(n2)
+    x_hat = tx - np.dot(tx, n_hat) * n_hat
+    if np.linalg.norm(x_hat) < 1e-9:
+        return None
+    x_hat /= np.linalg.norm(x_hat)
+    y_hat = np.cross(n_hat, x_hat)
+
+    # add_extrusion extrudes along `normal` by `depth`; the mapped extrude vector must stay ~parallel
+    # to the transformed plane normal (no oblique-prism support here) → else facet-fallback.
+    ev = R @ (float(ext.depth) * nd)
+    depth2 = float(np.dot(ev, n_hat))
+    if np.linalg.norm(ev - depth2 * n_hat) > 1e-6 * (abs(depth2) + 1.0):
+        return None
+    if depth2 < 0:  # extrude flipped → flip the frame so depth stays positive (add_extrusion req.)
+        n_hat, y_hat, depth2 = -n_hat, -y_hat, -depth2
+    if depth2 <= 1e-12:
+        return None
+
+    # A non-uniform in-plane scale turns circles into ellipses — a circular-arc Seg can't represent
+    # that, so bail (facet) when the profile has arcs and the in-plane scale is anisotropic.
+    sx, sy = np.linalg.norm(R @ xd), np.linalg.norm(R @ yd)
+    anisotropic = abs(sx - sy) > 1e-6 * max(sx, sy, 1.0)
+    if anisotropic and any(s.kind == "arc" for loop in [ext.outer, *ext.inners] for s in loop):
+        return None
+
+    def to2d(p2):
+        q = R @ (float(p2[0]) * xd + float(p2[1]) * yd)  # W@(o+..) - W@o = R@(..)
+        return (float(np.dot(q, x_hat)), float(np.dot(q, y_hat)))
+
+    def tf_loop(segs):
+        out = []
+        for s in segs:
+            if s.kind == "arc":
+                out.append(Seg("arc", to2d(s.start), to2d(s.end), mid=to2d(s.mid)))
+            else:
+                out.append(Seg(s.kind, to2d(s.start), to2d(s.end)))
+        return out
+
+    new_origin = tuple((Wm @ np.array([o[0], o[1], o[2], 1.0]))[:3])
+    return Extrusion(
+        origin=new_origin,
+        xdir=tuple(x_hat),
+        normal=tuple(n_hat),
+        depth=depth2,
+        outer=tf_loop(ext.outer),
+        inners=[tf_loop(loop) for loop in ext.inners],
+        name=ext.name,
+        color=ext.color,
+    )
+
+
 def extrusion_from_geometry(geom, *, name="obj", color=None, translate=(0.0, 0.0, 0.0)):
     """Build an :class:`Extrusion` from an adapy ``Geometry`` whose solid is a
     plain ``ExtrudedAreaSolid``. Returns None if the geometry is not a supported
@@ -1300,6 +1422,16 @@ def extrusion_from_geometry(geom, *, name="obj", color=None, translate=(0.0, 0.0
     normal = tuple(float(v) for v in pos.axis)
 
     profile = solid.swept_area
+    if not hasattr(profile, "outer_curve"):
+        # Parametric profile (Rectangle/I/T from an IFC import) — convert to a
+        # concrete outline first, same seam the tessellation backends use.
+        from ada.api.beams.geom_beams import parametric_profile_to_arbitrary
+
+        try:
+            profile = parametric_profile_to_arbitrary(profile)
+        except NotImplementedError as e:
+            logger.warning("%s: swept profile %s not convertible (%s); skipping", name, type(profile).__name__, e)
+            return None
     outer = _curve_to_segs(profile.outer_curve, is_outer=True)
     if outer is None:
         return None
@@ -1494,15 +1626,50 @@ def write_step_stream(
             geom, name, color, translate = _object_geom_meta(obj)
             done = False
             if geom is not None:
-                ext = extrusion_from_geometry(
-                    geom, name=name, color=color, translate=translate
-                ) or _primitive_to_extrusion(geom, name=name, color=color, translate=translate)
-                if ext is not None:
-                    writer.add_extrusion(ext)
-                    done = True
-                elif writer.add_brep(geom.geometry, name=name, color=color, translate=translate) is not None:
-                    # B-rep fallback: imported shapes, pure shells, analytic faces
-                    done = True
+                # transforms ride obj.geom (the mapped-item mesh-level instances); solid_geom()
+                # strips them. World order (matching the tessellation path + the ifcopenshell oracle)
+                # is placement @ transform[k] @ local — so bake the LOCAL geometry (obj.geom.geometry,
+                # pre-placement) under self._tf = P @ transform[k].
+                obj_geom = getattr(obj, "geom", None)
+                transforms = getattr(obj_geom, "transforms", None) if obj_geom is not None else None
+                if transforms:
+                    # Mapped / instanced shape: N world 4x4s from a multi-instance IfcMappedItem. The
+                    # analytic writers place a single solid (dropping N-1 instances). Emit ONE solid
+                    # per instance, ANALYTICALLY where possible — transform the Extrusion (exact
+                    # planar faces + line/arc edges preserved, no tessellation) and emit via
+                    # add_extrusion. Only a transform the analytic form can't carry (oblique/elliptic
+                    # under shear) falls back to a faceted bake — facet-but-present, never dropped.
+                    import numpy as np
+
+                    from ada.geom import Geometry
+
+                    P = np.asarray(obj.placement.get_matrix4x4(), dtype=float)
+                    base_ext = extrusion_from_geometry(
+                        Geometry(name, obj_geom.geometry), name=name, color=color
+                    )
+                    n_ok = 0
+                    for m in transforms:
+                        W = P @ np.asarray(m, dtype=float)
+                        placed = _transform_extrusion(base_ext, W) if base_ext is not None else None
+                        if placed is not None:
+                            writer.add_extrusion(placed)
+                            n_ok += 1
+                        elif writer.add_baked_instances(
+                            obj_geom.geometry, name=name, color=color, transforms=[tuple(W.ravel())]
+                        ) > 0:
+                            n_ok += 1
+                    if n_ok > 0:
+                        done = True
+                else:
+                    ext = extrusion_from_geometry(
+                        geom, name=name, color=color, translate=translate
+                    ) or _primitive_to_extrusion(geom, name=name, color=color, translate=translate)
+                    if ext is not None:
+                        writer.add_extrusion(ext)
+                        done = True
+                    elif writer.add_brep(geom.geometry, name=name, color=color, translate=translate) is not None:
+                        # B-rep fallback: imported shapes, pure shells, analytic faces
+                        done = True
             emitted += 1 if done else 0
             skipped += 0 if done else 1
             if progress_callback is not None:
@@ -1518,6 +1685,25 @@ def _axis_or(d, default):
     return list(d) if d is not None else list(default)
 
 
+def _edge_curve_value_sig(g):
+    """A value signature of an edge's underlying curve (see _brep_oriented's key).
+    Mirrors ada.cadit.ngeom.deserialize._edge_curve_sig, duplicated here so the
+    streaming writer stays numpy-free for the slim worker."""
+    if g is None:
+        return None
+    tname = type(g).__name__
+    pos = getattr(g, "position", None)
+    loc = tuple(float(v) for v in pos.location) if pos is not None else None
+    if hasattr(g, "radius"):
+        return (tname, loc, float(g.radius))
+    if hasattr(g, "semi_axis1"):
+        return (tname, loc, float(g.semi_axis1), float(g.semi_axis2))
+    cps = getattr(g, "control_points_list", None)
+    if cps is not None:
+        return (tname, tuple(tuple(float(v) for v in p) for p in cps))
+    return (tname, loc)
+
+
 def _object_geom_meta(obj):
     """(geom, name, color, translate) for a physical object, or (None, ...) if it
     has no usable solid geometry. Shared by the extrusion and B-rep emit paths."""
diff --git a/src/ada/cadit/step/write/stream_step_to_ifc.py b/src/ada/cadit/step/write/stream_step_to_ifc.py
index fd64673ed..bc2095148 100644
--- a/src/ada/cadit/step/write/stream_step_to_ifc.py
+++ b/src/ada/cadit/step/write/stream_step_to_ifc.py
@@ -157,7 +157,21 @@ def _curve(self, lines, g):
             return self._bspline_curve(lines, g)
         return None
 
-    def _edge_curve(self, lines, ec):
+    def _pcurve_bspline_2d(self, lines, pc):
+        """Emit a :class:`Pcurve2dBSpline` as a 2D IfcBSplineCurveWithKnots (UV space —
+        control points are raw parameter pairs, never transformed)."""
+        cps = self._refs(
+            [self._emit(lines, f"IfcCartesianPoint(({_r(p[0])},{_r(p[1])}))") for p in pc.control_points_2d]
+        )
+        common = (
+            f"{int(pc.degree)},{cps},.UNSPECIFIED.,{_b(bool(pc.closed))},.F.,"
+            f"{self._ilist(pc.knot_multiplicities)},{self._rlist(pc.knots)},.UNSPECIFIED."
+        )
+        if pc.weights:
+            return self._emit(lines, f"IfcRationalBSplineCurveWithKnots({common},{self._rlist(pc.weights)})")
+        return self._emit(lines, f"IfcBSplineCurveWithKnots({common})")
+
+    def _edge_curve(self, lines, ec, pcurve=None, surf_id=None):
         g = ec.edge_geometry
         import ada.geom.curves as cu
 
@@ -167,23 +181,33 @@ def _edge_curve(self, lines, ec):
             p0, p1 = ec.start, ec.end
             d = _unit(_sub(p1, p0))
             crv = self._emit(lines, f"IfcLine(#{self._pt(lines, p0)},#{self._vec(lines, d)})")
+        if pcurve is not None and surf_id is not None:
+            # Carry the coedge's UV p-curve: without it a trimmed analytic face
+            # (joint-cut cylinder, exppc B-spline) can't rebuild its wire on
+            # re-import ('wire build failed' in adacpp). The reader recovers it
+            # from IfcSurfaceCurve.AssociatedGeometry[0].ReferenceCurve.
+            pcv = self._emit(lines, f"IfcPcurve(#{surf_id},#{self._pcurve_bspline_2d(lines, pcurve)})")
+            crv = self._emit(lines, f"IfcSurfaceCurve(#{crv},(#{pcv}),.CURVE3D.)")
         v0, v1 = self._vertex(lines, ec.start), self._vertex(lines, ec.end)
         return self._emit(lines, f"IfcEdgeCurve(#{v0},#{v1},#{crv},{_b(ec.same_sense)})")
 
-    def _oriented_edge(self, lines, oe):
+    def _oriented_edge(self, lines, oe, surf_id=None):
         ec = getattr(oe, "edge_element", oe)
-        key = id(ec)
+        pcurve = getattr(oe, "pcurve", None)
+        # The p-curve lives on the coedge (face-specific UV), so a pcurve-carrying
+        # edge is cached per (edge, surface) — the bare 3D form stays shared.
+        key = (id(ec), surf_id) if pcurve is not None else id(ec)
         edge_id = self._ecache.get(key)
         if edge_id is None:
-            edge_id = self._edge_curve(lines, ec)
+            edge_id = self._edge_curve(lines, ec, pcurve=pcurve, surf_id=surf_id)
             self._ecache[key] = edge_id
         return self._emit(lines, f"IfcOrientedEdge($,$,#{edge_id},{_b(oe.orientation)})")
 
-    def _loop(self, lines, loop):
+    def _loop(self, lines, loop, surf_id=None):
         import ada.geom.curves as cu
 
         if isinstance(loop, cu.EdgeLoop):
-            oe = [self._oriented_edge(lines, e) for e in loop.edge_list]
+            oe = [self._oriented_edge(lines, e, surf_id=surf_id) for e in loop.edge_list]
             if not oe:
                 return None
             return self._emit(lines, f"IfcEdgeLoop({self._refs(oe)})")
@@ -248,7 +272,7 @@ def _face(self, lines, face):
             return None
         bounds = []
         for i, fb in enumerate(face.bounds):
-            loop = self._loop(lines, fb.bound)
+            loop = self._loop(lines, fb.bound, surf_id=surf)
             if loop is None:
                 return None
             kw = "IfcFaceOuterBound" if i == 0 else "IfcFaceBound"
diff --git a/src/ada/cadit/step/write/stream_step_to_mesh.py b/src/ada/cadit/step/write/stream_step_to_mesh.py
index be3b51fc2..910fbf259 100644
--- a/src/ada/cadit/step/write/stream_step_to_mesh.py
+++ b/src/ada/cadit/step/write/stream_step_to_mesh.py
@@ -12,6 +12,7 @@
 import struct
 from typing import Callable
 
+from ada.cad.registry import DEFAULT_STREAM_TESS_ANGULAR_DEG
 from ada.config import logger
 
 ProgressFn = Callable[[str, float], None]
@@ -23,7 +24,7 @@ def stream_step_to_mesh(
     fmt: str,
     *,
     deflection: float = 2.0,
-    angular_deg: float = 20.0,
+    angular_deg: float = DEFAULT_STREAM_TESS_ANGULAR_DEG,
     on_progress: ProgressFn | None = None,
 ) -> dict:
     """Stream a STEP file to ``fmt`` ('stl' | 'obj'), one solid at a time. Returns
diff --git a/src/ada/cadit/visual_parity.py b/src/ada/cadit/visual_parity.py
index 8fd5db20c..1f2f7b86a 100644
--- a/src/ada/cadit/visual_parity.py
+++ b/src/ada/cadit/visual_parity.py
@@ -28,11 +28,26 @@
     from ada import Assembly
 
 # Structure-preserving formats: (writer(assembly, path), reader(path) -> Assembly, suffix).
-# STEP is written via the OCC writer (full geometry, not just extrusions) and
-# read via the streaming reader with an OCC fallback (reader="auto").
+# STEP is written via the non-OCC stream writer (the kernel-free AP242 path prod uses), which
+# preserves mapped/instanced shapes the OCC writer drops; it falls back to OCC per-file only for
+# solids the analytic stream writer can't yet author (swept/revolved/tapered). Read via the
+# streaming reader with an OCC fallback (reader="auto").
 _FORMAT_IO: dict[str, tuple[Callable, Callable, str]] = {}
 
 
+def _write_step_parity(assembly, path) -> None:
+    """Write STEP for the parity round-trip via the non-OCC stream writer (matches the prod
+    ifc/step→step converter path, and preserves multi-instance mapped shapes the OCC writer
+    collapses). If the stream writer skipped any solid it can't author analytically
+    (swept/revolved/tapered), re-write the whole file with the OCC writer, which covers those —
+    so the leg stays lossless either way. (A model mixing mapped instances AND swept solids would
+    lose the mapped instances to the OCC rewrite; none exist in the corpus and the stream writer's
+    coverage is being extended to remove even that.)"""
+    stats = assembly.to_stp(path, writer="stream")
+    if isinstance(stats, dict) and stats.get("skipped", 0) > 0:
+        assembly.to_stp(path, writer="occ")
+
+
 def _register_default_formats() -> None:
     if _FORMAT_IO:
         return
@@ -40,7 +55,7 @@ def _register_default_formats() -> None:
 
     _FORMAT_IO["ifc"] = (lambda a, p: a.to_ifc(p), lambda p: ada.from_ifc(p), ".ifc")
     _FORMAT_IO["xml"] = (lambda a, p: a.to_genie_xml(p), lambda p: ada.from_genie_xml(p), ".xml")
-    _FORMAT_IO["step"] = (lambda a, p: a.to_stp(p), lambda p: ada.from_step(p, reader="auto"), ".step")
+    _FORMAT_IO["step"] = (_write_step_parity, lambda p: ada.from_step(p, reader="auto"), ".step")
 
 
 def visualized_element_count(scene: "trimesh.Scene") -> int:
@@ -48,7 +63,9 @@ def visualized_element_count(scene: "trimesh.Scene") -> int:
 
     Counts mesh / polyline entries one-per-object (build the scene with
     ``merge_meshes=False``); excludes the placeholder point cloud the converter
-    seeds for otherwise-empty scenes.
+    seeds for otherwise-empty scenes, and zero-vertex entries (the OCC STEP
+    fallback reader materializes one empty Shape from a geometry-less file —
+    it renders nothing, so it must not count as an element).
     """
     import trimesh
 
@@ -56,13 +73,39 @@ def visualized_element_count(scene: "trimesh.Scene") -> int:
     for geom in scene.geometry.values():
         if isinstance(geom, trimesh.PointCloud):
             continue  # empty-scene placeholder
+        if len(getattr(geom, "vertices", ())) == 0:
+            continue  # degenerate/empty body — renders nothing
         n += 1
     return n
 
 
 def assembly_element_count(assembly: "Assembly") -> int:
-    """Visualized-element count for an adapy Assembly (unmerged scene)."""
-    return visualized_element_count(assembly.to_trimesh_scene(merge_meshes=False))
+    """Visualized-element count for an adapy Assembly.
+
+    Counted from the raw tessellation stream — one MeshStore per renderable
+    object, the exact set ``meshes_to_trimesh(merge_meshes=False)`` turns into
+    scene entries — WITHOUT assembling a trimesh scene. Scene assembly
+    (trimesh objects, materials, normals) was ~1/3 of a parity cell's wall
+    time and contributes nothing to the count. Same exclusions as
+    :func:`visualized_element_count`: point clouds (the empty-scene
+    placeholder) and zero-vertex stores (degenerate bodies render nothing)."""
+    from itertools import chain
+
+    from ada.occ.tessellating import BatchTessellator
+    from ada.visit.gltf.meshes import MeshType
+
+    bt = BatchTessellator()
+    # Mirror tessellate_part's object set: physical objects (pipes as
+    # segments) + welds, which live in their own per-Part container.
+    objects = chain(assembly.get_all_physical_objects(pipe_to_segments=True), assembly.get_all_welds())
+    n = 0
+    for ms in bt.batch_tessellate(objects):
+        if ms is None or ms.type == MeshType.POINTS:
+            continue
+        if len(ms.position) == 0:
+            continue
+        n += 1
+    return n
 
 
 @dataclass
@@ -127,6 +170,23 @@ def load_assembly_auto(path: str | Path) -> "Assembly":
     raise ValueError(f"visual_parity: no loader for source suffix {ext!r}")
 
 
+def _count_curve_set_roots(path: str | Path, size_limit: int = 64_000_000) -> int:
+    """Number of loose curve/geometric-set roots (one per placed curve body — e.g. an evaluated
+    alignment reference curve) in a STEP file. The solid-only native reader skips these; each is a
+    distinct GEOMETRIC_CURVE_SET / GEOMETRIC_SET entity definition. Size-bounded (such wireframe
+    bodies are tiny; a multi-GB solid assembly carries none worth a full scan)."""
+    try:
+        p = Path(path)
+        if p.stat().st_size > size_limit:
+            return 0
+        data = p.read_bytes()
+    except OSError:
+        return 0
+    # "GEOMETRIC_CURVE_SET(" does not contain "GEOMETRIC_SET(" as a substring, so counting both
+    # names never double-counts.
+    return data.count(b"GEOMETRIC_CURVE_SET(") + data.count(b"GEOMETRIC_SET(")
+
+
 def _count_step_instances(path: str | Path) -> int:
     """Number of placed solid instances in a STEP file. Counted by streaming the
     native parser and reading each solid's transform list from the metadata —
@@ -134,6 +194,9 @@ def _count_step_instances(path: str | Path) -> int:
     the count). Falls back to the pure-Python streaming reader."""
     from ada.cadit.step.read.native_reader import native_adacpp_step_available
 
+    # Native StepNgeomStream counts the solids; add the loose curve/geometric-set roots it can't
+    # see (one per placed curve body). This keeps native grouping/transform semantics instead of a
+    # whole-model reload, which would ungroup an OCC-exploded multi-face solid and over-count.
     if native_adacpp_step_available():
         import adacpp
 
@@ -141,7 +204,7 @@ def _count_step_instances(path: str | Path) -> int:
         for _nbytes, meta in adacpp.cad.StepNgeomStream(str(path)):
             tf = meta.transforms
             total += len(tf) if tf else 1
-        return total
+        return total + _count_curve_set_roots(path)
 
     import ada
 
@@ -173,7 +236,12 @@ def _count_step_product_instances(path: str | Path) -> int | None:
         key = tuple(ip[0][-1]) if (ip and ip[0]) else ("root", meta.id)
         n = len(meta.transforms) or 1
         groups[key] = max(groups.get(key, 0), n)
-    return sum(groups.values())
+    # The native StepNgeomStream is solid-only but GROUPS a multi-face solid (OCC's to_stp splits a
+    # sectioned/swept or sewn multi-shell solid into many SHELL_BASED_SURFACE_MODEL roots) back into
+    # its one owning product. A whole-model reload would UNGROUP that explosion and massively
+    # over-count, so instead of deferring we keep the grouped solid count and ADD the loose
+    # curve/geometric-set roots (one per placed curve body) the native reader can't see.
+    return sum(groups.values()) + _count_curve_set_roots(path)
 
 
 def _count_ifc_proxies(path: str | Path) -> int:
@@ -528,6 +596,13 @@ def cross_format_parity(
                 # source and the IFC leg. Grouping by owning product restores the
                 # one-element-per-object convention both other legs use.
                 n = _count_step_product_instances(out) if fmt == "step" else None
+                if fmt == "step" and n == 0:
+                    # The native stream counter sees only solid/B-rep roots — a
+                    # wireframe-only output (GEOMETRIC_CURVE_SET wire bodies)
+                    # counts 0 there even though the geometry is present. A
+                    # 0-count file is small by construction, so the exact reload
+                    # count is affordable.
+                    n = None
                 counts[fmt] = n if n is not None else assembly_element_count(reader(out))
             except Exception as ex:  # noqa: BLE001 - record and continue with the other formats
                 errors[fmt] = f"{type(ex).__name__}: {ex}"
diff --git a/src/ada/comms/rest/app.py b/src/ada/comms/rest/app.py
index a677a2b36..53b2fc7f1 100644
--- a/src/ada/comms/rest/app.py
+++ b/src/ada/comms/rest/app.py
@@ -230,6 +230,26 @@ async def lifespan(app: FastAPI):
                 _worker_prune_loop(queue),
                 name="worker-prune",
             )
+        # Worker-registry snapshot refresher. Prime it once now (a single
+        # ~1s NATS scan at boot) so the very first /config.js is warm, then
+        # keep it fresh in the background — the config endpoints read the
+        # cached snapshot instead of hitting NATS on the request path.
+        app.state.worker_registry_task = None
+        if queue.enabled:
+            await _refresh_worker_registry()
+            app.state.worker_registry_task = asyncio.create_task(
+                _worker_registry_refresh_loop(),
+                name="worker-registry-refresh",
+            )
+        # Completed-job KV cleanup. Keeps the shared bucket lean (the KV is a
+        # transient progress cache; durable history lives in Postgres/S3) so
+        # keys() scans stay cheap and never storm NATS again.
+        app.state.job_cleanup_task = None
+        if queue.enabled:
+            app.state.job_cleanup_task = asyncio.create_task(
+                _job_cleanup_loop(queue),
+                name="job-kv-cleanup",
+            )
         yield
         # Cancel scheduler + issue bot first so a tick in flight
         # doesn't try to use a pool / queue that's about to be torn
@@ -239,6 +259,8 @@ async def lifespan(app: FastAPI):
             "issue_bot_task",
             "profile_parser_task",
             "worker_prune_task",
+            "worker_registry_task",
+            "job_cleanup_task",
         ):
             task = getattr(app.state, attr, None)
             if task is not None and not task.done():
@@ -278,6 +300,41 @@ async def healthz() -> Response:
         # Public — load balancers + readiness probes hit this.
         return Response(status_code=200)
 
+    # Cached worker-registry snapshot, refreshed off the request path by
+    # ``_worker_registry_refresh_loop``. ``queue.list_workers()`` is an
+    # N+1 over NATS KV (list keys, then one round-trip per worker key);
+    # the SPA fetches ``/config.js`` (and later ``/api/config``) on its
+    # critical startup path, and each of those endpoints derived exts /
+    # conversions / utilities by calling ``list_workers()`` 2-3 times.
+    # That put 2.5-4s of blocking NATS latency on every page load. The
+    # helpers below now read this snapshot synchronously so page load
+    # never waits on NATS; the background task keeps it fresh (~3s). The
+    # snapshot changes on worker-heartbeat timescales, so a few seconds
+    # of staleness is immaterial to the picker / capability matrix.
+    # Empty until the first refresh tick (same observable state as a
+    # queue-disabled deploy — the SPA falls back to its static set).
+    _worker_registry: dict = {"workers": [], "image_tag": None, "ts": 0.0}
+
+    async def _refresh_worker_registry() -> None:
+        """Snapshot the worker registry + worker image tag into
+        ``_worker_registry``. Defensive: a failed NATS call is logged and
+        leaves the previous snapshot in place rather than blanking it."""
+        if not queue.enabled:
+            return
+        try:
+            workers = await queue.list_workers()
+        except Exception:
+            logger.exception("worker registry refresh: list_workers failed")
+            return
+        image_tag = _worker_registry.get("image_tag")
+        try:
+            image_tag = await queue.get_meta("worker_image_tag")
+        except Exception:
+            logger.exception("worker registry refresh: get_meta failed")
+        _worker_registry["workers"] = workers
+        _worker_registry["image_tag"] = image_tag
+        _worker_registry["ts"] = time.time()
+
     async def _is_accepted_source(key: str) -> bool:
         """``is_supported_source`` plus a check against the workers'
         advertised extra extensions. Use this on every upload / bake
@@ -311,11 +368,7 @@ async def _worker_advertised_exts() -> list[str]:
         """
         if not queue.enabled:
             return []
-        try:
-            workers = await queue.list_workers()
-        except Exception:
-            logger.exception("config: failed to read worker registry")
-            return []
+        workers = _worker_registry["workers"]
         out: set[str] = set()
         for w in workers:
             for raw in w.get("source_exts") or []:
@@ -348,11 +401,7 @@ async def _worker_advertised_conversions() -> list[dict]:
         """
         if not queue.enabled:
             return []
-        try:
-            workers = await queue.list_workers()
-        except Exception:
-            logger.exception("config: failed to read worker registry for matrix")
-            return []
+        workers = _worker_registry["workers"]
         merged: dict[str, set[str]] = {}
         # from → target → option-name → option-dict. Per-job knob schemas are unioned across workers:
         # for an enum option (e.g. step_glb_pipeline) the enum VALUES are unioned, so an engine that
@@ -414,11 +463,7 @@ async def _worker_advertised_utilities() -> list[dict]:
         """
         if not queue.enabled:
             return []
-        try:
-            workers = await queue.list_workers()
-        except Exception:
-            logger.exception("config: failed to read worker registry for utilities")
-            return []
+        workers = _worker_registry["workers"]
         by_name: dict[str, dict] = {}
         for w in workers:
             for spec in w.get("utilities") or []:
@@ -437,12 +482,8 @@ async def api_config() -> JSONResponse:
         # publishes its tag on startup. Either may be missing in dev /
         # local runs; the SPA hides the row when both are empty.
         viewer_tag = os.environ.get("ADA_IMAGE_TAG", "").strip() or None
-        worker_tag: str | None = None
-        if queue.enabled:
-            try:
-                worker_tag = await queue.get_meta("worker_image_tag")
-            except Exception:
-                logger.exception("config: failed to read worker image tag")
+        # Cached snapshot — no NATS on the request path (see _worker_registry).
+        worker_tag: str | None = _worker_registry["image_tag"] if queue.enabled else None
         extra_source_exts = await _worker_advertised_exts()
         # Subset of stream-readable extensions that the legacy /convert
         # pipeline does NOT handle. The SPA uses this to pick between
@@ -641,17 +682,15 @@ async def api_rpc(
         payload = await request.body()
         if not payload:
             raise HTTPException(status_code=400, detail="empty body")
-        # Pull the worker-advertised extension set so the file lister
-        # can flag plug-in formats (e.g. .odb when an abaqus-capability
-        # worker is online) instead of silently dropping them. Cheap
-        # NATS KV read; failures degrade to the static list.
-        try:
-            extra_source_exts = frozenset(await _worker_advertised_exts())
-        except Exception:
-            logger.exception("rpc: failed to read worker-advertised exts")
-            extra_source_exts = frozenset()
+        # Hand dispatch a lazy provider for the worker-advertised extension
+        # set (used only by the file lister, to flag plug-in formats like
+        # .odb when an abaqus-capability worker is online). Passing it lazily
+        # keeps the worker-registry read off every non-LIST_FILE command —
+        # server-info, view-file, etc. no longer pay it — so worker-listing
+        # never gates file-finding. The read itself is a cached in-memory
+        # lookup (see _worker_registry) that degrades to the static list.
         try:
-            reply = await dispatch(payload, storage, scope, extra_source_exts=extra_source_exts)
+            reply = await dispatch(payload, storage, scope, exts_provider=_worker_advertised_exts)
         except Exception as exc:
             logger.exception("rpc dispatch failed")
             raise HTTPException(status_code=500, detail=str(exc)) from exc
@@ -684,6 +723,17 @@ async def api_me(
         for p in projects:
             scopes.append({"kind": "project", "id": p["id"], "name": p["name"]})
 
+        # Corpus scopes are admin-only (scope_can_access gates them). Advertise
+        # them here so an admin can browse + visualise corpus files straight from
+        # the main storage panel — the same list/convert flow every other scope
+        # uses. Non-admins never see them; the backend rejects the scope anyway.
+        if user.is_admin and pool is not None:
+            try:
+                for c in await db_module.list_corpora(pool):
+                    scopes.append({"kind": "corpus", "id": c["slug"], "name": c["name"]})
+            except Exception:
+                logger.exception("api_me: listing corpora failed")
+
         return JSONResponse(
             {
                 "sub": user.sub,
@@ -1811,11 +1861,20 @@ async def api_scope_convert(
         if not queue.enabled:
             raise HTTPException(status_code=503, detail="conversion disabled (no NATS configured)")
 
+        # A re-conversion (gallery "Re-convert") always re-runs and writes to the SEPARATE
+        # ``_reconvert/`` namespace, so it never overwrites the ``_derived/`` audit product in a
+        # corpus scope. Regular converts keep the cached ``_derived/`` short-circuit below.
+        reconvert = bool(body.get("reconvert"))
         try:
-            derived_key = derived_key_for(source_key, target_format, step=step, field=field)
+            if reconvert:
+                from .converter import reconvert_key_for
+
+                derived_key = reconvert_key_for(source_key, target_format)
+            else:
+                derived_key = derived_key_for(source_key, target_format, step=step, field=field)
         except UnsupportedFormat as exc:
             raise HTTPException(status_code=415, detail=str(exc)) from exc
-        if await storage.exists(scope_obj, derived_key):
+        if not reconvert and await storage.exists(scope_obj, derived_key):
             await _audit(
                 request,
                 user,
@@ -1849,6 +1908,8 @@ async def api_scope_convert(
                 step=step,
                 field=field,
                 conversion_options=conversion_options,
+                derived_key=derived_key if reconvert else None,
+                force_rebuild=reconvert,
             )
         except Exception as exc:
             logger.exception("enqueue failed")
@@ -2845,6 +2906,49 @@ def _next_fire(cron_expr: str, *, after=None):
         base = after or datetime.now(timezone.utc)
         return croniter(cron_expr, base).get_next(datetime)
 
+    async def _worker_registry_refresh_loop() -> None:
+        """Background task: refresh the cached worker-registry snapshot
+        (:data:`_worker_registry`) every ``REFRESH_INTERVAL_S`` so the
+        config endpoints never call ``list_workers()`` (an N+1 over NATS
+        KV) on the request path. Defensive — a failed tick keeps the last
+        good snapshot; only ``asyncio.CancelledError`` exits (shutdown)."""
+        # 15s (was 3s): the refresh does a KV keys() scan, and worker
+        # capabilities/tags only change on a worker's ~15s heartbeat, so a
+        # tighter interval bought nothing but scan traffic. Cheap now that the
+        # KV is kept lean (see _job_cleanup_loop), but no reason to over-poll.
+        REFRESH_INTERVAL_S = 15.0
+        logger.info("worker registry refresh: starting (every %ss)", REFRESH_INTERVAL_S)
+        try:
+            while True:
+                await asyncio.sleep(REFRESH_INTERVAL_S)
+                await _refresh_worker_registry()
+        except asyncio.CancelledError:
+            logger.info("worker registry refresh: stopped")
+            raise
+
+    async def _job_cleanup_loop(q) -> None:
+        """Background task: periodically drop completed job entries from the KV
+        so the shared bucket stays small. The KV is a transient in-flight
+        progress cache only — the durable record lives in Postgres (audit) and
+        S3 (blobs/profiles). Without this, terminal job entries piled up
+        (observed: 47k), so every worker-registry keys() scan replayed the whole
+        bucket and stormed NATS. Grace keeps a completed job readable long
+        enough for a polling client to see its final state. Defensive per tick;
+        only CancelledError exits."""
+        CLEANUP_INTERVAL_S = 300.0
+        GRACE_S = 900.0  # keep terminal jobs ~15min so the frontend's final poll still resolves
+        logger.info("job KV cleanup: starting (every %ss, grace %ss)", CLEANUP_INTERVAL_S, GRACE_S)
+        try:
+            while True:
+                await asyncio.sleep(CLEANUP_INTERVAL_S)
+                try:
+                    await q.purge_completed_jobs(grace_s=GRACE_S)
+                except Exception:
+                    logger.exception("job KV cleanup: tick failed")
+        except asyncio.CancelledError:
+            logger.info("job KV cleanup: stopped")
+            raise
+
     async def _worker_prune_loop(q) -> None:
         """Background task: hourly, hard-prune worker registry entries unseen for
         ``WORKER_PRUNE_AFTER_S`` (2 days). Defensive — one failed tick is logged, not fatal; only
@@ -3371,20 +3475,26 @@ async def _run_issue_bot_for_conversion(pool, row: dict) -> None:
         )
 
     async def _dispatch_auto_validation(pool, parent: dict) -> None:
-        """Append a validation (cross-format parity) pass to a finished
+        """Dispatch the validation (cross-format parity) pass of an
         ``auto_validate`` conversion run — *into the same run*, not a new one.
-        The run's total grows by the parity cell count and it reopens to
-        ``running`` until those cells land (then it re-finishes). The claim
-        already stamped the parent so this runs once; failures are logged but
-        never break the poller tick."""
+        Runs dispatched with an upfront reservation (``validate_total > 0``)
+        already count these cells in their total, so dispatch consumes the
+        reservation; pre-reservation runs get their total extended (and
+        reopen from ``finished``) as before. The claim already stamped the
+        parent so this runs once; failures are logged but never break the
+        poller tick."""
         try:
             s = _parse_scope(parent["scope"], _SystemUser())
             s = await _resolve_project_scope(pool, s)
         except Exception:
             logger.exception("auto-validate: scope resolution failed for run %s", parent["id"])
+            if (parent.get("validate_total") or 0) > 0:
+                # Release the reservation — no parity cells will ever be
+                # enqueued, so the run must not hang 'running' on them.
+                await db_module.consume_audit_run_validation_reserve(pool, parent["id"], 0)
             return
-        # Awaited (not fire-and-forget) so the run is reopened with its parity
-        # cells before the issue-bot drain in the same tick can claim it.
+        # Awaited (not fire-and-forget) so the run holds its parity cells
+        # before the issue-bot drain in the same tick can claim it.
         try:
             await _audit_dispatch(
                 parent["id"],
@@ -3395,6 +3505,7 @@ async def _dispatch_auto_validation(pool, parent: dict) -> None:
                 False,
                 validate_only=True,
                 extend=True,
+                consume_reserve=(parent.get("validate_total") or 0) > 0,
             )
             logger.info("auto-validate: appended validation cells to run %s", parent["id"])
         except Exception:
@@ -3421,11 +3532,13 @@ async def _issue_bot_loop(pool) -> None:
         try:
             while True:
                 try:
-                    # Auto-validate first: a finished auto_validate run gets its
-                    # parity cells appended (reopening it to 'running'), so the
-                    # issue-bot below only claims a run once it's *truly* done —
-                    # conversions and validation together. Claimed once (the
-                    # claim stamps auto_validate_dispatched_at).
+                    # Auto-validate first: an auto_validate run whose conversion
+                    # cells have landed gets its parity cells dispatched (the
+                    # run stays 'running' on its upfront-reserved total; legacy
+                    # finished runs reopen), so the issue-bot below only claims
+                    # a run once it's *truly* done — conversions and validation
+                    # together. Claimed once (the claim stamps
+                    # auto_validate_dispatched_at).
                     while True:
                         parent = await db_module.claim_audit_run_for_auto_validate(pool)
                         if parent is None:
@@ -3454,23 +3567,23 @@ async def _issue_bot_loop(pool) -> None:
             logger.info("issue-bot poller: stopped")
             raise
 
-    async def _audit_run_list_cells(
-        scope_obj: Scope,
+    def _audit_cells_for_files(
+        files,
         validate_only: bool,
     ) -> list[tuple[str, str]]:
-        """Enumerate the (source_key, target_format) cells for an audit
-        run over ``scope_obj`` — the scope's non-derived, supported
-        source files crossed with the converter matrix. ``validate_only``
-        emits only per-source ``parity`` cells. Shared by the NATS
-        dispatcher, the WASM dispatcher, and the cells endpoint so the
-        three never disagree on what a run covers. May raise on a scope
-        listing failure (caller decides how to surface it)."""
-        from .converter import ConverterRegistry, is_derived_key, is_supported_source
+        """Pure cell enumeration over an already-fetched file listing —
+        lets the dispatcher derive both the conversion grid and the
+        parity-cell reservation from ONE listing, so the two counts
+        can't disagree on what files existed at dispatch time."""
+        from .converter import ConverterRegistry, is_hidden_key, is_supported_source
 
-        files = await storage.list(scope_obj)
         cells: list[tuple[str, str]] = []
         for f in files:
-            if is_derived_key(f.key):
+            # Skip ALL internal namespaces, not just _derived/: _overlays/ (utility previews) and
+            # _reconvert/ (gallery throwaway re-conversions) are not corpus sources and must never
+            # become audit cells. is_hidden_key covers all three; is_derived_key did not match
+            # _reconvert/ (deliberately not a derived product), so it leaked into runs.
+            if is_hidden_key(f.key):
                 continue
             if not is_supported_source(f.key):
                 continue
@@ -3488,6 +3601,20 @@ async def _audit_run_list_cells(
                     cells.append((f.key, target_format))
         return cells
 
+    async def _audit_run_list_cells(
+        scope_obj: Scope,
+        validate_only: bool,
+    ) -> list[tuple[str, str]]:
+        """Enumerate the (source_key, target_format) cells for an audit
+        run over ``scope_obj`` — the scope's non-derived, supported
+        source files crossed with the converter matrix. ``validate_only``
+        emits only per-source ``parity`` cells. Shared by the NATS
+        dispatcher, the WASM dispatcher, and the cells endpoint so the
+        three never disagree on what a run covers. May raise on a scope
+        listing failure (caller decides how to surface it)."""
+        files = await storage.list(scope_obj)
+        return _audit_cells_for_files(files, validate_only)
+
     async def _audit_dispatch(
         run_id: str,
         scope_obj: Scope,
@@ -3497,6 +3624,8 @@ async def _audit_dispatch(
         force_rebuild: bool = False,
         validate_only: bool = False,
         extend: bool = False,
+        reserve_validation: bool = False,
+        consume_reserve: bool = False,
     ) -> None:
         """Enumerate the scope's files × the converter matrix and
         enqueue one regular convert job per cell. Cached cells
@@ -3509,12 +3638,21 @@ async def _audit_dispatch(
         measurement runs where a 4-hour audit re-run mustn't
         short-circuit 80% of cells against prior outputs.
 
-        ``extend`` *appends* the enumerated cells to an already-finished run
-        (growing its total + reopening it) instead of setting the total from
-        scratch — the auto-validation pass uses this to fold its parity cells
-        into the conversion run rather than spawning a separate run. With
-        ``extend`` an empty cell set is a no-op (the finished run is left as
-        is) rather than a zero-total finish.
+        ``reserve_validation`` (auto-validate runs) counts the parity cells
+        into the run's total upfront — as ``validate_total`` — so the total
+        is complete from the very start instead of growing when the
+        validation pass begins. The parity cells themselves are enqueued
+        later by the auto-validate poller, which fires once the conversion
+        cells alone have landed.
+
+        ``extend`` *appends* the enumerated cells to an existing run instead
+        of setting the total from scratch — used by the validation pass.
+        With ``consume_reserve`` (a run dispatched with
+        ``reserve_validation``) the reserved count is swapped for the actual
+        parity cell count, so the total only moves by scope drift between
+        the two enumerations. Without it (manual Validate on a finished run,
+        or pre-reservation rows) the total grows by the parity cell count
+        and the run reopens; an empty cell set is then a no-op.
 
         Errors during enumeration / enqueue surface as a ``failed``
         audit row on the cell that tripped them — the run still
@@ -3528,19 +3666,37 @@ async def _audit_dispatch(
         # if it gets zero, so a typo'd scope shows up immediately in
         # the UI rather than as a perpetually-running ghost.
         try:
-            cells = await _audit_run_list_cells(scope_obj, validate_only)
+            files = await storage.list(scope_obj)
         except Exception:
             logger.exception("audit run %s: scope listing failed", run_id)
-            if not extend:
-                await db_module.set_audit_run_total(pool, run_id, 0)
+            if extend:
+                if consume_reserve:
+                    # Release the reservation so the run can finish instead of
+                    # hanging forever on cells that will never be enqueued.
+                    await db_module.consume_audit_run_validation_reserve(pool, run_id, 0)
+                return
+            await db_module.set_audit_run_total(pool, run_id, 0)
             return
+        cells = _audit_cells_for_files(files, validate_only)
 
         if extend:
-            if not cells:
-                return  # nothing to append; leave the finished run untouched
-            await db_module.extend_audit_run_total(pool, run_id, len(cells))
+            if consume_reserve:
+                # Swap the upfront reservation for the actual parity cell
+                # count (finishes the run right here when that count is 0).
+                await db_module.consume_audit_run_validation_reserve(pool, run_id, len(cells))
+                if not cells:
+                    return
+            else:
+                if not cells:
+                    return  # nothing to append; leave the finished run untouched
+                await db_module.extend_audit_run_total(pool, run_id, len(cells))
         else:
-            await db_module.set_audit_run_total(pool, run_id, len(cells))
+            # Reserve the auto-validation parity cells in the total now — the
+            # counter-bump finish check compares against the full total, so
+            # the run stays 'running' through the gap between the last
+            # conversion cell and the poller dispatching the parity cells.
+            reserved = len(_audit_cells_for_files(files, True)) if reserve_validation else 0
+            await db_module.set_audit_run_total(pool, run_id, len(cells) + reserved, validate_total=reserved)
             if not cells:
                 return
 
@@ -3794,6 +3950,9 @@ async def admin_audit_run_create(
                 pool,
                 force_rebuild,
                 validate_only,
+                # Count the auto-validation parity cells into the run total
+                # from the start (dispatched later by the poller).
+                reserve_validation=auto_validate,
             )
         return JSONResponse(run, status_code=202)
 
@@ -3927,9 +4086,76 @@ async def admin_audit_run_re_dispatch(
                 pool,
                 prior["force_rebuild"],
                 False,
+                reserve_validation=prior["auto_validate"],
             )
         return JSONResponse(run, status_code=202)
 
+    @admin.post("/audit/runs/{run_id}/rerun-cell")
+    async def admin_audit_run_rerun_cell(
+        run_id: str,
+        request: Request,
+        user: User = Depends(auth_module.current_user),
+    ) -> JSONResponse:
+        """Re-run one cell of an existing run in place (right-click → Rerun).
+
+        Enqueues a single force-rebuild conversion for ``{key, target}`` against
+        the run's own scope/pool, re-points the cell's audit row at the new job
+        and reopens the run (``db.reset_audit_cell_for_rerun``). The worker's
+        normal completion path updates the row and re-finishes the run, so the
+        counters, the sum-of-cells runtime and the grid cell all reflect the
+        fresh result — no full re-dispatch of the other 900+ cells."""
+        from .converter import derived_key_for
+
+        body = await request.json()
+        key = (body or {}).get("key")
+        target = (body or {}).get("target")
+        if not key or not target:
+            raise HTTPException(status_code=400, detail="key and target are required")
+        if target == "parity":
+            raise HTTPException(
+                status_code=400,
+                detail="parity cells have no derived product — use Re-validate on the run instead",
+            )
+
+        pool = _require_pool(request)
+        prior = await db_module.get_audit_run(pool, run_id)
+        if prior is None:
+            raise HTTPException(status_code=404, detail="audit run not found")
+        worker_pool = prior["worker_pool"]
+        if isinstance(worker_pool, str) and worker_pool.strip().lower() == _WASM_POOL:
+            raise HTTPException(status_code=400, detail="cannot re-run a single cell of a wasm run from the server")
+        if not queue.enabled:
+            raise HTTPException(status_code=503, detail="conversion disabled (no NATS configured)")
+
+        s = _parse_scope(prior["scope"], user)
+        s = await _resolve_project_scope(pool, s)
+        if not await scope_can_access(user, s, pool):
+            raise HTTPException(status_code=403, detail="forbidden")
+
+        try:
+            derived_key_for(key, target)  # validate the target is convertible for this source
+        except Exception as exc:
+            raise HTTPException(status_code=400, detail=f"not a convertible cell: {exc}") from exc
+
+        try:
+            job = await queue.enqueue(
+                key,
+                target,
+                scope_kind=s.kind,
+                scope_id=s.id,
+                target_capability=worker_pool,
+                force_rebuild=True,
+            )
+        except Exception as exc:
+            logger.exception("rerun-cell enqueue failed for %s -> %s", key, target)
+            raise HTTPException(status_code=503, detail=f"enqueue failed: {exc}") from exc
+
+        found = await db_module.reset_audit_cell_for_rerun(pool, run_id, key, target, job.job_id)
+        if not found:
+            raise HTTPException(status_code=404, detail="cell not found in this run")
+        run = await db_module.get_audit_run(pool, run_id)
+        return JSONResponse(run, status_code=202)
+
     @admin.post("/audit/runs/{run_id}/validate")
     async def admin_audit_run_validate(
         run_id: str,
@@ -4123,6 +4349,27 @@ async def admin_corpora_create(
             raise
         return JSONResponse(row, status_code=201)
 
+    @admin.patch("/corpora/{slug}")
+    async def admin_corpora_update(slug: str, request: Request) -> JSONResponse:
+        """Update a corpus's display name / description.
+
+        Body: ``{"name": "...", "description": "..."}`` — name required
+        non-empty, empty description clears it. The slug itself is
+        immutable: it's baked into the storage prefix
+        (``corpus/<slug>/``) and scope URLs, so renaming it would
+        orphan the bucket bytes.
+        """
+        pool = _require_pool(request)
+        body = await request.json() if await request.body() else {}
+        name = (body.get("name") or "").strip()
+        description = (body.get("description") or "").strip() or None
+        if not name:
+            raise HTTPException(status_code=400, detail="name required")
+        row = await db_module.update_corpus(pool, slug, name=name, description=description)
+        if row is None:
+            raise HTTPException(status_code=404, detail=f"corpus {slug!r} not found")
+        return JSONResponse(row)
+
     @admin.delete("/corpora/{slug}")
     async def admin_corpora_archive(slug: str, request: Request) -> JSONResponse:
         """Soft-delete a corpus by slug. Storage bytes are NOT wiped —
@@ -5046,7 +5293,9 @@ async def admin_clear_metrics(request: Request) -> JSONResponse:
                     entry["profile_key"],
                     exc,
                 )
-                blob_errors.append(f"{entry['profile_key']}: {exc}")
+                # Report only the failed key to the client; the exception detail is logged
+                # above (avoid leaking backend/stack-trace text in the response).
+                blob_errors.append(entry["profile_key"])
         return JSONResponse(
             {
                 "rows_cleared": result["rows_cleared"],
@@ -5063,6 +5312,7 @@ async def admin_audit(
         scope_id: str | None = None,
         action: str | None = None,
         target: str | None = None,
+        status: str | None = None,
         key: str | None = None,
         before_id: int | None = None,
         limit: int = 100,
@@ -5073,6 +5323,8 @@ async def admin_audit(
         key_like = (key or "").strip() or None
         # ``target`` filters by the conversion's target format (glb / ifc / step / …).
         target_format = (target or "").strip().lstrip(".").lower() or None
+        # ``status`` filters by job state (queued / running / done / error).
+        status_norm = (status or "").strip().lower() or None
         rows = await db_module.list_audit(
             pool,
             user_sub=user_sub,
@@ -5080,6 +5332,7 @@ async def admin_audit(
             scope_id=scope_id,
             action=action,
             target_format=target_format,
+            statuses=[status_norm] if status_norm else None,
             key_like=key_like,
             limit=limit,
             before_id=before_id,
@@ -5473,9 +5726,11 @@ async def admin_keys_copy_from(
                 # default raises ``copy-if-not-exists not supported``); the
                 # application-layer dst_keys pre-check is the real collision guard.
                 await storage.copy(src_scope, key, scope_obj, key, overwrite=True)
-            except Exception as exc:
+            except Exception:
+                # Full detail is logged; return a generic reason so backend/stack-trace
+                # text isn't exposed in the response (CodeQL py/stack-trace-exposure).
                 logger.exception("admin: copy failed for %s (%s -> %s)", key, src_raw, scope_obj.prefix())
-                failed.append({"key": key, "reason": str(exc)})
+                failed.append({"key": key, "reason": "copy failed"})
                 continue
             dst_keys.add(key)
             copied.append({"key": key})
@@ -5495,12 +5750,8 @@ async def config_js() -> PlainTextResponse:
         import json as _json
 
         viewer_tag = os.environ.get("ADA_IMAGE_TAG", "").strip() or None
-        worker_tag: str | None = None
-        if queue.enabled:
-            try:
-                worker_tag = await queue.get_meta("worker_image_tag")
-            except Exception:
-                logger.exception("config.js: failed to read worker image tag")
+        # Cached snapshot — no NATS on the request path (see _worker_registry).
+        worker_tag: str | None = _worker_registry["image_tag"] if queue.enabled else None
         extra_source_exts = await _worker_advertised_exts()
         streaming_only_exts = sorted(e for e in extra_source_exts if e not in LEGACY_CONVERT_EXTS)
         conversion_matrix = await _worker_advertised_conversions()
diff --git a/src/ada/comms/rest/converter.py b/src/ada/comms/rest/converter.py
index b5d27b577..dfc6af238 100644
--- a/src/ada/comms/rest/converter.py
+++ b/src/ada/comms/rest/converter.py
@@ -430,6 +430,20 @@ def derived_key_for(
     return f"_derived/{src}.{fmt}"
 
 
+def reconvert_key_for(source_key: str, target_format: str = "glb") -> str:
+    """Output key for a user-triggered *re-conversion* (gallery "Re-convert" button).
+
+    Lives in a SEPARATE ``_reconvert/`` namespace from the ``_derived/`` convert cache, so a
+    re-convert never overwrites the audit-run product in a corpus scope — the derived cache
+    stays exactly as the audit produced it. One blob per (source, format): re-converting the
+    same file again overwrites its own ``_reconvert/`` blob (throwaway, not accumulating).
+    """
+    fmt = target_format.lstrip(".").lower()
+    if fmt not in TARGET_FORMATS:
+        raise UnsupportedFormat(f"unknown target format: {target_format!r}")
+    return f"_reconvert/{source_key.strip('/')}.{fmt}"
+
+
 # Suffix appended to derived keys for cached result-meta JSON. Lives in
 # the same _derived/ namespace, so it's hidden from the user file list
 # but still scoped to the source.
@@ -486,7 +500,7 @@ def is_derived_key(key: str) -> bool:
 # ephemeral overlay as a source's derived product.
 def is_hidden_key(key: str) -> bool:
     k = key.lstrip("/")
-    return k.startswith("_derived/") or k.startswith("_overlays/")
+    return k.startswith("_derived/") or k.startswith("_overlays/") or k.startswith("_reconvert/")
 
 
 def is_versions_artefact_key(key: str) -> bool:
@@ -942,7 +956,10 @@ def _have(mod: str) -> bool:
     _STEP_GLB_PIPELINE_ADACPP_CGAL,
     _STEP_GLB_PIPELINE_ADACPP_HYBRID,
 )
-_GLB_TESS_ENGINE_DEFAULT = _STEP_GLB_PIPELINE_OCC
+# Advertised default for the non-STEP →GLB engine option. Kept in lockstep with the RUNTIME default
+# (`_default_glb_tess_engine`, which returns libtess2 whenever adacpp is importable) so the SPA/audit
+# UI reflects the path actually taken. libtess2 gracefully degrades to OCC on an adacpp-less pool.
+_GLB_TESS_ENGINE_DEFAULT = _STEP_GLB_PIPELINE_LIBTESS2
 _GLB_ENGINE_TO_STREAM = {
     _STEP_GLB_PIPELINE_LIBTESS2: "libtess2",
     _STEP_GLB_PIPELINE_ADACPP_OCC: "occ",
@@ -951,6 +968,270 @@ def _have(mod: str) -> bool:
 }
 
 
+# ---------------------------------------------------------------------------
+# Serializer × Tessellator matrix — SINGLE SOURCE OF TRUTH for the SPA's
+# reconvert dropdowns (gallery tools + ConversionRow). Two user-facing axes:
+#
+#   * serializer  — WHICH code path drives the →GLB conversion:
+#         cpp      pure-C++ adacpp  (STEP: adacpp-native; IFC: native_ifc_to_glb)
+#         python   Python-orchestrated (ada import + BatchTessellator/stream reader)
+#         wasm     client-side, runs entirely in the browser (no server round-trip)
+#   * tessellator — WHICH kernel meshes the geometry. It is DEPENDENT on the
+#                   serializer (enum_by): the server `python` serializer exposes
+#                   the full kernel choice; `cpp` pins libtess2; the client `wasm`
+#                   serializer exposes its two in-browser engines (native embind
+#                   module / Pyodide wheels).
+#
+# The frontend renders both dropdowns purely from the option schema advertised
+# on the conversion matrix (``labels`` + ``enum_by``) and sends back opaque
+# ``{serializer, tessellator}`` tokens — it hardcodes NONE of this vocabulary.
+# The backend resolver (:func:`_apply_glb_serializer`) folds those tokens into
+# the existing engine knobs (``step_glb_pipeline`` / ``glb_tess_engine``) plus
+# the native-vs-python routing. The client serializer carries ``runtime="client"``
+# so the SPA routes it to the in-browser pipeline instead of the worker; it
+# never reaches this resolver.
+_GLB_SERIALIZER_CPP = "cpp"
+_GLB_SERIALIZER_PYTHON = "python"
+_GLB_SERIALIZER_WASM = "wasm"
+
+# Human labels for every serializer token (superset; each row advertises only
+# the subset that applies to its source family).
+_GLB_SERIALIZER_LABELS = {
+    _GLB_SERIALIZER_CPP: "C++ (adacpp native)",
+    _GLB_SERIALIZER_PYTHON: "Python (ada)",
+    _GLB_SERIALIZER_WASM: "WASM (browser)",
+}
+# Serializers that execute in the browser — the SPA routes these to its
+# in-browser pipeline and gates them on client capability (wasmSupport).
+_GLB_CLIENT_SERIALIZERS = frozenset({_GLB_SERIALIZER_WASM})
+
+_GLB_TESS_LABELS = {
+    "native": "Native (libtess2)",
+    "pyocc": "PythonOCC (OCC)",
+    "adacpp-occ": "adacpp OCC",
+    "cgal": "adacpp CGAL",
+    "ifc-hybrid": "ifcOpenShell hybrid",
+    "occ": "OCC streaming reader",
+    # client-side (wasm serializer) engines:
+    "wasm-native": "Native (WASM module)",
+    "pyodide": "Pyodide (wasm wheels)",
+}
+
+# Per (serializer, source-family) the tessellator tokens offered. ``step`` =
+# STEP/STP sources (own streaming reader + OCC reader); ``generic`` = every
+# other →GLB source (ifc / xml / sat / fem / obj / stl) driven by to_gltf's
+# BatchTessellator. The lists ARE the enum_by mapping the frontend uses to
+# repopulate the tessellator dropdown when the serializer changes.
+_GLB_SERIALIZER_TESS = {
+    (_GLB_SERIALIZER_CPP, "step"): ["native"],
+    (_GLB_SERIALIZER_CPP, "generic"): ["native"],
+    (_GLB_SERIALIZER_PYTHON, "step"): ["native", "pyocc", "adacpp-occ", "cgal", "ifc-hybrid", "occ"],
+    (_GLB_SERIALIZER_PYTHON, "generic"): ["native", "pyocc", "adacpp-occ", "cgal", "ifc-hybrid"],
+    (_GLB_SERIALIZER_WASM, "step"): ["wasm-native", "pyodide"],
+    (_GLB_SERIALIZER_WASM, "generic"): ["wasm-native", "pyodide"],
+}
+# Serializer ordering per family (default is the first entry). cpp is the
+# default server path for both; the client serializer comes last.
+_GLB_SERIALIZER_ORDER = (
+    _GLB_SERIALIZER_CPP,
+    _GLB_SERIALIZER_PYTHON,
+    _GLB_SERIALIZER_WASM,
+)
+
+# tessellator token → effective engine knob, reusing the existing pipeline
+# identities so there is exactly one definition of each engine.
+_TESS_TO_STEP_PIPELINE = {
+    "native": _STEP_GLB_PIPELINE_LIBTESS2,
+    "pyocc": _STEP_GLB_PIPELINE_OCC,
+    "occ": _STEP_GLB_PIPELINE_OCC,
+    "adacpp-occ": _STEP_GLB_PIPELINE_ADACPP_OCC,
+    "cgal": _STEP_GLB_PIPELINE_ADACPP_CGAL,
+    "ifc-hybrid": _STEP_GLB_PIPELINE_ADACPP_HYBRID,
+}
+_TESS_TO_GLB_ENGINE = {
+    "native": _STEP_GLB_PIPELINE_LIBTESS2,
+    "pyocc": _STEP_GLB_PIPELINE_OCC,
+    "adacpp-occ": _STEP_GLB_PIPELINE_ADACPP_OCC,
+    "cgal": _STEP_GLB_PIPELINE_ADACPP_CGAL,
+    "ifc-hybrid": _STEP_GLB_PIPELINE_ADACPP_HYBRID,
+}
+
+
+def _glb_source_family(source_ext: str) -> str:
+    """'step' for STEP/STP sources, else 'generic' — selects the serializer
+    tessellator vocabulary + engine-knob axis."""
+    return "step" if source_ext.lower().lstrip(".") in ("step", "stp") else "generic"
+
+
+def _glb_serializer_options(source_ext: str) -> list[dict]:
+    """Build the ``serializer`` + dependent ``tessellator`` enum options for a
+    →GLB row. Single source: vocabulary, labels, defaults and the
+    serializer→tessellator dependency all come from the module spec above, so
+    the frontend can render the two dependent dropdowns without hardcoding any
+    of it. ``enum_by`` maps each serializer value to its allowed tessellator
+    tokens; ``runtime='client'`` flags the browser-side serializers."""
+    fam = _glb_source_family(source_ext)
+    serializers = [s for s in _GLB_SERIALIZER_ORDER if (s, fam) in _GLB_SERIALIZER_TESS]
+    enum_by = {s: list(_GLB_SERIALIZER_TESS[(s, fam)]) for s in serializers}
+    # Union of tessellator tokens across serializers, ordered by first appearance.
+    tess_tokens: list[str] = []
+    for s in serializers:
+        for tok in enum_by[s]:
+            if tok not in tess_tokens:
+                tess_tokens.append(tok)
+    default_ser = serializers[0]
+    return [
+        {
+            "name": "serializer",
+            "type": "enum",
+            "title": "Serializer",
+            "default": default_ser,
+            "enum": serializers,
+            "labels": {s: _GLB_SERIALIZER_LABELS[s] for s in serializers},
+            "runtime": {s: ("client" if s in _GLB_CLIENT_SERIALIZERS else "server") for s in serializers},
+            "description": (
+                "Conversion code path for →GLB. 'cpp' = pure-C++ adacpp (fastest, lowest memory); "
+                "'python' = Python-orchestrated (lets you pick the tessellation kernel below); "
+                "'wasm' / 'pyodide' run entirely in your browser (no server round-trip)."
+            ),
+        },
+        {
+            "name": "tessellator",
+            "type": "enum",
+            # Mesh target → this axis meshes the geometry ("Tessellator"). (For B-rep targets the
+            # analogous axis is titled "Writer" — same mechanism, set on those rows.)
+            "title": "Tessellator",
+            "default": enum_by[default_ser][0],
+            "enum": tess_tokens,
+            "labels": {t: _GLB_TESS_LABELS.get(t, t) for t in tess_tokens},
+            # Dependent dropdown: the valid tessellators for each serializer. The
+            # frontend repopulates + reselects when the serializer changes.
+            "enum_by": enum_by,
+            "depends_on": "serializer",
+            "description": (
+                "Tessellation kernel. Only the 'python' serializer exposes a choice; the other "
+                "serializers pin their own kernel."
+            ),
+        },
+    ]
+
+
+def _apply_glb_serializer(
+    source_ext: str,
+    serializer: str | None,
+    tessellator: str | None,
+    *,
+    step_glb_pipeline: str | None,
+    glb_tess_engine: str | None,
+) -> tuple[str | None, str | None, bool]:
+    """Fold ``serializer`` / ``tessellator`` tokens into the effective engine
+    knobs. Returns ``(step_glb_pipeline, glb_tess_engine, force_python)``.
+
+    ``force_python`` tells IFC→GLB to bypass the pure-native path and route
+    through the ifcopenshell import + BatchTessellator (so the chosen kernel
+    actually takes effect). When ``serializer`` is unset the explicit knobs
+    (and their env/defaults) are returned untouched — full back-compat with the
+    admin panel + ``ADAPY_*`` env selection. Client serializers never reach a
+    worker, so they are treated as no-ops here."""
+    if not serializer or serializer in _GLB_CLIENT_SERIALIZERS:
+        return step_glb_pipeline, glb_tess_engine, False
+    fam = _glb_source_family(source_ext)
+    if serializer == _GLB_SERIALIZER_CPP:
+        if fam == "step":
+            step_glb_pipeline = _STEP_GLB_PIPELINE_ADACPP_NATIVE
+        # generic/IFC 'cpp' = the native_ifc_to_glb default path — nothing to force.
+        return step_glb_pipeline, glb_tess_engine, False
+    if serializer == _GLB_SERIALIZER_PYTHON:
+        tok = tessellator or _GLB_SERIALIZER_TESS[(_GLB_SERIALIZER_PYTHON, fam)][0]
+        if fam == "step":
+            step_glb_pipeline = _TESS_TO_STEP_PIPELINE.get(tok, _STEP_GLB_PIPELINE_LIBTESS2)
+        else:
+            glb_tess_engine = _TESS_TO_GLB_ENGINE.get(tok, _GLB_TESS_ENGINE_DEFAULT)
+        return step_glb_pipeline, glb_tess_engine, True
+    return step_glb_pipeline, glb_tess_engine, False
+
+
+# ---------------------------------------------------------------------------
+# B-rep → B-rep (step→ifc, ifc→step) path options. Same shared frontend selector
+# as the →GLB rows, but the second axis is a WRITER (no tessellation happens),
+# titled "Writer" via the backend. The writer mirrors the serializer 1:1 — each
+# code path has exactly one B-rep emitter — so the writer dropdown is
+# informational (one entry per serializer), consistent with how cpp→glb pins its
+# tessellator. Client (wasm) B-rep writers run in-browser via the adacpp wasm
+# writer modules.
+_BREP_SERIALIZER_LABELS = {
+    _GLB_SERIALIZER_CPP: "C++ (adacpp native)",
+    _GLB_SERIALIZER_PYTHON: "Python (OCC)",
+    _GLB_SERIALIZER_WASM: "WASM (browser)",
+}
+# serializer -> (writer token, writer label). One writer per path.
+_BREP_SERIALIZER_WRITER = {
+    _GLB_SERIALIZER_CPP: ("native", "Native (adacpp B-rep)"),
+    _GLB_SERIALIZER_PYTHON: ("occ", "OCC / ifcopenshell"),
+    _GLB_SERIALIZER_WASM: ("wasm-native", "Native (WASM)"),
+}
+_BREP_SERIALIZER_ORDER = (_GLB_SERIALIZER_CPP, _GLB_SERIALIZER_PYTHON, _GLB_SERIALIZER_WASM)
+
+
+def _brep_serializer_options(source_ext: str, target: str) -> list[dict]:
+    """serializer + dependent ``writer`` options for a B-rep→B-rep row (single-sourced, like
+    :func:`_glb_serializer_options`). The writer axis is titled "Writer" and mirrors the serializer."""
+    serializers = list(_BREP_SERIALIZER_ORDER)
+    enum_by = {s: [_BREP_SERIALIZER_WRITER[s][0]] for s in serializers}
+    writer_tokens: list[str] = []
+    for s in serializers:
+        for tok in enum_by[s]:
+            if tok not in writer_tokens:
+                writer_tokens.append(tok)
+    writer_labels = {_BREP_SERIALIZER_WRITER[s][0]: _BREP_SERIALIZER_WRITER[s][1] for s in serializers}
+    default_ser = serializers[0]
+    return [
+        {
+            "name": "serializer",
+            "type": "enum",
+            "title": "Serializer",
+            "default": default_ser,
+            "enum": serializers,
+            "labels": {s: _BREP_SERIALIZER_LABELS[s] for s in serializers},
+            "runtime": {s: ("client" if s in _GLB_CLIENT_SERIALIZERS else "server") for s in serializers},
+            "description": (
+                f"Conversion code path for →{target.upper()}. 'cpp' = pure-C++ adacpp B-rep writer "
+                "(fastest, dep-free); 'python' = the OpenCASCADE / ifcopenshell writer; 'wasm' runs "
+                "the adacpp writer entirely in your browser (no server round-trip)."
+            ),
+        },
+        {
+            "name": "tessellator",  # wire key kept stable across targets; DISPLAYED as "Writer"
+            "type": "enum",
+            "title": "Writer",
+            "default": enum_by[default_ser][0],
+            "enum": writer_tokens,
+            "labels": writer_labels,
+            "enum_by": enum_by,
+            "depends_on": "serializer",
+            "description": "B-rep writer. Mirrors the serializer — each code path has one writer.",
+        },
+    ]
+
+
+def _conversion_path_options(source_ext: str, target: str) -> list[dict]:
+    """The shared serializer × (tessellator|writer) path options for a (source, target) row. Mesh
+    targets (glb) get the tessellator axis; B-rep targets (ifc/step) get the writer axis. Single
+    source of the vocabulary for the frontend selector."""
+    t = target.lstrip(".").lower()
+    if t == "glb":
+        return _glb_serializer_options(source_ext)
+    if t in ("ifc", "step"):
+        return _brep_serializer_options(source_ext, t)
+    return []
+
+
+def _brep_writer_is_python(serializer: str | None) -> bool:
+    """A B-rep→B-rep serializer that routes to the Python/OCC writer (vs the native adacpp emitter).
+    Client (wasm) serializers never reach the worker, so they are not 'python' here."""
+    return serializer == _GLB_SERIALIZER_PYTHON
+
+
 def _default_glb_tess_engine() -> str:
     """Default engine for the non-STEP →GLB (scene) path: ``libtess2`` when adacpp is importable,
     else the OCC BatchTessellator. OCC's prism tessellation of curved B-spline plates is
@@ -2209,15 +2490,16 @@ def _register_ada_loadable() -> None:
     }
 
     # Non-STEP →GLB tessellation engine (xml / ifc / sat / fem / obj / stl → glb). Same engines
-    # as STEP but driving to_gltf's BatchTessellator stream selector; default OCC (libtess2 opt-in).
+    # as STEP but driving to_gltf's BatchTessellator stream selector; default libtess2 (adacpp-aware,
+    # matching the runtime `_default_glb_tess_engine`), degrading to OCC on an adacpp-less pool.
     glb_tess_engine_option = {
         "name": "glb_tess_engine",
         "type": "enum",
         "default": _GLB_TESS_ENGINE_DEFAULT,
         "enum": list(_GLB_TESS_ENGINES),
         "description": (
-            "→GLB tessellation engine. 'occ-builtin' (default) is the OpenCASCADE tessellator. "
-            "'libtess2' is adacpp's OCC-free boundary tessellator — renders curved surfaces OCC "
+            "→GLB tessellation engine. 'libtess2' (default) is adacpp's OCC-free boundary "
+            "tessellator — renders curved surfaces OCC "
             "drops and avoids the OCC optimal-bbox cost on curved-heavy models (per-geom fallback "
             "to OCC when a geometry isn't yet NGEOM-serializable). 'adacpp-occ' / 'adacpp-cgal' / "
             "'adacpp-hybrid' use adacpp's taxonomy kernels. Engines needing adacpp fall back to OCC "
@@ -2312,8 +2594,17 @@ def _h(
                 step_glb_pipeline=None,
                 glb_tess_engine=None,
                 strict_tess=None,
+                serializer=None,
+                tessellator=None,
                 **_kw,
             ):
+                # The friendly serializer/tessellator dropdowns resolve into the existing engine
+                # knobs (single-sourced by _apply_glb_serializer); explicit step_glb_pipeline /
+                # glb_tess_engine still work when serializer is unset.
+                step_glb_pipeline, glb_tess_engine, _force_python = _apply_glb_serializer(
+                    _ext, serializer, tessellator,
+                    step_glb_pipeline=step_glb_pipeline, glb_tess_engine=glb_tess_engine,
+                )
                 return _via_ada(
                     src,
                     _ext,
@@ -2333,10 +2624,12 @@ def _h(
                 # STEP sources: streaming toggle + the STEP engine selector (incl. the OCC
                 # streaming reader). Other →glb sources: the BatchTessellator engine toggle.
                 # strict_tess (fail-on-OCC-fallback) applies to the non-STEP BatchTessellator path.
+                # The serializer/tessellator dropdowns are added on every →glb row.
                 if ext in {".step", ".stp"}:
                     row_options = glb_options + [step_streamer_option, step_glb_pipeline_option, strict_tess_option]
                 else:
                     row_options = glb_options + [glb_tess_engine_option, strict_tess_option]
+                row_options = row_options + _glb_serializer_options(ext)
             elif tgt in ("ifc", "xml") and ext in _FEM_SOURCE_EXTS:
                 row_options = fem_to_objects_options
             else:
@@ -2401,6 +2694,40 @@ def _h(src, on_progress, *, _ext=ext, step=None, field=None, source_uri=None, **
         ConverterRegistry.register(ext, "glb", _h)
 
 
+def _via_ifc_stream_to_glb(
+    src_path: pathlib.Path,
+    on_progress: ProgressFn,
+    *,
+    glb_tess_engine: str | None = None,
+    strict_tess: bool | None = None,
+    force_python: bool = False,
+) -> bytes | pathlib.Path:
+    """IFC → GLB, fully native (adacpp ``stream_ifc_to_glb``: pure-C++ IfcResolver → libtess2 →
+    merge-by-colour GLB, no ifcopenshell/OCC), with a graceful fallback to the ifcopenshell
+    ``from_ifc`` → GLB path. The native GLB carries geometry + per-mesh colour + the spatial tree +
+    names — viewer-equivalent (IFC property sets never live in the GLB; they are fetched on selection).
+    Falls back when adacpp's native entry is absent, the run raises, or it produces 0 products (e.g. an
+    IFC of only tessellated face-sets the analytic resolver skips).
+
+    ``force_python`` (serializer='python') bypasses the pure-native path entirely so the chosen
+    ``glb_tess_engine`` kernel actually drives the ifcopenshell import + BatchTessellator."""
+    from ada.config import logger
+
+    from ada.cadit.ifc.native_ifc_to_glb import native_ifc_glb_available, native_ifc_to_glb
+
+    if not force_python and native_ifc_glb_available():
+        try:
+            out_path = pathlib.Path(tempfile.mkstemp(suffix=".glb")[1])
+            stats = native_ifc_to_glb(src_path, out_path, on_progress=on_progress)
+            if stats.get("solids", 0) > 0:
+                logger.info("native IFC->GLB: %s", stats)
+                return out_path
+            logger.info("native IFC->GLB produced 0 products; falling back to from_ifc")
+        except Exception as exc:  # noqa: BLE001
+            logger.info("native IFC->GLB failed (%s); falling back to from_ifc", exc)
+    return _via_ada(src_path, ".ifc", "glb", on_progress, glb_tess_engine=glb_tess_engine, strict_tess=strict_tess)
+
+
 def _register_step_stream_exports() -> None:
     # STEP/STP exports that bypass the full-OCC Assembly (which OOM-kills / times
     # out on multi-GB CAD assemblies). Registered AFTER _register_ada_loadable so
@@ -2425,10 +2752,14 @@ def _h_step(src, on_progress, *, _ext=ext, **_kw):
 
         ConverterRegistry.register(ext, "step", _h_step)
 
-        def _h_ifc(src, on_progress, *, _ext=ext, **_kw):
+        def _h_ifc(src, on_progress, *, _ext=ext, serializer=None, tessellator=None, **_kw):
+            # serializer=python routes to the OCC/ifcopenshell writer; cpp (default) uses the native
+            # streaming adacpp B-rep emitter. wasm serializers run client-side (never reach here).
+            if _brep_writer_is_python(serializer):
+                return _via_ada(src, _ext, "ifc", on_progress)
             return _via_step_stream_to_ifc(src, on_progress)
 
-        ConverterRegistry.register(ext, "ifc", _h_ifc)
+        ConverterRegistry.register(ext, "ifc", _h_ifc, options=_conversion_path_options(ext, "ifc"))
 
         def _h_xml(src, on_progress, *, _ext=ext, **_kw):
             return _via_step_stream_to_xml(src, on_progress)
@@ -2445,10 +2776,43 @@ def _h_xml(src, on_progress, *, _ext=ext, **_kw):
         _native_ifc2step = False
     if _native_ifc2step:
 
-        def _h_ifc2step(src, on_progress, **_kw):
+        def _h_ifc2step(src, on_progress, *, serializer=None, tessellator=None, **_kw):
+            # serializer=python routes to the OCC ifc→step writer; cpp (default) uses the native
+            # adacpp B-rep reader → AP242 writer. wasm serializers run client-side.
+            if _brep_writer_is_python(serializer):
+                return _via_ada(src, ".ifc", "step", on_progress)
             return _via_ifc_to_step(src, on_progress)
 
-        ConverterRegistry.register(".ifc", "step", _h_ifc2step)
+        ConverterRegistry.register(
+            ".ifc", "step", _h_ifc2step, options=_conversion_path_options(".ifc", "step")
+        )
+
+    # IFC → GLB via the native adacpp IFC pipeline (no ifcopenshell/OCC), overriding the generic
+    # from_ifc → GLB. Gated on the native verb; degrades to from_ifc per _via_ifc_stream_to_glb's
+    # own fallback (absent verb / error / 0 products), so this is always safe to register.
+    try:
+        from ada.cadit.ifc.native_ifc_to_glb import native_ifc_glb_available
+
+        _native_ifc2glb = native_ifc_glb_available()
+    except Exception:  # noqa: BLE001
+        _native_ifc2glb = False
+    if _native_ifc2glb:
+
+        def _h_ifc2glb(src, on_progress, *, glb_tess_engine=None, strict_tess=None,
+                       serializer=None, tessellator=None, **_kw):
+            _step_pipe, glb_tess_engine, force_python = _apply_glb_serializer(
+                ".ifc", serializer, tessellator,
+                step_glb_pipeline=None, glb_tess_engine=glb_tess_engine,
+            )
+            return _via_ifc_stream_to_glb(
+                src, on_progress, glb_tess_engine=glb_tess_engine,
+                strict_tess=strict_tess, force_python=force_python,
+            )
+
+        # Preserve the serializer/tessellator + engine options declared on the generic ifc→glb row.
+        ConverterRegistry.register(
+            ".ifc", "glb", _h_ifc2glb, options=ConverterRegistry.options_for(".ifc", "glb")
+        )
 
 
 def _register_glb_to_mesh() -> None:
diff --git a/src/ada/comms/rest/db.py b/src/ada/comms/rest/db.py
index ed574567b..576c34faa 100644
--- a/src/ada/comms/rest/db.py
+++ b/src/ada/comms/rest/db.py
@@ -531,6 +531,78 @@ async def _bump_audit_run_counter(
     )
 
 
+async def reset_audit_cell_for_rerun(
+    pool: asyncpg.Pool,
+    run_id: str,
+    key: str,
+    target_format: str,
+    new_job_id: str,
+) -> bool:
+    """Re-point a single audit cell at a fresh conversion job so it can be
+    re-run in place, keeping the run's counters and total correct.
+
+    One row exists per cell in a run (the dispatcher inserts it ``queued`` and
+    the worker updates it by ``job_id``). To re-run one cell we: undo the
+    counter its prior terminal status bumped (so ``failed`` drops when a
+    previously-failed cell is retried), clear its result fields, attach the new
+    ``job_id`` and set it back to ``queued``, and reopen the run. The worker's
+    normal completion path (``update_audit_by_job`` → the counter bump)
+    then re-increments and re-finishes the run exactly as for a first run.
+
+    Returns False if the cell isn't part of the run (nothing to re-run)."""
+    async with pool.acquire() as conn:
+        async with conn.transaction():
+            row = await conn.fetchrow(
+                """
+                SELECT id, status FROM audit_log
+                WHERE audit_run_id = $1 AND key = $2 AND target_format = $3
+                ORDER BY id DESC
+                LIMIT 1
+                """,
+                run_id,
+                key,
+                target_format,
+            )
+            if row is None:
+                return False
+            prior_col = _AUDIT_RUN_COUNTER_FOR_STATUS.get(row["status"] or "")
+            await conn.execute(
+                """
+                UPDATE audit_log
+                SET job_id = $2, status = 'queued', error = NULL, traceback = NULL,
+                    duration_ms = NULL, cpu_user_ms = NULL, cpu_sys_ms = NULL,
+                    peak_rss_kb = NULL, read_bytes = NULL, write_bytes = NULL,
+                    profile_key = NULL, log_key = NULL, ts = NOW()
+                WHERE id = $1
+                """,
+                row["id"],
+                new_job_id,
+            )
+            # Undo the prior terminal counter (if any) and reopen the run. The
+            # column name comes from a closed allowlist so the f-string is safe.
+            dec = f"{prior_col} = GREATEST({prior_col} - 1, 0)," if prior_col else ""
+            await conn.execute(
+                f"""
+                UPDATE audit_runs
+                SET {dec}
+                    -- Fold the idle gap since this run last finished into idle_ms
+                    -- (same as extend_audit_run_total). Then when the re-run cell
+                    -- lands and re-finishes the run, the wall-clock duration grows
+                    -- ONLY by the re-run's own delta, not the days-long gap since
+                    -- the original run. RHS reads the pre-update finished_at.
+                    idle_ms = idle_ms + CASE
+                        WHEN status <> 'aborted' AND finished_at IS NOT NULL
+                        THEN GREATEST(0, (EXTRACT(EPOCH FROM (NOW() - finished_at)) * 1000)::bigint)
+                        ELSE 0 END,
+                    status = CASE WHEN status = 'aborted' THEN 'aborted' ELSE 'running' END,
+                    finished_at = CASE WHEN status = 'aborted' THEN finished_at ELSE NULL END
+                WHERE id = $1
+                """,
+                run_id,
+            )
+            return True
+
+
 async def active_audit_summary(pool: asyncpg.Pool) -> dict:
     """Aggregate state of currently-``running`` audit runs.
 
@@ -1175,6 +1247,32 @@ async def create_corpus(
     return _corpus_row(row)
 
 
+async def update_corpus(
+    pool: asyncpg.Pool,
+    slug: str,
+    *,
+    name: str,
+    description: str | None,
+) -> dict | None:
+    """Update a live corpus's display name / description. The slug is
+    immutable — it's baked into the storage prefix (``corpus/<slug>/``)
+    and scope URLs, so renaming it would orphan the bucket bytes.
+    Returns the updated row, or None when the slug isn't live."""
+    row = await pool.fetchrow(
+        """
+        UPDATE corpora
+        SET name = $2, description = $3
+        WHERE slug = $1 AND archived_at IS NULL
+        RETURNING id, slug, name, description, created_at,
+                  created_by, archived_at
+        """,
+        slug,
+        name,
+        description,
+    )
+    return _corpus_row(row) if row else None
+
+
 async def get_corpus_by_slug(
     pool: asyncpg.Pool,
     slug: str,
@@ -1239,6 +1337,9 @@ def _opt(col: str):
         "status": r["status"],
         "note": r["note"],
         "total": r["total"],
+        # Parity cells reserved in ``total`` for the auto-validation pass but
+        # not yet enqueued (0 once the pass dispatches, or for non-auto runs).
+        "validate_total": _opt("validate_total") or 0,
         "ok": r["ok"],
         "failed": r["failed"],
         "skipped": r["skipped"],
@@ -1247,6 +1348,11 @@ def _opt(col: str):
         # Idle time excluded from the run's active duration (gap before a later
         # validation pass). The UI shows (finished_at - started_at) - idle_ms.
         "idle_ms": _opt("idle_ms") or 0,
+        # Sum of every cell's own duration_ms — the run's active compute time,
+        # independent of wall clock (which parallel workers compress and a
+        # single-cell re-run inflates with idle). Recomputes whenever a cell's
+        # row changes, so a re-run's new timing is reflected immediately.
+        "cells_duration_ms": _opt("cells_duration_ms") or 0,
         "force_rebuild": _opt("force_rebuild") or False,
         "auto_validate": _opt("auto_validate") or False,
         "parent_run_id": str(parent_run_id) if parent_run_id else None,
@@ -1309,21 +1415,31 @@ async def set_audit_run_total(
     pool: asyncpg.Pool,
     run_id: str,
     total: int,
+    *,
+    validate_total: int = 0,
 ) -> None:
     """Set the dispatched-job count after enqueue completes. If
     ``total`` is 0 (no jobs to run — empty scope or no viable cells),
     the run is marked ``finished`` immediately so the UI doesn't show
-    a perpetually-running row."""
+    a perpetually-running row.
+
+    ``validate_total`` reserves that many of the ``total`` cells for the
+    auto-validation parity pass, which is dispatched later (once the
+    conversion cells have landed) — so the run's total is complete from
+    the start. The reservation is consumed by
+    :func:`consume_audit_run_validation_reserve`."""
     await pool.execute(
         """
         UPDATE audit_runs
         SET total = $2,
+            validate_total = $3,
             status = CASE WHEN $2 = 0 THEN 'finished' ELSE status END,
             finished_at = CASE WHEN $2 = 0 THEN NOW() ELSE finished_at END
         WHERE id = $1
         """,
         run_id,
         total,
+        validate_total,
     )
 
 
@@ -1354,6 +1470,45 @@ async def extend_audit_run_total(pool: asyncpg.Pool, run_id: str, delta: int) ->
     )
 
 
+async def consume_audit_run_validation_reserve(
+    pool: asyncpg.Pool,
+    run_id: str,
+    actual: int,
+) -> None:
+    """Swap a run's reserved validation-cell count for the ``actual``
+    number of parity cells enumerated at dispatch time.
+
+    ``total`` was set upfront to conversions + reservation; here it is
+    corrected by (actual - validate_total) — normally zero, non-zero only
+    when the scope's files changed between the two enumerations — and the
+    reservation is cleared. If the corrected total is already met (e.g.
+    ``actual`` is 0 because the parity enumeration failed or the sources
+    vanished), the run finishes here since no counter-bump will arrive to
+    do it. Aborted runs only get their bookkeeping corrected."""
+    await pool.execute(
+        """
+        UPDATE audit_runs
+        SET total = total - validate_total + $2,
+            validate_total = 0,
+            finished_at = CASE
+                WHEN status = 'aborted' THEN finished_at
+                WHEN ok + failed + skipped >= total - validate_total + $2
+                    THEN COALESCE(finished_at, NOW())
+                ELSE finished_at
+            END,
+            status = CASE
+                WHEN status = 'aborted' THEN 'aborted'
+                WHEN ok + failed + skipped >= total - validate_total + $2
+                    THEN 'finished'
+                ELSE status
+            END
+        WHERE id = $1
+        """,
+        run_id,
+        actual,
+    )
+
+
 async def delete_audit_run(pool: asyncpg.Pool, run_id: str) -> tuple[bool, list[str]]:
     """Delete an audit run and its audit_log rows. ``audit_parity`` rows cascade
     on the run delete; ``audit_log`` is ON DELETE SET NULL, so we remove those
@@ -1393,9 +1548,11 @@ async def list_audit_runs(
     rows = await pool.fetch(
         f"""
         SELECT id, seq, scope, worker_pool, trigger, started_at, finished_at,
-               status, note, total, ok, failed, skipped, created_by, idle_ms,
+               status, note, total, validate_total, ok, failed, skipped, created_by, idle_ms,
                force_rebuild, auto_validate, parent_run_id, auto_validate_dispatched_at,
-               issue_bot_status, issue_bot_last_error, issue_bot_synced_at
+               issue_bot_status, issue_bot_last_error, issue_bot_synced_at,
+               (SELECT COALESCE(SUM(duration_ms), 0)::bigint FROM audit_log
+                WHERE audit_run_id = audit_runs.id) AS cells_duration_ms
         FROM audit_runs
         {where}
         ORDER BY started_at DESC
@@ -1410,9 +1567,11 @@ async def get_audit_run(pool: asyncpg.Pool, run_id: str) -> dict | None:
     row = await pool.fetchrow(
         """
         SELECT id, seq, scope, worker_pool, trigger, started_at, finished_at,
-               status, note, total, ok, failed, skipped, created_by, idle_ms,
+               status, note, total, validate_total, ok, failed, skipped, created_by, idle_ms,
                force_rebuild, auto_validate, parent_run_id, auto_validate_dispatched_at,
-               issue_bot_status, issue_bot_last_error, issue_bot_synced_at
+               issue_bot_status, issue_bot_last_error, issue_bot_synced_at,
+               (SELECT COALESCE(SUM(duration_ms), 0)::bigint FROM audit_log
+                WHERE audit_run_id = audit_runs.id) AS cells_duration_ms
         FROM audit_runs WHERE id = $1
         """,
         run_id,
@@ -1803,26 +1962,39 @@ async def claim_audit_run_for_issue_bot(
 
 
 async def claim_audit_run_for_auto_validate(pool: asyncpg.Pool):
-    """Atomically claim the oldest finished ``auto_validate`` run whose
-    validation pass hasn't been dispatched yet. Stamps
-    ``auto_validate_dispatched_at`` in the same statement so a concurrent tick
-    / replica can't double-fire. Returns the claimed run row or ``None``."""
+    """Atomically claim the oldest ``auto_validate`` run that is ready for its
+    validation pass. Two shapes qualify:
+
+    * a run whose parity cells were reserved upfront (``validate_total > 0``)
+      and whose conversion cells have all landed — it is still ``running``
+      because the reserved cells keep the counter-bump finish check from
+      tripping;
+    * a pre-reservation run (``validate_total = 0``) that already finished —
+      its validation extends the total, the legacy behaviour.
+
+    Stamps ``auto_validate_dispatched_at`` in the same statement so a
+    concurrent tick / replica can't double-fire. Returns the claimed run row
+    or ``None``."""
     row = await pool.fetchrow(
         """
         UPDATE audit_runs
         SET auto_validate_dispatched_at = NOW()
         WHERE id = (
             SELECT id FROM audit_runs
-            WHERE status = 'finished'
-              AND auto_validate = TRUE
+            WHERE auto_validate = TRUE
               AND auto_validate_dispatched_at IS NULL
-            ORDER BY finished_at ASC NULLS LAST
+              AND (
+                    (validate_total > 0 AND status = 'running'
+                        AND ok + failed + skipped >= total - validate_total)
+                 OR (validate_total = 0 AND status = 'finished')
+              )
+            ORDER BY started_at ASC NULLS LAST
             LIMIT 1
             FOR UPDATE SKIP LOCKED
         )
         RETURNING id, scope, worker_pool, trigger, started_at, finished_at,
-                  status, note, total, ok, failed, skipped, created_by,
-                  force_rebuild, auto_validate, parent_run_id,
+                  status, note, total, validate_total, ok, failed, skipped,
+                  created_by, force_rebuild, auto_validate, parent_run_id,
                   issue_bot_status, issue_bot_last_error, issue_bot_synced_at
         """,
     )
diff --git a/src/ada/comms/rest/handlers.py b/src/ada/comms/rest/handlers.py
index 86c8c8970..cf42a33c6 100644
--- a/src/ada/comms/rest/handlers.py
+++ b/src/ada/comms/rest/handlers.py
@@ -18,6 +18,7 @@
 
 import os
 import threading
+from collections.abc import Awaitable, Callable, Iterable
 from pathlib import PurePosixPath
 
 from ada.comms.fb.fb_server_gen import ServerProcessInfoDC
@@ -242,15 +243,17 @@ async def dispatch(
     storage: Storage,
     scope: Scope,
     *,
-    extra_source_exts: frozenset[str] | None = None,
+    exts_provider: Callable[[], Awaitable[Iterable[str]]] | None = None,
 ) -> bytes | None:
     """Deserialize, dispatch (passing the request's scope to handlers),
     return serialized response (or None for no-reply).
 
-    ``extra_source_exts`` is the set of source extensions advertised by
-    online capability workers — only LIST_FILE_OBJECTS uses it today
-    (to surface plug-in formats like .odb in the storage overview).
-    Other handlers ignore the argument.
+    ``exts_provider`` lazily yields the set of source extensions
+    advertised by online capability workers. Only LIST_FILE_OBJECTS
+    consumes it (to surface plug-in formats like .odb in the storage
+    overview), so it is resolved *inside* that branch — every other
+    command (server info, view-file, ...) skips the worker-registry read
+    entirely, keeping worker-listing off the critical file-listing path.
     """
 
     message = deserialize_root_message(payload)
@@ -259,5 +262,11 @@ async def dispatch(
         logger.info("REST: unsupported command_type %s", message.command_type)
         return _error_reply(message, f"command_type {message.command_type} not supported in REST mode")
     if message.command_type == CommandTypeDC.LIST_FILE_OBJECTS:
+        extra_source_exts: frozenset[str] = frozenset()
+        if exts_provider is not None:
+            try:
+                extra_source_exts = frozenset(await exts_provider())
+            except Exception:
+                logger.exception("rpc: failed to read worker-advertised exts")
         return await handler(message, storage, scope, extra_source_exts)
     return await handler(message, storage, scope)
diff --git a/src/ada/comms/rest/migrations/021_audit_run_validate_total.sql b/src/ada/comms/rest/migrations/021_audit_run_validate_total.sql
new file mode 100644
index 000000000..45e6aa486
--- /dev/null
+++ b/src/ada/comms/rest/migrations/021_audit_run_validate_total.sql
@@ -0,0 +1,17 @@
+-- 021_audit_run_validate_total.sql — count the validation pass upfront.
+--
+-- ``validate_total`` reserves the auto-validation parity cells inside a
+-- run's ``total`` at *initial* dispatch, so the run's cell count is
+-- complete from the start instead of growing when the validation pass
+-- begins. While the reservation is outstanding the run stays 'running'
+-- (the counter-bump finish check compares against the full total); the
+-- auto-validate poller claims the run once the conversion cells alone
+-- have landed (ok + failed + skipped >= total - validate_total) and the
+-- validation dispatch *consumes* the reservation — re-counting the
+-- parity cells against the scope's current files and folding any drift
+-- into ``total`` — rather than extending it.
+--
+-- Runs without auto-validate (and pre-migration rows) keep
+-- validate_total = 0 and the old extend-on-finish behaviour.
+
+ALTER TABLE audit_runs ADD COLUMN validate_total INT NOT NULL DEFAULT 0;
diff --git a/src/ada/comms/rest/queue.py b/src/ada/comms/rest/queue.py
index 744c7612e..3a8849965 100644
--- a/src/ada/comms/rest/queue.py
+++ b/src/ada/comms/rest/queue.py
@@ -397,6 +397,49 @@ async def update(self, job_id: str, **fields) -> Job | None:
     async def _put(self, job: Job) -> None:
         await self._kv.put(job.job_id, job.to_json())
 
+    # Terminal statuses whose KV entry is disposable once the client has had a
+    # chance to read the final state. The durable record lives in Postgres
+    # (audit_log / audit runs) and S3 (derived blobs, profiles) — the KV is only
+    # a transient progress cache for in-flight polling.
+    _TERMINAL_STATUSES = frozenset({JOB_STATUS_DONE, JOB_STATUS_ERROR, "cancelled"})
+
+    async def purge_completed_jobs(self, grace_s: float = 600.0) -> int:
+        """Drop KV entries for jobs that reached a terminal state more than
+        ``grace_s`` ago, so the bucket stays small and ``keys()`` scans stay
+        cheap. Without this, completed job-status entries accumulated forever
+        (observed: 47k entries), turning every registry scan into a full-bucket
+        replay that hammered NATS. ``__meta_*`` keys are never touched."""
+        if self._kv is None:
+            return 0
+        try:
+            keys = await self._kv.keys()
+        except (BucketNotFoundError, Exception):
+            return 0
+        cutoff = time.time() - grace_s
+        purged = 0
+        for key in keys:
+            if key.startswith(self._META_KEY_PREFIX):
+                continue
+            try:
+                entry = await self._kv.get(key)
+            except KeyNotFoundError:
+                continue
+            except Exception:
+                continue
+            try:
+                job = Job.from_json(entry.value)
+            except Exception:
+                continue
+            if job.status in self._TERMINAL_STATUSES and (job.updated_at or 0.0) < cutoff:
+                try:
+                    await self._kv.purge(key)
+                    purged += 1
+                except Exception:
+                    pass
+        if purged:
+            logger.info("queue: purged %d completed job entr(ies) from the KV", purged)
+        return purged
+
     # --- meta-state helpers ------------------------------------------
     #
     # The shared KV bucket also holds small operational metadata under
diff --git a/src/ada/comms/rest/storage_ops.py b/src/ada/comms/rest/storage_ops.py
index e0dfeef44..eeafd1d9a 100644
--- a/src/ada/comms/rest/storage_ops.py
+++ b/src/ada/comms/rest/storage_ops.py
@@ -143,7 +143,9 @@ async def delete_blob_cascade(storage: Storage, scope_obj: Scope, key: str) -> d
                         k,
                         exc,
                     )
-                    tree_errors.append(f"{k}: {exc}")
+                    # Report only the failed key to the client; the exception detail is
+                    # logged above (avoid leaking backend/stack-trace text in the response).
+                    tree_errors.append(k)
             return {"deleted": deleted_tree, "errors": tree_errors}
 
         # Plain single-blob derived (legacy GLB, meta cache,
@@ -152,7 +154,7 @@ async def delete_blob_cascade(storage: Storage, scope_obj: Scope, key: str) -> d
             await storage.delete(scope_obj, clean)
         except Exception as exc:
             logger.exception("storage-op: delete failed for %s", clean)
-            raise HTTPException(status_code=500, detail=str(exc)) from exc
+            raise HTTPException(status_code=500, detail="delete failed") from exc
         return {"deleted": [clean], "errors": []}
 
     # Source delete: also reap every derived blob keyed off this
@@ -190,8 +192,11 @@ async def delete_blob_cascade(storage: Storage, scope_obj: Scope, key: str) -> d
                 continue
             if k == clean:
                 logger.exception("storage-op: delete failed for source %s", clean)
-                raise HTTPException(status_code=500, detail=str(exc)) from exc
-            errors.append(f"{k}: {exc}")
+                raise HTTPException(status_code=500, detail="delete failed") from exc
+            # Report only the failed key to the client; log the exception detail server-side
+            # (avoid leaking backend/stack-trace text in the response).
+            logger.warning("storage-op: failed to delete derived %s: %s", k, exc)
+            errors.append(k)
 
     return {"deleted": deleted, "errors": errors}
 
@@ -230,8 +235,10 @@ async def rename_key_cascade(
     try:
         await storage.rename(scope_obj, old_key, new_key, overwrite=True)
     except Exception as exc:
+        # Full detail logged; return a generic reason so backend/stack-trace text isn't
+        # exposed in the response (CodeQL py/stack-trace-exposure).
         logger.exception("storage-op: rename failed for %s -> %s", old_key, new_key)
-        return {"key": old_key, "reason": str(exc)}
+        return {"key": old_key, "reason": "rename failed"}
 
     live_keys.discard(old_key)
     live_keys.add(new_key)
@@ -274,7 +281,8 @@ async def rename_key_cascade(
                 sk_new,
                 exc,
             )
-            sibling_errors.append(f"{sk_old}: {exc}")
+            # Report only the failed key to the client; exception detail is logged above.
+            sibling_errors.append(sk_old)
 
     return {
         "old": old_key,
diff --git a/src/ada/comms/rest/subprocess_convert.py b/src/ada/comms/rest/subprocess_convert.py
index a19efb884..15e5a5399 100644
--- a/src/ada/comms/rest/subprocess_convert.py
+++ b/src/ada/comms/rest/subprocess_convert.py
@@ -441,6 +441,33 @@ def _child_progress(stage: str, frac: float) -> None:
                     _move_into_result(os.fspath(out), result_path)
                 else:
                     raise TypeError(f"convert returned {type(out).__name__}, expected bytes or a path")
+                # Emit per-conversion quality tallies for the parent to fold into convert_meta
+                # (marker-line channel, same as the C++ [STEPPROF-JSON] profiler). Best-effort:
+                # a tally failure must never fail an otherwise-successful conversion.
+                try:
+                    from ada.occ.tessellating import consume_mesh_distortion_stats, consume_tess_fallback_stats
+
+                    fb = consume_tess_fallback_stats()
+                    if fb.get("count"):
+                        _sys.stderr.write("[TESSFALLBACK-JSON] " + json.dumps(fb) + "\n")
+                    md = consume_mesh_distortion_stats()
+                    if md.get("distorted_tris"):
+                        _sys.stderr.write("[MESHHEALTH-JSON] " + json.dumps(md) + "\n")
+                except Exception:
+                    pass
+                # Triangle tally -> convert_meta["tri_stats"] (regression signal, see tess_stats).
+                # Native mesh conversions record it directly; for GLB (no tri count in the return)
+                # parse the output's JSON chunk. Best-effort — never fail a good conversion.
+                try:
+                    from ada.cadit.step.tess_stats import consume_tri_stats, count_glb_tri_stats
+
+                    ts = consume_tri_stats()
+                    if not ts.get("n_tris") and target_format in ("glb", "gltf"):
+                        ts = count_glb_tri_stats(result_path)
+                    if ts.get("n_tris"):
+                        _sys.stderr.write("[TRISTATS-JSON] " + json.dumps(ts) + "\n")
+                except Exception:
+                    pass
                 _flush_std()
                 os._exit(0)
             except BaseException as exc:  # noqa: BLE001 — propagate verbatim
diff --git a/src/ada/comms/rest/worker.py b/src/ada/comms/rest/worker.py
index 668be7c08..d6b305c63 100644
--- a/src/ada/comms/rest/worker.py
+++ b/src/ada/comms/rest/worker.py
@@ -15,6 +15,7 @@
 from __future__ import annotations
 
 import asyncio
+import ctypes
 import functools
 import os
 import pathlib
@@ -58,6 +59,36 @@ def _scope_of(job: Job) -> Scope:
     return Scope.shared()
 
 
+_LIBC_MALLOC_TRIM: object = None  # cached glibc malloc_trim, or False when unavailable
+
+
+def _trim_parent_memory() -> None:
+    """Return glibc's freed-but-retained arena memory to the OS in the long-lived worker PARENT
+    after each job. The parent forks per conversion; the freed per-job allocations it makes itself
+    (reading the child's captured log, parsing the marker JSON / cpp profile, building convert_meta,
+    the metrics-sample lists) pile up in glibc's arena free-lists rather than returning to the OS, so
+    parent RSS creeps up across a run (measured on a 23h prod worker: 218 MB fresh -> 540-840 MB idle,
+    higher mid-run). Because every conversion is a fork, the child INHERITS the parent's address space
+    (COW, counted in the child's RSS), so a bloated parent lifts EVERY conversion's baseline — enough
+    to push a big-model fork (469826) over the per-job memory watchdog, and the parent+child sum over
+    the 6 GiB pod limit (the run-90 pod OOM / Exit 137). Trimming after each job keeps the parent flat.
+    glibc-only; a best-effort no-op elsewhere. Disable with ADA_WORKER_NO_MALLOC_TRIM."""
+    global _LIBC_MALLOC_TRIM
+    if _LIBC_MALLOC_TRIM is None:
+        if os.environ.get("ADA_WORKER_NO_MALLOC_TRIM"):
+            _LIBC_MALLOC_TRIM = False
+        else:
+            try:
+                _LIBC_MALLOC_TRIM = ctypes.CDLL("libc.so.6").malloc_trim
+            except (OSError, AttributeError):
+                _LIBC_MALLOC_TRIM = False
+    if _LIBC_MALLOC_TRIM:
+        try:
+            _LIBC_MALLOC_TRIM(0)
+        except Exception:  # noqa: BLE001 — memory hygiene must never fail a job
+            pass
+
+
 # How long the pull-subscriber waits per fetch round before re-issuing.
 # Short enough to react to shutdown; long enough not to spam NATS.
 FETCH_TIMEOUT = 5.0
@@ -82,6 +113,21 @@ def _scope_of(job: Job) -> Scope:
 # stays free to fire these.
 IN_PROGRESS_REFRESH_SECONDS = 30
 
+# Liveness heartbeat. The worker touches this file whenever its JetStream pull loop iterates
+# (idle / between jobs) or an in-flight conversion reports progress. A k8s livenessProbe checks the
+# file's mtime is fresh: if the pull loop stalls — e.g. the durable consumer wedged after a NATS
+# restart, leaving the pod "Running" but no longer fetching (num_waiting=0) — the file goes stale and
+# k8s restarts the pod, instead of it sitting silently broken while jobs pile up unconsumed.
+WORKER_LIVENESS_FILE = os.environ.get("WORKER_LIVENESS_FILE", "/tmp/worker-alive")
+
+
+def _touch_liveness() -> None:
+    try:
+        with open(WORKER_LIVENESS_FILE, "w") as fh:
+            fh.write(str(time.time()))
+    except OSError:
+        logger.debug("worker: liveness touch failed", exc_info=True)
+
 # Per-source-suffix sidecar files that the worker co-downloads next to
 # the main payload so format-specific readers find them by basename.
 # Keep this conservative — a 404 on an absent sibling is silent, but
@@ -201,6 +247,95 @@ def _convert_meta_for(job: "Job", env_overrides: dict | None) -> dict | None:
     return meta or None
 
 
+def _attach_cpp_profiles(convert_meta: dict | None, log_bytes: bytes | None) -> None:
+    """Parse the adacpp pipeline profiler's machine-readable summaries out of the
+    captured child output into ``convert_meta["cpp_profile"]``.
+
+    When the ``profile_conversions`` toggle is on, the child runs with
+    ``ADACPP_STEP_PROFILE=1`` and each instrumented C++ pipeline prints ONE
+    ``[STEPPROF-JSON] {...}`` line at teardown (phase wall/RSS, VmHWM peak,
+    per-solid stats, parallelism/IO pressure, per-thread utilisation). Attaching
+    them to convert_meta puts the C++ side in the audit Metrics panel with the
+    same visibility as the Python timings. No-op when profiling was off (no
+    marker lines) or the log is empty."""
+    if not isinstance(convert_meta, dict) or not log_bytes:
+        return
+    import json
+
+    marker = b"[STEPPROF-JSON] "
+    profiles: list[dict] = []
+    for line in log_bytes.splitlines():
+        i = line.find(marker)
+        if i < 0:
+            continue
+        try:
+            profiles.append(json.loads(line[i + len(marker) :].decode("utf-8", "replace")))
+        except (ValueError, UnicodeDecodeError):
+            continue  # a torn/interleaved line must not fail the job
+    if profiles:
+        convert_meta["cpp_profile"] = profiles
+
+    # Per-conversion quality flags emitted by the child (subprocess_convert). Currently the
+    # NGEOM(libtess2/adacpp)->OCC fallback tally — a conversion that silently completed on OCC
+    # instead of the selected stream kernel. Surfaced as a cell flag in the audit grid.
+    fb_marker = b"[TESSFALLBACK-JSON] "
+    for line in log_bytes.splitlines():
+        i = line.find(fb_marker)
+        if i < 0:
+            continue
+        try:
+            fb = json.loads(line[i + len(fb_marker) :].decode("utf-8", "replace"))
+        except (ValueError, UnicodeDecodeError):
+            continue
+        if isinstance(fb, dict) and fb.get("count"):
+            convert_meta["occ_fallback"] = fb  # {count, reasons, geoms}
+        break
+
+    mh_marker = b"[MESHHEALTH-JSON] "
+    for line in log_bytes.splitlines():
+        i = line.find(mh_marker)
+        if i < 0:
+            continue
+        try:
+            mh = json.loads(line[i + len(mh_marker) :].decode("utf-8", "replace"))
+        except (ValueError, UnicodeDecodeError):
+            continue
+        if isinstance(mh, dict) and mh.get("distorted_tris"):
+            convert_meta["mesh_flags"] = mh  # {n_tris, distorted_tris, distorted_frac}
+        break
+
+    # Triangle tally — total output triangles (+ primitive/solid counts when known). The primary
+    # run-to-run regression signal: a tessellation-density change or a dropped solid moves n_tris.
+    ts_marker = b"[TRISTATS-JSON] "
+    for line in log_bytes.splitlines():
+        i = line.find(ts_marker)
+        if i < 0:
+            continue
+        try:
+            ts = json.loads(line[i + len(ts_marker) :].decode("utf-8", "replace"))
+        except (ValueError, UnicodeDecodeError):
+            continue
+        if isinstance(ts, dict) and ts.get("n_tris"):
+            convert_meta["tri_stats"] = ts  # {n_tris, engine?, n_primitives?, n_solids?, ...}
+        break
+
+    # Geometry health — faces with a real trim boundary that tessellated to zero triangles (silently
+    # dropped geometry, e.g. the SURFACE_OF_LINEAR_EXTRUSION drops). Flagged in the audit grid so this
+    # class of bug is caught without visual inspection.
+    gh_marker = b"[GEOMHEALTH-JSON] "
+    for line in log_bytes.splitlines():
+        i = line.find(gh_marker)
+        if i < 0:
+            continue
+        try:
+            gh = json.loads(line[i + len(gh_marker) :].decode("utf-8", "replace"))
+        except (ValueError, UnicodeDecodeError):
+            continue
+        if isinstance(gh, dict) and gh.get("dropped_faces"):
+            convert_meta["geom_health"] = gh  # {dropped_faces, total_faces}
+        break
+
+
 def _capture_worker_packages() -> list[dict]:
     """Snapshot the worker env's installed packages — the conda-meta manifest
     (authoritative for occt / pythonocc-core / ada-cpp / ifcopenshell / numpy …)
@@ -1161,6 +1296,10 @@ async def _process_one(
         # sibling jobs / the parent worker keep their pristine env.
         profile_enabled = False
         env_overrides: dict[str, str] = {}
+        # Initialised here (not only inside the ``db_pool is not None`` block below) so a worker
+        # that came up without a DB pool — e.g. it raced Postgres during a restart — still converts
+        # with code defaults instead of crashing every job with UnboundLocalError on ``timeout_s``.
+        timeout_s: float | None = None
         if db_pool is not None:
 
             async def _read_bool_setting(key: str) -> str | None:
@@ -1172,6 +1311,14 @@ async def _read_bool_setting(key: str) -> str | None:
 
             v = await _read_bool_setting("profile_conversions")
             profile_enabled = (v or "").strip().lower() in {"1", "true", "yes", "on"}
+            if profile_enabled:
+                # The C++ sibling of the cProfile artefact: adacpp's env-gated
+                # [STEPPROF] pipeline profiler (phase wall times, RSS at phase
+                # boundaries, VmHWM peak, per-solid stats, parallelism/IO
+                # pressure) prints to stderr, which the captured job Log keeps.
+                # Applied inside the child fork only, so sibling jobs and the
+                # parent worker keep their pristine env.
+                env_overrides["ADACPP_STEP_PROFILE"] = "1"
 
             # Optional per-job wall-clock budget. Empty / 0 / non-
             # numeric leaves the watchdog off so legitimately-long
@@ -1181,7 +1328,6 @@ async def _read_bool_setting(key: str) -> str | None:
             # convert subprocess after the deadline and SIGKILLs
             # 30 s later if it's still alive.
             timeout_minutes_raw = await _read_bool_setting("conversion_timeout_minutes")
-            timeout_s: float | None = None
             try:
                 tm = float((timeout_minutes_raw or "").strip())
                 if tm > 0:
@@ -1293,6 +1439,7 @@ async def _read_bool_setting(key: str) -> str | None:
 
         async def _on_progress(stage: str, frac: float) -> None:
             nonlocal last_kv_write
+            _touch_liveness()  # a long conversion blocks the pull loop; progress keeps liveness fresh
             now = time.monotonic()
             if now - last_kv_write < 0.25 and frac < 1.0:
                 return
@@ -1307,6 +1454,7 @@ async def _on_progress(stage: str, frac: float) -> None:
         # behind for post-mortem instead of an empty metrics_samples
         # column.
         async def _on_sample(sample: ConvertSample) -> None:
+            _touch_liveness()  # fires every ~2s during a subprocess conversion
             if db_pool is None:
                 return
             try:
@@ -1556,6 +1704,7 @@ async def _cancel_check() -> bool:
             metrics = dict(iresult.final_metrics)
             metrics["profile_key"] = await _maybe_upload_profile_bytes(iresult.profile_bytes)
             metrics["log_key"] = await _maybe_upload_log_bytes(iresult.log_bytes)
+            _attach_cpp_profiles(convert_meta, iresult.log_bytes)
             metrics["convert_meta"] = convert_meta
             await _audit_done(
                 db_pool,
@@ -1647,6 +1796,7 @@ async def _cancel_check() -> bool:
             metrics = dict(iresult.final_metrics)
             metrics["profile_key"] = await _maybe_upload_profile_bytes(iresult.profile_bytes)
             metrics["log_key"] = await _maybe_upload_log_bytes(iresult.log_bytes)
+            _attach_cpp_profiles(convert_meta, iresult.log_bytes)
             metrics["convert_meta"] = convert_meta
             await _audit_done(
                 db_pool,
@@ -1673,6 +1823,7 @@ async def _cancel_check() -> bool:
         metrics = dict(iresult.final_metrics)
         metrics["profile_key"] = await _maybe_upload_profile_bytes(iresult.profile_bytes)
         metrics["log_key"] = await _maybe_upload_log_bytes(iresult.log_bytes)
+        _attach_cpp_profiles(convert_meta, iresult.log_bytes)
         metrics["convert_meta"] = convert_meta
 
         await queue.update(job_id, status=JOB_STATUS_DONE, stage="ready", progress=1.0, error=None)
@@ -1691,14 +1842,61 @@ async def _cancel_check() -> bool:
             pass
 
 
+def _warm_convert_imports() -> None:
+    """Pre-import the heavy CAD C-extensions in the worker PARENT so every
+    ``os.fork()``ed conversion child (see subprocess_convert) inherits them
+    copy-on-write instead of re-importing per job.
+
+    Without this, an IFC child faults in ifcopenshell(.geom) and a SAT child
+    faults in OCC.Core — hundreds of MB of ``.so`` pages — on EVERY job; on a
+    cold/pressured page cache that measured ~20-40s of near-zero-CPU I/O-wait
+    per conversion (STEP's native adacpp reader was unaffected). Pre-importing
+    keeps the pages referenced by the long-lived parent and out of every child's
+    hot path. Per-module guard: a slim/scoped pool lacking a backend just skips it.
+
+    NOTE: the durable fix is routing IFC/SAT conversions through adacpp + the
+    native C++ IFC reader/writer so these deps aren't loaded at all (native STEP
+    already is). Until every target format is wired natively, IFC->{stl,obj,xml}
+    and SAT still go through ada.from_ifc / ada.from_acis; this removes their
+    per-fork re-import tax in the meantime.
+    """
+    import importlib
+
+    for mod, why in (
+        ("ada.cadit.ifc.store", "ifcopenshell + ifcopenshell.geom"),
+        ("ada.occ.tessellating", "OCC.Core tessellation + backends"),
+    ):
+        t0 = time.perf_counter()
+        try:
+            importlib.import_module(mod)
+        except Exception as exc:  # scoped/slim pool without this backend — skip
+            logger.info("worker: warm-import skipped %s (%s): %s", mod, why, exc)
+            continue
+        logger.info("worker: warm-imported %s (%s) in %.2fs", mod, why, time.perf_counter() - t0)
+
+
 async def _run() -> None:
+    # Make the worker's own lifecycle logs visible. The "ada" logger otherwise
+    # inherits root's WARNING level, which silently drops every worker: INFO
+    # line (booting / connected / registered / subscribing / ready) — leaving a
+    # healthy idle worker indistinguishable from a hung one in `kubectl logs`.
+    # This is the worker process only; the viewer configures its own logging.
+    # ADA_WORKER_LOG_LEVEL overrides (e.g. WARNING to quiet a chatty pool).
+    from ada.config import configure_logger
+
+    configure_logger()  # attach the stdout StreamHandler (no-op if already attached)
+    logger.setLevel(os.environ.get("ADA_WORKER_LOG_LEVEL", "INFO").upper())
+
     settings = load_settings()
     if settings.queue.url is None:
         raise SystemExit("ADA_VIEWER_NATS_URL not set; nothing for the worker to do")
 
+    logger.info("worker: booting capabilities=%s", os.environ.get("ADA_WORKER_CAPABILITIES", "base"))
     storage = Storage.from_settings(settings)
     queue = JobQueue(settings.queue)
+    logger.info("worker: connecting to NATS subject=%s", settings.queue.subject)
     await queue.connect()
+    logger.info("worker: connected to NATS")
 
     # Optional importer hook: capability workers built FROM the base
     # image often need to populate the connection-spec registry (or
@@ -1899,6 +2097,15 @@ async def _publish_registration() -> None:
     )
     sub = await queue.pull_subscribe(primary_capability)
 
+    # Warm the heavy CAD imports in this (parent) process before the per-job fork
+    # loop below, so forked children inherit them copy-on-write instead of paying
+    # a cold re-import per conversion. Base pool only — capability pools
+    # (weld-gen/abaqus) run foreign images with their own deps. Run in a thread so
+    # a slow cold import (OCC/ifcopenshell off a cold page cache) doesn't stall the
+    # event loop's NATS keepalive while the worker is still starting up.
+    if "base" in {c.lower() for c in capabilities}:
+        await asyncio.get_running_loop().run_in_executor(None, _warm_convert_imports)
+
     stop = asyncio.Event()
 
     def _signal_handler() -> None:
@@ -1932,8 +2139,10 @@ async def _heartbeat_loop() -> None:
     # Keep the parameter on _process_one for now (callers may still
     # pass it) but no longer create one here.
     logger.info("worker: ready, polling %s", settings.queue.subject)
+    _touch_liveness()  # seed the heartbeat before the first fetch so the probe has a fresh mtime
     try:
         while not stop.is_set():
+            _touch_liveness()  # each pull round — a stalled fetch lets this go stale -> livenessProbe restart
             try:
                 msgs = await sub.fetch(batch=FETCH_BATCH, timeout=FETCH_TIMEOUT)
             except asyncio.TimeoutError:
@@ -2066,6 +2275,9 @@ async def _keep_alive(m=msg, jid=job_id) -> None:
                     except Exception:
                         pass
                     await msg.ack()
+                    # Release the freed-but-retained arena memory this job left in the parent, so it
+                    # doesn't accumulate across the run and inflate the next conversion's fork baseline.
+                    _trim_parent_memory()
     finally:
         heartbeat_task.cancel()
         try:
diff --git a/src/ada/config.py b/src/ada/config.py
index 325b4527e..e8d90540e 100644
--- a/src/ada/config.py
+++ b/src/ada/config.py
@@ -148,6 +148,22 @@ class Config:
                 ConfigEntry("import_raise_exception_on_failed_advanced_face", bool, False),
             ],
         ),
+        ConfigSection(
+            "cad",
+            [
+                # Lazy shape store: keep imported CAD solids as compact blobs (NGEOM
+                # buffers from the native readers / pickled ada.geom otherwise) in a
+                # shared ShapeStore, minting ShapeProxy objects that hydrate geometry
+                # on demand (weakref-cached). ~5x lower resident memory on large STEP
+                # imports (a 778 MB / 7291-solid STEP: 2.6 GB -> ~0.5 GB settled). On by default; set
+                # ADA_CAD_LAZY_SHAPE_STORE=false to materialise eager Shapes as before.
+                ConfigEntry("lazy_shape_store", bool, True, required=False),
+                # Compress stored blobs (zlib-1, ~3x on B-rep buffers) at the cost of a
+                # decompress copy per hydration/fast-path access — trades the zero-copy
+                # property for a smaller resident floor.
+                ConfigEntry("shape_store_compress", bool, False, required=False),
+            ],
+        ),
         ConfigSection(
             "occ_tess",
             [
diff --git a/src/ada/core/utils.py b/src/ada/core/utils.py
index 3943cd6ff..94322a388 100644
--- a/src/ada/core/utils.py
+++ b/src/ada/core/utils.py
@@ -197,8 +197,10 @@ def to_real(v) -> float | list[float]:
 
 
 def round_array(arr: np.ndarray) -> np.ndarray:
-    # roundoff only on nonzero entries, zeros stay exact
-    mask = arr != 0
-    out = arr.copy()
-    out[mask] = np.vectorize(roundoff)(arr[mask])
-    return out
+    # Same roundoff (Decimal, HALF_EVEN) per element — replacing it with
+    # np.round shifts borderline values enough to drop ~59 of 104k FEM shells
+    # in plate conversion, so the semantics must stay. Every caller passes a
+    # 3-vector, where constructing an np.vectorize per call was ~70% of the
+    # cost (637k calls on a 100k-shell model spent ~28s here) — a plain loop
+    # keeps the exact values at a fraction of the overhead.
+    return np.array([roundoff(x) if x != 0 else x for x in np.asarray(arr, dtype=float)], dtype=float)
diff --git a/src/ada/core/vector_transforms.py b/src/ada/core/vector_transforms.py
index e5bff1a68..dabaffc64 100644
--- a/src/ada/core/vector_transforms.py
+++ b/src/ada/core/vector_transforms.py
@@ -456,3 +456,114 @@ def compute_orientation_vec(
 
     # Convert back to tuples for caching
     return tuple(xvec), tuple(yvec), tuple(zvec)
+
+
+def _round_rows_unique(a: np.ndarray) -> np.ndarray:
+    """round_array over the rows of ``a`` (m,3), Decimal-rounding each UNIQUE row once.
+
+    FEM meshes repeat orientations heavily (co-planar plate patches share their
+    frame), so deduplicating before the per-component ``roundoff`` keeps the exact
+    scalar semantics at a fraction of the Decimal cost."""
+    from ada.core.utils import roundoff
+
+    uniq, inv = np.unique(a, axis=0, return_inverse=True)
+    out = np.empty_like(uniq)
+    for i in range(uniq.shape[0]):
+        row = uniq[i]
+        out[i] = [roundoff(x) if x != 0 else x for x in row]
+    return out[inv.reshape(-1)]
+
+
+def shell_orientations_bulk(pts: np.ndarray) -> tuple[np.ndarray, np.ndarray, np.ndarray]:
+    """Vectorized orientation math for ``m`` flat FEM shell k-gons (m, k, 3).
+
+    Replicates, array-wise and in the same floating-point operation order, the
+    scalar chain CurvePoly2d.from_fem_shell runs per element:
+    ``normal_to_points_in_plane`` -> ``calc_yvec`` ->
+    ``compute_orientation_vec(x, y, z)`` -> ``compute_orientation_vec(x, None, z)``
+    (each vector normalized once on construction and once inside
+    compute_orientation_vec, then Decimal-rounded via round_array — see
+    :func:`_round_rows_unique`).
+
+    Returns ``(ok, rot1, rotf)``: ``ok (m,)`` False for rows the scalar path must
+    handle (duplicate points, (near-)parallel edge vectors, zero-length axes —
+    the scalar code has dedupe/rescan branches there), ``rot1``/``rotf`` (m,3,3)
+    with rows (xdir, ydir, zdir) — the projection and final frames.
+    """
+    pts = np.asarray(pts, dtype=float)
+    m, k, _ = pts.shape
+
+    def _cross(a, b):
+        # component order identical to normal_to_points_in_plane / fast_cross
+        out = np.empty_like(a)
+        out[:, 0] = a[:, 1] * b[:, 2] - a[:, 2] * b[:, 1]
+        out[:, 1] = a[:, 2] * b[:, 0] - a[:, 0] * b[:, 2]
+        out[:, 2] = a[:, 0] * b[:, 1] - a[:, 1] * b[:, 0]
+        return out
+
+    def _norm(a):
+        # np.linalg.norm(v) for a 1-D length-3 vector == sqrt(v.v), summed in
+        # component order
+        return np.sqrt(a[:, 0] * a[:, 0] + a[:, 1] * a[:, 1] + a[:, 2] * a[:, 2])
+
+    # normal_to_points_in_plane: v1 = p3 - p1, v2 = p2 - p1, normal = v1 x v2
+    v1 = pts[:, 2] - pts[:, 0]
+    v2 = pts[:, 1] - pts[:, 0]
+    normal = _cross(v1, v2)
+    n_len = _norm(normal)
+    v1_len = _norm(v1)
+    v2_len = _norm(v2)
+
+    # Degenerate-row escape (handled by the scalar path's dedupe / parallel-rescan
+    # branches): any duplicated corner, edge vectors (near-)parallel, or a
+    # zero-length first edge. The parallel test is a conservative superset of the
+    # scalar ``is_parallel`` (sin(angle) < tol): escaping a borderline row to the
+    # scalar path only costs time, never correctness.
+    dup = np.zeros(m, dtype=bool)
+    for i in range(k):
+        for j in range(i + 1, k):
+            dup |= np.all(pts[:, i] == pts[:, j], axis=1)
+    denom = v1_len * v2_len
+    # sin(angle) == |v1 x v2| / (|v1||v2|); escape at 2x the scalar is_parallel
+    # tolerance so every row the scalar rescan branch would touch goes scalar.
+    from ada.config import Config
+
+    par_tol = 2.0 * float(Config().general_point_tol)
+    near_parallel = n_len <= par_tol * np.where(denom > 0, denom, 1.0)
+    x_raw = pts[:, 1] - pts[:, 0]
+    x_len = _norm(x_raw)
+    ok = ~(dup | near_parallel | (denom == 0) | (x_len == 0) | (n_len == 0))
+
+    safe = lambda d: np.where(d == 0, 1.0, d)  # noqa: E731 - masked rows are already not-ok
+    n_hat = normal / safe(n_len)[:, None]
+    x_hat = x_raw / safe(x_len)[:, None]
+    y_raw = _cross(n_hat, x_hat)  # calc_yvec(x, z) == fast_cross(z, x)
+    y_len = _norm(y_raw)
+    # compute_orientation_vec rebuilds the frame from a global reference when a
+    # derived yvec degenerates (norm < 1e-9) — those rows must go scalar.
+    ok &= y_len >= 1e-9
+    y_hat = y_raw / safe(y_len)[:, None]
+
+    # compute_orientation_vec(x_hat, y_hat, n_hat): all three supplied -> each is
+    # re-normalized (Direction.get_normalized divides by its own norm again) and
+    # Decimal-rounded.
+    def _renorm_round(a):
+        ln = _norm(a)
+        return _round_rows_unique(a / safe(ln)[:, None])
+
+    x1 = _renorm_round(x_hat)
+    y1 = _renorm_round(y_hat)
+    z1 = _renorm_round(n_hat)
+
+    # compute_orientation_vec(x1, None, z1): y = calc_yvec(x1, z1) = z1 x x1, then
+    # all three re-normalized + rounded.
+    yf_raw = _cross(z1, x1)
+    yf_len = _norm(yf_raw)
+    ok &= yf_len >= 1e-9
+    xf = _renorm_round(x1)
+    yf = _round_rows_unique(yf_raw / safe(yf_len)[:, None])
+    zf = _renorm_round(z1)
+
+    rot1 = np.stack([x1, y1, z1], axis=1)
+    rotf = np.stack([xf, yf, zf], axis=1)
+    return ok, rot1, rotf
diff --git a/src/ada/factories.py b/src/ada/factories.py
index 58213c29a..6a5ac2f90 100644
--- a/src/ada/factories.py
+++ b/src/ada/factories.py
@@ -45,9 +45,18 @@ def from_pickle(pickle_file: str | os.PathLike) -> Assembly:
 
 
 def from_ifc(
-    ifc_file: os.PathLike | ifcopenshell.file, units=Units.M, name="Ada", cad_config: "CadConfig | None" = None
+    ifc_file: os.PathLike | ifcopenshell.file,
+    units=Units.M,
+    name="Ada",
+    cad_config: "CadConfig | None" = None,
+    reader: Literal["ifcopenshell", "native"] | None = None,
 ) -> Assembly:
-    """Create an Assembly object from an IFC file."""
+    """Create an Assembly object from an IFC file.
+
+    ``reader="native"`` uses adacpp's pure-C++ IFC reader (no ifcopenshell/OCC) to build a
+    geometry-shapes tree — pairs with ``Assembly.to_ifc(writer="native")`` for a fully native
+    round-trip. Default (``ifcopenshell``) is the full typed reader (Beam/Plate/Pipe/...).
+    """
     if isinstance(ifc_file, (os.PathLike, str)):
         ifc_file = pathlib.Path(ifc_file).resolve().absolute()
         logger.info(f'Reading "{ifc_file.name}"')
@@ -55,7 +64,7 @@ def from_ifc(
         logger.info("Reading IFC file object")
 
     a = Assembly(units=units, name=name, cad_config=cad_config)
-    a.read_ifc(ifc_file)
+    a.read_ifc(ifc_file, reader=reader)
     return a
 
 
@@ -70,7 +79,7 @@ def from_step(
     colour=None,
     opacity: float = 1.0,
     include_shells: bool = False,
-    reader: Literal["occ", "stream", "auto", "tolerant"] | None = None,
+    reader: Literal["occ", "stream", "auto", "tolerant", "native"] | None = None,
     product_tree: bool = False,
 ) -> Assembly:
     """Create an Assembly object from a STEP file.
diff --git a/src/ada/fem/formats/mesh_faces.py b/src/ada/fem/formats/mesh_faces.py
index b8130abed..e971714c4 100644
--- a/src/ada/fem/formats/mesh_faces.py
+++ b/src/ada/fem/formats/mesh_faces.py
@@ -56,13 +56,20 @@ def from_value(cls, value) -> "MergeStrategy":
 
 @dataclass
 class FaceData:
-    """A single planar CAD face, as raw data (no Plate object)."""
+    """A single CAD face, as raw data (no Plate object).
+
+    Planar faces carry their ``outline``; the analytic strategies (SURFACE /
+    PANEL) additionally emit recognised curved patches with ``geom_face`` set
+    to the analytic ``ada.geom`` AdvancedFace (trimmed cylinder / B-spline
+    panel) — ``outline`` is empty for those and consumers that can only take
+    polygons must request ``allow_analytic=False`` instead."""
 
     name: str
     outline: np.ndarray  # (k, 3) global coordinates
     normal: np.ndarray  # (3,) unit normal
     material: str
     thickness: float
+    geom_face: object | None = None  # ada.geom.surfaces.AdvancedFace for analytic patches
 
 
 # ── substrate ───────────────────────────────────────────────────────────────
@@ -1163,6 +1170,102 @@ def iter_fem_analytic_faces(
                     yield _facet_flat_face(prims, j)
 
 
+def _analytic_face_data(
+    fem,
+    ndigits: int,
+    *,
+    reconstruct_curved: bool,
+    allow_analytic: bool,
+    angle_tol: float = 30.0,
+    min_patch_quads: int = 12,
+) -> Iterator[FaceData]:
+    """SURFACE/PANEL strategies as :class:`FaceData` (the plate-metadata form).
+
+    Same patch machinery as :func:`iter_fem_analytic_faces`, with one addition it
+    doesn't need: every analytic face must carry a valid (material, thickness)
+    pair — the analytic iterator feeds a surface model where that metadata is
+    irrelevant, but a FaceData consumer builds plates from it. Cylinder patches
+    are therefore subdivided by (material, thickness) before fitting; a tube
+    whose wall thickness changes mid-length becomes one analytic face per
+    uniform segment. Patches that fail the fit — or all of them when
+    ``allow_analytic`` is False — fall to the coplanar flat merge, so geometry
+    is never dropped."""
+    prims = _combined_shell_primitives(fem)
+    if prims is None or len(prims) == 0:
+        return
+
+    patches = list(_surface_patches(prims, angle_tol, ndigits))
+    patch_cls = [(pt, classify_patch(prims, pt) if len(pt) >= min_patch_quads else "planar") for pt in patches]
+
+    consumed_elids: set = set()
+    if reconstruct_curved:
+        # Structured-quad B-spline pass (PANEL): per quad block, split into uniform
+        # (material, thickness) sub-blocks so each recovered panel face carries
+        # plate metadata; cylinder patches stay analytic below.
+        cyl_elids = {_elid_of(prims.names[j]) for pt, c in patch_cls if c == "cylinder" for j in pt}
+        for blk in _shell_blocks(fem):
+            if blk.conn.shape[1] != 4:
+                continue
+            groups: dict[tuple, list[int]] = {}
+            for r in range(blk.conn.shape[0]):
+                groups.setdefault((blk.materials[r], round(float(blk.thicknesses[r]), ndigits)), []).append(r)
+            for (mat, _tq), rows in groups.items():
+                idx = np.asarray(rows, dtype=np.int64)
+                sub = _ShellBlock(
+                    coords=blk.coords,
+                    conn=blk.conn[idx],
+                    el_ids=blk.el_ids[idx],
+                    materials=[blk.materials[r] for r in rows],
+                    thicknesses=blk.thicknesses[idx],
+                )
+                t = float(blk.thicknesses[rows[0]])
+                for face, panel_elids in _reconstruct_curved_panels(
+                    sub, cyl_elids, ndigits, angle_tol, min_patch_quads
+                ):
+                    if allow_analytic:
+                        yield FaceData(
+                            f"panel_e{min(panel_elids)}", np.empty((0, 3)), np.zeros(3), mat, t, geom_face=face
+                        )
+                        consumed_elids.update(panel_elids)
+                    # allow_analytic=False: leave the elements in the flat remainder.
+
+    cyl_prims: set = set()
+    if allow_analytic:
+        for patch, cls in patch_cls:
+            if cls != "cylinder":
+                continue
+            groups2: dict[tuple, list[int]] = {}
+            for j in patch:
+                if _elid_of(prims.names[j]) in consumed_elids:
+                    continue
+                groups2.setdefault((prims.mats[j], round(float(prims.ts[j]), ndigits)), []).append(j)
+            for (mat, _tq), sub_patch in groups2.items():
+                if len(sub_patch) < min_patch_quads:
+                    continue  # too small a uniform segment — flat merge handles it
+                cf = fit_cylinder_params(prims, sub_patch)
+                if cf is None:
+                    continue
+                # Joint-cut trimmed faces: bounded to the patch's real extent (a brace
+                # cut at a joint stops at the cut, not the full tube). Each edge carries
+                # a UV pcurve, which the IFC B-rep emitter now writes as
+                # IfcSurfaceCurve/IfcPcurve and the reader recovers — so these round-trip.
+                # Fall back to the full seam-template tube only if the trim won't resolve.
+                faces = cylinder_trim_faces(prims, sub_patch, cf, ndigits) or cylinder_fit_to_faces(cf)
+                t = float(prims.ts[sub_patch[0]])
+                base = _elid_of(prims.names[sub_patch[0]])
+                for i, face in enumerate(faces):
+                    yield FaceData(f"cyl_e{base}_{i}", np.empty((0, 3)), np.zeros(3), mat, t, geom_face=face)
+                cyl_prims.update(sub_patch)
+
+    remainder = [
+        j
+        for j in range(len(prims))
+        if j not in cyl_prims and (not consumed_elids or _elid_of(prims.names[j]) not in consumed_elids)
+    ]
+    if remainder:
+        yield from _coplanar_subset(prims, remainder, ndigits)
+
+
 @dataclass
 class _Tube:
     """One tube member for the solids path: a fitted cylinder's mid-surface radius ``r`` + wall
@@ -1512,7 +1615,12 @@ def classify_patch(prims: "_Primitives", patch: list[int], *, plane_tol: float =
 
 
 def faces_from_fem(
-    fem, strategy=MergeStrategy.COPLANAR, ndigits: int = 6, *, max_dev: float | None = None
+    fem,
+    strategy=MergeStrategy.COPLANAR,
+    ndigits: int = 6,
+    *,
+    max_dev: float | None = None,
+    allow_analytic: bool = True,
 ) -> Iterator[FaceData]:
     """Yield merged CAD faces for a single ``FEM`` mesh (one part).
 
@@ -1523,12 +1631,28 @@ def faces_from_fem(
     ``PLANAR`` grows flat patches (within ``max_dev``, auto if None) and emits one
     flat face per patch — the near-term FEM→CAD plate-count reducer that recovers
     large flat panels coplanar's exact bucketing misses and piecewise-flattens curved
-    skin. ``SURFACE`` (curved → one B-spline face) is not wired into the writer yet."""
+    skin.
+
+    ``SURFACE`` runs the analytic auto-detect over the whole mesh: cylinder
+    patches (split by material+thickness so each face carries valid plate
+    metadata) emit as trimmed analytic AdvancedFaces via ``geom_face``; the
+    remainder falls to the coplanar merge. ``PANEL`` adds the structured-quad
+    B-spline curved-panel pass on top (its grid recovery can over-merge folded
+    regions — see :func:`iter_fem_analytic_faces` — so it stays opt-in).
+    ``allow_analytic=False`` keeps those strategies polygon-only for consumers
+    that can't express curved surfaces (Genie XML): recognised patches then
+    merge as their coplanar flats instead — geometry is never dropped."""
     strategy = MergeStrategy.from_value(strategy)
-    if strategy in (MergeStrategy.SURFACE, MergeStrategy.PANEL):
-        raise NotImplementedError(f"merge strategy {strategy.value!r} not yet wired into the vectorized face source")
     if fem is None or len(fem.elements) == 0:
         return
+    if strategy in (MergeStrategy.SURFACE, MergeStrategy.PANEL):
+        yield from _analytic_face_data(
+            fem,
+            ndigits,
+            reconstruct_curved=strategy == MergeStrategy.PANEL,
+            allow_analytic=allow_analytic,
+        )
+        return
     for blk in _shell_blocks(fem):
         prims = _block_primitives(blk)
         if len(prims) == 0:
@@ -1552,16 +1676,24 @@ def faces_from_fem(
 
 
 def iter_faces(
-    part, strategy=MergeStrategy.COPLANAR, ndigits: int = 6, *, max_dev: float | None = None
+    part,
+    strategy=MergeStrategy.COPLANAR,
+    ndigits: int = 6,
+    *,
+    max_dev: float | None = None,
+    allow_analytic: bool = True,
 ) -> Iterator[FaceData]:
     """Yield merged CAD faces for every FEM mesh under ``part`` (Part or Assembly).
 
     Object-free: walks each sub-part's array-backed shell mesh, never building
-    Plate/Elem objects.
+    Plate/Elem objects. ``allow_analytic=False`` keeps the SURFACE/PANEL
+    strategies polygon-only (see :func:`faces_from_fem`).
     """
     parts = part.get_all_parts_in_assembly(include_self=True) if hasattr(part, "get_all_parts_in_assembly") else [part]
     for p in parts:
-        yield from faces_from_fem(getattr(p, "fem", None), strategy, ndigits, max_dev=max_dev)
+        yield from faces_from_fem(
+            getattr(p, "fem", None), strategy, ndigits, max_dev=max_dev, allow_analytic=allow_analytic
+        )
 
 
 def _coplanar_block(prims: _Primitives, ndigits: int) -> Iterator[FaceData]:
diff --git a/src/ada/fem/formats/utils.py b/src/ada/fem/formats/utils.py
index e527159e4..8da49dbf4 100644
--- a/src/ada/fem/formats/utils.py
+++ b/src/ada/fem/formats/utils.py
@@ -568,13 +568,83 @@ def convert_shell_elem_to_plates(
 
 
 def convert_part_shell_elements_to_plates(p: Part) -> Plates:
+    """Shell elements -> Plates, with the per-element orientation math vectorized.
+
+    A gather pass mirrors :func:`convert_shell_elem_to_plates` exactly (section
+    guards + warnings, material consolidation, coplanarity split of warped
+    quads, the tri-branch material quirk and its try/except), producing one
+    entry per output plate in element order. The geometry then runs once per
+    polygon arity through :meth:`CurvePoly2d.from_fem_shells_batch` — the same
+    floating-point ops as ``from_fem_shell``, batched — which on a 100k-shell
+    model removes ~1/3 of the FEM->concept wall time. Rows the bulk math
+    escapes (degenerate corners/edges) fall back to the scalar constructor.
+    """
+    import numpy as np
+
+    from ada import Plate
+    from ada.api.curves import CurvePoly2d
+    from ada.base.types import GeomRepr
+    from ada.core.vector_utils import is_coplanar
+
     # One shared material cache for every shell in the part — see the note
     # in convert_shell_elem_to_plates on why a per-element dict was O(N²).
     mat_dict: dict = {}
-    return Plates(
-        list(chain.from_iterable(convert_shell_elem_to_plates(sh, p, mat_dict) for sh in p.fem.elements.shell)),
-        parent=p,
-    )
+
+    # (name, pts (k,3), thickness, material, catch_errors) — one per output plate.
+    entries: list[tuple] = []
+    for elem in p.fem.elements.shell:
+        fem_sec = elem.fem_sec
+        if fem_sec is None or fem_sec.material is None:
+            logger.warning(f"Shell element {elem.id} has no section/material; skipping plate conversion")
+            continue
+        if fem_sec.type == GeomRepr.SOLID or getattr(fem_sec, "thickness", None) is None:
+            logger.warning(f"Shell-shaped element {elem.id} has a solid/thickness-less section; not a plate, skipping")
+            continue
+        fem_sec.material.parent = p
+        new_mat = mat_dict.get(fem_sec.material.name, None)
+        if new_mat is None:
+            new_mat = p.materials.add(fem_sec.material.copy_to(fem_sec.material.name, parent=p))
+            mat_dict[fem_sec.material.name] = new_mat
+
+        t = fem_sec.thickness
+        nodes = elem.nodes
+        if len(nodes) == 4:
+            n0, n1, n2, n3 = nodes[0].p, nodes[1].p, nodes[2].p, nodes[3].p
+            if is_coplanar(*n0, *n1, *n2, *n3):
+                entries.append((f"sh{elem.id}", np.array((n0, n1, n2, n3), dtype=float), t, new_mat, False))
+            else:
+                entries.append((f"sh{elem.id}", np.array((n0, n1, n2), dtype=float), t, new_mat, False))
+                entries.append((f"sh{elem.id}_1", np.array((n0, n2, n3), dtype=float), t, new_mat, False))
+        else:
+            # The scalar path binds the tri branch to the raw (unconsolidated)
+            # section material and wraps it in try/except — both preserved.
+            entries.append((f"sh{elem.id}", np.array([n.p for n in nodes], dtype=float), t, fem_sec.material, True))
+
+    # Vectorized geometry per polygon arity, results realigned to entry order.
+    polys: list = [None] * len(entries)
+    by_k: dict[int, list[int]] = {}
+    for i, e in enumerate(entries):
+        by_k.setdefault(e[1].shape[0], []).append(i)
+    for _k, idxs in by_k.items():
+        batch = CurvePoly2d.from_fem_shells_batch(np.stack([entries[i][1] for i in idxs]), parent=p)
+        for i, poly in zip(idxs, batch):
+            polys[i] = poly
+
+    plates = []
+    for (name, pts, t, mat, catch_errors), poly in zip(entries, polys):
+        try:
+            if poly is None:
+                pl = Plate.from_fem_shell(name, [q for q in pts], t, mat=mat, parent=p)
+            else:
+                pl = Plate(name, poly, t, mat=mat, parent=p)
+        except BaseException as e:
+            if not catch_errors:
+                raise
+            logger.error(f"Unable to convert {name} to plate due to {e}")
+            continue
+        plates.append(pl)
+
+    return Plates(plates, parent=p)
 
 
 def convert_part_elem_bm_to_beams(p: Part) -> Beams:
diff --git a/src/ada/geom/booleans.py b/src/ada/geom/booleans.py
index 7699b376c..21134c8bb 100644
--- a/src/ada/geom/booleans.py
+++ b/src/ada/geom/booleans.py
@@ -19,14 +19,14 @@ def from_str(cls, value) -> BoolOpEnum:
         return enum_map.get(value.lower())
 
 
-@dataclass
+@dataclass(slots=True)
 class BooleanResult:
     first_operand: Any
     second_operand: Any
     operator: BoolOpEnum
 
 
-@dataclass
+@dataclass(slots=True)
 class BooleanOperation:
     second_operand: Geometry
     operator: BoolOpEnum
diff --git a/src/ada/geom/curve_discretize.py b/src/ada/geom/curve_discretize.py
index d51ab7276..40204961f 100644
--- a/src/ada/geom/curve_discretize.py
+++ b/src/ada/geom/curve_discretize.py
@@ -126,4 +126,17 @@ def discretize_curve(curve, deflection: float = 0.1, max_angle: float = 0.35) ->
                 return None
             _append(out, seg_pts)
         return out
+    if type(curve) is cu.TrimmedCurve and isinstance(curve.basis_curve, cu.Line):
+        # Line basis: point trims are the endpoints; parameter trims evaluate on
+        # P(t) = pnt + t*dir (the reader keeps the vector magnitude in ``dir``).
+        b = curve.basis_curve
+
+        def _pt(t):
+            if not isinstance(t, (int, float)):
+                return tuple(np.asarray(t, float))
+            p = np.asarray(b.pnt, float)
+            d = np.asarray(b.dir, float)
+            return tuple(float(v) for v in p + float(t) * d)
+
+        return [_pt(curve.trim1), _pt(curve.trim2)]
     return None
diff --git a/src/ada/geom/curves.py b/src/ada/geom/curves.py
index 9a1cb5ebb..8ad4942f4 100644
--- a/src/ada/geom/curves.py
+++ b/src/ada/geom/curves.py
@@ -30,8 +30,10 @@
     "TrimmedCurve",
     "CompositeCurve",
     "Clothoid",
+    "CosineSpiral",
     "CurveSegment",
     "GradientCurve",
+    "SegmentedReferenceCurve",
     "PCurve",
     "PointOnCurve",
     "OffsetCurve3D",
@@ -39,7 +41,7 @@
 ]
 
 
-@dataclass
+@dataclass(slots=True)
 class Line:
     """
     IFC4x3 https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcLine.htm
@@ -56,7 +58,7 @@ def __post_init__(self):
             self.dir = Direction(*self.dir)
 
 
-@dataclass
+@dataclass(slots=True)
 class ArcLine:
     """
     IFC4x3 https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcArcIndex.htm
@@ -87,12 +89,12 @@ def __iter__(self):
         return iter((self.start, self.midpoint, self.end))
 
 
-@dataclass
+@dataclass(slots=True)
 class PolyLine:
     points: list[Point]
 
 
-@dataclass
+@dataclass(slots=True)
 class TrimmedCurve:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcTrimmedCurve.htm)
@@ -111,7 +113,7 @@ class TrimmedCurve:
     master_representation: str = "PARAMETER"
 
 
-@dataclass
+@dataclass(slots=True)
 class CompositeCurveSegment:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcCompositeCurveSegment.htm)
@@ -124,7 +126,7 @@ class CompositeCurveSegment:
     transition: str = "CONTINUOUS"
 
 
-@dataclass
+@dataclass(slots=True)
 class CompositeCurve:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcCompositeCurve.htm)
@@ -137,7 +139,7 @@ class CompositeCurve:
     self_intersect: bool = False
 
 
-@dataclass
+@dataclass(slots=True)
 class Clothoid:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcClothoid.htm)
@@ -153,26 +155,50 @@ class Clothoid:
     clothoid_constant: float
 
 
-@dataclass
+@dataclass(slots=True)
+class CosineSpiral:
+    """
+    IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/lexical/IfcCosineSpiral.htm)
+
+    A transition spiral whose curvature varies as a cosine of arc length. With A1 =
+    ``cosine_term``, A0 = ``constant_term`` (optional) and L the length over which the cosine
+    completes half a period (the containing CurveSegment's length), the heading angle is
+    ``theta(s) = s/A0 + (L/(pi*A1))*sin(pi*s/L)`` and the curvature ``kappa(s) = 1/A0 +
+    (1/A1)*cos(pi*s/L)``. Position is obtained by integrating ``(cos theta, sin theta)`` (no
+    closed form) about the 2D placement (``location`` + unit ``ref_direction``).
+    """
+
+    location: Iterable  # 2D placement origin
+    ref_direction: Iterable  # 2D unit tangent at s=0
+    cosine_term: float  # A1 (required)
+    constant_term: float | None = None  # A0 (optional)
+
+
+@dataclass(slots=True)
 class CurveSegment:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcCurveSegment.htm)
 
     A ``parent_curve`` restricted to the arc-length range [segment_start, segment_start +
-    segment_length] and positioned in the containing curve by a 2D placement (``location`` +
-    unit ``ref_direction``). Distinct from CompositeCurveSegment (no SameSense; carries its own
+    segment_length] and positioned in the containing curve by a placement (``location`` + unit
+    ``ref_direction``). Distinct from CompositeCurveSegment (no SameSense; carries its own
     placement + parametric range). segment_length may be negative (parameter decreases).
+
+    ``location``/``ref_direction`` are 2D for the planar (horizontal/vertical) curves, but 3D for
+    the cant segments of an IfcSegmentedReferenceCurve (IfcAxis2Placement3D) — the extra vertical
+    component of ``location`` is the superelevation offset baked onto the base curve. Planar
+    consumers slice ``location[:2]``, so the 3D form is backward-compatible.
     """
 
     transition: str
-    location: Iterable  # 2D placement origin (segment start position)
-    ref_direction: Iterable  # 2D unit tangent at the segment start
+    location: Iterable  # placement origin (2D planar, 3D for cant segments)
+    ref_direction: Iterable  # unit tangent at the segment start (2D planar, 3D for cant)
     segment_start: float
     segment_length: float
     parent_curve: CURVE_GEOM_TYPES
 
 
-@dataclass
+@dataclass(slots=True)
 class GradientCurve:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcGradientCurve.htm)
@@ -186,7 +212,24 @@ class GradientCurve:
     self_intersect: bool = False
 
 
-@dataclass
+@dataclass(slots=True)
+class SegmentedReferenceCurve:
+    """
+    IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/lexical/IfcSegmentedReferenceCurve.htm)
+
+    A 3D curve defined in the linear parameter space of its ``base_curve`` (typically an
+    IfcGradientCurve giving x,y,z along arc length). Its ``segments`` carry the cant
+    (superelevation): each maps a parameter range of the base curve to a vertical offset applied
+    perpendicular to the base curve axis, producing the rail reference curve. The horizontal
+    (x,y) is that of the base curve unchanged; only the vertical (z) is displaced by the cant.
+    """
+
+    base_curve: "GradientCurve"
+    segments: list["CurveSegment"]
+    self_intersect: bool = False
+
+
+@dataclass(slots=True)
 class IndexedPolyCurve:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcIndexedPolyCurve.htm)
@@ -257,12 +300,12 @@ def to_points2d(self):
         return local_points
 
 
-@dataclass
+@dataclass(slots=True)
 class GeometricCurveSet:
     elements: list[CURVE_GEOM_TYPES]
 
 
-@dataclass
+@dataclass(slots=True)
 class Circle:
     """
     IFC4x3 https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcCircle.htm
@@ -273,7 +316,7 @@ class Circle:
     radius: float
 
 
-@dataclass
+@dataclass(slots=True)
 class Ellipse:
     """
     IFC4x3 https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcEllipse.htm
@@ -285,7 +328,7 @@ class Ellipse:
     semi_axis2: float
 
 
-@dataclass
+@dataclass(slots=True)
 class Parabola:
     """STEP AP242 https://www.steptools.com/stds/stp_aim/html/t_parabola.html
 
@@ -296,7 +339,7 @@ class Parabola:
     focal_dist: float
 
 
-@dataclass
+@dataclass(slots=True)
 class PointOnCurve:
     """STEP AP242 t_point_on_curve — a point located at ``parameter`` on a basis curve."""
 
@@ -304,7 +347,7 @@ class PointOnCurve:
     parameter: float
 
 
-@dataclass
+@dataclass(slots=True)
 class OffsetCurve3D:
     """STEP AP242 t_offset_curve_3d — a curve offset from a basis curve by ``distance``."""
 
@@ -314,7 +357,7 @@ class OffsetCurve3D:
     ref_direction: "Direction | None" = None
 
 
-@dataclass
+@dataclass(slots=True)
 class Hyperbola:
     """STEP AP242 https://www.steptools.com/stds/stp_aim/html/t_hyperbola.html
 
@@ -356,7 +399,7 @@ def from_str(value: str) -> KnotType:
         return KnotType(value)
 
 
-@dataclass
+@dataclass(slots=True)
 class BSplineCurveWithKnots:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcBSplineCurveWithKnots.htm)
@@ -373,7 +416,7 @@ class BSplineCurveWithKnots:
     knot_spec: KnotType
 
 
-@dataclass
+@dataclass(slots=True)
 class PCurve:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcPcurve.htm)
@@ -383,7 +426,7 @@ class PCurve:
     reference_curve: CURVE_GEOM_TYPES
 
 
-@dataclass
+@dataclass(slots=True)
 class RationalBSplineCurveWithKnots(BSplineCurveWithKnots):
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcRationalBSplineCurveWithKnots.htm)
@@ -392,7 +435,7 @@ class RationalBSplineCurveWithKnots(BSplineCurveWithKnots):
     weights_data: list[float]
 
 
-@dataclass
+@dataclass(slots=True)
 class Edge:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcEdge.htm)
@@ -430,7 +473,7 @@ def __iter__(self):
         return iter((self.start, self.end))
 
 
-@dataclass
+@dataclass(slots=True)
 class Pcurve2dBSpline:
     """A 2D B-spline curve in the parameter space (UV) of a surface — the
     p-curve attached to a coedge in ACIS / STEP / IFC. Carrying the
@@ -450,7 +493,7 @@ class Pcurve2dBSpline:
     closed: bool = False
 
 
-@dataclass
+@dataclass(slots=True)
 class OrientedEdge(Edge):
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcOrientedEdge.htm)
@@ -479,7 +522,7 @@ class OrientedEdge(Edge):
     t_end: float | None = None
 
 
-@dataclass
+@dataclass(slots=True)
 class EdgeCurve(Edge):
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcEdgeCurve.htm)
@@ -490,7 +533,7 @@ class EdgeCurve(Edge):
     same_sense: bool
 
 
-@dataclass
+@dataclass(slots=True)
 class PolyLoop:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcPolyLoop.htm)
@@ -499,7 +542,7 @@ class PolyLoop:
     polygon: list[Point]
 
 
-@dataclass
+@dataclass(slots=True)
 class EdgeLoop:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcEdgeLoop.htm)
@@ -526,4 +569,12 @@ class EdgeLoop:
     TrimmedCurve,
     CompositeCurve,
     Edge,
+    # Loose curve collection (STEP GEOMETRIC_CURVE_SET wireframe bodies) — a
+    # curve body like its members, so every curve-body path treats it as one.
+    GeometricCurveSet,
+    # NB: the analytic alignment types (Clothoid / CosineSpiral / GradientCurve /
+    # SegmentedReferenceCurve) are intentionally NOT here — they are intermediate curves consumed
+    # by the alignment evaluator and never stored as a Shape's geometry (the reader converts them
+    # to a sampled PolyLine, which IS a curve body). Listing them would misclassify a swept
+    # solid's GradientCurve directrix as a bare wire body.
 )
diff --git a/src/ada/geom/placement.py b/src/ada/geom/placement.py
index 46b87ac25..b9ea72ab2 100644
--- a/src/ada/geom/placement.py
+++ b/src/ada/geom/placement.py
@@ -30,7 +30,7 @@ def ZV() -> Direction:  # noqa
     return Direction(0, 0, 1)
 
 
-@dataclass
+@dataclass(slots=True)
 class Axis2Placement3D:
 
     location: Point | Iterable = field(default_factory=O)
@@ -52,13 +52,13 @@ def get_pdir(self):
         return Direction(*np.cross(self.axis, self.ref_direction))
 
 
-@dataclass
+@dataclass(slots=True)
 class IfcLocalPlacement:
     relative_placement: Axis2Placement3D
     placement_rel_to: IfcLocalPlacement | None = None
 
 
-@dataclass
+@dataclass(slots=True)
 class Axis1Placement:
     location: Point
     axis: Direction
diff --git a/src/ada/geom/solids.py b/src/ada/geom/solids.py
index 2d0a629d5..76773b557 100644
--- a/src/ada/geom/solids.py
+++ b/src/ada/geom/solids.py
@@ -17,7 +17,7 @@
 )
 
 
-@dataclass
+@dataclass(slots=True)
 class ExtrudedAreaSolid:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3_0_0/lexical/IfcExtrudedAreaSolid.htm)
@@ -30,7 +30,7 @@ class ExtrudedAreaSolid:
     extruded_direction: Direction
 
 
-@dataclass
+@dataclass(slots=True)
 class ExtrudedAreaSolidTapered(ExtrudedAreaSolid):
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3_0_0/lexical/IfcExtrudedAreaSolidTapered.htm)
@@ -39,7 +39,7 @@ class ExtrudedAreaSolidTapered(ExtrudedAreaSolid):
     end_swept_area: ProfileDef
 
 
-@dataclass
+@dataclass(slots=True)
 class RevolvedAreaSolid:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcRevolvedAreaSolid.htm)
@@ -52,7 +52,7 @@ class RevolvedAreaSolid:
     angle: float
 
 
-@dataclass
+@dataclass(slots=True)
 class FixedReferenceSweptAreaSolid:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3_0_0/lexical/IfcFixedReferenceSweptAreaSolid.htm)
@@ -69,7 +69,7 @@ class FixedReferenceSweptAreaSolid:
     fixed_reference: Direction = field(default_factory=lambda: Direction(0.0, 0.0, 1.0))
 
 
-@dataclass
+@dataclass(slots=True)
 class SweptDiskSolid:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcSweptDiskSolid.htm)
@@ -88,7 +88,7 @@ class SweptDiskSolid:
     fillet_radius: float | None = None
 
 
-@dataclass
+@dataclass(slots=True)
 class Box:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcBlock.htm)
@@ -118,7 +118,7 @@ def from_2points(p1: Point, p2: Point) -> Box:
         return Box.from_xyz_and_dims(x, y, z, x_length, y_length, z_length)
 
 
-@dataclass
+@dataclass(slots=True)
 class RectangularPyramid:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3_0_0/lexical/IfcRectangularPyramid.htm)
@@ -131,7 +131,7 @@ class RectangularPyramid:
     z_length: float
 
 
-@dataclass
+@dataclass(slots=True)
 class Cone:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3_0_0/lexical/IfcRightCircularCone.htm)
@@ -152,7 +152,7 @@ def from_2points(p1: Point, p2: Point, r: float) -> Cone:
         return Cone(axis3d, r, height)
 
 
-@dataclass
+@dataclass(slots=True)
 class Cylinder:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3_0_0/lexical/IfcRightCircularCylinder.htm)
@@ -173,7 +173,7 @@ def from_2points(p1: Point, p2: Point, r: float) -> Cylinder:
         return Cylinder(axis3d, r, height)
 
 
-@dataclass
+@dataclass(slots=True)
 class Sphere:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3_0_0/lexical/IfcSphere.htm)
@@ -184,7 +184,7 @@ class Sphere:
     radius: float
 
 
-@dataclass
+@dataclass(slots=True)
 class Torus:
     """STEP AP242 https://www.steptools.com/stds/stp_aim/html/t_torus.html
 
@@ -196,7 +196,7 @@ class Torus:
     minor_radius: float
 
 
-@dataclass
+@dataclass(slots=True)
 class AdvancedBrep:
     """
     IFC4x3 (https://ifc43-docs.standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/lexical/IfcAdvancedBrep.htm)
@@ -205,7 +205,7 @@ class AdvancedBrep:
     outer: ConnectedFaceSet
 
 
-@dataclass
+@dataclass(slots=True)
 class FacetedBrep:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcFacetedBrep.htm)
diff --git a/src/ada/geom/surfaces.py b/src/ada/geom/surfaces.py
index 3f404231e..22d869372 100644
--- a/src/ada/geom/surfaces.py
+++ b/src/ada/geom/surfaces.py
@@ -12,12 +12,12 @@
 
 
 # STEP AP242 and IFC 4x3
-@dataclass
+@dataclass(slots=True)
 class Plane:
     position: Axis2Placement3D
 
 
-@dataclass
+@dataclass(slots=True)
 class CylindricalSurface:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcCylindricalSurface.htm)
@@ -28,7 +28,7 @@ class CylindricalSurface:
     radius: float
 
 
-@dataclass
+@dataclass(slots=True)
 class ConicalSurface:
     """
     STEP AP242 (https://www.steptools.com/stds/stp_aim/html/t_conical_surface.html)
@@ -46,7 +46,7 @@ class ConicalSurface:
     semi_angle: float  # Cone half-angle in radians
 
 
-@dataclass
+@dataclass(slots=True)
 class SphericalSurface:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcSphericalSurface.htm)
@@ -57,7 +57,7 @@ class SphericalSurface:
     radius: float
 
 
-@dataclass
+@dataclass(slots=True)
 class ToroidalSurface:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcToroidalSurface.htm)
@@ -83,12 +83,12 @@ def from_str(profile_type: str) -> "ProfileType":
             raise ValueError(f"Invalid profile type {profile_type}")
 
 
-@dataclass
+@dataclass(slots=True)
 class ProfileDef:
     profile_type: ProfileType
 
 
-@dataclass
+@dataclass(slots=True)
 class ArbitraryProfileDef(ProfileDef):
     """
     IFC4x3 https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcArbitraryProfileDefWithVoids.htm
@@ -99,7 +99,7 @@ class ArbitraryProfileDef(ProfileDef):
     profile_name: str = None
 
 
-@dataclass
+@dataclass(slots=True)
 class FaceBound:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcFaceBound.htm)
@@ -109,7 +109,7 @@ class FaceBound:
     orientation: bool
 
 
-@dataclass
+@dataclass(slots=True)
 class Face:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcFace.htm)
@@ -118,7 +118,7 @@ class Face:
     bounds: list[FaceBound]
 
 
-@dataclass
+@dataclass(slots=True)
 class FaceSurface(Face):
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcFaceSurface.htm)
@@ -129,7 +129,7 @@ class FaceSurface(Face):
     same_sense: bool = True
 
 
-@dataclass
+@dataclass(slots=True)
 class ConnectedFaceSet:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcConnectedFaceSet.htm)
@@ -139,7 +139,7 @@ class ConnectedFaceSet:
     cfs_faces: list["Face | FaceSurface"]
 
 
-@dataclass
+@dataclass(slots=True)
 class FaceBasedSurfaceModel:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcFaceBasedSurfaceModel.htm)
@@ -148,7 +148,7 @@ class FaceBasedSurfaceModel:
     fbsm_faces: list[ConnectedFaceSet]
 
 
-@dataclass
+@dataclass(slots=True)
 class CurveBoundedPlane:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcCurveBoundedPlane.htm)
@@ -159,13 +159,13 @@ class CurveBoundedPlane:
     inner_boundaries: list[geo_cu.CURVE_GEOM_TYPES] = field(default_factory=list)
 
 
-@dataclass
+@dataclass(slots=True)
 class HalfSpaceSolid:
     base_surface: Plane
     agreement_flag: bool = True
 
 
-@dataclass
+@dataclass(slots=True)
 class SurfaceOfLinearExtrusion:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcSurfaceOfLinearExtrusion.htm)
@@ -177,7 +177,7 @@ class SurfaceOfLinearExtrusion:
     depth: float
 
 
-@dataclass
+@dataclass(slots=True)
 class SurfaceOfRevolution:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcSurfaceOfRevolution.htm)
@@ -193,7 +193,7 @@ class SurfaceOfRevolution:
     position: Axis2Placement3D = None
 
 
-@dataclass
+@dataclass(slots=True)
 class RectangularTrimmedSurface:
     """STEP AP242 https://www.steptools.com/stds/stp_aim/html/t_rectangular_trimmed_surface.html
 
@@ -209,7 +209,7 @@ class RectangularTrimmedSurface:
     vsense: bool = True
 
 
-@dataclass
+@dataclass(slots=True)
 class OffsetSurface:
     """STEP AP242 https://www.steptools.com/stds/stp_aim/html/t_offset_surface.html
 
@@ -221,7 +221,7 @@ class OffsetSurface:
     self_intersect: bool = False
 
 
-@dataclass
+@dataclass(slots=True)
 class PointOnSurface:
     """STEP AP242 t_point_on_surface — a point at (u, v) on a basis surface."""
 
@@ -230,7 +230,7 @@ class PointOnSurface:
     v: float
 
 
-@dataclass
+@dataclass(slots=True)
 class RectangularCompositeSurface:
     """STEP AP242 t_rectangular_composite_surface — a grid of surface patches.
 
@@ -240,7 +240,7 @@ class RectangularCompositeSurface:
     segments: list
 
 
-@dataclass
+@dataclass(slots=True)
 class IShapeProfileDef(ProfileDef):
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcIShapeProfileDef.htm)
@@ -255,7 +255,7 @@ class IShapeProfileDef(ProfileDef):
     flange_slope: float
 
 
-@dataclass
+@dataclass(slots=True)
 class TShapeProfileDef(ProfileDef):
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcTShapeProfileDef.htm)
@@ -272,7 +272,7 @@ class TShapeProfileDef(ProfileDef):
     flange_slope: float
 
 
-@dataclass
+@dataclass(slots=True)
 class CircleProfileDef(ProfileDef):
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcCircleProfileDef.htm)
@@ -281,7 +281,7 @@ class CircleProfileDef(ProfileDef):
     radius: float
 
 
-@dataclass
+@dataclass(slots=True)
 class TriangulatedFaceSet:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcTriangulatedFaceSet.htm)
@@ -292,7 +292,7 @@ class TriangulatedFaceSet:
     indices: list[int]
 
 
-@dataclass
+@dataclass(slots=True)
 class PolygonalFaceSet:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcPolygonalFaceSet.htm)
@@ -307,7 +307,7 @@ class PolygonalFaceSet:
     closed: bool = True
 
 
-@dataclass
+@dataclass(slots=True)
 class RectangleProfileDef(ProfileDef):
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcRectangleProfileDef.htm)
@@ -335,7 +335,7 @@ def from_str(value: str) -> BSplineSurfaceForm:
         return BSplineSurfaceForm(value)
 
 
-@dataclass
+@dataclass(slots=True)
 class BSplineSurface:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcBSplineSurface.htm)
@@ -350,7 +350,7 @@ class BSplineSurface:
     self_intersect: bool
 
 
-@dataclass
+@dataclass(slots=True)
 class BSplineSurfaceWithKnots(BSplineSurface):
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcBSplineSurfaceWithKnots.htm)
@@ -385,7 +385,7 @@ def to_json(self):
         }
 
 
-@dataclass
+@dataclass(slots=True)
 class RationalBSplineSurfaceWithKnots(BSplineSurfaceWithKnots):
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcRationalBSplineSurfaceWithKnots.htm)
@@ -394,7 +394,7 @@ class RationalBSplineSurfaceWithKnots(BSplineSurfaceWithKnots):
     weights_data: list[list[float]]
 
 
-@dataclass
+@dataclass(slots=True)
 class ClosedShell:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcClosedShell.htm)
@@ -403,7 +403,7 @@ class ClosedShell:
     cfs_faces: list[Face | FaceSurface | Plane]
 
 
-@dataclass
+@dataclass(slots=True)
 class OpenShell:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcClosedShell.htm)
@@ -412,7 +412,7 @@ class OpenShell:
     cfs_faces: list[Face | FaceSurface | Plane]
 
 
-@dataclass
+@dataclass(slots=True)
 class AdvancedFace:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcAdvancedFace.htm)
@@ -435,7 +435,7 @@ class AdvancedFace:
     same_sense: bool = True
 
 
-@dataclass
+@dataclass(slots=True)
 class WireFilledFace:
     """A face defined only by its boundary wire — filled by OCC.
 
@@ -451,7 +451,7 @@ class WireFilledFace:
     bounds: list[FaceBound]
 
 
-@dataclass
+@dataclass(slots=True)
 class ShellBasedSurfaceModel:
     """
     IFC4x3 (https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcShellBasedSurfaceModel.htm)
diff --git a/src/ada/occ/geom/__init__.py b/src/ada/occ/geom/__init__.py
index 0f52d3968..e469750d6 100644
--- a/src/ada/occ/geom/__init__.py
+++ b/src/ada/occ/geom/__init__.py
@@ -62,8 +62,13 @@ def geom_to_occ_geom(geom: Geometry) -> TopoDS_Shape | TopoDS_Solid:
         occ_geom = geo_su.make_open_shell_from_geom(geometry)
     elif isinstance(geometry, su.ShellBasedSurfaceModel):
         occ_geom = geo_su.make_shell_from_shell_based_surface_geom(geometry)
+    elif isinstance(geometry, su.ConnectedFaceSet):
+        # The native NGEOM reader's B-rep root form (closed/open not recorded in the buffer).
+        occ_geom = geo_su.make_shell_from_connected_face_set_geom(geometry)
     elif isinstance(geometry, su.PolygonalFaceSet):
         occ_geom = geo_su.make_shell_from_polygonal_face_set_geom(geometry)
+    elif isinstance(geometry, su.TriangulatedFaceSet):
+        occ_geom = geo_su.make_shell_from_triangulated_face_set_geom(geometry)
 
     # Standalone boolean tree (ada.geom.booleans.BooleanResult): recursively build both operands
     # (each may itself be a BooleanResult) and apply the OCC boolean. This is the root-geometry form
diff --git a/src/ada/occ/geom/curves.py b/src/ada/occ/geom/curves.py
index 7fcd5a4bd..8f02a0192 100644
--- a/src/ada/occ/geom/curves.py
+++ b/src/ada/occ/geom/curves.py
@@ -1,7 +1,7 @@
 import math
 
 from OCC.Core.BRepBuilderAPI import BRepBuilderAPI_MakeEdge, BRepBuilderAPI_MakeWire
-from OCC.Core.GC import GC_MakeArcOfCircle
+from OCC.Core.GC import GC_MakeArcOfCircle, GC_MakeArcOfEllipse
 from OCC.Core.Geom import Geom_BSplineCurve
 from OCC.Core.GeomAPI import GeomAPI_PointsToBSpline, GeomAPI_ProjectPointOnCurve
 from OCC.Core.gp import gp_Ax2, gp_Circ, gp_Dir, gp_Elips, gp_Pnt
@@ -365,21 +365,60 @@ def make_wire_from_ellipse(ellipse: geo_cu.Ellipse) -> TopoDS_Wire:
 def make_wire_from_trimmed_curve(tc: geo_cu.TrimmedCurve) -> TopoDS_Wire:
     """Build a bounded wire from a TrimmedCurve.
 
-    Supports the two common geometric cases with Cartesian-point trims: a Line basis (straight
-    segment between the trims) and a Circle basis (arc between the trims). Parameter-only trims
-    and other bases are not yet built into OCC geometry."""
+    Trims may be Cartesian points or parameter values (angles for conic bases,
+    normalized to radians at read time; line parameters scale the direction
+    vector, whose IfcVector magnitude the reader preserves). Bases: Line,
+    Circle, Ellipse."""
+    import numpy as np
+
     from ada.geom.points import Point
 
+    def _p3(v) -> list[float]:
+        vals = [float(x) for x in v]
+        return vals + [0.0] * (3 - len(vals))
+
     basis = tc.basis_curve
-    p1, p2 = tc.trim1, tc.trim2
-    if not (isinstance(p1, Point) and isinstance(p2, Point)):
-        raise NotImplementedError("TrimmedCurve OCC build currently requires Cartesian-point trims")
+    t1, t2 = tc.trim1, tc.trim2
+    sense = bool(tc.sense_agreement)
 
     if isinstance(basis, geo_cu.Line):
-        edge = BRepBuilderAPI_MakeEdge(point3d(p1), point3d(p2)).Edge()
-    elif isinstance(basis, geo_cu.Circle):
-        circ = gp_Circ(gp_Ax2(gp_Pnt(*basis.position.location), gp_Dir(*basis.position.axis)), float(basis.radius))
-        arc = GC_MakeArcOfCircle(circ, point3d(p1), point3d(p2), bool(tc.sense_agreement)).Value()
+
+        def _line_pt(t) -> gp_Pnt:
+            if isinstance(t, Point):
+                return point3d(t)
+            w = np.asarray(_p3(basis.pnt)) + float(t) * np.asarray(_p3(basis.dir))
+            return gp_Pnt(*[float(v) for v in w])
+
+        edge = BRepBuilderAPI_MakeEdge(_line_pt(t1), _line_pt(t2)).Edge()
+    elif isinstance(basis, (geo_cu.Circle, geo_cu.Ellipse)):
+        pos = basis.position
+        loc = np.asarray(_p3(pos.location))
+        z = np.asarray(_p3(pos.axis) if pos.axis is not None else [0, 0, 1])
+        x = np.asarray(_p3(pos.ref_direction) if getattr(pos, "ref_direction", None) is not None else [1, 0, 0])
+        z = z / (np.linalg.norm(z) or 1.0)
+        x = x / (np.linalg.norm(x) or 1.0)
+        y = np.cross(z, x)
+        # Parameter trims are measured from the position's x axis — build the
+        # gp frame with the explicit XDirection (the 2-arg gp_Ax2 picks an
+        # arbitrary one).
+        ax2 = gp_Ax2(gp_Pnt(*loc), gp_Dir(*z), gp_Dir(*x))
+        if isinstance(basis, geo_cu.Circle):
+            sa1 = sa2 = float(basis.radius)
+            conic = gp_Circ(ax2, sa1)
+        else:
+            sa1, sa2 = float(basis.semi_axis1), float(basis.semi_axis2)
+            conic = gp_Elips(ax2, sa1, sa2)
+
+        def _conic_pt(t) -> gp_Pnt:
+            if isinstance(t, Point):
+                return point3d(t)
+            w = loc + sa1 * np.cos(float(t)) * x + sa2 * np.sin(float(t)) * y
+            return gp_Pnt(*[float(v) for v in w])
+
+        if isinstance(basis, geo_cu.Circle):
+            arc = GC_MakeArcOfCircle(conic, _conic_pt(t1), _conic_pt(t2), sense).Value()
+        else:
+            arc = GC_MakeArcOfEllipse(conic, _conic_pt(t1), _conic_pt(t2), sense).Value()
         edge = BRepBuilderAPI_MakeEdge(arc).Edge()
     else:
         raise NotImplementedError(f"TrimmedCurve OCC build not implemented for basis {type(basis)}")
@@ -523,10 +562,68 @@ def make_wire_from_curve(outer_curve: geo_cu.CURVE_GEOM_TYPES):
         return make_wire_from_trimmed_curve(outer_curve)
     elif isinstance(outer_curve, geo_cu.CompositeCurve):
         return make_wire_from_composite_curve(outer_curve)
+    elif isinstance(outer_curve, geo_cu.GradientCurve):
+        return make_wire_from_gradient_curve(outer_curve)
+    elif isinstance(outer_curve, geo_cu.PolyLine):
+        return make_wire_from_polyline(outer_curve)
+    elif isinstance(outer_curve, geo_cu.GeometricCurveSet):
+        # Loose curve collection (STEP wireframe body): the members are
+        # independent curves, so build a compound of wires rather than
+        # forcing them into one connected wire.
+        from OCC.Core.BRep import BRep_Builder
+        from OCC.Core.TopoDS import TopoDS_Compound
+
+        builder = BRep_Builder()
+        compound = TopoDS_Compound()
+        builder.MakeCompound(compound)
+        for element in outer_curve.elements:
+            builder.Add(compound, make_wire_from_curve(element))
+        return compound
     else:
         raise NotImplementedError(f"Unsupported curve type {type(outer_curve)}")
 
 
+def make_wire_from_gradient_curve(curve: geo_cu.GradientCurve) -> TopoDS_Wire:
+    """Alignment directrix (IFC4x3 IfcGradientCurve): clothoid segments have no
+    analytic OCC curve, so build a polyline wire from the shared alignment
+    evaluator's sampling — the same discretization the adacpp backend sweeps."""
+    import numpy as np
+
+    from ada.cadit.ngeom._alignment_sweep import gradient_curve_points
+
+    pts = gradient_curve_points(curve, n_per=100)
+    wire_maker = BRepBuilderAPI_MakeWire()
+    for a, b in zip(pts[:-1], pts[1:]):
+        if float(np.linalg.norm(b - a)) < 1e-9:
+            continue
+        edge = BRepBuilderAPI_MakeEdge(
+            gp_Pnt(float(a[0]), float(a[1]), float(a[2])), gp_Pnt(float(b[0]), float(b[1]), float(b[2]))
+        ).Edge()
+        wire_maker.Add(edge)
+    return wire_maker.Wire()
+
+
+def make_wire_from_polyline(curve: geo_cu.PolyLine) -> TopoDS_Wire:
+    """A sampled polyline (e.g. an evaluated alignment reference curve) -> a polyline wire, so it
+    round-trips through the OCC B-rep exporters (STEP GEOMETRIC_CURVE_SET, IFC)."""
+    import numpy as np
+
+    pts = [np.asarray(p, dtype=float) for p in curve.points]
+    wire_maker = BRepBuilderAPI_MakeWire()
+    added = 0
+    for a, b in zip(pts[:-1], pts[1:]):
+        if float(np.linalg.norm(b - a)) < 1e-9:
+            continue
+        edge = BRepBuilderAPI_MakeEdge(
+            gp_Pnt(float(a[0]), float(a[1]), float(a[2])), gp_Pnt(float(b[0]), float(b[1]), float(b[2]))
+        ).Edge()
+        wire_maker.Add(edge)
+        added += 1
+    if added == 0:
+        raise NotImplementedError("PolyLine has no non-degenerate segments to build a wire from")
+    return wire_maker.Wire()
+
+
 def make_wire_from_face_bound(face_bound: geo_su.FaceBound) -> TopoDS_Wire:
     if isinstance(face_bound.bound, geo_cu.PolyLoop):
         return make_wire_from_poly_loop(face_bound.bound)
diff --git a/src/ada/occ/geom/solids.py b/src/ada/occ/geom/solids.py
index e569f7b79..7d1d86f6c 100644
--- a/src/ada/occ/geom/solids.py
+++ b/src/ada/occ/geom/solids.py
@@ -11,6 +11,7 @@
 from OCC.Extend.TopologyUtils import TopologyExplorer
 
 import ada.geom.solids as geo_so
+from ada.config import logger
 from ada.geom.direction import Direction
 from ada.geom.points import Point
 from ada.occ.geom.curves import make_wire_from_curve
@@ -203,7 +204,13 @@ def make_fixed_reference_swept_area_shape_from_geom(frs: geo_so.FixedReferenceSw
     pipe_builder.Add(profile_wire, True, False)  # with contact and correction
 
     pipe_builder.Build()
-    pipe_builder.MakeSolid()
+    try:
+        pipe_builder.MakeSolid()
+    except RuntimeError as e:
+        # An open/non-closable sweep (e.g. a sampled alignment spine) still
+        # yields a valid shell — renderable and exportable — so degrade to it
+        # rather than dropping the body.
+        logger.warning(f"FixedReferenceSweptAreaSolid: MakeSolid failed ({e}); exporting the swept shell")
     swept_solid = pipe_builder.Shape()
 
     location = frs.position.location.tolist()
diff --git a/src/ada/occ/geom/surfaces.py b/src/ada/occ/geom/surfaces.py
index 196fdc4ec..4bc221333 100644
--- a/src/ada/occ/geom/surfaces.py
+++ b/src/ada/occ/geom/surfaces.py
@@ -74,6 +74,45 @@ def make_face_from_poly_loop(poly_loop: PolyLoop) -> TopoDS_Shape:
     return BRepBuilderAPI_MakeFace(wire).Shape()
 
 
+def _loop_newell(loop: PolyLoop):
+    """Newell area-vector of a planar loop — magnitude 2*area, direction the winding normal.
+    Robust for non-convex polygons."""
+    import numpy as np
+
+    pts = np.asarray([list(p)[:3] for p in loop.polygon], float)
+    n = np.zeros(3)
+    for i in range(len(pts)):
+        n += np.cross(pts[i], pts[(i + 1) % len(pts)])
+    return n
+
+
+def make_planar_face_from_bounds(bounds) -> TopoDS_Shape:
+    """Planar (IfcFace / faceted-brep) face from its ``FaceBound`` list: the first loop is the
+    outer boundary, any further loops are cut as holes. The old faceted-brep path used only
+    ``bounds[0]`` and dropped inner bounds, so a face with an opening (e.g. a basin's rim, whose
+    IfcFaceOuterBound carries an IfcFaceBound hole for the mouth) built as a solid cap.
+
+    A hole wire must wind opposite to the outer for MakeFace to subtract it, and sources are
+    inconsistent about the inner loop's stored direction — so decide per inner loop from its
+    winding relative to the outer normal rather than trusting a fixed convention."""
+    import numpy as np
+
+    outer = bounds[0].bound
+    if not isinstance(outer, PolyLoop):
+        raise NotImplementedError(f"Only PolyLoop bounds supported for Face, not {type(outer)}")
+    onrm = _loop_newell(outer)
+    mk = BRepBuilderAPI_MakeFace(make_wire_from_poly_loop(outer), True)  # True: plane inferred from the wire
+    for fb in bounds[1:]:
+        inner = fb.bound
+        if not isinstance(inner, PolyLoop):
+            raise NotImplementedError(f"Only PolyLoop inner bounds supported for Face, not {type(inner)}")
+        inner_wire = make_wire_from_poly_loop(inner)
+        if float(np.dot(_loop_newell(inner), onrm)) > 0.0:  # inner winds like the outer -> reverse to cut a hole
+            inner_wire.Reverse()
+        mk.Add(inner_wire)
+    return mk.Face()
+
+
 def make_face_from_indexed_poly_curve_geom(curve: geo_cu.IndexedPolyCurve) -> TopoDS_Shape:
     wire = make_wire_from_indexed_poly_curve_geom(curve)
     return BRepBuilderAPI_MakeFace(wire).Shape()
@@ -89,19 +128,16 @@ def make_face_from_circle(circle: geo_cu.Circle):
 
 
 def make_shell_from_face_based_surface_geom(surface: FaceBasedSurfaceModel) -> TopoDS_Shape:
-    occ_face = None
-    for face in surface.fbsm_faces:
-        for cfs_face in face.cfs_faces:
-            if not isinstance(cfs_face.bound, PolyLoop):
-                raise NotImplementedError("Only PolyLoop bounds are supported")
-            new_face = make_face_from_poly_loop(cfs_face.bound)
-            if occ_face is None:
-                occ_face = new_face
-            else:
-                # Fuse the new face with the existing face
-                occ_face = BRepAlgoAPI_Fuse(new_face, occ_face).Shape()
-
-    return occ_face
+    """Build an IfcFaceBasedSurfaceModel — a set of IfcConnectedFaceSets — into an OCC compound of
+    shells, mirroring make_shell_from_shell_based_surface_geom. Each connected face set is built by
+    the shared face-set builder (which reads each Face's ``bounds`` correctly), so an n-face surface
+    model renders and exports instead of erroring on the old ``cfs_face.bound`` assumption."""
+    builder = BRep_Builder()
+    compound = TopoDS_Compound()
+    builder.MakeCompound(compound)
+    for cfs in surface.fbsm_faces:
+        builder.Add(compound, make_shell_from_connected_face_set_geom(cfs))
+    return compound
 
 
 def make_shell_from_curve_bounded_plane_geom(surface: geo_su.CurveBoundedPlane) -> TopoDS_Shape:
@@ -1903,10 +1939,9 @@ def _add_cfs_faces_to_shell(builder: BRep_Builder, occ_shell: TopoDS_Shell, cfs_
         elif type(cfs_face) is geo_su.Face:
             n_faces += 1
             try:
-                outer = cfs_face.bounds[0].bound
-                if not isinstance(outer, PolyLoop):
-                    raise NotImplementedError(f"Only PolyLoop bounds supported for Face, not {type(outer)}")
-                face = make_face_from_poly_loop(outer)
+                # bounds[0] is the outer loop; any further bounds are holes (openings)
+                # in this planar face — build them so an IfcFace with a hole doesn't cap.
+                face = make_planar_face_from_bounds(cfs_face.bounds)
                 builder.UpdateFace(face, 1e-6)
                 builder.Add(occ_shell, face)
             except Exception as ex:
@@ -1977,6 +2012,24 @@ def make_open_shell_from_geom(shell: geo_su.OpenShell) -> TopoDS_Shell:
     return occ_shell
 
 
+def make_shell_from_connected_face_set_geom(cfs: geo_su.ConnectedFaceSet) -> TopoDS_Shell:
+    """Bare CONNECTED_FACE_SET — the native NGEOM reader's B-rep root form (the buffer
+    does not record whether the source shell was closed). Build the faces like the
+    closed/open shells above and let OCC determine closedness, so a manifold solid
+    B-rep read natively behaves like the Python reader's ClosedShell downstream."""
+    builder = BRep_Builder()
+    occ_shell = TopoDS_Shell()
+    builder.MakeShell(occ_shell)
+    _add_cfs_faces_to_shell(builder, occ_shell, cfs.cfs_faces)
+    try:
+        from OCC.Core.BRep import BRep_Tool
+
+        occ_shell.Closed(BRep_Tool.IsClosed(occ_shell))
+    except Exception:  # noqa: BLE001 - closedness flag is an optimisation, not correctness
+        pass
+    return occ_shell
+
+
 def make_shell_from_polygonal_face_set_geom(pfs: geo_su.PolygonalFaceSet) -> TopoDS_Shape:
     """Build an IfcPolygonalFaceSet — a shared point list plus n-gon faces — into a sewn
     OCC shell. Each face is a planar polygon wire (1-based indices into the point list);
@@ -2007,6 +2060,38 @@ def make_shell_from_polygonal_face_set_geom(pfs: geo_su.PolygonalFaceSet) -> Top
     return sewing.SewedShape()
 
 
+def make_shell_from_triangulated_face_set_geom(tfs: geo_su.TriangulatedFaceSet) -> TopoDS_Shape:
+    """Build an IfcTriangulatedFaceSet — a shared point list plus flat 1-based index
+    triples — into a sewn OCC shell, same treatment as the polygonal face set. Needed
+    for B-rep exports (STEP/IFC) of mesh-native bodies; tessellation itself takes the
+    direct mesh path and never comes here."""
+    coords = tfs.coordinates
+    idx = [int(i) for i in tfs.indices]
+    sewing = BRepBuilderAPI_Sewing(1e-6)
+    n_faces = 0
+    for k in range(0, len(idx), 3):
+        tri = idx[k : k + 3]
+        poly = BRepBuilderAPI_MakePolygon()
+        for i in tri:
+            poly.Add(point3d(coords[i - 1]))
+        poly.Close()
+        if not poly.IsDone():
+            logger.warning("TriangulatedFaceSet: skipping triangle %s (could not build wire)", tri)
+            continue
+        face_maker = BRepBuilderAPI_MakeFace(poly.Wire(), True)
+        if not face_maker.IsDone():
+            logger.warning("TriangulatedFaceSet: skipping degenerate triangle %s", tri)
+            continue
+        sewing.Add(face_maker.Face())
+        n_faces += 1
+
+    if n_faces == 0:
+        raise UnableToCreateTesselationFromSolidOCCGeom("TriangulatedFaceSet produced no usable faces")
+
+    sewing.Perform()
+    return sewing.SewedShape()
+
+
 def make_shell_from_shell_based_surface_geom(sbsm: geo_su.ShellBasedSurfaceModel) -> TopoDS_Shape:
     """Build an IfcShellBasedSurfaceModel — a set of open/closed shells — into a single OCC
     compound of shells, so a multi-shell wall/cladding surface renders and exports."""
@@ -2029,7 +2114,13 @@ def make_face_from_curve(outer_curve: geo_cu.CURVE_GEOM_TYPES):
     elif isinstance(outer_curve, geo_cu.Circle):
         return make_face_from_circle(outer_curve)
     else:
-        raise NotImplementedError("Only IndexedPolyCurve is implemented")
+        # Composite / trimmed / ellipse outlines (e.g. IFC profile curves
+        # stitched from IfcTrimmedCurve segments) — build the wire through
+        # the generic dispatcher and face it planar.
+        from ada.occ.geom.curves import make_wire_from_curve
+
+        wire = make_wire_from_curve(outer_curve)
+        return BRepBuilderAPI_MakeFace(wire, True).Shape()
 
 
 def make_profile_from_geom(area: geo_su.ProfileDef) -> TopoDS_Shape | TopoDS_Face:
diff --git a/src/ada/occ/store.py b/src/ada/occ/store.py
index a2d38e4d9..59d8825b9 100644
--- a/src/ada/occ/store.py
+++ b/src/ada/occ/store.py
@@ -99,9 +99,9 @@ def safe_geom(obj_, name_ref=None):
                 _g = getattr(obj_, "geom", None)
                 if _g is not None and isinstance(getattr(_g, "geometry", None), CURVE_GEOM_TUPLE):
                     try:
-                        from ada.occ.geom.curves import make_wire_from_curve
+                        from ada.cad import active_backend
 
-                        occ_geom = make_wire_from_curve(_g.geometry)
+                        occ_geom = active_backend().build(_g)
                     except (NotImplementedError, ImportError) as e:
                         logger.warning(f"Skipping {getattr(obj_, 'name', obj_)!r} in STEP export: {e}")
                         return None
diff --git a/src/ada/occ/tessellating.py b/src/ada/occ/tessellating.py
index 4f9f483ba..1b935c59b 100644
--- a/src/ada/occ/tessellating.py
+++ b/src/ada/occ/tessellating.py
@@ -44,6 +44,94 @@ def _is_topods_shape(shape) -> bool:
     return isinstance(shape, TopoDS_Shape)
 
 
+# Per-conversion tally of silent NGEOM(libtess2/adacpp-*)->OCC tessellation fallbacks. Incremented
+# at the single choke point (_log_tess_fallback), which is only reached when a stream pipeline was
+# actually selected — so every hit is a genuine "the OCC-free path fell back to OCC" event. The
+# convert subprocess reads + resets this at teardown and emits it to the audit (convert_meta), so a
+# conversion that quietly completed on OCC instead of libtess2 is flagged rather than invisible.
+from collections import Counter as _Counter
+
+TESS_FALLBACK_STATS: dict = {"count": 0, "reasons": _Counter(), "geoms": _Counter()}
+
+
+def _record_tess_fallback(reason: str, geom_type: str) -> None:
+    TESS_FALLBACK_STATS["count"] += 1
+    # Keep the reason label short + bounded (the strings are fixed call-site literals).
+    TESS_FALLBACK_STATS["reasons"][reason.split(":")[0][:40]] += 1
+    TESS_FALLBACK_STATS["geoms"][geom_type] += 1
+
+
+def consume_tess_fallback_stats() -> dict:
+    """Return the accumulated fallback tally and reset it (per-conversion scope)."""
+    s = {
+        "count": int(TESS_FALLBACK_STATS["count"]),
+        "reasons": dict(TESS_FALLBACK_STATS["reasons"]),
+        "geoms": dict(TESS_FALLBACK_STATS["geoms"]),
+    }
+    TESS_FALLBACK_STATS["count"] = 0
+    TESS_FALLBACK_STATS["reasons"].clear()
+    TESS_FALLBACK_STATS["geoms"].clear()
+    return s
+
+
+# Per-conversion tally of "crows-nest" spike triangles across every tessellated mesh. Fed by the
+# scene builders as they collect meshes (raw triangles, so no meshopt decode) and read out at
+# teardown into convert_meta for a per-cell audit flag. A spike is a thin (needle: aspect =
+# emax^2 / 2*area large) triangle that touches an OUTLIER vertex — one whose distance from the mesh's
+# robust (median) centroid exceeds _SPIKE_OUTLIER_K × the median vertex distance, i.e. a vertex shot
+# out past the body. The outlier test is what separates a real spike from benign geometry that a
+# raw aspect/reach test over-flags: a deep thin extrusion's side slivers, or a coarse curved surface,
+# are thin and reach across the bbox but their vertices sit ON the body, not outside it. Mirrors the
+# frontend meshStats "maxSpike" metric that drives the "distorted" gallery walk.
+_DISTORTION_ASPECT = 8.0  # emax^2/(2*area) above this = thin/needle (equilateral ~= 3.5)
+_SPIKE_OUTLIER_K = 4.0  # vertex dist > this × median vertex dist from the centroid = an outlier
+_DISTORTION_SAMPLE_CAP = 300_000  # sample huge meshes so the scan stays sub-ms; count is scaled back
+MESH_DISTORTION_STATS: dict = {"n_tris": 0, "distorted": 0}
+
+
+def accumulate_mesh_distortion(positions, indices) -> None:
+    """Tally crows-nest spike triangles in one mesh (best-effort, vectorized, sampled)."""
+    try:
+        v = np.asarray(positions, dtype=float).reshape(-1, 3)
+        idx = np.asarray(indices, dtype=np.int64).reshape(-1, 3)
+    except Exception:  # noqa: BLE001 - a malformed buffer must never fail a conversion
+        return
+    n = len(idx)
+    if n == 0 or len(v) == 0:
+        return
+    # Outlier vertices: distance from the median-per-axis centroid > K × the median distance.
+    centroid = np.median(v, axis=0)
+    vdist = np.linalg.norm(v - centroid, axis=1)
+    med = float(np.median(vdist))
+    is_outlier = (vdist > _SPIKE_OUTLIER_K * med) if med > 1e-9 else np.zeros(len(v), dtype=bool)
+    scale = 1.0
+    if n > _DISTORTION_SAMPLE_CAP:
+        step = n // _DISTORTION_SAMPLE_CAP + 1
+        idx = idx[::step]
+        scale = n / max(len(idx), 1)
+    tv = v[idx]
+    e0 = tv[:, 1] - tv[:, 0]
+    area2 = np.linalg.norm(np.cross(e0, tv[:, 2] - tv[:, 0]), axis=1)  # 2*area
+    emax = np.maximum.reduce(
+        [np.linalg.norm(e0, axis=1), np.linalg.norm(tv[:, 2] - tv[:, 1], axis=1), np.linalg.norm(tv[:, 0] - tv[:, 2], axis=1)]
+    )
+    with np.errstate(divide="ignore", invalid="ignore"):
+        aspect = np.where(area2 > 1e-20, emax * emax / area2, np.inf)
+    touches_outlier = is_outlier[idx].any(axis=1)  # any of the tri's 3 vertices is an outlier
+    distorted = int(((aspect > _DISTORTION_ASPECT) & touches_outlier & (emax > 1e-9)).sum())
+    MESH_DISTORTION_STATS["n_tris"] += int(n)
+    MESH_DISTORTION_STATS["distorted"] += int(round(distorted * scale))
+
+
+def consume_mesh_distortion_stats() -> dict:
+    """Return the distortion tally and reset it (per-conversion scope)."""
+    n = int(MESH_DISTORTION_STATS["n_tris"])
+    d = int(MESH_DISTORTION_STATS["distorted"])
+    MESH_DISTORTION_STATS["n_tris"] = 0
+    MESH_DISTORTION_STATS["distorted"] = 0
+    return {"n_tris": n, "distorted_tris": d, "distorted_frac": (d / n if n else 0.0)}
+
+
 def _mesh_store_area(ms) -> float:
     """Total triangle area of a tessellated ``MeshStore`` (position soup +
     indices). Used to gauge whether a curved-plate prism actually covered its
@@ -152,6 +240,36 @@ def _vertex_normals(positions: np.ndarray, faces: np.ndarray) -> np.ndarray:
     return (normals / lengths).reshape(-1).astype("float32")
 
 
+def _emit_with_geom_transforms(ms: "MeshStore", ada_obj):
+    """Yield ``ms`` once per world transform on the object's Geometry wrapper, baking each 4x4
+    into the vertex positions (and inverse-transpose into the normals, so non-uniform scale renders
+    correctly). ``Geometry.transforms`` carries per-instance placements the geometry itself can't
+    hold — e.g. an IfcMappedItem instanced N times, or a mapped item with a non-rigid (scale/shear)
+    transform that can't be baked into an analytic solid. No transforms → yield ``ms`` unchanged."""
+    transforms = getattr(getattr(ada_obj, "geom", None), "transforms", None)
+    if not transforms:
+        yield ms
+        return
+    base = np.asarray(ms.position, dtype=np.float64).reshape(-1, 3)
+    base_n = None
+    if ms.normal is not None and len(ms.normal):
+        base_n = np.asarray(ms.normal, dtype=np.float64).reshape(-1, 3)
+    for mat in transforms:
+        m = np.asarray(mat, dtype=np.float64)
+        pos = (np.c_[base, np.ones(len(base))] @ m.T)[:, :3].astype(np.float32).reshape(-1)
+        nrm = None
+        if base_n is not None:
+            try:
+                nm = np.linalg.inv(m[:3, :3]).T  # inverse-transpose: correct under non-uniform scale
+            except np.linalg.LinAlgError:
+                nm = m[:3, :3]
+            n = base_n @ nm.T
+            ln = np.linalg.norm(n, axis=1, keepdims=True)
+            ln[ln == 0] = 1.0
+            nrm = (n / ln).astype(np.float32).reshape(-1)
+        yield MeshStore(ms.index, ms.matrix, pos, ms.indices, nrm, ms.material, ms.type, ms.node_ref)
+
+
 def _thicken_face_mesh(positions: np.ndarray, faces: np.ndarray, thickness: float):
     """Extrude an open face mesh into a closed thin solid along a single vector — the
     area-weighted average surface normal × ``thickness`` — matching OCC's
@@ -200,7 +318,10 @@ def tessellate_edges(shape: TopoDS_Edge, deflection=0.01) -> LineMesh:
     if shape.ShapeType() == TopAbs_EDGE:
         edges = [shape]
     else:
-        edges = list(TopologyExplorer(shape).edges()) or [shape]
+        # A shape with no edges at all (e.g. an empty compound from a
+        # geometry-less STEP product) has nothing to discretize — passing the
+        # shape itself would trip discretize_edge's TopoDS_Edge assert.
+        edges = list(TopologyExplorer(shape).edges())
 
     verts: list = []
     indices: list = []
@@ -590,6 +711,20 @@ def tessellate_occ_geom(
                 if fixed is not None:
                     tess_shape = tessellate_shape(fixed, self.quality, self.render_edges, self.parallel)
                     indices = tess_shape.faces
+            if len(indices) == 0:
+                # Wire-only body (e.g. a GEOMETRIC_CURVE_SET STEP wireframe read
+                # back through the OCC fallback reader): there is no face to
+                # mesh, but the edges are real geometry — downgrade to line
+                # rendering instead of returning an empty mesh. Guarded so a
+                # non-OCC handle just keeps the empty result.
+                try:
+                    edge_tess = tessellate_edges(occ_geom)
+                except Exception:  # noqa: BLE001
+                    edge_tess = None
+                if edge_tess is not None and len(edge_tess.positions):
+                    tess_shape = edge_tess
+                    indices = edge_tess.indices
+                    mesh_type = MeshType.LINES
 
         mat_id = self.material_store.get(geom_color, None)
         if mat_id is None:
@@ -613,20 +748,30 @@ def _direct_line_meshstore(self, geom: Geometry, node_ref) -> MeshStore | None:
         ada.geom.curve_discretize sampler — parity-tested against OCC discretize_edge). Also lets
         line geometry render on wasm (no pythonocc). Returns None for curve kinds with no native
         sampler (e.g. B-spline), which fall through to the OCC discretization path."""
+        import ada.geom.curves as geo_cu
         from ada.geom.curve_discretize import discretize_curve
 
         deflection = float(os.environ.get("ADA_LINE_DEFLECTION", "0.01"))
-        pts = discretize_curve(geom.geometry, deflection=deflection)
-        if not pts or len(pts) < 2:
+        # A GeometricCurveSet is several independent curves in one body — each
+        # element gets its own polyline (no connector segment between them).
+        curves = geom.geometry.elements if isinstance(geom.geometry, geo_cu.GeometricCurveSet) else [geom.geometry]
+        pts: list = []
+        idx: list = []
+        for c in curves:
+            c_pts = discretize_curve(c, deflection=deflection)
+            if not c_pts or len(c_pts) < 2:
+                return None  # unsupported element — fall back to the OCC path
+            off = len(pts)
+            pts.extend(c_pts)
+            # GL_LINES endpoint pairs: (0,1),(1,2),... — connected polyline (the
+            # glTF store reshapes indices to (n/2, 2) segments).
+            for i in range(len(c_pts) - 1):
+                idx.extend((off + i, off + i + 1))
+        if len(pts) < 2:
             return None
 
         # Flat xyz buffer (the gltf store does position.reshape(len/3, 3)).
         position = np.array([c for p in pts for c in (float(p[0]), float(p[1]), float(p[2]))], dtype=np.float32)
-        # GL_LINES endpoint pairs: (0,1),(1,2),... — connected polyline (the glTF store reshapes
-        # indices to (n/2, 2) segments).
-        idx: list = []
-        for i in range(len(pts) - 1):
-            idx.extend((i, i + 1))
         mat_id = self.material_store.get(geom.color, None)
         if mat_id is None:
             mat_id = len(self.material_store)
@@ -635,6 +780,50 @@ def _direct_line_meshstore(self, geom: Geometry, node_ref) -> MeshStore | None:
             node_ref, None, position, np.array(idx, dtype=np.uint32), None, mat_id, MeshType.LINES, node_ref
         )
 
+    def _direct_triangulated_meshstore(self, geom: Geometry, node_ref) -> MeshStore | None:
+        """Face-set geometry that already IS (or trivially becomes) a triangle mesh — emit it
+        directly instead of round-tripping through a kernel build + re-tessellation:
+
+          * TriangulatedFaceSet (IfcTriangulatedFaceSet) — coords + triangle index list as-is.
+          * PolygonalFaceSet (IfcPolygonalFaceSet) — shared coords + n-gon faces; fan-triangulate
+            each face in 3D. This keeps the ORIGINAL vertices (unlike inferring a plane and
+            projecting, which flattens non-planar faces and wrecks the mesh), and no backend has a
+            B-rep build for it — so without this it falls back to OCC.
+
+        Returns None for every other kind."""
+        import ada.geom.surfaces as geo_su
+
+        g = geom.geometry
+        normal = None
+        if isinstance(g, geo_su.TriangulatedFaceSet):
+            if not g.coordinates or not g.indices:
+                return None
+            position = np.asarray(g.coordinates, dtype=np.float32).reshape(-1)
+            indices = np.asarray(g.indices, dtype=np.uint32) - 1  # IFC indices are 1-based
+            if g.normals and len(g.normals) == len(g.coordinates):
+                normal = np.asarray(g.normals, dtype=np.float32).reshape(-1)
+        elif isinstance(g, geo_su.PolygonalFaceSet):
+            if not g.coordinates or not g.faces:
+                return None
+            position = np.asarray([list(p)[:3] for p in g.coordinates], dtype=np.float32).reshape(-1)
+            n_coords = len(g.coordinates)
+            tri: list[int] = []
+            for face in g.faces:
+                f = [i - 1 for i in face if 0 < i <= n_coords]  # IFC 1-based -> 0-based
+                for k in range(1, len(f) - 1):  # fan-triangulate the n-gon (keeps 3D vertices)
+                    tri += (f[0], f[k], f[k + 1])
+            if not tri:
+                return None
+            indices = np.asarray(tri, dtype=np.uint32)
+        else:
+            return None
+
+        mat_id = self.material_store.get(geom.color, None)
+        if mat_id is None:
+            mat_id = len(self.material_store)
+            self.material_store[geom.color] = mat_id
+        return MeshStore(node_ref, None, position, indices, normal, mat_id, MeshType.TRIANGLES, node_ref)
+
     def tessellate_geom(
         self,
         geom: Geometry,
@@ -656,6 +845,12 @@ def tessellate_geom(
             if direct is not None:
                 return direct
 
+        # Pre-tessellated geometry: pass the triangles straight through.
+        if mesh_type == MeshType.TRIANGLES:
+            direct = self._direct_triangulated_meshstore(geom, node_ref)
+            if direct is not None:
+                return direct
+
         # NGEOM stream path (opt-in via ADA_STREAM_TESS_PIPELINE=libtess2|occ|cgal|hybrid):
         # serialize ada.geom + tessellate in one adacpp call instead of the OCC build +
         # BRepMesh below. Returns None when the env is unset or the active backend has no
@@ -712,6 +907,7 @@ def _log_tess_fallback(node_ref, pipeline: str, reason: str, geom: Geometry | No
             inner = getattr(geom, "geometry", geom)
             gt = type(getattr(inner, "geometry", inner)).__name__
         msg = f"NGEOM pipeline {pipeline!r} fell back to OCC for {node_ref!r} (geom={gt}): {reason}"
+        _record_tess_fallback(reason, gt)
         # Strict mode: a fall back to OCC is a hard failure, so a conversion can enforce/measure
         # 100% stream-kernel (libtess2/adacpp-*) coverage rather than silently completing on OCC.
         if os.environ.get("ADA_STREAM_TESS_STRICT", "").strip().lower() not in ("", "0", "false", "no", "off"):
@@ -728,32 +924,81 @@ def _tessellate_geom_via_stream(self, geom: Geometry, node_ref, force_pipeline:
         pipeline = os.environ.get("ADA_STREAM_TESS_PIPELINE") or force_pipeline
         if not pipeline:
             return None
+        # A pre-triangulated / polygonal face set is already a mesh — emit it directly (3D
+        # fan-triangulation, original vertices). libtess2 can't take it and inferring a plane per
+        # face would flatten non-planar faces; this keeps it OCC-free without that distortion.
+        direct = self._direct_triangulated_meshstore(geom, node_ref)
+        if direct is not None:
+            return direct
         be = active_backend()
         if not hasattr(be, "tessellate_stream"):
             self._log_tess_fallback(node_ref, pipeline, "active backend has no tessellate_stream", geom)
             return None
-        gi = geom.geometry.geometry if hasattr(geom.geometry, "geometry") else geom.geometry
-        defl = float(os.environ.get("ADA_STREAM_TESS_DEFLECTION", "2.0"))
-        ang = float(os.environ.get("ADA_STREAM_TESS_ANGULAR", "20.0"))
+        # Pass the Geometry wrapper through: the serializer unwraps it and folds any
+        # bool_operations into a BOOLEAN_RESULT chain, so IFC clipping cuts and API
+        # booleans reach the stream kernel instead of being dropped with the wrapper.
+        from ada.cad.registry import stream_tess_defaults, stream_tess_model_scale
+
+        defl, ang = stream_tess_defaults()
         try:
-            bm = be.tessellate_stream([(str(node_ref), gi)], pipeline=pipeline, deflection=defl, angular_deg=ang)
+            bm = be.tessellate_stream(
+                [(str(node_ref), geom)],
+                pipeline=pipeline,
+                deflection=defl,
+                angular_deg=ang,
+                model_scale=stream_tess_model_scale(),
+            )
         except Exception as e:  # noqa: BLE001 - fall back to the OCC build path on any stream failure
             self._log_tess_fallback(node_ref, pipeline, f"tessellate_stream raised {type(e).__name__}: {e}", geom)
             return None
+        ms = self._mesh_store_from_batch(bm, node_ref, geom.color)
+        if ms is None:
+            self._log_tess_fallback(node_ref, pipeline, "empty mesh (geom type not NGEOM-serializable)", geom)
+        return ms
+
+    def _tessellate_blob_via_stream(self, blob, node_ref, color) -> MeshStore | None:
+        """Tessellate a lazy shape's stored NGEOM buffer directly — no hydration, no
+        re-serialization: the ShapeStore blob goes straight to the C++ kernel."""
+        pipeline = os.environ.get("ADA_STREAM_TESS_PIPELINE")
+        if not pipeline:
+            return None
+        be = active_backend()
+        if not hasattr(be, "tessellate_stream_buffer"):
+            return None
+        from ada.cad.registry import stream_tess_defaults, stream_tess_model_scale
+
+        defl, ang = stream_tess_defaults()
+        try:
+            bm = be.tessellate_stream_buffer(
+                blob, pipeline=pipeline, deflection=defl, angular_deg=ang, model_scale=stream_tess_model_scale()
+            )
+        except Exception as e:  # noqa: BLE001 - fall back to the hydrate path on any stream failure
+            self._log_tess_fallback(
+                node_ref, pipeline, f"tessellate_stream_buffer raised {type(e).__name__}: {e}", None
+            )
+            return None
+        return self._mesh_store_from_batch(bm, node_ref, color)
+
+    def _mesh_store_from_batch(self, bm, node_ref, color) -> MeshStore | None:
         pos = getattr(bm, "positions", None)
         idx = getattr(bm, "indices", None)
         if pos is None or idx is None or len(idx) == 0:
-            self._log_tess_fallback(node_ref, pipeline, "empty mesh (geom type not NGEOM-serializable)", geom)
             return None
         pos = np.ascontiguousarray(pos, dtype=np.float32)
         idx = np.ascontiguousarray(idx, dtype=np.uint32)
         nrm = getattr(bm, "normals", None)
         nrm = np.ascontiguousarray(nrm, dtype=np.float32) if nrm is not None and len(nrm) else None
-        mat_id = self.material_store.get(geom.color, None)
+        mat_id = self.material_store.get(color, None)
         if mat_id is None:
             mat_id = len(self.material_store)
-            self.material_store[geom.color] = mat_id
-        return MeshStore(node_ref, None, pos, idx, nrm, mat_id, MeshType.TRIANGLES, node_ref)
+            self.material_store[color] = mat_id
+        # Curve-only bodies (alignment axes, trimmed/segmented curves) tessellate to LINES;
+        # the batch carries the glTF primitive mode so they render as lines, not triangles.
+        try:
+            mtype = MeshType.from_int(getattr(bm, "mesh_type", 4))
+        except ValueError:
+            mtype = MeshType.TRIANGLES
+        return MeshStore(node_ref, None, pos, idx, nrm, mat_id, mtype, node_ref)
 
     def batch_tessellate(
         self,
@@ -766,16 +1011,35 @@ def batch_tessellate(
 
         for obj in objects:
             if isinstance(obj, BackendGeom):
+                from ada.api.shapes import ShapeProxy
+
                 ada_obj = obj
                 geom_repr = render_override.get(obj.guid, GeomRepr.SOLID)
                 # A Shape carrying a bare curve geometry (sectionless SAT wire body, open
-                # wireframe) has no solid/shell — render it as glTF line geometry.
+                # wireframe — incl. one round-tripped through IFC into the lazy store) has
+                # no solid/shell — render it as glTF line geometry. Lazy proxies answer
+                # from their store record instead of hydrating the whole tree.
                 if geom_repr == GeomRepr.SOLID:
-                    _g = getattr(obj, "geom", None)
-                    if _g is not None and isinstance(getattr(_g, "geometry", None), _CURVE_GEOM_TUPLE):
-                        geom_repr = GeomRepr.LINE
+                    if isinstance(obj, ShapeProxy):
+                        if obj.is_bare_curve():
+                            geom_repr = GeomRepr.LINE
+                    else:
+                        _g = getattr(obj, "geom", None)
+                        if _g is not None and isinstance(getattr(_g, "geometry", None), _CURVE_GEOM_TUPLE):
+                            geom_repr = GeomRepr.LINE
                 node_ref = graph_store.hash_map.get(obj.guid) if graph_store is not None else getattr(obj, "guid", None)
 
+                # Lazy-blob fast path: a ShapeProxy backed by an NGEOM buffer tessellates
+                # straight from the stored blob when the stream kernel is selected — no
+                # ada.geom hydration and no re-serialization for the whole model.
+                if geom_repr == GeomRepr.SOLID and isinstance(obj, ShapeProxy):
+                    blob = obj.ngeom_blob()
+                    if blob is not None:
+                        ms_blob = self._tessellate_blob_via_stream(blob, node_ref, obj.color)
+                        if ms_blob is not None:
+                            yield ms_blob
+                            continue
+
                 # PlateCurved: prism-extrude the BSpline face by
                 # thickness so the GLB ships a solid (matching what
                 # a flat Plate produces) rather than a thin shell.
@@ -1090,6 +1354,19 @@ def batch_tessellate(
                 logger.error(e)
             except UnableToCreateCurveOCCGeom as e:
                 logger.error(e)
+            except TessellationFallbackError:
+                raise  # strict mode: a kernel fallback must fail the conversion, not skip a shape
+            except Exception as e:  # noqa: BLE001
+                # A single unbuildable shape (e.g. a B-rep face whose trim wire
+                # won't reconstruct) must not sink the whole export — log loudly
+                # and continue with the rest of the model. tessellate_geom has
+                # already logged the full context at ERROR before re-raising.
+                logger.error(
+                    "skipping %s %r after tessellation failure: %s",
+                    type(ada_obj).__name__ if ada_obj is not None else "geometry",
+                    getattr(ada_obj, "name", None),
+                    e,
+                )
             if ms is not None:
                 # Treat an empty MeshStore the same as a thrown
                 # tessellation error: BRepMesh produced 0 triangles
@@ -1103,7 +1380,7 @@ def batch_tessellate(
                 pos_n = 0 if pos is None else (len(pos) if hasattr(pos, "__len__") else 0)
                 idx_n = 0 if idx is None else (len(idx) if hasattr(idx, "__len__") else 0)
                 if pos_n > 0 and idx_n > 0:
-                    yield ms
+                    yield from _emit_with_geom_transforms(ms, ada_obj)
                     continue
                 logger.error(
                     "PlateCurved %r: tessellation produced empty mesh (pos=%d idx=%d)",
@@ -1204,15 +1481,19 @@ def meshes_to_trimesh(
     ) -> trimesh.Scene:
         import trimesh
 
-        all_shapes = sorted(shapes_tess_iter, key=lambda x: x.material)
+        # Group by (material, mesh type): a merged glTF primitive is a single type, and
+        # concatenate_stores can't mix triangle stores (with normals) and line/point stores
+        # (without) — a scene carrying both solids and line geometry (e.g. an alignment reference
+        # curve alongside a swept solid) would otherwise crash the normal concatenation.
+        all_shapes = sorted(shapes_tess_iter, key=lambda x: (x.material, x.type.value))
 
         # filter out all shapes associated with an animation,
         base_frame = graph.top_level.name if graph is not None else "root"
 
         scene = trimesh.Scene(base_frame=base_frame)
-        for mat_id, meshes in groupby(all_shapes, lambda x: x.material):
+        for (mat_id, _mtype), meshes in groupby(all_shapes, lambda x: (x.material, x.type)):
             if merge_meshes:
-                merged_store = concatenate_stores(meshes)
+                merged_store = concatenate_stores(list(meshes))
                 merged_mesh_to_trimesh_scene(
                     scene, merged_store, self.get_mat_by_id(mat_id), mat_id, graph, apply_transform=apply_transform
                 )
@@ -1247,8 +1528,15 @@ def tessellate_part(
             graph_store=graph,
         )
 
+        # Tally distorted (degenerate/sliver) triangles for the per-cell audit flag as meshes
+        # stream past — raw triangles, before GLB/meshopt encoding. Best-effort, never alters output.
+        def _scanned(it):
+            for ms in it:
+                accumulate_mesh_distortion(getattr(ms, "position", None), getattr(ms, "indices", None))
+                yield ms
+
         scene = self.meshes_to_trimesh(
-            shapes_tess_iter, graph, merge_meshes=params.merge_meshes, apply_transform=params.apply_transform
+            _scanned(shapes_tess_iter), graph, merge_meshes=params.merge_meshes, apply_transform=params.apply_transform
         )
 
         return scene
diff --git a/src/ada/sections/profiles.py b/src/ada/sections/profiles.py
index 49c2b5c64..afc427473 100644
--- a/src/ada/sections/profiles.py
+++ b/src/ada/sections/profiles.py
@@ -143,6 +143,20 @@ def iprofiles(sec: Section, return_solid) -> SectionProfile:
         p8 = (-tw / 2, -h / 2 + tfbtn)
         p9 = (-tw / 2, h / 2 - tftop)
         p10 = (-wtop / 2, h / 2 - tftop)
+        # Round the four web/flange junctions (p4,p5,p8,p9) when the section carries a fillet
+        # radius (IfcIShapeProfileDef.FilletRadius, stored in ``r``). CurvePoly2d reads the 3rd
+        # tuple element as a per-vertex fillet radius and inserts the arc. A radius that won't
+        # fit (>= the flange overhang or half the web depth) is skipped — it would self-
+        # intersect the outline.
+        r = getattr(sec, "r", None)
+        overhang = (wtop - tw) / 2
+        web_half = h / 2 - max(tftop, tfbtn)
+        if r and 0 < r < min(overhang, web_half):
+
+            def _fil(pt):
+                return (pt[0], pt[1], r)
+
+            p4, p5, p8, p9 = _fil(p4), _fil(p5), _fil(p8), _fil(p9)
         input_curve = [c1, c2, p3, p4, p5, p6, c4, c3, p7, p8, p9, p10]
         outer_curve = build_joined(input_curve)
 
diff --git a/src/ada/visit/rendering/resources/index.zip b/src/ada/visit/rendering/resources/index.zip
index 03821ec74..a12629c2e 100644
Binary files a/src/ada/visit/rendering/resources/index.zip and b/src/ada/visit/rendering/resources/index.zip differ
diff --git a/src/ada/visit/scene_handling/scene_from_object.py b/src/ada/visit/scene_handling/scene_from_object.py
index 5417815a5..8bf4ab7a6 100644
--- a/src/ada/visit/scene_handling/scene_from_object.py
+++ b/src/ada/visit/scene_handling/scene_from_object.py
@@ -46,6 +46,13 @@ def scene_from_object(physical_object: BackendGeom, converter: SceneConverter) -
 
     mesh_stores = list(bt.batch_tessellate(physical_objects))
 
+    # Tally distorted (degenerate/sliver) triangles for the per-cell audit flag — raw triangles
+    # here, before any GLB/meshopt encoding. Best-effort; never affects the scene.
+    from ada.occ.tessellating import accumulate_mesh_distortion
+
+    for _ms in mesh_stores:
+        accumulate_mesh_distortion(getattr(_ms, "position", None), getattr(_ms, "indices", None))
+
     mesh_map = []
     for mat_id, meshes in groupby(mesh_stores, lambda x: x.material):
         meshes = list(meshes)
diff --git a/src/ada/visit/scene_handling/scene_from_step_stream.py b/src/ada/visit/scene_handling/scene_from_step_stream.py
index 0f9fc47d9..ab60efb43 100644
--- a/src/ada/visit/scene_handling/scene_from_step_stream.py
+++ b/src/ada/visit/scene_handling/scene_from_step_stream.py
@@ -185,9 +185,17 @@ def _tessellate_geom_worker(geom):
         _pipeline = os.environ.get("ADA_STREAM_TESS_PIPELINE")
         if _pipeline and hasattr(be, "tessellate_stream"):
             defl = float(os.environ.get("ADA_STREAM_TESS_DEFLECTION", "2.0"))
-            ang = float(os.environ.get("ADA_STREAM_TESS_ANGULAR", "20.0"))
+            from ada.cad.registry import DEFAULT_STREAM_TESS_ANGULAR_DEG
+            ang = float(os.environ.get("ADA_STREAM_TESS_ANGULAR", str(DEFAULT_STREAM_TESS_ANGULAR_DEG)))
+            # Adaptive coarsening: relax the angular ceiling on features small vs the whole model, so a
+            # large assembly (e.g. the boiler's asm_22) doesn't over-tessellate every small pipe/torus
+            # into a slivery "crows nest". model_scale (the model bbox diagonal) is estimated once by
+            # the parent and passed via env; 0 => off (fixed angular), matching native_step_to_glb.
+            mscale = float(os.environ.get("ADA_STREAM_TESS_MODEL_SCALE", "0") or "0")
             gi = geom.geometry.geometry if hasattr(geom.geometry, "geometry") else geom.geometry
-            bm = be.tessellate_stream([(gid or "0", gi)], pipeline=_pipeline, deflection=defl, angular_deg=ang)
+            bm = be.tessellate_stream(
+                [(gid or "0", gi)], pipeline=_pipeline, deflection=defl, angular_deg=ang, model_scale=mscale
+            )
             _pos = getattr(bm, "positions", None)
             _idx = getattr(bm, "indices", None)
             if _pos is None or _idx is None or len(_idx) == 0:
@@ -488,6 +496,26 @@ def _tessellate_stream(source: StepStreamSource, graph, bt, sink) -> dict:
     if unit_scale != 1.0:
         logger.info("scene_from_step_stream: scaling length unit to metres (factor %g)", unit_scale)
 
+    # Adaptive tessellation coarsening (matches native_step_to_glb): estimate the model bbox diagonal
+    # once and expose it to the pool workers via env (they inherit it), so the libtess2 path relaxes
+    # density on features small vs the whole model instead of over-tessellating every small pipe/torus
+    # into a slivery crows-nest. Only when the libtess2 stream path is active and not already set;
+    # gated by ADA_STREAM_TESS_ADAPTIVE (default on, "0/false/off" disables). unit_scale-corrected.
+    import os
+
+    if os.environ.get("ADA_STREAM_TESS_PIPELINE") and "ADA_STREAM_TESS_MODEL_SCALE" not in os.environ:
+        _adaptive = (os.environ.get("ADA_STREAM_TESS_ADAPTIVE") or "").strip().lower() not in {"0", "false", "no", "off"}
+        if _adaptive:
+            try:
+                from ada.cadit.step.model_scale import estimate_step_model_scale
+
+                _ms = estimate_step_model_scale(source.path) * unit_scale
+                if _ms > 0.0:
+                    os.environ["ADA_STREAM_TESS_MODEL_SCALE"] = repr(_ms)
+                    logger.info("scene_from_step_stream: adaptive tessellation model_scale=%.1f", _ms)
+            except Exception as exc:  # noqa: BLE001 - estimation is best-effort; fall back to fixed angular
+                logger.debug("model_scale estimate failed (%s); fixed-angular tessellation", exc)
+
     root = graph.top_level
     on_progress = source.on_progress
 
diff --git a/src/frontend/src/components/admin/AuditLogTab.tsx b/src/frontend/src/components/admin/AuditLogTab.tsx
index 0ab28a582..99566c773 100644
--- a/src/frontend/src/components/admin/AuditLogTab.tsx
+++ b/src/frontend/src/components/admin/AuditLogTab.tsx
@@ -20,6 +20,8 @@ import {
 const ACTIONS = ["", "upload", "download", "convert", "view", "render"];
 const KINDS = ["", "shared", "project", "user"];
 const TARGETS = ["", "glb", "ifc", "xml", "step", "stl", "obj", "sat"];
+// Job states the queue writes (queue.py JOB_STATUS_*) — server-side filter.
+const STATUSES = ["", "queued", "running", "done", "error"];
 
 const PROFILE_SETTING_KEY = "profile_conversions";
 
@@ -205,6 +207,12 @@ const AuditLogTab: React.FC = () => {
                         onChange={(v) => onFilter({target: v || undefined})}
                         placeholder="any target"
                     />
+                    <FilterSelect
+                        options={STATUSES}
+                        value={filters.status || ""}
+                        onChange={(v) => onFilter({status: v || undefined})}
+                        placeholder="any state"
+                    />
                     <FilterInput
                         placeholder="filename / path…"
                         value={filters.key || ""}
@@ -783,6 +791,88 @@ const WorkerPackages: React.FC<{imageTag: string}> = ({imageTag}) => {
     );
 };
 
+// adacpp [STEPPROF-JSON] pipeline summaries (captured when "Profile conversions"
+// is on): per-pipeline phase wall/RSS breakdown, kernel-exact peak (VmHWM),
+// per-solid stats, achieved parallelism / IO pressure and per-thread utilisation
+// — the C++ sibling of the Python profile below.
+const CppProfilePanel: React.FC<{profiles: import("@/services/viewerApi").CppProfile[]}> = ({profiles}) => (
+    <div className="pt-2 border-t border-gray-800 space-y-3">
+        <div className="text-[11px] uppercase tracking-wide text-gray-400">C++ pipeline profile</div>
+        {profiles.map((p, i) => {
+            const wall = p.wall_ms > 0 ? p.wall_ms : 1;
+            return (
+                <div key={`${p.label}-${i}`} className="space-y-1">
+                    <dl className="grid grid-cols-[max-content_1fr] gap-x-4 gap-y-0.5 font-mono text-[11px]">
+                        <dt className="text-gray-400">Pipeline</dt>
+                        <dd className="text-emerald-300">{p.label}</dd>
+                        <dt className="text-gray-400">Wall</dt>
+                        <dd>{formatDuration(p.wall_ms)}</dd>
+                        <dt className="text-gray-400">Peak RSS</dt>
+                        <dd>{formatBytes(p.peak_rss_mb * 1024 * 1024)} <span className="text-gray-500">(VmHWM)</span></dd>
+                        {p.cpu_s != null && (
+                            <><dt className="text-gray-400">CPU</dt>
+                            <dd>{p.cpu_s.toFixed(1)} s{p.parallelism != null ? ` — ${p.parallelism.toFixed(2)}x cores busy` : ""}</dd></>
+                        )}
+                        {(p.solids ?? 0) > 0 && (
+                            <><dt className="text-gray-400">Solids</dt>
+                            <dd>{p.solids}{(p.tris ?? 0) > 0 ? ` (${p.tris} tris, max ${p.max_tris_solid}/solid)` : ""}</dd></>
+                        )}
+                        {p.disk_read_mb != null && p.disk_read_mb > 0 && (
+                            <><dt className="text-gray-400">Disk read</dt>
+                            <dd>{p.disk_read_mb.toFixed(0)} MB physical{p.majflt != null ? `, ${p.majflt} major faults` : ""}</dd></>
+                        )}
+                    </dl>
+                    {p.phases.length > 0 && (
+                        <table className="w-full text-[11px] font-mono">
+                            <thead>
+                                <tr className="text-gray-500 text-left">
+                                    <th className="font-normal pr-2">phase</th>
+                                    <th className="font-normal pr-2 text-right">ms</th>
+                                    <th className="font-normal pr-2 text-right">RSS</th>
+                                    <th className="font-normal w-1/3">share</th>
+                                </tr>
+                            </thead>
+                            <tbody>
+                                {p.phases.map((ph) => (
+                                    <tr key={ph.name} className="text-gray-300">
+                                        <td className="pr-2 break-all">{ph.name}</td>
+                                        <td className="pr-2 text-right">{Math.round(ph.ms)}</td>
+                                        <td className="pr-2 text-right">{Math.round(ph.rss_mb)} MB</td>
+                                        <td>
+                                            <div className="bg-gray-800 rounded-sm h-2 w-full">
+                                                <div
+                                                    className="bg-sky-600 rounded-sm h-2"
+                                                    style={{width: `${Math.min(100, (ph.ms / wall) * 100).toFixed(1)}%`}}
+                                                />
+                                            </div>
+                                        </td>
+                                    </tr>
+                                ))}
+                            </tbody>
+                        </table>
+                    )}
+                    {p.notes && Object.keys(p.notes).length > 0 && (
+                        <dl className="grid grid-cols-[max-content_1fr] gap-x-4 gap-y-0.5 font-mono text-[11px]">
+                            {Object.entries(p.notes).map(([k, v]) => (
+                                <React.Fragment key={k}>
+                                    <dt className="text-gray-500 break-all">{k}</dt>
+                                    <dd className="text-gray-300">{v}</dd>
+                                </React.Fragment>
+                            ))}
+                        </dl>
+                    )}
+                    {(p.threads?.length ?? 0) > 0 && (
+                        <div className="text-[11px] font-mono text-gray-400">
+                            threads:{" "}
+                            {p.threads!.map((t) => `t${t.tid}=${Math.round(t.busy_ms)}ms/${t.solids}s`).join("  ")}
+                        </div>
+                    )}
+                </div>
+            );
+        })}
+    </div>
+);
+
 const MetricsTab: React.FC<{
     entry: AuditEntry;
     onDownloadProfile: () => void;
@@ -812,6 +902,9 @@ const MetricsTab: React.FC<{
                 <MetricRow label="Write"    value={formatBytes(entry.write_bytes)}/>
             </dl>
             {entry.convert_meta && <ConvertEngine meta={entry.convert_meta}/>}
+            {(entry.convert_meta?.cpp_profile?.length ?? 0) > 0 && (
+                <CppProfilePanel profiles={entry.convert_meta!.cpp_profile!}/>
+            )}
             {entry.worker_image_tag && <WorkerPackages imageTag={entry.worker_image_tag}/>}
             <MetricsHistoryChart
                 auditId={entry.id}
diff --git a/src/frontend/src/components/admin/AuditRunsTab.tsx b/src/frontend/src/components/admin/AuditRunsTab.tsx
index 80632bc45..8d9c41a49 100644
--- a/src/frontend/src/components/admin/AuditRunsTab.tsx
+++ b/src/frontend/src/components/admin/AuditRunsTab.tsx
@@ -1,6 +1,9 @@
 import React, {useCallback, useEffect, useMemo, useRef, useState} from "react";
 import {viewerApi, AuditRun, AuditRunJob, AuditCellHistoryRow, Corpus} from "@/services/viewerApi";
 import {runWasmAuditSweep, WasmSweepProgress} from "@/services/audit/wasmSweep";
+import {runtime} from "@/runtime/config";
+import {useAuditToastStore} from "@/state/auditToastStore";
+import {view_in_3d} from "@/utils/scene/handlers/view_in_3d";
 
 // Synthetic worker-pool value routing a run to the in-browser WASM engine.
 const WASM_POOL = "wasm";
@@ -56,13 +59,27 @@ function fmtMs(n: number | null | undefined): string {
     return `${(n / 1000).toFixed(1)} s`;
 }
 
-function fmtRunDuration(run: AuditRun): string {
-    if (!run.started_at) return "—";
-    const start = new Date(run.started_at).getTime();
-    const end = run.finished_at ? new Date(run.finished_at).getTime() : Date.now();
-    // Subtract idle time (the gap before a validation pass appended hours
-    // later) so the duration is active-block time, not wall clock.
-    const ms = Math.max(0, end - start - (run.idle_ms ?? 0));
+type RuntimeMode = "cells" | "wall";
+
+// Two equally-relevant views of a run's runtime, switched by the overview toggle:
+//   "cells" — SUM of every cell's own duration_ms: the real compute cost. Immune
+//             to worker parallelism and to a single-cell re-run reopening the run
+//             (which would inflate wall clock with the idle gap since the first
+//             run). Recomputes server-side whenever a cell's row changes.
+//   "wall"  — active wall clock (finished−started−idle): how long the operator
+//             actually waited, which parallelism compresses below the cell sum.
+// "cells" falls back to wall clock for older runs / in-flight rows with no sum yet.
+function fmtRunDuration(run: AuditRun, mode: RuntimeMode): string {
+    const sum = run.cells_duration_ms;
+    let ms: number;
+    if (mode === "cells" && sum != null && sum > 0) {
+        ms = sum;
+    } else {
+        if (!run.started_at) return "—";
+        const start = new Date(run.started_at).getTime();
+        const end = run.finished_at ? new Date(run.finished_at).getTime() : Date.now();
+        ms = Math.max(0, end - start - (run.idle_ms ?? 0));
+    }
     if (ms < 60_000) return `${(ms / 1000).toFixed(0)}s`;
     if (ms < 3600_000) return `${(ms / 60_000).toFixed(0)}m`;
     return `${(ms / 3600_000).toFixed(1)}h`;
@@ -152,12 +169,77 @@ const METRIC_COLOR_BUCKETS: {cls: string}[] = [
     {cls: "bg-red-900/60 border-red-600 text-red-100"},              // outlier
 ];
 
+// The derived-blob key a cell produced. Mirrors the server's
+// derived_key_for convention: _derived/<source>.<target>, except a glb
+// target of a source that is already a .glb has no derivation.
+function cellDerivedKey(file: string, target: string): string {
+    if (target === "glb" && file.toLowerCase().endsWith(".glb")) return file;
+    return `_derived/${file}.${target}`;
+}
+
+// Whether a cell's product can be opened in the 3D viewer. The viewer mounts
+// GLB directly and converts any target the converter can turn into GLB
+// (ifc/step/xml/...); parity has no artifact, and a non-done cell has nothing
+// cached to open. Mirrors ConversionRow's canPreview gate.
+function cellViewable(job: AuditRunJob | undefined): boolean {
+    if (!job || !job.key || !job.target_format) return false;
+    if (!(job.status === "done" || job.status === "ok")) return false;
+    const t = job.target_format;
+    if (t === "glb") return true;
+    if (t === "parity") return false;
+    return runtime.conversionTargetsFor(t).includes("glb");
+}
+
+type CellFlag = {key: string; label: string; title: string; cls: string};
+
+// Per-source quality flags, aggregated across the row's cells' convert_meta. Mirrors the
+// PerformanceTab "streaming" pill idea: a compact badge per detected issue.
+//   occ_fallback — the NGEOM/libtess2 (OCC-free) tessellation silently fell back to OCC.
+//   distorted    — a converted mesh has heavily distorted (degenerate/sliver) triangles.
+function sourceFlags(cells: Map<string, AuditRunJob>, targets: string[], file: string): CellFlag[] {
+    let occ = 0;
+    let distorted = 0;
+    let dropped = 0;
+    for (const t of targets) {
+        const cm = cells.get(`${file}::${t}`)?.convert_meta;
+        if (!cm) continue;
+        occ += cm.occ_fallback?.count ?? 0;
+        distorted += cm.mesh_flags?.distorted_tris ?? 0;
+        dropped = Math.max(dropped, cm.geom_health?.dropped_faces ?? 0);
+    }
+    const flags: CellFlag[] = [];
+    if (dropped > 0)
+        flags.push({
+            key: "dropped",
+            label: "dropped faces",
+            title: `${dropped} face(s) with a trim boundary tessellated to zero triangles — silently dropped geometry (e.g. a swept/extruded surface the kernel couldn't mesh)`,
+            cls: "bg-red-900/50 border-red-700 text-red-200",
+        });
+    if (occ > 0)
+        flags.push({
+            key: "occ",
+            label: "occ fallback",
+            title: `${occ} object(s) fell back from the libtess2 stream kernel to OCC`,
+            cls: "bg-amber-900/50 border-amber-700 text-amber-200",
+        });
+    if (distorted > 0)
+        flags.push({
+            key: "distorted",
+            label: "distorted tris",
+            title: `${distorted} heavily distorted (degenerate/sliver) triangle(s) in a converted mesh`,
+            cls: "bg-red-900/50 border-red-700 text-red-200",
+        });
+    return flags;
+}
+
 const RunGrid: React.FC<{
     jobs: AuditRunJob[];
     metric: MetricKey;
     onCellHistory: (file: string, target: string) => void;
     onCellDetails: (file: string, target: string) => void;
-}> = ({jobs, metric, onCellHistory, onCellDetails}) => {
+    onCellOpen: (file: string, target: string) => void;
+    onCellRerun: (file: string, target: string) => void;
+}> = ({jobs, metric, onCellHistory, onCellDetails, onCellOpen, onCellRerun}) => {
     const grid = useMemo(() => buildGrid(jobs), [jobs]);
 
     // Right-click (desktop) / long-press (touch) context menu for a cell.
@@ -301,6 +383,9 @@ const RunGrid: React.FC<{
                                 .{t}
                             </th>
                         ))}
+                        <th className="px-2 py-1 border-b border-gray-700 font-medium text-gray-300 text-left" title="Per-source quality flags (OCC fallback, distorted triangles)">
+                            flags
+                        </th>
                     </tr>
                 </thead>
                 <tbody>
@@ -331,6 +416,17 @@ const RunGrid: React.FC<{
                                     </td>
                                 );
                             })}
+                            <td className="px-2 py-1 border-b border-gray-800 whitespace-nowrap">
+                                {sourceFlags(grid.cells, grid.targets, file).map((f) => (
+                                    <span
+                                        key={f.key}
+                                        className={`inline-block mr-1 px-1.5 py-0.5 rounded-sm border text-[10px] ${f.cls}`}
+                                        title={f.title}
+                                    >
+                                        {f.label}
+                                    </span>
+                                ))}
+                            </td>
                         </tr>
                     ))}
                 </tbody>
@@ -346,6 +442,18 @@ const RunGrid: React.FC<{
                     <div className="px-3 py-1 text-[10px] text-gray-500 font-mono truncate max-w-[240px]">
                         {menu.file} · .{menu.target}
                     </div>
+                    {cellViewable(grid.cells.get(`${menu.file}::${menu.target}`)) && (
+                        <button
+                            type="button"
+                            className="w-full text-left px-3 py-1 text-emerald-300 hover:bg-gray-700"
+                            onClick={() => {
+                                onCellOpen(menu.file, menu.target);
+                                setMenu(null);
+                            }}
+                        >
+                            Open in viewer ↗
+                        </button>
+                    )}
                     <button
                         type="button"
                         className="w-full text-left px-3 py-1 text-gray-200 hover:bg-gray-700"
@@ -366,6 +474,18 @@ const RunGrid: React.FC<{
                     >
                         Show history
                     </button>
+                    {menu.target !== "parity" && (
+                        <button
+                            type="button"
+                            className="w-full text-left px-3 py-1 text-sky-300 hover:bg-gray-700"
+                            onClick={() => {
+                                onCellRerun(menu.file, menu.target);
+                                setMenu(null);
+                            }}
+                        >
+                            Rerun cell ↻
+                        </button>
+                    )}
                 </div>
             )}
         </div>
@@ -1004,6 +1124,18 @@ const AuditRunsTab: React.FC = () => {
     const [selectedRun, setSelectedRun] = useState<AuditRun | null>(null);
     const [selectedJobs, setSelectedJobs] = useState<AuditRunJob[]>([]);
     const [metric, setMetric] = useState<MetricKey>("status");
+    // Runtime shown in the overview: sum-of-cell-times vs active wall clock.
+    // Persisted so the operator's choice sticks across visits.
+    const [runtimeMode, setRuntimeMode] = useState<RuntimeMode>(
+        () => (localStorage.getItem("auditRuntimeMode") === "wall" ? "wall" : "cells"),
+    );
+    useEffect(() => { localStorage.setItem("auditRuntimeMode", runtimeMode); }, [runtimeMode]);
+    // Ambient "audit sweep in progress" toast (shown over the viewer) — operators can hide it here.
+    const toastHidden = useAuditToastStore((s) => s.hidden);
+    const toggleToast = useAuditToastStore((s) => s.toggle);
+    // New-run form: collapsible on mobile (always visible on md+). Auto-collapses
+    // when a run is opened so the run detail owns the small screen.
+    const [formOpen, setFormOpen] = useState(true);
     const [listError, setListError] = useState<string | null>(null);
     const [detailError, setDetailError] = useState<string | null>(null);
     // Cell whose cross-run history modal is open (from the grid context menu).
@@ -1050,6 +1182,9 @@ const AuditRunsTab: React.FC = () => {
 
     const onSelectRun = useCallback((runId: string) => {
         setSelectedId(runId);
+        // Collapse the new-run form on mobile so the selected run's grid gets
+        // the viewport (no-op visually on md+, where the form is always shown).
+        setFormOpen(false);
         void loadDetail(runId);
     }, [loadDetail]);
 
@@ -1062,7 +1197,21 @@ const AuditRunsTab: React.FC = () => {
 
     return (
         <div className="flex flex-col h-full">
-            <TriggerForm onCreated={loadRuns}/>
+            {/* Mobile-only collapse header for the new-run form. On md+ the form
+                is always shown (this button is hidden), matching desktop where
+                screen space isn't scarce. */}
+            <button
+                type="button"
+                onClick={() => setFormOpen((o) => !o)}
+                className="md:hidden flex items-center justify-between w-full px-3 py-2 border-b border-gray-800 bg-gray-900/40 text-xs text-gray-200"
+                aria-expanded={formOpen}
+            >
+                <span>New audit run</span>
+                <span className="text-gray-400">{formOpen ? "▾ hide" : "▸ show"}</span>
+            </button>
+            <div className={(formOpen ? "block" : "hidden") + " md:block"}>
+                <TriggerForm onCreated={loadRuns}/>
+            </div>
 
             <div className="flex-1 min-h-0 flex flex-col md:flex-row overflow-hidden">
                 {/* History list. Side-by-side w-80 on md+; full-width
@@ -1083,6 +1232,45 @@ const AuditRunsTab: React.FC = () => {
                     "flex-1 min-h-0 border-b border-gray-800 overflow-auto " +
                     (showHistory ? "block" : "hidden md:block")
                 }>
+                    {/* Overview toggle: show each run's runtime as the sum of its
+                        cell times or as active wall clock. Both are relevant —
+                        cells = compute cost, wall = time waited. Sticky so it
+                        stays put while the list scrolls. */}
+                    <div className="sticky top-0 z-10 flex items-center justify-between gap-2 px-3 py-1.5 border-b border-gray-800 bg-gray-900/80 backdrop-blur text-[11px] text-gray-400">
+                        <div className="flex items-center gap-1.5">
+                            <span>Runtime</span>
+                            <div className="inline-flex rounded-sm border border-gray-700 overflow-hidden">
+                                <button
+                                    type="button"
+                                    onClick={() => setRuntimeMode("cells")}
+                                    className={"px-2 py-0.5 " + (runtimeMode === "cells"
+                                        ? "bg-blue-700 text-white" : "text-gray-300 hover:bg-gray-800")}
+                                    title="Sum of every cell's own runtime — the real compute cost, immune to worker parallelism and single-cell re-runs."
+                                >
+                                    Σ cells
+                                </button>
+                                <button
+                                    type="button"
+                                    onClick={() => setRuntimeMode("wall")}
+                                    className={"px-2 py-0.5 border-l border-gray-700 " + (runtimeMode === "wall"
+                                        ? "bg-blue-700 text-white" : "text-gray-300 hover:bg-gray-800")}
+                                    title="Active wall-clock time (finished − started − idle) — how long the run actually took to watch."
+                                >
+                                    wall
+                                </button>
+                            </div>
+                        </div>
+                        <button
+                            type="button"
+                            onClick={toggleToast}
+                            className={"px-2 py-0.5 rounded-sm border " + (toastHidden
+                                ? "border-gray-700 text-gray-400 hover:bg-gray-800"
+                                : "border-blue-700 bg-blue-900/40 text-blue-200 hover:bg-blue-900/60")}
+                            title="Show/hide the ambient 'audit sweep in progress' toast over the viewer."
+                        >
+                            {toastHidden ? "◌ toast off" : "● toast on"}
+                        </button>
+                    </div>
                     {listError && (
                         <div className="text-xs text-red-400 px-3 py-2">{listError}</div>
                     )}
@@ -1127,7 +1315,9 @@ const AuditRunsTab: React.FC = () => {
                                     </div>
                                     <div className="text-gray-400 mt-0.5 flex justify-between">
                                         <span>{run.ok + run.failed + run.skipped} / {run.total}</span>
-                                        <span>{fmtRunDuration(run)}</span>
+                                        <span title={runtimeMode === "cells" ? "sum of cell runtimes" : "active wall clock"}>
+                                            {fmtRunDuration(run, runtimeMode)}
+                                        </span>
                                     </div>
                                     {run.total > 0 && (
                                         <div className="h-1 bg-gray-700 rounded-sm overflow-hidden mt-1">
@@ -1253,6 +1443,24 @@ const AuditRunsTab: React.FC = () => {
                                     metric={metric}
                                     onCellHistory={(file, target) => setHistoryCell({key: file, target})}
                                     onCellDetails={(file, target) => setDetailsCell({file, target})}
+                                    onCellOpen={(file, target) => {
+                                        // Load the cell's cached product into the
+                                        // underlying scene, from the RUN's scope
+                                        // (may differ from the browsed one).
+                                        void view_in_3d(file, cellDerivedKey(file, target), selectedRun.scope);
+                                    }}
+                                    onCellRerun={(file, target) => {
+                                        // Re-run just this cell in place (force rebuild). Reopens
+                                        // the run; the poller then streams the fresh result in.
+                                        void (async () => {
+                                            try {
+                                                await viewerApi.adminAuditRunRerunCell(selectedRun.id, file, target);
+                                                await loadDetail(selectedRun.id);
+                                            } catch (e) {
+                                                window.alert(`Rerun failed: ${(e as Error).message}`);
+                                            }
+                                        })();
+                                    }}
                                 />
                             </div>
                         </>
diff --git a/src/frontend/src/components/admin/CorpusTab.tsx b/src/frontend/src/components/admin/CorpusTab.tsx
index b114d6020..08c8fb6e5 100644
--- a/src/frontend/src/components/admin/CorpusTab.tsx
+++ b/src/frontend/src/components/admin/CorpusTab.tsx
@@ -1,7 +1,15 @@
 import React, {useCallback, useEffect, useMemo, useRef, useState} from "react";
 import {Corpus, FileEntry, viewerApi} from "@/services/viewerApi";
-import {buildFileTree} from "@/utils/storage/fileTree";
-import FileTreeView from "./FileTreeView";
+import {
+    buildFileTree,
+    collectFolderPaths,
+    loadPendingFolders,
+    previewKeyList,
+    savePendingFolders,
+} from "@/utils/storage/fileTree";
+import FileTreeView, {FileTreeMutations} from "./FileTreeView";
+import FolderPickerModal from "@/components/common/FolderPickerModal";
+import {scopeUrlPart} from "@/state/scopeStore";
 
 // Admin tab — manage proprietary regression corpora (M3 of the audit
 // panel design in plan/v2/notes_admin_audit_panel.md).
@@ -14,6 +22,13 @@ import FileTreeView from "./FileTreeView";
 //
 // The trigger form on the Audit Runs tab picks a corpus by slug from
 // the same /admin/corpora list this tab maintains.
+//
+// Tree mode carries the storage panel's organize affordances (via the
+// shared FileTreeView mutations): rename / move / delete files and
+// folders, drag-and-drop moves, client-side pending folders, and a
+// checkbox / shift+arrow multi-select feeding a bulk Move/Delete
+// toolbar. Server ops go through the admin endpoints (corpus scopes
+// are admin-only on every axis).
 
 const SLUG_RE = /^[a-z0-9]+(?:-[a-z0-9]+)*$/;
 
@@ -24,6 +39,24 @@ function fmtBytes(n: number): string {
     return `${(n / 1024 / 1024 / 1024).toFixed(2)} GB`;
 }
 
+function dirnameOf(key: string): string {
+    const i = key.lastIndexOf("/");
+    return i >= 0 ? key.slice(0, i) : "";
+}
+
+function basenameOf(key: string): string {
+    return key.split("/").pop() ?? key;
+}
+
+function normKey(key: string): string {
+    return key.replace(/^\/+/, "");
+}
+
+// Batch size for chunked server-side moves/copies. Every chunk is still
+// a Garage-side CopyObject (no file bytes through the browser) — the
+// chunking only exists so the progress counter ticks between requests.
+const OP_CHUNK = 8;
+
 // Flat-list ⇄ folder-tree representation switch. Storage is flat on the
 // server; tree mode just groups the keys' "/" segments. Shared by the
 // corpus file overview and the copy-from-scope modal.
@@ -173,10 +206,7 @@ const CopyFromScopeModal: React.FC<{
                 const me = await viewerApi.me();
                 setScopes(
                     me.scopes
-                        .map((s) => ({
-                            name: s.name,
-                            url: s.kind === "user" ? "user:me" : s.kind === "shared" ? "shared" : `project:${s.id}`,
-                        }))
+                        .map((s) => ({name: s.name, url: scopeUrlPart(s)}))
                         .filter((s) => s.url !== dstScope),
                 );
             } catch (e) {
@@ -384,10 +414,35 @@ const CopyFromScopeModal: React.FC<{
     );
 };
 
-const CorpusFiles: React.FC<{corpus: Corpus}> = ({corpus}) => {
+const CorpusFiles: React.FC<{
+    corpus: Corpus;
+    /** Name/description saved — the parent re-fetches the corpora list
+     * so the sidebar and this header pick up the new values. */
+    onMetaUpdated: () => void;
+}> = ({corpus, onMetaUpdated}) => {
     const scope = `corpus:${corpus.slug}`;
     const [files, setFiles] = useState<FileEntry[]>([]);
     const [err, setErr] = useState<string | null>(null);
+    // Transient success line (e.g. copy-to-personal outcome).
+    const [note, setNote] = useState<string | null>(null);
+    // In-flight batch operation (move / delete / copy) — rendered as a
+    // spinner status bar under the button row so a drag-drop move of
+    // many files visibly runs until the listing refreshes. The ref
+    // mirrors it so callbacks can reject overlapping batches without
+    // stale-closure issues (concurrent moves would race server-side).
+    const [busy, setBusy] = useState<string | null>(null);
+    const busyRef = useRef(false);
+    const beginOp = (msg: string): boolean => {
+        if (busyRef.current) return false;
+        busyRef.current = true;
+        setBusy(msg);
+        return true;
+    };
+    const updateOp = (msg: string) => setBusy(msg);
+    const endOp = () => {
+        busyRef.current = false;
+        setBusy(null);
+    };
     const [uploading, setUploading] = useState<string | null>(null);
     const [progress, setProgress] = useState(0);
     const [copyOpen, setCopyOpen] = useState(false);
@@ -421,36 +476,184 @@ const CorpusFiles: React.FC<{corpus: Corpus}> = ({corpus}) => {
 
     useEffect(() => { void reload(); }, [reload]);
 
-    const onPick = useCallback(async (e: React.ChangeEvent<HTMLInputElement>) => {
-        const files = Array.from(e.target.files ?? []);
-        if (files.length === 0) return;
+    // Client-side "pending" empty folders — storage is prefix-based so
+    // they have no server representation until a file lands in them.
+    // Persisted per corpus scope; pruned once a real key appears
+    // underneath (same mechanics as StorageBrowser).
+    const [pendingFolders, setPendingFolders] = useState<string[]>(
+        () => loadPendingFolders("corpus", scope),
+    );
+    useEffect(() => {
+        savePendingFolders("corpus", scope, pendingFolders);
+    }, [scope, pendingFolders]);
+    useEffect(() => {
+        setPendingFolders((prev) => {
+            const next = prev.filter(
+                (p) => !files.some((f) => normKey(f.key).startsWith(p + "/")),
+            );
+            return next.length === prev.length ? prev : next;
+        });
+    }, [files]);
+    const removePendingFoldersUnder = (path: string) => {
+        setPendingFolders((prev) =>
+            prev.filter((p) => p !== path && !p.startsWith(path + "/")),
+        );
+    };
+    // Rename/move of a pending (empty) folder is pure client state.
+    const rekeyPendingFolders = (oldPath: string, newPath: string) => {
+        setPendingFolders((prev) => prev.map((p) => (
+            p === oldPath
+                ? newPath
+                : p.startsWith(oldPath + "/")
+                    ? newPath + p.slice(oldPath.length)
+                    : p
+        )));
+    };
+    const folderHasKeys = useCallback(
+        (path: string) => files.some((f) => normKey(f.key).startsWith(path + "/")),
+        [files],
+    );
+
+    // Inline name/description editor in the header. The slug is
+    // immutable (storage prefix + scope URLs hang off it), so only the
+    // display fields are editable. Seeded from the current corpus row
+    // each time the editor opens.
+    const [editingMeta, setEditingMeta] = useState(false);
+    const [metaName, setMetaName] = useState("");
+    const [metaDesc, setMetaDesc] = useState("");
+    const [metaBusy, setMetaBusy] = useState(false);
+    const openMetaEdit = () => {
+        setMetaName(corpus.name);
+        setMetaDesc(corpus.description ?? "");
+        setEditingMeta(true);
+    };
+    const saveMeta = async () => {
+        const name = metaName.trim();
+        if (!name) {
+            setErr("name required");
+            return;
+        }
+        setMetaBusy(true);
+        try {
+            await viewerApi.adminCorpusUpdate(corpus.slug, {
+                name,
+                description: metaDesc.trim() || null,
+            });
+            setEditingMeta(false);
+            setErr(null);
+            onMetaUpdated();
+        } catch (e) {
+            setErr((e as Error).message || "corpus update failed");
+        } finally {
+            setMetaBusy(false);
+        }
+    };
+
+    // Where the tree's "new folder" inline input shows ("" = top level).
+    const [newFolderAt, setNewFolderAt] = useState<string | null>(null);
+    // Destination-folder modal shared by the upload and move flows.
+    const [picker, setPicker] = useState<{
+        title: string;
+        allowRoot?: boolean;
+        submitLabel?: string;
+        onPick: (folder: string) => Promise<void> | void;
+    } | null>(null);
+
+    // Multi-select (tree mode): checkbox / shift+arrow selection set
+    // feeding the bulk Move/Delete toolbar. Dragging a selected row
+    // drags the whole set (FileTreeView handles that).
+    const [selected, setSelected] = useState<Set<string>>(() => new Set());
+    const setSelection = useCallback((keys: string[], select: boolean) => {
+        setSelected((prev) => {
+            const next = new Set(prev);
+            if (select) keys.forEach((k) => next.add(k));
+            else keys.forEach((k) => next.delete(k));
+            return next;
+        });
+    }, []);
+    const clearSelection = () => setSelected(new Set());
+    // Drop selection entries whose keys vanished (moved/renamed/deleted).
+    useEffect(() => {
+        setSelected((prev) => {
+            const live = new Set(files.map((f) => f.key));
+            const next = new Set(Array.from(prev).filter((k) => live.has(k)));
+            return next.size === prev.size ? prev : next;
+        });
+    }, [files]);
+
+    const existingFolderPaths = useMemo(
+        () => Array.from(new Set([
+            ...collectFolderPaths(files, (f) => f.key),
+            ...pendingFolders,
+        ])).sort((a, b) => a.localeCompare(b)),
+        [files, pendingFolders],
+    );
+
+    // Failed uploads from the last batch — drives the retry dialog.
+    // Holds the actual File objects so Retry can re-attempt without
+    // re-picking them from disk.
+    const [uploadFailures, setUploadFailures] = useState<{
+        folder?: string;
+        failed: Array<{file: File; reason: string}>;
+    } | null>(null);
+
+    // Upload a batch sequentially into an optional folder prefix. Pin
+    // autoConvert:false so we don't auto-generate derived blobs for
+    // corpus uploads — the audit dispatcher does that on demand when
+    // the sweep fires. Files whose destination key already exists in
+    // the corpus are skipped, never overwritten (same semantics as the
+    // copy flows). A failed file doesn't abort the batch — failures
+    // land in the retry dialog.
+    const uploadFilesTo = useCallback(async (list: File[], folder?: string) => {
+        if (list.length === 0) return;
         setErr(null);
-        // Reuse the existing per-scope upload path. Pin autoConvert:false so we
-        // don't auto-generate derived blobs for corpus uploads — the audit
-        // dispatcher does that on demand when the sweep fires. Sequential; a
-        // failed file is reported without aborting the batch.
+        setNote(null);
+        const existing = new Set(files.map((f) => normKey(f.key)));
+        const targetKey = (file: File) => (folder ? `${folder}/${file.name}` : file.name);
+        const skipped = list.filter((f) => existing.has(targetKey(f)));
+        const toUpload = list.filter((f) => !existing.has(targetKey(f)));
         const {uploadFile} = await import("@/utils/scene/handlers/upload_source_file");
-        const failures: string[] = [];
-        for (let i = 0; i < files.length; i++) {
-            const file = files[i];
-            setUploading(files.length > 1 ? `${file.name} (${i + 1}/${files.length})` : file.name);
+        const failed: Array<{file: File; reason: string}> = [];
+        for (let i = 0; i < toUpload.length; i++) {
+            const file = toUpload[i];
+            setUploading(toUpload.length > 1 ? `${file.name} (${i + 1}/${toUpload.length})` : file.name);
             setProgress(0);
             try {
                 await uploadFile(file, {
                     autoConvert: false,
                     scope,
+                    folder,
                     onProgress: (loaded, total) => setProgress(total > 0 ? loaded / total : 0),
                 });
             } catch (e) {
-                failures.push(`${file.name}: ${(e as Error).message || "upload failed"}`);
+                failed.push({file, reason: (e as Error).message || "upload failed"});
             }
         }
         setUploading(null);
         setProgress(0);
-        if (inputRef.current) inputRef.current.value = "";
-        if (failures.length) setErr(failures.join("; "));
         await reload();
-    }, [scope, reload]);
+        const bits: string[] = [];
+        const uploaded = toUpload.length - failed.length;
+        if (uploaded > 0) bits.push(`uploaded ${uploaded}`);
+        if (skipped.length > 0) bits.push(`skipped ${skipped.length} (already in corpus)`);
+        if (bits.length > 0) setNote(bits.join(" · "));
+        if (failed.length > 0) setUploadFailures({folder, failed});
+    }, [files, scope, reload]);
+
+    // Upload button flow: pick the files first, then prompt for the
+    // destination folder — an existing folder, a new path, or the top
+    // level (the default).
+    const onPickUpload = useCallback((e: React.ChangeEvent<HTMLInputElement>) => {
+        const picked = Array.from(e.target.files ?? []);
+        if (inputRef.current) inputRef.current.value = "";
+        if (picked.length === 0) return;
+        setPicker({
+            title: `Upload ${picked.length} file${picked.length === 1 ? "" : "s"} to`,
+            allowRoot: true,
+            submitLabel: "Upload",
+            onPick: (folder) => void uploadFilesTo(picked, folder || undefined),
+        });
+    }, [uploadFilesTo]);
 
     const onDelete = useCallback(async (key: string) => {
         if (!confirm(`Delete ${key} from ${corpus.slug}? This can't be undone.`)) return;
@@ -462,24 +665,313 @@ const CorpusFiles: React.FC<{corpus: Corpus}> = ({corpus}) => {
         }
     }, [scope, corpus.slug, reload]);
 
+    const alertFailures = (failed: Array<{key: string; reason: string}>) => {
+        if (failed.length > 0) {
+            window.alert(failed.map((f) => `${f.key}: ${f.reason}`).join("\n"));
+        }
+    };
+
+    const runFolderMove = useCallback(async (folderPath: string, newPath: string) => {
+        if (newPath === folderPath) return;
+        const count = files.filter((f) => normKey(f.key).startsWith(folderPath + "/")).length;
+        if (!beginOp(
+            `Moving folder "${folderPath}" → "${newPath}" (${count} file${count === 1 ? "" : "s"})…`,
+        )) return;
+        try {
+            const allKeys = files.map((f) => f.key);
+            const r = await viewerApi.adminRenameOrMoveFolder(scope, folderPath, newPath, allKeys);
+            alertFailures(r.failed);
+            removePendingFoldersUnder(folderPath);
+            await reload();
+        } catch (e) {
+            setErr((e as Error).message || "folder move failed");
+        } finally {
+            endOp();
+        }
+    }, [files, scope, reload]);
+
+    const moveKeys = useCallback(async (keys: string[], destFolder: string) => {
+        const label = destFolder ? `${destFolder}/` : "root /";
+        if (!beginOp(`Moving 0/${keys.length} to ${label}…`)) return;
+        try {
+            if (destFolder === "") {
+                // Move-to-root: the move endpoint requires a non-empty
+                // folder, so root moves are per-key renames to the
+                // basename.
+                let done = 0;
+                for (const k of keys) {
+                    updateOp(`Moving ${done + 1}/${keys.length} to ${label}…`);
+                    await viewerApi.adminRenameKey(scope, k, basenameOf(k));
+                    done++;
+                }
+            } else {
+                const failed: Array<{key: string; reason: string}> = [];
+                for (let i = 0; i < keys.length; i += OP_CHUNK) {
+                    const chunk = keys.slice(i, i + OP_CHUNK);
+                    updateOp(`Moving ${Math.min(i + chunk.length, keys.length)}/${keys.length} to ${label}…`);
+                    const r = await viewerApi.adminMoveKeysToFolder(scope, chunk, destFolder);
+                    failed.push(...r.failed);
+                }
+                alertFailures(failed);
+            }
+            clearSelection();
+            await reload();
+        } catch (e) {
+            setErr((e as Error).message || "move failed");
+        } finally {
+            endOp();
+        }
+    }, [scope, reload]);
+
+    // Folder subtree lands at ``destFolder``/``basename`` ("" = root).
+    const moveFolderTo = (path: string, destFolder: string) => {
+        const base = basenameOf(path);
+        const newPath = destFolder ? `${destFolder}/${base}` : base;
+        if (!folderHasKeys(path)) {
+            rekeyPendingFolders(path, newPath);
+            return;
+        }
+        void runFolderMove(path, newPath);
+    };
+
+    // Shared by the bulk toolbar and the Delete key: confirm with an
+    // overview of exactly what goes, then delete sequentially.
+    const deleteKeysWithConfirm = useCallback(async (keys: string[]) => {
+        if (keys.length === 0) return;
+        if (!confirm(
+            `Delete ${keys.length} file${keys.length === 1 ? "" : "s"} from ${corpus.slug}? ` +
+            "This can't be undone.\n\n" +
+            previewKeyList(keys),
+        )) return;
+        if (!beginOp(`Deleting 0/${keys.length}…`)) return;
+        try {
+            let done = 0;
+            for (const k of keys) {
+                updateOp(`Deleting ${done + 1}/${keys.length}…`);
+                await viewerApi.adminDeleteBlob(scope, k);
+                done++;
+            }
+            setSelected(new Set());
+            await reload();
+        } catch (e) {
+            setErr((e as Error).message || "delete failed");
+        } finally {
+            endOp();
+        }
+    }, [scope, corpus.slug, reload]);
+
+    // Server-side copy (Garage CopyObject) corpus → the caller's
+    // personal scope, preserving keys. Existing keys are skipped, not
+    // overwritten — same semantics as the copy-into-corpus modal.
+    const copyToPersonal = useCallback(async (keys: string[]) => {
+        if (keys.length === 0) return;
+        if (!beginOp(`Copying 0/${keys.length} to your files…`)) return;
+        setNote(null);
+        try {
+            let copied = 0;
+            let skipped = 0;
+            const failed: Array<{key: string; reason: string}> = [];
+            for (let i = 0; i < keys.length; i += OP_CHUNK) {
+                const chunk = keys.slice(i, i + OP_CHUNK);
+                updateOp(`Copying ${Math.min(i + chunk.length, keys.length)}/${keys.length} to your files…`);
+                const r = await viewerApi.adminCopyKeysFromScope("user:me", scope, chunk);
+                copied += r.copied.length;
+                skipped += r.skipped.length;
+                failed.push(...r.failed);
+            }
+            alertFailures(failed);
+            setNote(
+                `copied ${copied} to your files` +
+                (skipped > 0 ? ` · skipped ${skipped} (already there)` : ""),
+            );
+        } catch (e) {
+            setErr((e as Error).message || "copy to personal scope failed");
+        } finally {
+            endOp();
+        }
+    }, [scope]);
+
+    const mutations: FileTreeMutations = {
+        renameFile: (key, newName) => {
+            const dir = dirnameOf(key);
+            const newKey = dir ? `${dir}/${newName}` : newName;
+            void (async () => {
+                try {
+                    await viewerApi.adminRenameKey(scope, key, newKey);
+                    await reload();
+                } catch (e) {
+                    setErr((e as Error).message || "rename failed");
+                }
+            })();
+        },
+        renameFolder: (path, newName) => {
+            const parent = dirnameOf(path);
+            const newPath = parent ? `${parent}/${newName}` : newName;
+            if (!folderHasKeys(path)) {
+                rekeyPendingFolders(path, newPath);
+                return;
+            }
+            void runFolderMove(path, newPath);
+        },
+        moveKeys: (keys, destFolder) => void moveKeys(keys, destFolder),
+        moveFolder: moveFolderTo,
+        deleteFile: (key) => void onDelete(key),
+        deleteFolder: (path, fileCount) => {
+            if (fileCount === 0) {
+                // Pending (empty) folder — pure client state.
+                removePendingFoldersUnder(path);
+                return;
+            }
+            const prefix = path + "/";
+            const targets = files.filter((f) => normKey(f.key).startsWith(prefix));
+            if (!confirm(
+                `Delete folder "${path}" and its ${fileCount} file${fileCount === 1 ? "" : "s"} ` +
+                `from ${corpus.slug}? This can't be undone.\n\n` +
+                previewKeyList(targets.map((t) => t.key)),
+            )) return;
+            void (async () => {
+                if (!beginOp(`Deleting 0/${targets.length} from "${path}"…`)) return;
+                try {
+                    // Sequential: deletes cascade derived blobs server-side
+                    // and parallel calls would race on the storage listing.
+                    let done = 0;
+                    for (const t of targets) {
+                        updateOp(`Deleting ${done + 1}/${targets.length} from "${path}"…`);
+                        await viewerApi.adminDeleteBlob(scope, t.key);
+                        done++;
+                    }
+                    removePendingFoldersUnder(path);
+                    await reload();
+                } catch (e) {
+                    setErr((e as Error).message || "folder delete failed");
+                } finally {
+                    endOp();
+                }
+            })();
+        },
+        createFolder: (parent, name) => {
+            // ``_derived`` is where the converter parks derived blobs —
+            // a user folder with that name would collide with the cache
+            // prefix.
+            if (!parent && name === "_derived") {
+                window.alert(`"${name}" is a reserved name`);
+                return;
+            }
+            const path = parent ? `${parent}/${name}` : name;
+            setPendingFolders((prev) => (prev.includes(path) ? prev : [...prev, path]));
+        },
+        requestMoveFile: (key) => setPicker({
+            title: `Move "${key}" to folder`,
+            onPick: (folder) => void moveKeys([key], folder),
+        }),
+        requestMoveFolder: (path) => setPicker({
+            title: `Move folder "${path}" into`,
+            onPick: (dest) => moveFolderTo(path, dest),
+        }),
+        deleteKeys: (keys) => void deleteKeysWithConfirm(keys),
+        uploadTo: (folder, list) => void uploadFilesTo(list, folder || undefined),
+        downloadFile: (key) => void viewerApi.downloadBlob(scope, key, basenameOf(key)),
+    };
+
+    const onMoveSelected = () => {
+        const keys = Array.from(selected);
+        if (keys.length === 0) return;
+        setPicker({
+            title: `Move ${keys.length} file${keys.length === 1 ? "" : "s"} to folder`,
+            onPick: (folder) => void moveKeys(keys, folder),
+        });
+    };
+
+    const showTree = viewMode === "tree" &&
+        (files.length > 0 || pendingFolders.length > 0 || newFolderAt !== null);
+
     return (
         <div className="flex flex-col h-full">
             <div className="px-3 py-2 border-b border-gray-800 flex items-center justify-between gap-3">
-                <div className="text-xs text-gray-300 min-w-0">
-                    <div className="font-mono truncate">{corpus.slug}</div>
-                    {corpus.description && (
-                        <div className="text-gray-500 truncate">{corpus.description}</div>
-                    )}
-                </div>
+                {!editingMeta ? (
+                    <div className="text-xs text-gray-300 min-w-0 flex items-start gap-1.5">
+                        <div className="min-w-0">
+                            <div className="font-mono truncate">
+                                {corpus.slug}
+                                <span className="text-gray-400 font-sans"> · {corpus.name}</span>
+                            </div>
+                            {corpus.description && (
+                                <div className="text-gray-500 truncate">{corpus.description}</div>
+                            )}
+                        </div>
+                        <button
+                            type="button"
+                            onClick={openMetaEdit}
+                            title="Edit name / description (slug is immutable)"
+                            aria-label="Edit corpus name and description"
+                            className="shrink-0 text-gray-500 hover:text-gray-200 leading-none px-1"
+                        >
+                            ✎
+                        </button>
+                    </div>
+                ) : (
+                    <form
+                        className="flex flex-col gap-1 min-w-0 flex-1 max-w-md text-xs"
+                        onSubmit={(e) => {
+                            e.preventDefault();
+                            void saveMeta();
+                        }}
+                    >
+                        <div className="font-mono text-gray-500">{corpus.slug}</div>
+                        <input
+                            type="text"
+                            value={metaName}
+                            onChange={(e) => setMetaName(e.target.value)}
+                            placeholder="Name"
+                            autoFocus
+                            className="bg-gray-900 border border-gray-600 rounded-sm px-2 py-1 text-gray-100"
+                        />
+                        <input
+                            type="text"
+                            value={metaDesc}
+                            onChange={(e) => setMetaDesc(e.target.value)}
+                            placeholder="Description (optional)"
+                            onKeyDown={(e) => {
+                                if (e.key === "Escape") setEditingMeta(false);
+                            }}
+                            className="bg-gray-900 border border-gray-600 rounded-sm px-2 py-1 text-gray-100"
+                        />
+                        <div className="flex gap-2">
+                            <button
+                                type="submit"
+                                disabled={metaBusy}
+                                className="bg-blue-700 hover:bg-blue-600 disabled:opacity-50 text-white px-2 py-0.5 rounded-sm"
+                            >
+                                {metaBusy ? "Saving…" : "Save"}
+                            </button>
+                            <button
+                                type="button"
+                                onClick={() => setEditingMeta(false)}
+                                disabled={metaBusy}
+                                className="text-gray-300 hover:bg-gray-800 px-2 py-0.5 rounded-sm"
+                            >
+                                Cancel
+                            </button>
+                        </div>
+                    </form>
+                )}
                 <div className="flex items-center gap-2 shrink-0">
-                    {files.length > 0 && (
-                        <ViewModeToggle mode={viewMode} onChange={setViewMode}/>
+                    <ViewModeToggle mode={viewMode} onChange={setViewMode}/>
+                    {viewMode === "tree" && (
+                        <button
+                            type="button"
+                            onClick={() => setNewFolderAt("")}
+                            disabled={!!uploading}
+                            className="bg-gray-700 hover:bg-gray-600 disabled:opacity-50 text-white text-sm px-3 py-1 rounded-sm"
+                        >
+                            New folder
+                        </button>
                     )}
                     <input
                         ref={inputRef}
                         type="file"
                         multiple
-                        onChange={onPick}
+                        onChange={onPickUpload}
                         className="hidden"
                         disabled={!!uploading}
                     />
@@ -511,11 +1003,59 @@ const CorpusFiles: React.FC<{corpus: Corpus}> = ({corpus}) => {
                     onCopied={() => void reload()}
                 />
             )}
+            {busy && (
+                <div className="flex items-center gap-2 px-3 py-1.5 border-b border-gray-800 bg-blue-900/20 text-xs text-blue-300">
+                    <span
+                        className="inline-block w-3.5 h-3.5 border-2 border-current border-t-transparent rounded-full animate-spin shrink-0"
+                        aria-hidden="true"
+                    />
+                    <span className="truncate" role="status">{busy}</span>
+                </div>
+            )}
             {err && (
                 <div className="text-xs text-red-400 px-3 py-2">{err}</div>
             )}
+            {note && !err && !busy && (
+                <div className="text-xs text-emerald-400 px-3 py-2">{note}</div>
+            )}
+            {viewMode === "tree" && selected.size > 0 && (
+                <div className="mx-3 my-2 px-2 py-1.5 rounded-sm border border-gray-700 bg-gray-800/95 flex items-center gap-2 flex-wrap">
+                    <span className="text-xs text-white whitespace-nowrap">
+                        {selected.size} selected
+                    </span>
+                    <button
+                        type="button"
+                        onClick={onMoveSelected}
+                        className="bg-gray-700 hover:bg-gray-600 active:bg-gray-800 text-white text-xs px-2 py-1 rounded-sm cursor-pointer"
+                    >
+                        Move…
+                    </button>
+                    <button
+                        type="button"
+                        onClick={() => void copyToPersonal(Array.from(selected))}
+                        title="Server-side copy into your personal scope (same keys; existing files are skipped)"
+                        className="bg-gray-700 hover:bg-gray-600 active:bg-gray-800 text-white text-xs px-2 py-1 rounded-sm cursor-pointer"
+                    >
+                        Copy to my files
+                    </button>
+                    <button
+                        type="button"
+                        onClick={() => void deleteKeysWithConfirm(Array.from(selected))}
+                        className="bg-red-800 hover:bg-red-700 active:bg-red-900 text-white text-xs px-2 py-1 rounded-sm cursor-pointer"
+                    >
+                        Delete
+                    </button>
+                    <button
+                        type="button"
+                        onClick={clearSelection}
+                        className="ml-auto bg-gray-600 hover:bg-gray-500 text-white text-xs px-2 py-1 rounded-sm cursor-pointer"
+                    >
+                        Cancel
+                    </button>
+                </div>
+            )}
             <div className="flex-1 min-h-0 overflow-auto">
-                {files.length === 0 && !err && (
+                {files.length === 0 && !err && pendingFolders.length === 0 && newFolderAt === null && (
                     <div className="text-xs text-gray-500 italic px-3 py-4">
                         No files yet. Upload representative source files (STEP /
                         IFC / RMED / etc.) to drive regression sweeps from the
@@ -547,7 +1087,7 @@ const CorpusFiles: React.FC<{corpus: Corpus}> = ({corpus}) => {
                                     <td className="text-right px-3 py-1 border-b border-gray-800">
                                         <button
                                             type="button"
-                                            onClick={() => onDelete(f.key)}
+                                            onClick={() => void onDelete(f.key)}
                                             className="text-red-400 hover:text-red-300 text-xs"
                                         >
                                             delete
@@ -558,29 +1098,95 @@ const CorpusFiles: React.FC<{corpus: Corpus}> = ({corpus}) => {
                         </tbody>
                     </table>
                 )}
-                {files.length > 0 && viewMode === "tree" && (
+                {showTree && (
                     <div className="px-1 py-1">
                         <FileTreeView
-                            nodes={buildFileTree(files, (f) => f.key)}
+                            nodes={buildFileTree(files, (f) => f.key, pendingFolders)}
                             getKey={(f) => f.key}
                             namespace="corpus"
                             scope={scope}
+                            selection={{selected, onSelect: setSelection}}
+                            mutations={mutations}
+                            extraFileMenuItems={(key) => [{
+                                key: "copy-to-personal",
+                                label: "Copy to my files",
+                                title: "Server-side copy into your personal scope (same key; skipped if it already exists)",
+                                onClick: () => void copyToPersonal([key]),
+                            }]}
+                            newFolderAt={newFolderAt}
+                            onNewFolderAtChange={setNewFolderAt}
                             renderFileTail={(f) => (
-                                <span className="flex items-center gap-3">
-                                    <span className="text-gray-400 font-mono">{fmtBytes(f.size)}</span>
-                                    <button
-                                        type="button"
-                                        onClick={() => onDelete(f.key)}
-                                        className="text-red-400 hover:text-red-300 text-xs"
-                                    >
-                                        delete
-                                    </button>
-                                </span>
+                                <span className="text-gray-400 font-mono">{fmtBytes(f.size)}</span>
                             )}
                         />
                     </div>
                 )}
             </div>
+            <FolderPickerModal
+                open={picker !== null}
+                title={picker?.title ?? ""}
+                existingFolders={existingFolderPaths}
+                allowRoot={picker?.allowRoot}
+                submitLabel={picker?.submitLabel}
+                onCancel={() => setPicker(null)}
+                onPick={(folder) => {
+                    const action = picker?.onPick;
+                    setPicker(null);
+                    if (action) void action(folder);
+                }}
+            />
+            {/* Failed-uploads overview + retry. Not portaled — like the
+                copy-from-scope modal it renders inside the admin panel's
+                stacking context, so z-50 suffices here. Retry re-runs
+                only the failed files (the skip-existing pre-check makes
+                a partially-succeeded upload a safe no-op). */}
+            {uploadFailures && (
+                <div className="fixed inset-0 z-50 flex items-center justify-center bg-black/60 p-4">
+                    <div className="bg-gray-900 border border-gray-700 rounded-md w-full max-w-lg max-h-[70vh] flex flex-col">
+                        <div className="px-4 py-3 border-b border-gray-700 text-sm font-semibold text-gray-100">
+                            {uploadFailures.failed.length} upload{uploadFailures.failed.length === 1 ? "" : "s"} failed
+                            {uploadFailures.folder ? (
+                                <span className="text-gray-400 font-normal"> → {uploadFailures.folder}/</span>
+                            ) : null}
+                        </div>
+                        <div className="flex-1 min-h-0 overflow-auto px-4 py-2">
+                            <ul className="space-y-1 text-xs">
+                                {uploadFailures.failed.map(({file, reason}) => (
+                                    <li key={file.name} className="flex justify-between items-baseline gap-3">
+                                        <span className="font-mono text-gray-200 truncate" title={file.name}>
+                                            {file.name}
+                                        </span>
+                                        <span className="text-red-400 truncate shrink-0 max-w-[50%]" title={reason}>
+                                            {reason}
+                                        </span>
+                                    </li>
+                                ))}
+                            </ul>
+                        </div>
+                        <div className="px-4 py-3 border-t border-gray-700 flex justify-end gap-2">
+                            <button
+                                type="button"
+                                onClick={() => setUploadFailures(null)}
+                                className="text-sm px-3 py-1 rounded-sm text-gray-300 hover:bg-gray-800"
+                            >
+                                Close
+                            </button>
+                            <button
+                                type="button"
+                                disabled={!!uploading}
+                                onClick={() => {
+                                    const {folder, failed} = uploadFailures;
+                                    setUploadFailures(null);
+                                    void uploadFilesTo(failed.map((f) => f.file), folder);
+                                }}
+                                className="bg-blue-700 hover:bg-blue-600 disabled:opacity-50 text-white text-sm px-3 py-1 rounded-sm"
+                            >
+                                Retry {uploadFailures.failed.length} file{uploadFailures.failed.length === 1 ? "" : "s"}
+                            </button>
+                        </div>
+                    </div>
+                </div>
+            )}
         </div>
     );
 };
@@ -711,7 +1317,7 @@ const CorpusTab: React.FC = () => {
                                     ← corpora
                                 </button>
                             </div>
-                            <CorpusFiles key={selected.slug} corpus={selected}/>
+                            <CorpusFiles key={selected.slug} corpus={selected} onMetaUpdated={loadCorpora}/>
                         </>
                     )}
                 </div>
diff --git a/src/frontend/src/components/admin/FileTreeView.tsx b/src/frontend/src/components/admin/FileTreeView.tsx
index 4b9373912..689e90726 100644
--- a/src/frontend/src/components/admin/FileTreeView.tsx
+++ b/src/frontend/src/components/admin/FileTreeView.tsx
@@ -8,14 +8,43 @@ import FileTypeIcon from "../icons/FileTypeIcon";
 import FolderClosedIcon from "../icons/FolderClosedIcon";
 import FolderOpenIcon from "../icons/FolderOpenIcon";
 import ChevronRightIcon from "../icons/ChevronRightIcon";
+import InlineNameInput from "@/components/common/InlineNameInput";
+import {RowKebabMenu, KebabMenuItem} from "@/components/common/RowKebabMenu";
 
-// Generic, read-mostly folder-tree view shared by the admin Corpus tab's
-// file overview and its "Copy from scope" modal. Storage stays flat on the
-// server; folders are presentational (a key's "/" segments). The tree shape
-// itself is built by the caller via ``buildFileTree`` from
-// ``@/utils/storage/fileTree`` — this component only renders + manages
-// collapse state, mirroring StorageBrowser's row look (indent per depth,
-// chevron + folder glyph, file rows) without its drag/rename/scene machinery.
+// Generic folder-tree view shared by the admin Corpus tab's file
+// overview, its "Copy from scope" modal, and the utility file picker.
+// Storage stays flat on the server; folders are presentational (a
+// key's "/" segments). The tree shape itself is built by the caller
+// via ``buildFileTree`` from ``@/utils/storage/fileTree`` — this
+// component renders + manages collapse state, mirroring
+// StorageBrowser's row look (indent per depth, chevron + folder
+// glyph, file rows).
+//
+// Read-only by default. Passing ``mutations`` turns on the organize
+// affordances from the storage panel: per-row kebab menus (rename /
+// move / delete / new subfolder / upload here), inline rename inputs,
+// and drag-and-drop moves between folders (plus a move-to-root strip).
+// The component owns the interaction state; the server semantics —
+// endpoints, confirm dialogs, list reloads — stay with the caller.
+
+// Drag payload MIMEs. Deliberately distinct from StorageBrowser's
+// ``application/x-adapy-keys`` (which carries a bare key array): the
+// payload here embeds the source scope and drops verify it, so a drag
+// that strays in from another panel (possibly another scope) is
+// ignored instead of mis-moved. Types are readable during dragover,
+// the payload only on drop — presence of the type alone distinguishes
+// internal drags from OS-file drops.
+const TREE_KEYS_MIME = "application/x-adapy-tree-keys";
+const TREE_FOLDER_MIME = "application/x-adapy-tree-folder";
+
+function dirnameOf(key: string): string {
+    const i = key.lastIndexOf("/");
+    return i >= 0 ? key.slice(0, i) : "";
+}
+
+function basenameOf(key: string): string {
+    return key.split("/").pop() ?? key;
+}
 
 export interface FileTreeSelection {
     selected: ReadonlySet<string>;
@@ -24,6 +53,39 @@ export interface FileTreeSelection {
     onSelect: (keys: string[], select: boolean) => void;
 }
 
+/** Write affordances. All semantics (server calls, confirm dialogs,
+ * list reloads, pending-folder bookkeeping) live in the caller — the
+ * tree only runs the interaction (menus, inline inputs, drag & drop)
+ * and validates names before dispatching. */
+export interface FileTreeMutations {
+    /** Inline rename committed: new basename for the file (no "/"). */
+    renameFile: (key: string, newName: string) => void;
+    /** Inline rename committed: new single-segment name for the folder. */
+    renameFolder: (path: string, newName: string) => void;
+    /** Drag-drop move of file keys into ``destFolder`` ("" = root). */
+    moveKeys: (keys: string[], destFolder: string) => void;
+    /** Drag-drop move of a whole folder under ``destFolder`` ("" = root). */
+    moveFolder: (folderPath: string, destFolder: string) => void;
+    deleteFile: (key: string) => void;
+    /** ``fileCount`` = files under the prefix; 0 means a client-side
+     * pending (empty) folder the caller can drop without a server call. */
+    deleteFolder: (path: string, fileCount: number) => void;
+    /** Bulk delete — the Delete key targets the whole selection when
+     * one exists. The caller confirms with an overview of the keys. */
+    deleteKeys?: (keys: string[]) => void;
+    /** "New folder" input committed (single-segment name; ``parent``
+     * "" = root). The caller materialises it (pending-folder state). */
+    createFolder: (parent: string, name: string) => void;
+    /** Open the caller's move-to-folder picker for one file. */
+    requestMoveFile?: (key: string) => void;
+    /** Open the caller's move-folder-into picker. */
+    requestMoveFolder?: (path: string) => void;
+    /** Upload OS files into a folder ("" = root) — used by the folder
+     * menu's "Upload here…" and by OS-file drops. Omit to disable both. */
+    uploadTo?: (folder: string, files: File[]) => void;
+    downloadFile?: (key: string) => void;
+}
+
 interface FileTreeViewProps<T> {
     nodes: FileTreeNode<T>[];
     /** Stable identity for a file entry — the storage key. */
@@ -39,6 +101,17 @@ interface FileTreeViewProps<T> {
     isDisabled?: (file: T) => boolean;
     /** Right-aligned per-file slot for actions / labels (size, delete, …). */
     renderFileTail?: (file: T) => React.ReactNode;
+    /** Enable the organize affordances (see FileTreeMutations). */
+    mutations?: FileTreeMutations;
+    /** Caller-specific kebab items appended between the standard file
+     * actions and Delete (e.g. the corpus tab's "Copy to my files"). */
+    extraFileMenuItems?: (key: string) => KebabMenuItem[];
+    /** Where the "new folder" inline input shows: "" = top level, a
+     * folder path = inside it, null/undefined = hidden. Owned by the
+     * caller so a header-level button can trigger root creation; the
+     * folder menu's "New subfolder…" routes through it too. */
+    newFolderAt?: string | null;
+    onNewFolderAtChange?: (v: string | null) => void;
 }
 
 // Every enabled descendant file key under a node — drives folder-level
@@ -90,6 +163,10 @@ export function FileTreeView<T>({
     selection,
     isDisabled,
     renderFileTail,
+    mutations,
+    extraFileMenuItems,
+    newFolderAt,
+    onNewFolderAtChange,
 }: FileTreeViewProps<T>): React.ReactElement {
     // Default fully collapsed; persisted per-scope so expand state survives
     // reloads but doesn't leak across scopes (matches StorageBrowser).
@@ -110,6 +187,259 @@ export function FileTreeView<T>({
             return next;
         });
     };
+    // Optimistic expand-state re-key after a rename/move dispatch —
+    // harmless if the server-side move fails (a stale entry just means
+    // a collapsed folder).
+    const rekeyExpanded = (oldPath: string, newPath: string) => {
+        setExpanded((prev) => {
+            const next = new Set<string>();
+            for (const p of prev) {
+                if (p === oldPath) next.add(newPath);
+                else if (p.startsWith(oldPath + "/")) next.add(newPath + p.slice(oldPath.length));
+                else next.add(p);
+            }
+            return next;
+        });
+    };
+
+    // Inline rename target. One at a time, like StorageBrowser.
+    const [renaming, setRenaming] = useState<{kind: "file" | "folder"; path: string} | null>(null);
+    // In-flight drag payload (for row dimming + the move-to-root strip).
+    const [dragKeys, setDragKeys] = useState<string[] | null>(null);
+    const [dragFolder, setDragFolder] = useState<string | null>(null);
+    // Folder path currently hovered by an accepted drag.
+    const [dropTarget, setDropTarget] = useState<string | null>(null);
+    // Keyboard-navigation focus, keyed `folder:<path>` / `file:<key>`.
+    // Pointer interactions move it too, so arrows continue from the
+    // last clicked row (mirrors StorageBrowser).
+    const [focusedKey, setFocusedKey] = useState<string | null>(null);
+    // Anchor for shift-click / shift+arrow range selection — the last
+    // file row toggled by any input path (same semantics as
+    // StorageBrowser's lastSelectedRef).
+    const lastToggledRef = useRef<string | null>(null);
+    const wrapRef = useRef<HTMLDivElement>(null);
+    useEffect(() => {
+        if (!focusedKey) return;
+        const el = wrapRef.current?.querySelector(
+            `[data-rowkey="${CSS.escape(focusedKey)}"]`,
+        ) as HTMLElement | null;
+        el?.scrollIntoView({block: "nearest"});
+    }, [focusedKey]);
+
+    // Hidden input backing the folder menu's "Upload here…". Clicked
+    // synchronously inside the menu item's onClick so the file picker
+    // keeps the user-activation gesture (iOS Safari refuses otherwise).
+    const uploadInputRef = useRef<HTMLInputElement>(null);
+    const uploadTargetRef = useRef<string>("");
+
+    const acceptsDrop = (e: React.DragEvent) =>
+        !!mutations &&
+        (e.dataTransfer.types.includes(TREE_KEYS_MIME) ||
+            e.dataTransfer.types.includes(TREE_FOLDER_MIME) ||
+            (!!mutations.uploadTo && e.dataTransfer.types.includes("Files")));
+
+    const onDragStartFile = (key: string) => (e: React.DragEvent) => {
+        // Dragging a selected row drags the whole selection; dragging
+        // an unselected row drags just that file (matches StorageBrowser).
+        const keys = selection?.selected.has(key)
+            ? Array.from(selection.selected)
+            : [key];
+        e.dataTransfer.setData(TREE_KEYS_MIME, JSON.stringify({scope, keys}));
+        e.dataTransfer.effectAllowed = "move";
+        setDragKeys(keys);
+    };
+    const onDragStartFolder = (path: string) => (e: React.DragEvent) => {
+        e.dataTransfer.setData(TREE_FOLDER_MIME, JSON.stringify({scope, path}));
+        e.dataTransfer.effectAllowed = "move";
+        setDragFolder(path);
+    };
+    const clearDragState = () => {
+        setDragKeys(null);
+        setDragFolder(null);
+        setDropTarget(null);
+    };
+
+    // Drop onto a folder path ("" = root). Internal drags move keys or
+    // a whole folder subtree; OS-file drops upload into the folder.
+    const handleDrop = (target: string, e: React.DragEvent) => {
+        e.preventDefault();
+        e.stopPropagation();
+        clearDragState();
+        if (!mutations) return;
+        const rawFolder = e.dataTransfer.getData(TREE_FOLDER_MIME);
+        if (rawFolder) {
+            let p: {scope?: unknown; path?: unknown};
+            try {
+                p = JSON.parse(rawFolder);
+            } catch {
+                return;
+            }
+            if (p.scope !== scope || typeof p.path !== "string") return;
+            const folderPath = p.path;
+            // No-ops: into itself, into its own subtree, or where it
+            // already lives.
+            if (target === folderPath || target.startsWith(folderPath + "/")) return;
+            if (dirnameOf(folderPath) === target) return;
+            const base = basenameOf(folderPath);
+            rekeyExpanded(folderPath, target ? `${target}/${base}` : base);
+            mutations.moveFolder(folderPath, target);
+            return;
+        }
+        const rawKeys = e.dataTransfer.getData(TREE_KEYS_MIME);
+        if (rawKeys) {
+            let p: {scope?: unknown; keys?: unknown};
+            try {
+                p = JSON.parse(rawKeys);
+            } catch {
+                return;
+            }
+            if (p.scope !== scope || !Array.isArray(p.keys)) return;
+            const keys = p.keys.filter(
+                (k): k is string => typeof k === "string" && dirnameOf(k) !== target,
+            );
+            if (keys.length > 0) mutations.moveKeys(keys, target);
+            return;
+        }
+        if (e.dataTransfer.files?.length && mutations.uploadTo) {
+            mutations.uploadTo(target, Array.from(e.dataTransfer.files));
+        }
+    };
+
+    // ── Commit handlers (validate, then dispatch to the caller) ─────
+    const onRenameFileCommit = (key: string, displayName: string, raw: string) => {
+        setRenaming(null);
+        if (!mutations) return;
+        const name = raw.trim();
+        if (!name || name === displayName) return;
+        if (name.includes("/")) {
+            window.alert("Name must not contain '/' — use Move to folder… instead");
+            return;
+        }
+        mutations.renameFile(key, name);
+    };
+    const onRenameFolderCommit = (path: string, raw: string) => {
+        setRenaming(null);
+        if (!mutations) return;
+        const name = raw.trim().replace(/^\/+|\/+$/g, "");
+        if (!name || name === basenameOf(path)) return;
+        if (name.includes("/")) {
+            window.alert("Rename must be a single name; use Move folder into… for nested moves");
+            return;
+        }
+        const parent = dirnameOf(path);
+        rekeyExpanded(path, parent ? `${parent}/${name}` : name);
+        mutations.renameFolder(path, name);
+    };
+    const onCreateFolderCommit = (parent: string, raw: string) => {
+        onNewFolderAtChange?.(null);
+        if (!mutations) return;
+        const name = raw.trim().replace(/^\/+|\/+$/g, "");
+        if (!name) return;
+        if (name.includes("/")) {
+            window.alert("Folder name must not contain '/'");
+            return;
+        }
+        setExpanded((prev) => {
+            const next = new Set(prev);
+            if (parent) next.add(parent);
+            next.add(parent ? `${parent}/${name}` : name);
+            return next;
+        });
+        mutations.createFolder(parent, name);
+    };
+
+    // ── Kebab menu builders ──────────────────────────────────────────
+    const fileMenuItems = (key: string): KebabMenuItem[] => {
+        if (!mutations) return [];
+        const items: KebabMenuItem[] = [];
+        if (mutations.downloadFile) {
+            items.push({
+                key: "download",
+                label: "Download",
+                onClick: () => mutations.downloadFile!(key),
+            });
+        }
+        items.push({
+            key: "rename",
+            label: "Rename…",
+            onClick: () => setRenaming({kind: "file", path: key}),
+        });
+        if (mutations.requestMoveFile) {
+            items.push({
+                key: "move-to-folder",
+                label: "Move to folder…",
+                onClick: () => mutations.requestMoveFile!(key),
+            });
+        }
+        items.push(...(extraFileMenuItems?.(key) ?? []));
+        items.push({
+            key: "delete",
+            label: "Delete",
+            destructive: true,
+            separatorBefore: true,
+            onClick: () => mutations.deleteFile(key),
+        });
+        return items;
+    };
+    const folderMenuItems = (path: string, fileCount: number): KebabMenuItem[] => {
+        if (!mutations) return [];
+        const items: KebabMenuItem[] = [];
+        if (mutations.uploadTo) {
+            items.push({
+                key: "upload-here",
+                label: "Upload here…",
+                onClick: () => {
+                    uploadTargetRef.current = path;
+                    uploadInputRef.current?.click();
+                },
+            });
+        }
+        items.push({
+            key: "new-subfolder",
+            label: "New subfolder…",
+            onClick: () => {
+                setExpanded((prev) => new Set(prev).add(path));
+                onNewFolderAtChange?.(path);
+            },
+        });
+        items.push({
+            key: "rename",
+            label: "Rename folder…",
+            title: "Sibling-name rename. Subfolders preserved.",
+            onClick: () => setRenaming({kind: "folder", path}),
+        });
+        if (mutations.requestMoveFolder) {
+            items.push({
+                key: "move-into",
+                label: "Move folder into…",
+                title: "Move under a destination prefix. Subfolders preserved.",
+                onClick: () => mutations.requestMoveFolder!(path),
+            });
+        }
+        items.push({
+            key: "delete",
+            label: `Delete folder (${fileCount} file${fileCount === 1 ? "" : "s"})`,
+            destructive: true,
+            separatorBefore: true,
+            onClick: () => mutations.deleteFolder(path, fileCount),
+        });
+        return items;
+    };
+
+    const newFolderInputRow = (parent: string, depth: number) => (
+        <li
+            className="flex items-center gap-1.5 px-2 py-1"
+            style={{paddingLeft: 8 + depth * 12}}
+        >
+            <FolderClosedIcon className="shrink-0 text-blue-400"/>
+            <InlineNameInput
+                initial=""
+                placeholder="New folder name"
+                onCommit={(v) => onCreateFolderCommit(parent, v)}
+                onCancel={() => onNewFolderAtChange?.(null)}
+            />
+        </li>
+    );
 
     const renderNode = (node: FileTreeNode<T>, depth: number): React.ReactNode => {
         const indentPx = depth * 12;
@@ -119,13 +449,44 @@ export function FileTreeView<T>({
             const checked = selection ? selection.selected.has(key) : false;
             const onRowSelect = () => {
                 if (!selection || disabled) return;
+                lastToggledRef.current = key;
                 selection.onSelect([key], !checked);
             };
+            // Shift+click selects the visible range from the anchor to
+            // this row (adds, never removes — matches StorageBrowser).
+            // ``flatRows`` is initialized before render evaluates this
+            // closure, so referencing it here is safe.
+            const onRowClick = (e: React.MouseEvent) => {
+                setFocusedKey(`file:${key}`);
+                if (!selection || disabled) return;
+                if (e.shiftKey && lastToggledRef.current && lastToggledRef.current !== key) {
+                    const fileKeys: string[] = [];
+                    for (const r of flatRows) {
+                        if (r.kind === "file" && !r.disabled) fileKeys.push(r.key);
+                    }
+                    const a = fileKeys.indexOf(lastToggledRef.current);
+                    const b = fileKeys.indexOf(key);
+                    if (a >= 0 && b >= 0) {
+                        const [lo, hi] = a < b ? [a, b] : [b, a];
+                        selection.onSelect(fileKeys.slice(lo, hi + 1), true);
+                        lastToggledRef.current = key;
+                        return;
+                    }
+                }
+                onRowSelect();
+            };
+            const isRenaming = renaming?.kind === "file" && renaming.path === key;
+            const menuItems = fileMenuItems(key);
+            const rowKey = `file:${key}`;
             return (
                 <li
-                    key={`file:${key}`}
+                    key={rowKey}
+                    data-rowkey={rowKey}
                     className={
                         "flex items-center gap-1.5 px-2 py-1 rounded select-none " +
+                        (dragKeys?.includes(key) ? "opacity-40 " : "") +
+                        (focusedKey === rowKey ? "ring-1 ring-blue-400/70 " : "") +
+                        (checked ? "bg-amber-700/30 " : "") +
                         (disabled
                             ? "opacity-50 "
                             : selection
@@ -133,7 +494,31 @@ export function FileTreeView<T>({
                                 : "hover:bg-gray-800/60 ")
                     }
                     style={{paddingLeft: 8 + indentPx}}
-                    onClick={onRowSelect}
+                    onClick={onRowClick}
+                    draggable={(!!mutations && !isRenaming) || undefined}
+                    onDragStart={mutations ? onDragStartFile(key) : undefined}
+                    onDragEnd={mutations ? clearDragState : undefined}
+                    // Internal drops on a file row are a no-op (folders are
+                    // the targets) — swallowed so they don't bubble to the
+                    // background handler and move to root. OS-file drops
+                    // land in the row's folder.
+                    onDragOver={mutations ? (e) => {
+                        if (!acceptsDrop(e)) return;
+                        e.preventDefault();
+                        e.stopPropagation();
+                    } : undefined}
+                    onDrop={mutations ? (e) => {
+                        e.preventDefault();
+                        e.stopPropagation();
+                        clearDragState();
+                        if (
+                            e.dataTransfer.getData(TREE_KEYS_MIME) ||
+                            e.dataTransfer.getData(TREE_FOLDER_MIME)
+                        ) return;
+                        if (e.dataTransfer.files?.length && mutations.uploadTo) {
+                            mutations.uploadTo(dirnameOf(key), Array.from(e.dataTransfer.files));
+                        }
+                    } : undefined}
                 >
                     {selection && (
                         <input
@@ -146,17 +531,36 @@ export function FileTreeView<T>({
                         />
                     )}
                     <FileTypeIcon name={key}/>
-                    <span
-                        className="font-mono text-xs text-gray-200 flex-1 min-w-0 truncate"
-                        title={key}
-                    >
-                        {node.displayName}
-                    </span>
+                    {isRenaming ? (
+                        <InlineNameInput
+                            initial={node.displayName}
+                            selectStem
+                            onCommit={(v) => onRenameFileCommit(key, node.displayName, v)}
+                            onCancel={() => setRenaming(null)}
+                        />
+                    ) : (
+                        <span
+                            className="font-mono text-xs text-gray-200 flex-1 min-w-0 truncate"
+                            title={key}
+                        >
+                            {node.displayName}
+                        </span>
+                    )}
                     {renderFileTail && (
                         <span className="shrink-0" onClick={(e) => e.stopPropagation()}>
                             {renderFileTail(node.file)}
                         </span>
                     )}
+                    {menuItems.length > 0 && (
+                        <span className="shrink-0" onClick={(e) => e.stopPropagation()}>
+                            <RowKebabMenu
+                                ariaLabel={`Actions for ${node.displayName}`}
+                                buttonClassName="h-6 w-6 text-gray-300 hover:bg-gray-700"
+                                header={<span className="font-mono" title={key}>{key}</span>}
+                                items={menuItems}
+                            />
+                        </span>
+                    )}
                 </li>
             );
         }
@@ -171,18 +575,43 @@ export function FileTreeView<T>({
             if (!selection || total === 0) return;
             selection.onSelect(fileKeys, !allSelected);
         };
+        const isRenaming = renaming?.kind === "folder" && renaming.path === node.path;
+        const menuItems = folderMenuItems(node.path, total);
+        const isDropTarget = dropTarget === node.path;
+        const rowKey = `folder:${node.path}`;
         return (
-            <React.Fragment key={`folder:${node.path}`}>
+            <React.Fragment key={rowKey}>
                 <li
+                    data-rowkey={rowKey}
                     className={
                         "flex items-center gap-1.5 px-2 py-1 rounded cursor-pointer " +
-                        "select-none hover:bg-gray-800/80"
+                        "select-none hover:bg-gray-800/80 " +
+                        (dragFolder === node.path ? "opacity-40 " : "") +
+                        (focusedKey === rowKey && !isDropTarget ? "ring-1 ring-blue-400/70 " : "") +
+                        (isDropTarget ? "ring-1 ring-blue-400 bg-blue-900/30 " : "")
                     }
                     style={{paddingLeft: 8 + indentPx}}
-                    onClick={() => toggleFolder(node.path)}
+                    onClick={() => {
+                        setFocusedKey(rowKey);
+                        toggleFolder(node.path);
+                    }}
                     role="button"
                     aria-expanded={isOpen}
                     aria-label={`${isOpen ? "Collapse" : "Expand"} folder ${node.name}`}
+                    draggable={(!!mutations && !isRenaming) || undefined}
+                    onDragStart={mutations ? onDragStartFolder(node.path) : undefined}
+                    onDragEnd={mutations ? clearDragState : undefined}
+                    onDragOver={mutations ? (e) => {
+                        if (!acceptsDrop(e)) return;
+                        e.preventDefault();
+                        e.stopPropagation();
+                        e.dataTransfer.dropEffect = "move";
+                        setDropTarget(node.path);
+                    } : undefined}
+                    onDragLeave={mutations ? () => {
+                        setDropTarget((prev) => (prev === node.path ? null : prev));
+                    } : undefined}
+                    onDrop={mutations ? (e) => handleDrop(node.path, e) : undefined}
                 >
                     {selection && (
                         <TriCheckbox
@@ -203,20 +632,188 @@ export function FileTreeView<T>({
                     ) : (
                         <FolderClosedIcon className="shrink-0 text-blue-400"/>
                     )}
-                    <span className="text-xs flex-1 min-w-0 truncate font-semibold text-gray-200">
-                        {node.name}/
+                    {isRenaming ? (
+                        <InlineNameInput
+                            initial={node.name}
+                            onCommit={(v) => onRenameFolderCommit(node.path, v)}
+                            onCancel={() => setRenaming(null)}
+                        />
+                    ) : (
+                        <span className="text-xs flex-1 min-w-0 truncate font-semibold text-gray-200">
+                            {node.name}/
+                        </span>
+                    )}
+                    <span className="text-[10px] text-gray-400 shrink-0">
+                        {total === 0 ? "empty" : total}
                     </span>
-                    <span className="text-[10px] text-gray-400 shrink-0">{total}</span>
+                    {menuItems.length > 0 && (
+                        <span className="shrink-0" onClick={(e) => e.stopPropagation()}>
+                            <RowKebabMenu
+                                ariaLabel={`Organize folder ${node.path}`}
+                                buttonClassName="h-6 w-6 text-gray-300 hover:bg-gray-700"
+                                header={<span className="font-mono">{node.path}/</span>}
+                                items={menuItems}
+                            />
+                        </span>
+                    )}
                 </li>
+                {isOpen && newFolderAt === node.path && newFolderInputRow(node.path, depth + 1)}
                 {isOpen && node.children.map((c) => renderNode(c, depth + 1))}
             </React.Fragment>
         );
     };
 
+    const showRootDropStrip =
+        (dragKeys !== null && dragKeys.some((k) => dirnameOf(k) !== "")) ||
+        (dragFolder !== null && dirnameOf(dragFolder) !== "");
+
+    // ── Keyboard navigation over the visible rows ────────────────────
+    // Flattened render order of what's currently on screen. Shift+
+    // Arrow extends the selection while moving focus (multi-select
+    // without a pointer); plain arrows just move focus. Space toggles
+    // the focused file; Enter toggles a folder; Delete removes the
+    // selection (or the focused row when nothing is selected).
+    type FlatRow =
+        | {kind: "folder"; path: string; count: number}
+        | {kind: "file"; key: string; disabled: boolean};
+    const flatRows: FlatRow[] = [];
+    {
+        const walk = (ns: FileTreeNode<T>[]) => {
+            for (const n of ns) {
+                if (n.kind === "folder") {
+                    flatRows.push({
+                        kind: "folder",
+                        path: n.path,
+                        count: collectFileKeys(n, getKey).length,
+                    });
+                    if (expanded.has(n.path)) walk(n.children);
+                } else {
+                    const k = getKey(n.file);
+                    flatRows.push({
+                        kind: "file",
+                        key: k,
+                        disabled: isDisabled?.(n.file) ?? false,
+                    });
+                }
+            }
+        };
+        walk(nodes);
+    }
+    const rowKeyOf = (r: FlatRow) => (r.kind === "folder" ? `folder:${r.path}` : `file:${r.key}`);
+
+    const onListKeyDown = (e: React.KeyboardEvent) => {
+        if (flatRows.length === 0) return;
+        if (!["ArrowUp", "ArrowDown", "ArrowLeft", "ArrowRight", "Enter", " ", "Delete"].includes(e.key)) return;
+        // Don't steal keys from the inline rename/new-folder inputs.
+        if ((e.target as HTMLElement).tagName === "INPUT") return;
+        e.preventDefault();
+        e.stopPropagation();
+        const idx = focusedKey ? flatRows.findIndex((r) => rowKeyOf(r) === focusedKey) : -1;
+        const row = idx >= 0 ? flatRows[idx] : null;
+        const selectRow = (r: FlatRow | null) => {
+            if (!selection || !r || r.kind !== "file" || r.disabled) return;
+            lastToggledRef.current = r.key;
+            selection.onSelect([r.key], true);
+        };
+        const focusAt = (i: number, extendSelection: boolean) => {
+            const clamped = Math.max(0, Math.min(flatRows.length - 1, i));
+            if (extendSelection) {
+                // Anchor the range on the row we're leaving, then take
+                // the row we land on with us.
+                selectRow(row);
+                selectRow(flatRows[clamped]);
+            }
+            setFocusedKey(rowKeyOf(flatRows[clamped]));
+        };
+        switch (e.key) {
+            case "ArrowDown":
+                focusAt(idx < 0 ? 0 : idx + 1, e.shiftKey);
+                break;
+            case "ArrowUp":
+                focusAt(idx < 0 ? flatRows.length - 1 : idx - 1, e.shiftKey);
+                break;
+            case "ArrowRight":
+                if (row?.kind === "folder" && !expanded.has(row.path)) toggleFolder(row.path);
+                break;
+            case "ArrowLeft":
+                if (row?.kind === "folder" && expanded.has(row.path)) toggleFolder(row.path);
+                break;
+            case "Enter":
+                if (row?.kind === "folder") toggleFolder(row.path);
+                break;
+            case " ":
+                if (row?.kind === "file" && selection && !row.disabled) {
+                    lastToggledRef.current = row.key;
+                    selection.onSelect([row.key], !selection.selected.has(row.key));
+                }
+                break;
+            case "Delete":
+                if (!mutations) break;
+                if (selection && selection.selected.size > 0) {
+                    // A selection takes precedence over the focused row —
+                    // no deleteKeys handler means no keyboard bulk delete
+                    // (never silently fall back to the focused file).
+                    mutations.deleteKeys?.(Array.from(selection.selected));
+                    break;
+                }
+                if (row?.kind === "file" && !row.disabled) {
+                    mutations.deleteFile(row.key);
+                } else if (row?.kind === "folder") {
+                    mutations.deleteFolder(row.path, row.count);
+                }
+                break;
+        }
+    };
+
     return (
-        <ul className="flex flex-col divide-y divide-gray-700/60 text-xs">
-            {nodes.map((n) => renderNode(n, 0))}
-        </ul>
+        <div
+            ref={wrapRef}
+            tabIndex={0}
+            onKeyDown={onListKeyDown}
+            className="focus:outline-hidden focus-visible:ring-1 focus-visible:ring-blue-500/40 rounded-sm"
+            // Background (non-row) drops land at root: internal drags
+            // move to root, OS files upload at top level. Folder rows
+            // stopPropagation when they handle a drop themselves.
+            onDragOver={mutations ? (e) => {
+                if (acceptsDrop(e)) e.preventDefault();
+            } : undefined}
+            onDrop={mutations ? (e) => handleDrop("", e) : undefined}
+        >
+            {mutations?.uploadTo && (
+                <input
+                    ref={uploadInputRef}
+                    type="file"
+                    multiple
+                    className="hidden"
+                    onChange={(e) => {
+                        const picked = Array.from(e.target.files ?? []);
+                        e.target.value = "";
+                        if (picked.length > 0) {
+                            mutations.uploadTo!(uploadTargetRef.current, picked);
+                        }
+                    }}
+                />
+            )}
+            {showRootDropStrip && (
+                <div
+                    className={
+                        "mb-1 px-2 py-1 text-[11px] text-gray-300 rounded-sm " +
+                        "border border-dashed border-blue-500/60 bg-blue-900/20"
+                    }
+                    onDragOver={(e) => {
+                        e.preventDefault();
+                        e.dataTransfer.dropEffect = "move";
+                    }}
+                    onDrop={(e) => handleDrop("", e)}
+                >
+                    Drop here to move to root /
+                </div>
+            )}
+            <ul className="flex flex-col divide-y divide-gray-700/60 text-xs">
+                {newFolderAt === "" && newFolderInputRow("", 0)}
+                {nodes.map((n) => renderNode(n, 0))}
+            </ul>
+        </div>
     );
 }
 
diff --git a/src/frontend/src/components/common/FolderPickerModal.tsx b/src/frontend/src/components/common/FolderPickerModal.tsx
index e6e331c4b..983623b2e 100644
--- a/src/frontend/src/components/common/FolderPickerModal.tsx
+++ b/src/frontend/src/components/common/FolderPickerModal.tsx
@@ -33,13 +33,21 @@ export interface FolderPickerModalProps {
     /** Button label — defaults to "Move". Folder-rename / move-into
      *  flows pass a more specific verb. */
     submitLabel?: string;
+    /** Offer a "Top level (root)" choice and make it the default.
+     *  Used by upload-destination prompts where root is the common
+     *  case; ``onPick`` receives ``""`` when it's chosen. Move flows
+     *  leave this off (a move to "" is handled by drag-to-root). */
+    allowRoot?: boolean;
 }
 
+type PickMode = "root" | "existing" | "new";
+
 const FolderPickerModal: React.FC<FolderPickerModalProps> = ({
-    open, title, existingFolders, initialNew, onCancel, onPick, submitLabel,
+    open, title, existingFolders, initialNew, onCancel, onPick, submitLabel, allowRoot,
 }) => {
     const hasExisting = existingFolders.length > 0;
-    const [mode, setMode] = useState<"existing" | "new">(hasExisting ? "existing" : "new");
+    const defaultMode: PickMode = allowRoot ? "root" : hasExisting ? "existing" : "new";
+    const [mode, setMode] = useState<PickMode>(defaultMode);
     const [selected, setSelected] = useState<string>(existingFolders[0] ?? "");
     const [newPath, setNewPath] = useState<string>(initialNew ?? "");
     const newInputRef = useRef<HTMLInputElement>(null);
@@ -49,10 +57,10 @@ const FolderPickerModal: React.FC<FolderPickerModalProps> = ({
     // would see stale state.
     useEffect(() => {
         if (!open) return;
-        setMode(hasExisting ? "existing" : "new");
+        setMode(defaultMode);
         setSelected(existingFolders[0] ?? "");
         setNewPath(initialNew ?? "");
-    }, [open, hasExisting, existingFolders, initialNew]);
+    }, [open, defaultMode, existingFolders, initialNew]);
 
     // Focus the new-folder input the moment the user switches to
     // that mode, mirroring the prompt() ergonomics.
@@ -65,6 +73,10 @@ const FolderPickerModal: React.FC<FolderPickerModalProps> = ({
     if (!open) return null;
 
     const submit = () => {
+        if (mode === "root") {
+            onPick("");
+            return;
+        }
         const value = mode === "existing" ? selected : newPath;
         const trimmed = value.trim().replace(/^\/+|\/+$/g, "");
         if (!trimmed) return;
@@ -73,7 +85,10 @@ const FolderPickerModal: React.FC<FolderPickerModalProps> = ({
 
     return createPortal(
         <div
-            className="fixed inset-0 z-50 flex items-start justify-center bg-black/40 p-4 sm:p-8 overflow-y-auto"
+            // z-[70]: body-portaled, so it must clear the floating admin
+            // panel host (fixed z-[60]) — the corpus tab's move/upload
+            // destination prompts open from inside it.
+            className="fixed inset-0 z-[70] flex items-start justify-center bg-black/40 p-4 sm:p-8 overflow-y-auto"
             onMouseDown={(e) => {
                 // Click on backdrop dismisses. Stop propagation
                 // inside the panel itself so a stray mousedown there
@@ -89,6 +104,21 @@ const FolderPickerModal: React.FC<FolderPickerModalProps> = ({
                     {title}
                 </div>
                 <div className="px-4 py-3 space-y-3 text-sm">
+                    {allowRoot && (
+                        <label className="flex items-start gap-2 cursor-pointer">
+                            <input
+                                type="radio"
+                                checked={mode === "root"}
+                                onChange={() => setMode("root")}
+                                className="mt-1 shrink-0"
+                            />
+                            <div className="flex-1 min-w-0">
+                                <div className="text-gray-200">
+                                    Top level <span className="text-gray-400 font-mono text-xs">/</span>
+                                </div>
+                            </div>
+                        </label>
+                    )}
                     {hasExisting && (
                         <label className="flex items-start gap-2 cursor-pointer">
                             <input
@@ -158,8 +188,9 @@ const FolderPickerModal: React.FC<FolderPickerModalProps> = ({
                         onClick={submit}
                         className="px-3 py-1 rounded-sm bg-blue-700 hover:bg-blue-600 text-xs disabled:opacity-50"
                         disabled={
-                            (mode === "existing" && !selected.trim()) ||
-                            (mode === "new" && !newPath.trim())
+                            mode !== "root" &&
+                            ((mode === "existing" && !selected.trim()) ||
+                                (mode === "new" && !newPath.trim()))
                         }
                     >
                         {submitLabel ?? "Move"}
diff --git a/src/frontend/src/components/common/InlineNameInput.tsx b/src/frontend/src/components/common/InlineNameInput.tsx
new file mode 100644
index 000000000..afe59e075
--- /dev/null
+++ b/src/frontend/src/components/common/InlineNameInput.tsx
@@ -0,0 +1,52 @@
+import React, {useEffect, useRef} from "react";
+
+// Inline name editor used for file/folder rename and new-folder
+// creation. Enter commits, Escape (or blur) cancels. ``selectStem``
+// pre-selects the basename-without-extension so a quick type replaces
+// the name but keeps the extension. Shared by the storage panel and
+// the admin corpus tree.
+const InlineNameInput: React.FC<{
+    initial: string;
+    placeholder?: string;
+    selectStem?: boolean;
+    onCommit: (value: string) => void;
+    onCancel: () => void;
+}> = ({initial, placeholder, selectStem, onCommit, onCancel}) => {
+    const inputRef = useRef<HTMLInputElement>(null);
+    useEffect(() => {
+        const el = inputRef.current;
+        if (!el) return;
+        el.focus();
+        if (selectStem) {
+            const dot = initial.lastIndexOf(".");
+            el.setSelectionRange(0, dot > 0 ? dot : initial.length);
+        } else {
+            el.select();
+        }
+        // eslint-disable-next-line react-hooks/exhaustive-deps
+    }, []);
+    return (
+        <input
+            ref={inputRef}
+            type="text"
+            defaultValue={initial}
+            placeholder={placeholder}
+            className={
+                "flex-1 min-w-0 bg-gray-800 border border-blue-500 rounded-sm " +
+                "px-1 py-0.5 text-xs text-gray-100 focus:outline-hidden"
+            }
+            onClick={(e) => e.stopPropagation()}
+            onPointerDown={(e) => e.stopPropagation()}
+            onKeyDown={(e) => {
+                if (e.key === "Enter") {
+                    onCommit((e.target as HTMLInputElement).value);
+                } else if (e.key === "Escape") {
+                    onCancel();
+                }
+            }}
+            onBlur={onCancel}
+        />
+    );
+};
+
+export default InlineNameInput;
diff --git a/src/frontend/src/components/common/PositionedMenu.tsx b/src/frontend/src/components/common/PositionedMenu.tsx
index a21c59980..73080bb7c 100644
--- a/src/frontend/src/components/common/PositionedMenu.tsx
+++ b/src/frontend/src/components/common/PositionedMenu.tsx
@@ -75,10 +75,19 @@ export const PositionedMenu: React.FC<PositionedMenuProps> = ({
             if (anchor.kind === "rect") {
                 const rect = anchor.getRect();
                 if (!rect) return;
-                setStyle({
-                    top: rect.bottom + 4,
-                    right: window.innerWidth - rect.right,
-                });
+                const menu = menuRef.current;
+                const w = menu?.offsetWidth ?? 180;
+                const h = menu?.offsetHeight ?? 160;
+                // Right-align the menu to the button (opens leftward) by default, but clamp the left
+                // edge into the viewport so a button near the left edge — e.g. the Properties kebab in
+                // the left-anchored info box — doesn't spill off-screen. Same for the right edge.
+                let left = rect.right - w;
+                left = Math.max(8, Math.min(left, window.innerWidth - w - 8));
+                // Below the button unless there's no room, then flip above.
+                let top = rect.bottom + 4;
+                if (top + h > window.innerHeight - 8)
+                    top = Math.max(8, rect.top - h - 4);
+                setStyle({top, left});
                 return;
             }
             // Point anchor: clamp to the viewport so a right-click near
@@ -129,7 +138,10 @@ export const PositionedMenu: React.FC<PositionedMenuProps> = ({
         <div
             ref={menuRef}
             role="menu"
-            className="fixed z-50 min-w-[180px] rounded-sm border border-gray-700 bg-gray-800 shadow-lg text-gray-100"
+            // z-[70]: body-portaled, so it must clear the floating admin
+            // panel host (fixed z-[60]) — the corpus tab's kebab/context
+            // menus open from inside it.
+            className="fixed z-[70] min-w-[180px] rounded-sm border border-gray-700 bg-gray-800 shadow-lg text-gray-100"
             style={style}
             onClick={(e) => e.stopPropagation()}
             onContextMenu={(e) => e.preventDefault()}
diff --git a/src/frontend/src/components/conversion/ConversionProgress.tsx b/src/frontend/src/components/conversion/ConversionProgress.tsx
index 5a40457cd..63a4ca160 100644
--- a/src/frontend/src/components/conversion/ConversionProgress.tsx
+++ b/src/frontend/src/components/conversion/ConversionProgress.tsx
@@ -6,6 +6,8 @@ import {useViewerPanelStore} from "@/state/viewerPanelStore";
 import {useScopeStore, scopeUrlPart} from "@/state/scopeStore";
 import {viewerApi} from "@/services/viewerApi";
 import {useLoadQueueStore, type LoadTask} from "@/state/loadQueueStore";
+import {useAuditToastStore} from "@/state/auditToastStore";
+import {useGalleryStore} from "@/state/galleryStore";
 
 // Shared dismiss button. Hit area is 28×28 (Apple HIG min is 44 but
 // the toast is dense; 28 still beats the 24 we shipped with and stays
@@ -580,6 +582,7 @@ function fmtCellElapsed(ms: number | null): string {
 const AuditActivityBadge: React.FC = () => {
     const isAdmin = useMeStore((s) => s.isAdmin);
     const openPanel = useViewerPanelStore((s) => s.openPanel);
+    const toastHidden = useAuditToastStore((s) => s.hidden);
     const [summary, setSummary] = useState<AuditActiveSummary | null>(null);
 
     useEffect(() => {
@@ -610,7 +613,7 @@ const AuditActivityBadge: React.FC = () => {
         };
     }, [isAdmin, summary && summary.running_runs > 0]);
 
-    if (!isAdmin || !summary || summary.running_runs === 0) return null;
+    if (!isAdmin || toastHidden || !summary || summary.running_runs === 0) return null;
     const {running_runs, pending_cells, current_cell} = summary;
     return (
         <button
@@ -665,6 +668,9 @@ const ConversionProgress = () => {
     const removeQueued = useLoadQueueStore((s) => s.removeQueued);
     const clearError = useLoadQueueStore((s) => s.clearError);
     const loadCurrentName = loadCurrent?.name ?? null;
+    // On mobile the gallery HUD is a bottom bar; lift the toast stack above it so the audit toast
+    // stacks on top of the gallery menu instead of overlapping. 0 (desktop/gallery-off) => default.
+    const galleryBarHeight = useGalleryStore((s) => s.mobileBarHeight);
 
     // The in-scene GLB download/parse is tracked as a conversionStore job under a
     // sentinel key (asyncModelLoader's LOAD_KEY). It's the SAME activity as the
@@ -722,7 +728,10 @@ const ConversionProgress = () => {
         // From the ``sm:`` breakpoint up we revert to the desktop
         // floating-pill style — anchored to the right, capped at
         // ``max-w-sm`` (24rem).
-        <div className="absolute bottom-4 left-4 right-4 sm:left-auto sm:max-w-sm z-50 flex flex-col gap-2 pointer-events-auto">
+        <div
+            className="absolute bottom-4 left-4 right-4 sm:left-auto sm:max-w-sm z-50 flex flex-col gap-2 pointer-events-auto"
+            style={galleryBarHeight > 0 ? {bottom: galleryBarHeight + 16} : undefined}
+        >
             <AuditActivityBadge/>
             {visibleSweeps.map(([scopeLabel, state]) => (
                 <CompressionToast
diff --git a/src/frontend/src/components/convert/ConversionRow.tsx b/src/frontend/src/components/convert/ConversionRow.tsx
index dd7712660..891464d3f 100644
--- a/src/frontend/src/components/convert/ConversionRow.tsx
+++ b/src/frontend/src/components/convert/ConversionRow.tsx
@@ -1,7 +1,9 @@
 import React, {useCallback, useEffect, useMemo, useState} from "react";
-import {convertViaServer} from "@/services/conversion/serverPipeline";
+import {convertWithSelection} from "@/services/conversion";
 import {viewerApi, TargetFormat} from "@/services/viewerApi";
 import {runtime, ConversionOption} from "@/runtime/config";
+import {SerializerTessellatorSelect} from "@/components/convert/SerializerTessellatorSelect";
+import type {SerializerSelection} from "@/services/conversion/serializerMatrix";
 import {useConversionStore} from "@/state/conversionStore";
 import {useConvertPageStore, ConvertRow} from "@/state/convertPageStore";
 import {scopeUrlPart, useScopeStore} from "@/state/scopeStore";
@@ -148,6 +150,10 @@ const ConversionRow: React.FC<{row: ConvertRow}> = ({row}) => {
     // Reset whenever ``target`` changes since the option schema is
     // (from, to)-specific.
     const [optionValues, setOptionValues] = useState<Record<string, OptionValue>>({});
+    // Serializer/tessellator pick — rendered as its own paired dropdowns
+    // (SerializerTessellatorSelect), not through the generic OptionWidget loop,
+    // because the tessellator choices depend on the serializer.
+    const [serializerSel, setSerializerSel] = useState<SerializerSelection>({});
 
     // Use the row's `target` if set, else the best-guess default.
     const target: TargetFormat = row.target ?? suggestedTarget(ext);
@@ -186,6 +192,7 @@ const ConversionRow: React.FC<{row: ConvertRow}> = ({row}) => {
     // new target's option set.
     useEffect(() => {
         setOptionValues({});
+        setSerializerSel({});
     }, [target]);
 
     const onConvert = useCallback(async () => {
@@ -200,11 +207,15 @@ const ConversionRow: React.FC<{row: ConvertRow}> = ({row}) => {
             for (const [k, v] of Object.entries(optionValues)) {
                 if (v !== undefined) conversionOptions[k] = v;
             }
-            await convertViaServer(
+            // convertWithSelection routes the serializer pick to the server or
+            // the in-browser (WASM/Pyodide) pipeline and folds the remaining
+            // option widgets in as extraOptions.
+            await convertWithSelection(
                 scopeUrlPart(current), row.sourceKey, target,
-                Object.keys(conversionOptions).length
-                    ? {conversionOptions}
-                    : undefined,
+                {
+                    selection: serializerSel,
+                    extraOptions: Object.keys(conversionOptions).length ? conversionOptions : undefined,
+                },
             );
         } catch (e) {
             // convertViaServer already writes the error to the
@@ -215,7 +226,7 @@ const ConversionRow: React.FC<{row: ConvertRow}> = ({row}) => {
         } finally {
             setSubmitting(false);
         }
-    }, [current, row.sourceKey, target, optionValues]);
+    }, [current, row.sourceKey, target, optionValues, serializerSel]);
 
     const onDownload = useCallback(async () => {
         if (!current || !job?.derivedKey) return;
@@ -343,15 +354,26 @@ const ConversionRow: React.FC<{row: ConvertRow}> = ({row}) => {
                     <span className="text-[11px] uppercase tracking-wider text-gray-500">
                         options
                     </span>
-                    {optionSchema.map((opt) => (
-                        <OptionWidget
-                            key={opt.name}
-                            opt={opt}
-                            value={optionValues[opt.name]}
-                            onChange={(v) => setOptionValues((prev) => ({...prev, [opt.name]: v}))}
-                            disabled={isRunning || submitting}
-                        />
-                    ))}
+                    {/* serializer + tessellator are a dependent pair — rendered by the shared
+                        component, not the generic widget loop. */}
+                    <SerializerTessellatorSelect
+                        ext={ext}
+                        target={target}
+                        value={serializerSel}
+                        onChange={setSerializerSel}
+                        disabled={isRunning || submitting}
+                    />
+                    {optionSchema
+                        .filter((opt) => opt.name !== "serializer" && opt.name !== "tessellator")
+                        .map((opt) => (
+                            <OptionWidget
+                                key={opt.name}
+                                opt={opt}
+                                value={optionValues[opt.name]}
+                                onChange={(v) => setOptionValues((prev) => ({...prev, [opt.name]: v}))}
+                                disabled={isRunning || submitting}
+                            />
+                        ))}
                 </div>
             )}
 
diff --git a/src/frontend/src/components/convert/SerializerTessellatorSelect.tsx b/src/frontend/src/components/convert/SerializerTessellatorSelect.tsx
new file mode 100644
index 000000000..ec2153d51
--- /dev/null
+++ b/src/frontend/src/components/convert/SerializerTessellatorSelect.tsx
@@ -0,0 +1,97 @@
+import React, {useCallback} from "react";
+import {
+    SerializerSelection,
+    serializerSchemaFor,
+    tessellatorsFor,
+    normalizeSelection,
+} from "@/services/conversion/serializerMatrix";
+
+// Two dependent dropdowns — Serializer × Tessellator — rendered entirely from
+// the backend-advertised matrix (labels + enum_by), never from a hardcoded
+// list. Changing the serializer repopulates the tessellator to the first
+// kernel that serializer allows. Shared by the gallery reconvert tool and the
+// /convert page ConversionRow so the two stay in lockstep.
+//
+// Emits a full {serializer, tessellator} pair on every change. The parent
+// decides routing (server vs in-browser) via serializerMatrix.normalizeSelection.
+export const SerializerTessellatorSelect: React.FC<{
+    ext: string;
+    target: string;
+    value: SerializerSelection;
+    onChange: (v: SerializerSelection) => void;
+    disabled?: boolean;
+    compact?: boolean;
+}> = ({ext, target, value, onChange, disabled = false, compact = false}) => {
+    const schema = serializerSchemaFor(ext, target);
+
+    const onSerializer = useCallback(
+        (serializer: string) => {
+            if (!schema) return;
+            // Reselect the tessellator to the first kernel this serializer allows.
+            const allowed = tessellatorsFor(schema, serializer);
+            onChange({serializer, tessellator: allowed[0]});
+        },
+        [schema, onChange],
+    );
+
+    const onTessellator = useCallback(
+        (tessellator: string) => {
+            if (!schema) return;
+            const {serializer} = normalizeSelection(schema, value);
+            onChange({serializer, tessellator});
+        },
+        [schema, value, onChange],
+    );
+
+    if (!schema) return null;
+
+    const {serializer, tessellator} = normalizeSelection(schema, value);
+    const tessTokens = tessellatorsFor(schema, serializer);
+    const serLabels = schema.serializer.labels ?? {};
+    const tessLabels = schema.tessellator.labels ?? {};
+    // Axis display names come from the backend (single source): "Tessellator" for mesh targets,
+    // "Writer" for B-rep targets. Fall back to the option name.
+    const serTitle = (schema.serializer.title ?? "serializer").toLowerCase();
+    const tessTitle = (schema.tessellator.title ?? schema.tessellator.name).toLowerCase();
+
+    const selCls = compact
+        ? "rounded-sm border border-gray-600 bg-gray-800 px-1 py-0.5 text-[11px] text-gray-100"
+        : "bg-gray-900 border border-gray-600 rounded-sm px-1 py-0.5 text-xs text-gray-100";
+    const lblCls = compact
+        ? "flex items-center gap-1 text-[11px] text-gray-300"
+        : "inline-flex items-center gap-1 text-xs text-gray-300";
+
+    return (
+        <>
+            <label className={lblCls} title={schema.serializer.description || serTitle}>
+                <span>{serTitle}:</span>
+                <select
+                    aria-label="Serializer"
+                    className={selCls}
+                    value={serializer}
+                    onChange={(e) => onSerializer(e.target.value)}
+                    disabled={disabled}
+                >
+                    {(schema.serializer.enum ?? []).map((v) => (
+                        <option key={v} value={v}>{serLabels[v] ?? v}</option>
+                    ))}
+                </select>
+            </label>
+            <label className={lblCls} title={schema.tessellator.description || tessTitle}>
+                <span>{tessTitle}:</span>
+                <select
+                    aria-label="Tessellator"
+                    className={selCls}
+                    value={tessellator}
+                    onChange={(e) => onTessellator(e.target.value)}
+                    // Pinned kernel (cpp): a single choice — show it, but there's nothing to pick.
+                    disabled={disabled || tessTokens.length <= 1}
+                >
+                    {tessTokens.map((v) => (
+                        <option key={v} value={v}>{tessLabels[v] ?? v}</option>
+                    ))}
+                </select>
+            </label>
+        </>
+    );
+};
diff --git a/src/frontend/src/components/info_box_scene/FacePickingToggle.tsx b/src/frontend/src/components/info_box_scene/FacePickingToggle.tsx
new file mode 100644
index 000000000..034c1b9aa
--- /dev/null
+++ b/src/frontend/src/components/info_box_scene/FacePickingToggle.tsx
@@ -0,0 +1,55 @@
+import React from "react";
+import {useOptionsStore} from "@/state/optionsStore";
+import {clearFaceHighlight} from "@/utils/mesh_select/faceHighlight";
+import {useObjectInfoStore} from "@/state/objectInfoStore";
+import {useSelectedObjectStore} from "@/state/useSelectedObjectStore";
+
+// Solid/Faces picking mode. Only rendered when the loaded model carries per-face regions
+// (face_ranges extras). "Faces" routes clicks through the raycast path so the exact source face
+// (STEP/IFC #id) resolves and shows in the object Properties panel — useful for pinpointing a
+// mis-tessellated face. "Solid" keeps the fast GPU object-pick.
+const FacePickingToggle: React.FC = () => {
+    const available = useOptionsStore((s) => s.faceRegionsAvailable);
+    const faces = useOptionsStore((s) => s.faceLevelPicking);
+    const setFaces = useOptionsStore((s) => s.setFaceLevelPicking);
+    if (!available) return null;
+
+    const btn = (active: boolean) =>
+        "flex-1 px-2 py-0.5 text-xs rounded-sm transition-colors " +
+        (active ? "bg-blue-700 text-white" : "bg-gray-700 text-gray-200 hover:bg-gray-600");
+
+    return (
+        <div className="flex items-center gap-2 py-1">
+            <span className="text-xs text-gray-300">Click picks:</span>
+            <div className="flex gap-1 flex-1" role="group" aria-label="Click picking mode">
+                <button
+                    type="button"
+                    className={btn(!faces)}
+                    onClick={() => {
+                        setFaces(false);
+                        clearFaceHighlight();
+                        useObjectInfoStore.getState().setClickedFace(null);
+                    }}
+                    aria-pressed={!faces}
+                >
+                    Solid
+                </button>
+                <button
+                    type="button"
+                    className={btn(faces)}
+                    onClick={() => {
+                        setFaces(true);
+                        // Drop any whole-object selection so Faces mode starts clean (only the next
+                        // clicked face gets the blue highlight).
+                        useSelectedObjectStore.getState().clearSelectedObjects();
+                    }}
+                    aria-pressed={faces}
+                >
+                    Faces
+                </button>
+            </div>
+        </div>
+    );
+};
+
+export default FacePickingToggle;
diff --git a/src/frontend/src/components/info_box_scene/MeshDistortionSection.tsx b/src/frontend/src/components/info_box_scene/MeshDistortionSection.tsx
new file mode 100644
index 000000000..cf93715a2
--- /dev/null
+++ b/src/frontend/src/components/info_box_scene/MeshDistortionSection.tsx
@@ -0,0 +1,244 @@
+import React, {useCallback, useEffect, useMemo, useRef, useState} from "react";
+import {useMeshPanelStore} from "@/state/meshPanelStore";
+import {useOptionsStore} from "@/state/optionsStore";
+import CollapsibleSection from "@/components/common/CollapsibleSection";
+import {collectGeomEntries, focusGeomEntry, endGeomWalk, type GeomEntry} from "@/utils/scene/galleryWalk";
+import {queryNameFromRangeId} from "@/utils/mesh_select/queryMeshDrawRange";
+import {refreshEdgeOverlays} from "@/utils/scene/refreshEdgeOverlays";
+
+// "Mesh" mode of the Scene panel (Scene dropdown → Mesh). Scans every geom in the scene for
+// "crows-nest" tessellation spikes — the same detector the gallery "distorted" walk uses
+// (utils/mesh_select/meshStats) — and lists the offenders in a distortion-sorted table. The two
+// spike thresholds are editable; "Rescan" re-runs at the current thresholds. Clicking a row selects
+// + frames that geom (triangle edges on) so the spike is visible. Rendered inside SceneInfoBox, which
+// supplies the panel chrome + the mode dropdown — so this is a bare section, no outer chrome.
+
+interface Row {
+    mesh: GeomEntry["mesh"];
+    rangeId: string;
+    triangles: number;
+    spike: number;
+    spikeTris: number;
+    name: string;
+}
+
+type SortKey = "spike" | "spikeTris" | "triangles" | "name";
+
+const num = (n: number, digits = 1) => (Number.isFinite(n) ? n.toFixed(digits) : "—");
+
+const MeshDistortionSection: React.FC = () => {
+    const {spikeAspectMin, spikeOutlierK, setSpikeAspectMin, setSpikeOutlierK, resetThresholds} =
+        useMeshPanelStore();
+    const {showEdges, setShowEdges, hideTessellationEdges, setHideTessellationEdges} = useOptionsStore();
+
+    const [rows, setRows] = useState<Row[]>([]);
+    const [scanning, setScanning] = useState(false);
+    const [scanned, setScanned] = useState(false);
+    const [isolate, setIsolate] = useState(false);
+    const [sortKey, setSortKey] = useState<SortKey>("spike");
+    const [sortDir, setSortDir] = useState<"asc" | "desc">("desc");
+    const [selectedRange, setSelectedRange] = useState<string | null>(null);
+    const scanSeq = useRef(0);
+
+    const rescan = useCallback(async () => {
+        const seq = ++scanSeq.current;
+        setScanning(true);
+        const entries = collectGeomEntries("distorted", {spikeAspectMin, spikeOutlierK});
+        if (scanSeq.current !== seq) return;
+        const base: Row[] = entries.map((e) => ({
+            mesh: e.mesh,
+            rangeId: e.rangeId,
+            triangles: e.triangles,
+            spike: e.spike,
+            spikeTris: e.spikeTris,
+            name: e.rangeId,
+        }));
+        setRows(base);
+        setScanning(false);
+        setScanned(true);
+        const names = await Promise.all(
+            base.map((r) => queryNameFromRangeId(r.mesh.unique_key, r.rangeId).catch(() => null)),
+        );
+        if (scanSeq.current !== seq) return;
+        setRows(base.map((r, i) => ({...r, name: names[i] || r.rangeId})));
+    }, [spikeAspectMin, spikeOutlierK]);
+
+    // Scan once when the Mesh mode is opened. Threshold edits don't auto-rescan (avoid a heavy
+    // full-scene scan on every keystroke) — the user hits Rescan.
+    useEffect(() => {
+        void rescan();
+        // eslint-disable-next-line react-hooks/exhaustive-deps
+    }, []);
+
+    const sorted = useMemo(() => {
+        const dir = sortDir === "desc" ? -1 : 1;
+        return [...rows].sort((a, b) => {
+            if (sortKey === "name") return dir * a.name.localeCompare(b.name);
+            return dir * (a[sortKey] - b[sortKey]);
+        });
+    }, [rows, sortKey, sortDir]);
+
+    const onSort = (key: SortKey) => {
+        if (key === sortKey) setSortDir((d) => (d === "desc" ? "asc" : "desc"));
+        else {
+            setSortKey(key);
+            setSortDir(key === "name" ? "asc" : "desc");
+        }
+    };
+
+    const onRowClick = (r: Row) => {
+        setSelectedRange(r.rangeId);
+        void focusGeomEntry(
+            {mesh: r.mesh, rangeId: r.rangeId, triangles: r.triangles, density: 0, spike: r.spike, spikeTris: r.spikeTris},
+            {hideUnselected: isolate, forceEdges: true},
+        );
+    };
+
+    const sortArrow = (key: SortKey) => (sortKey === key ? (sortDir === "desc" ? " ▼" : " ▲") : "");
+    const thClass = "sticky top-0 bg-gray-800 px-2 py-1 text-left font-semibold cursor-pointer select-none whitespace-nowrap";
+
+    return (
+        <div className="space-y-1">
+            <CollapsibleSection title="Options" defaultOpen>
+                <div className="space-y-2 pt-1">
+                    {/* Mesh triangle visibility — see the triangulation to judge tessellation/welding.
+                        Both rebuild the edge overlays live (no page/model reload). */}
+                    <div className="flex items-center gap-4 text-sm">
+                        <label className="flex items-center space-x-1">
+                            <input
+                                type="checkbox"
+                                className="no-drag"
+                                checked={showEdges}
+                                onChange={() => {
+                                    setShowEdges(!showEdges);
+                                    refreshEdgeOverlays();
+                                }}
+                            />
+                            <span>Mesh edges</span>
+                        </label>
+                        <label
+                            className="flex items-center space-x-1"
+                            title="Show every triangle edge (the tessellation grid), not just feature edges."
+                        >
+                            <input
+                                type="checkbox"
+                                className="no-drag"
+                                checked={!hideTessellationEdges}
+                                onChange={() => {
+                                    setHideTessellationEdges(!hideTessellationEdges);
+                                    refreshEdgeOverlays();
+                                }}
+                            />
+                            <span>Triangles</span>
+                        </label>
+                    </div>
+
+                    {/* Thresholds — edit then Rescan. */}
+                    <label className="flex items-center space-x-2 text-sm">
+                        <span className="w-40">Thin-triangle aspect ≥</span>
+                        <input
+                            type="range" min={1} max={50} step={1}
+                            value={spikeAspectMin}
+                            onChange={(e) => setSpikeAspectMin(parseFloat(e.target.value))}
+                            className="flex-1 no-drag"
+                        />
+                        <input
+                            type="number" min={1} max={50} step={1}
+                            value={spikeAspectMin}
+                            onChange={(e) => setSpikeAspectMin(parseFloat(e.target.value) || 1)}
+                            className="w-20 bg-gray-700 text-white p-1 rounded-sm no-drag"
+                        />
+                    </label>
+                    <label className="flex items-center space-x-2 text-sm">
+                        <span className="w-40">Outlier vertex K ≥</span>
+                        <input
+                            type="range" min={1} max={20} step={0.5}
+                            value={spikeOutlierK}
+                            onChange={(e) => setSpikeOutlierK(parseFloat(e.target.value))}
+                            className="flex-1 no-drag"
+                        />
+                        <input
+                            type="number" min={1} max={20} step={0.5}
+                            value={spikeOutlierK}
+                            onChange={(e) => setSpikeOutlierK(parseFloat(e.target.value) || 1)}
+                            className="w-20 bg-gray-700 text-white p-1 rounded-sm no-drag"
+                        />
+                    </label>
+                    <div className="flex items-center gap-2">
+                        <button
+                            className="bg-blue-700 pointer-fine:hover:bg-blue-600 text-white px-3 py-1 rounded-sm no-drag disabled:opacity-50"
+                            onClick={() => void rescan()}
+                            disabled={scanning}
+                        >
+                            {scanning ? "Scanning…" : "Rescan"}
+                        </button>
+                        <button
+                            className="bg-gray-700 pointer-fine:hover:bg-gray-600 text-white px-3 py-1 rounded-sm no-drag"
+                            onClick={resetThresholds}
+                            title="Reset thresholds to the gallery defaults"
+                        >
+                            Reset
+                        </button>
+                        <label className="flex items-center space-x-1 ml-auto">
+                            <input type="checkbox" className="no-drag" checked={isolate} onChange={() => setIsolate((v) => !v)}/>
+                            <span>Isolate</span>
+                        </label>
+                        <button
+                            className="bg-gray-700 pointer-fine:hover:bg-gray-600 text-white px-2 py-1 rounded-sm no-drag"
+                            onClick={() => {
+                                setSelectedRange(null);
+                                endGeomWalk();
+                            }}
+                            title="Clear selection / un-isolate"
+                        >
+                            Clear
+                        </button>
+                    </div>
+                </div>
+            </CollapsibleSection>
+
+            {/* Results table — collapsible, default collapsed; y-overflow, sortable, distortion-sorted. */}
+            <CollapsibleSection
+                title={`Distorted geoms${scanned ? ` (${rows.length})` : ""}${scanning ? " — scanning…" : ""}`}
+                defaultOpen={false}
+            >
+                {rows.length === 0 ? (
+                    <div className="text-sm text-gray-400 py-4 text-center">
+                        {scanning ? "Scanning scene…" : "No distorted geoms at these thresholds."}
+                    </div>
+                ) : (
+                    <div className="max-h-[50vh] overflow-y-auto border border-gray-700 rounded-sm">
+                        <table className="w-full text-xs border-collapse">
+                            <thead>
+                                <tr>
+                                    <th className={thClass} onClick={() => onSort("name")}>Geom{sortArrow("name")}</th>
+                                    <th className={`${thClass} text-right`} onClick={() => onSort("spike")}>Spike{sortArrow("spike")}</th>
+                                    <th className={`${thClass} text-right`} onClick={() => onSort("spikeTris")}>Spike tris{sortArrow("spikeTris")}</th>
+                                    <th className={`${thClass} text-right`} onClick={() => onSort("triangles")}>Tris{sortArrow("triangles")}</th>
+                                </tr>
+                            </thead>
+                            <tbody>
+                                {sorted.map((r) => (
+                                    <tr
+                                        key={`${r.mesh.unique_key}|${r.rangeId}`}
+                                        className={`cursor-pointer pointer-fine:hover:bg-gray-700 ${
+                                            selectedRange === r.rangeId ? "bg-blue-900" : ""
+                                        }`}
+                                        onClick={() => onRowClick(r)}
+                                    >
+                                        <td className="px-2 py-1 max-w-56 truncate" title={r.name}>{r.name}</td>
+                                        <td className="px-2 py-1 text-right font-mono">{num(r.spike)}</td>
+                                        <td className="px-2 py-1 text-right font-mono">{r.spikeTris}</td>
+                                        <td className="px-2 py-1 text-right font-mono">{r.triangles}</td>
+                                    </tr>
+                                ))}
+                            </tbody>
+                        </table>
+                    </div>
+                )}
+            </CollapsibleSection>
+        </div>
+    );
+};
+
+export default MeshDistortionSection;
diff --git a/src/frontend/src/components/info_box_scene/SceneInfoBox.tsx b/src/frontend/src/components/info_box_scene/SceneInfoBox.tsx
index 0cea5d2ec..45e17acb4 100644
--- a/src/frontend/src/components/info_box_scene/SceneInfoBox.tsx
+++ b/src/frontend/src/components/info_box_scene/SceneInfoBox.tsx
@@ -6,8 +6,10 @@ import LoadedModelsSection from "./LoadedModelsSection";
 import StatsSection from "./StatsSection";
 import GroupsSection from "./GroupsSection";
 import UtilitiesSection from "./UtilitiesSection";
+import FacePickingToggle from "./FacePickingToggle";
 import SectionPlanesPanel from "./SectionPlanesPanel";
 import FemConceptsPanel from "./FemConceptsPanel";
+import MeshDistortionSection from "./MeshDistortionSection";
 import {useSceneInfoStore} from "@/state/sceneInfoStore";
 
 // Container for everything that talks about the currently-loaded scene
@@ -26,12 +28,13 @@ const SceneInfoBox = () => {
                 <select
                     className="text-sm rounded-sm px-1 py-0.5 bg-gray-700 text-gray-100 border border-gray-600"
                     value={mode}
-                    onChange={(e) => setMode(e.target.value as "info" | "utilities" | "section" | "fem")}
+                    onChange={(e) => setMode(e.target.value as "info" | "utilities" | "section" | "fem" | "mesh")}
                 >
                     <option value="info">Info</option>
                     <option value="utilities">Utilities</option>
                     <option value="section">Section</option>
                     <option value="fem">FEM</option>
+                    <option value="mesh">Mesh</option>
                 </select>
             </div>
             {/* Flat list of every loaded model, whatever storage folder
@@ -42,6 +45,7 @@ const SceneInfoBox = () => {
             </CollapsibleSection>
             {mode === "info" ? (
                 <>
+                    <FacePickingToggle/>
                     <CollapsibleSection title="Stats" defaultOpen>
                         <StatsSection/>
                     </CollapsibleSection>
@@ -53,6 +57,8 @@ const SceneInfoBox = () => {
                 <UtilitiesSection/>
             ) : mode === "section" ? (
                 <SectionPlanesPanel/>
+            ) : mode === "mesh" ? (
+                <MeshDistortionSection/>
             ) : (
                 <FemConceptsPanel/>
             )}
diff --git a/src/frontend/src/components/info_box_selected_object/MeshStatsSection.tsx b/src/frontend/src/components/info_box_selected_object/MeshStatsSection.tsx
new file mode 100644
index 000000000..b20375b99
--- /dev/null
+++ b/src/frontend/src/components/info_box_selected_object/MeshStatsSection.tsx
@@ -0,0 +1,105 @@
+// Collapsible "Mesh" section for the selection inspector — tessellation
+// stats for the currently-selected geom(s), computed client-side from
+// the batched geometry buffer (no server round-trip). Aggregates across
+// a multi-selection: total triangles / vertices / surface area, and the
+// mesh density (triangles per m²) that the gallery "density" walk sorts
+// by. Renders nothing when the selection has no triangle geometry.
+
+import React, {useState} from "react";
+
+import {useViewerStores} from "@/state/AdaViewerContext";
+import {CustomBatchedMesh} from "@/utils/mesh_select/CustomBatchedMesh";
+import {computeRangeStats} from "@/utils/mesh_select/meshStats";
+
+const Chevron: React.FC<{open: boolean}> = ({open}) => (
+    <svg
+        width="10"
+        height="10"
+        viewBox="0 0 10 10"
+        aria-hidden="true"
+        className={`transition-transform ${open ? "rotate-90" : ""}`}
+    >
+        <path d="M3 1l4 4-4 4" stroke="currentColor" strokeWidth="1.4" fill="none" />
+    </svg>
+);
+
+const fmtInt = (v: number): string => Math.round(v).toLocaleString();
+
+// Compact SI-ish number: keep 3 significant figures without scientific
+// notation for the everyday range.
+const fmtNum = (v: number): string => {
+    if (!isFinite(v) || v === 0) return "0";
+    const abs = Math.abs(v);
+    if (abs >= 1000 || abs < 0.001) return v.toPrecision(3);
+    return v.toFixed(abs >= 100 ? 1 : abs >= 1 ? 2 : 3);
+};
+
+const Row: React.FC<{label: string; children: React.ReactNode}> = ({label, children}) => (
+    <tr>
+        <td className="pr-3 text-gray-500 align-top whitespace-nowrap">{label}</td>
+        <td className="font-mono text-gray-200">{children}</td>
+    </tr>
+);
+
+interface Agg {
+    geoms: number;
+    triangles: number;
+    vertices: number;
+    area: number;
+    volume: number;
+}
+
+const MeshStatsSection: React.FC = () => {
+    const {useSelectedObjectStore} = useViewerStores();
+    const selectedObjects = useSelectedObjectStore((s) => s.selectedObjects);
+    const [expanded, setExpanded] = useState(false);
+
+    const agg: Agg = {geoms: 0, triangles: 0, vertices: 0, area: 0, volume: 0};
+    selectedObjects.forEach((rangeIds, obj) => {
+        if (!(obj instanceof CustomBatchedMesh)) return;
+        rangeIds.forEach((rangeId) => {
+            const s = computeRangeStats(obj, rangeId);
+            if (!s) return;
+            agg.geoms += 1;
+            agg.triangles += s.triangles;
+            agg.vertices += s.vertices;
+            agg.area += s.area;
+            agg.volume += s.volume;
+        });
+    });
+
+    if (agg.geoms === 0) return null;
+
+    const density = agg.area > 0 ? agg.triangles / agg.area : 0;
+
+    return (
+        <div className="mt-2">
+            <button
+                type="button"
+                onClick={() => setExpanded((v) => !v)}
+                className="flex items-center gap-1 text-[12px] text-gray-100 hover:text-white"
+                aria-expanded={expanded}
+                aria-controls="object-mesh-stats"
+            >
+                <Chevron open={expanded} />
+                <span className="font-semibold">Mesh ({fmtInt(agg.triangles)} tris)</span>
+            </button>
+            {expanded && (
+                <div id="object-mesh-stats" className="mt-1 ml-4">
+                    <table className="text-[11px] border-separate border-spacing-y-0.5">
+                        <tbody>
+                            {agg.geoms > 1 && <Row label="Geoms:">{fmtInt(agg.geoms)}</Row>}
+                            <Row label="Triangles:">{fmtInt(agg.triangles)}</Row>
+                            <Row label="Vertices:">{fmtInt(agg.vertices)}</Row>
+                            <Row label="Surface area:">{fmtNum(agg.area)} m²</Row>
+                            <Row label="BBox volume:">{fmtNum(agg.volume)} m³</Row>
+                            <Row label="Density:">{fmtNum(density)} tris/m²</Row>
+                        </tbody>
+                    </table>
+                </div>
+            )}
+        </div>
+    );
+};
+
+export default MeshStatsSection;
diff --git a/src/frontend/src/components/info_box_selected_object/ObjectMetadataPanel.tsx b/src/frontend/src/components/info_box_selected_object/ObjectMetadataPanel.tsx
index bd43bf302..a48c00a50 100644
--- a/src/frontend/src/components/info_box_selected_object/ObjectMetadataPanel.tsx
+++ b/src/frontend/src/components/info_box_selected_object/ObjectMetadataPanel.tsx
@@ -2,11 +2,23 @@ import React, {useState} from 'react';
 import {selectInOtherModel} from '@/utils/scene/crossModelSelect';
 import type {LinkResult} from '@/state/lineageStore';
 import {useViewerStores} from '@/state/AdaViewerContext';
+import {useOptionsStore} from '@/state/optionsStore';
+import RowKebabMenu, {KebabMenuItem} from '@/components/common/RowKebabMenu';
+import {writeToClipboard} from '@/utils/clipboard/copySelectionNames';
 import ConnectionsSection from './ConnectionsSection';
+import MeshStatsSection from './MeshStatsSection';
 
-// Decimal places for the "Clicked at" coordinates, matching the
-// precision the old standalone block used before the fold-in.
-const COORD_PREC = 3;
+// Decimal-place choices offered in the Properties kebab menu for the "Clicked at" row. A small
+// model (a few units across) needs more decimals before nearby clicks show a different position.
+const DECIMAL_CHOICES = [1, 2, 3, 4, 6, 8];
+const COPIED_FEEDBACK_MS = 1500;
+
+const CheckIcon: React.FC = () => (
+    <svg viewBox="0 0 16 16" className="w-3.5 h-3.5" fill="none" stroke="currentColor"
+         strokeWidth="2" strokeLinecap="round" strokeLinejoin="round" aria-hidden>
+        <path d="M3 8.5l3.5 3.5L13 4"/>
+    </svg>
+);
 
 const Chevron: React.FC<{open: boolean}> = ({open}) => (
     <svg
@@ -203,20 +215,74 @@ const ClickedAtRow: React.FC = () => {
     const {useObjectInfoStore, useModelState} = useViewerStores();
     const clickCoord = useObjectInfoStore((s) => s.clickCoordinate);
     const zIsUp = useModelState((s) => s.zIsUp);
+    const decimals = useOptionsStore((s) => s.clickedCoordDecimals);
+    const [copied, setCopied] = useState(false);
     if (!clickCoord) return null;
-    const x = clickCoord.x.toFixed(COORD_PREC);
-    const y = clickCoord.y.toFixed(COORD_PREC);
-    const z = clickCoord.z.toFixed(COORD_PREC);
+    const x = clickCoord.x.toFixed(decimals);
+    const y = clickCoord.y.toFixed(decimals);
+    const z = clickCoord.z.toFixed(decimals);
     // Mirror the original axis-swap convention from CoordinateDisplay:
     // viewer scene is y-up by default, but adapy's Z-up world is what
     // users think in — so when zIsUp is set, show the world tuple
     // (x, y, z) directly; otherwise re-order to compensate.
-    const display = zIsUp ? `(${x}, ${y}, ${z})` : `(${x}, ${z}, ${y})`;
-    return <Row label="Clicked at:">{display}</Row>;
+    const ordered = zIsUp ? [x, y, z] : [x, z, y];
+    const display = `(${ordered.join(', ')})`;
+    // Clipboard gets the same numbers in the same displayed order, but as bare
+    // comma-separated floats (no parentheses) so they paste straight into code.
+    const onCopy = () => {
+        void writeToClipboard(ordered.join(', ')).then((ok) => {
+            if (!ok) return;
+            setCopied(true);
+            window.setTimeout(() => setCopied(false), COPIED_FEEDBACK_MS);
+        });
+    };
+    return (
+        <Row label="Clicked at:">
+            <button
+                type="button"
+                onClick={onCopy}
+                className="text-left text-gray-100 hover:text-white cursor-pointer"
+                title="Copy coordinates as comma-separated floats"
+            >
+                {copied ? `${display} ✓` : display}
+            </button>
+        </Row>
+    );
+};
+
+// Source face of the last click — shown only when face-level picking is on and a region resolved.
+// The #id is the STEP ADVANCED_FACE / IFC IfcFace entity id, so a mis-tessellated face can be named
+// exactly (not just "somewhere on this solid"); copyable for pasting into a bug report.
+const ClickedFaceRow: React.FC = () => {
+    const {useObjectInfoStore} = useViewerStores();
+    const face = useObjectInfoStore((s) => s.clickedFace);
+    const [copied, setCopied] = useState(false);
+    if (!face) return null;
+    const label = `#${face.faceId} (face ${face.seq})`;
+    const onCopy = () => {
+        void writeToClipboard(`#${face.faceId}`).then((ok) => {
+            if (!ok) return;
+            setCopied(true);
+            window.setTimeout(() => setCopied(false), COPIED_FEEDBACK_MS);
+        });
+    };
+    return (
+        <Row label="Face:">
+            <button
+                type="button"
+                onClick={onCopy}
+                className="text-left text-gray-100 hover:text-white cursor-pointer"
+                title="Copy the source face id"
+            >
+                {copied ? `${label} ✓` : label}
+            </button>
+        </Row>
+    );
 };
 
 const ObjectMetadataPanel: React.FC<Props> = ({data}) => {
     const {useObjectInfoStore, useLineageStore} = useViewerStores();
+    const showMeshStats = useOptionsStore((s) => s.showMeshStats);
     // Default collapsed: most clicks are just for selection / hide /
     // jump, not for inspecting properties. Folding keeps the info box
     // compact and the chevron tells the user where the data lives.
@@ -239,18 +305,35 @@ const ObjectMetadataPanel: React.FC<Props> = ({data}) => {
     // coordinate row and the cross-model link buttons.
     const meta = (effectiveData ?? null) as BeamMeta | PlateMeta | CurvedPlateMeta | null;
     const known = meta?.type === 'Beam' || meta?.type === 'Plate' || meta?.type === 'PlateCurved';
+    const decimals = useOptionsStore((s) => s.clickedCoordDecimals);
+    const setDecimals = useOptionsStore((s) => s.setClickedCoordDecimals);
+    const decimalItems: KebabMenuItem[] = DECIMAL_CHOICES.map((d) => ({
+        key: `dec-${d}`,
+        label: `${d} decimal${d === 1 ? '' : 's'}`,
+        // A check on the active choice; a blank same-width spacer keeps the labels aligned.
+        icon: d === decimals ? <CheckIcon /> : <span className="inline-block w-3.5" />,
+        onClick: () => setDecimals(d),
+    }));
     return (
         <div className="mt-2">
-            <button
-                type="button"
-                onClick={() => setExpanded((v) => !v)}
-                className="flex items-center gap-1 text-[12px] text-gray-100 hover:text-white"
-                aria-expanded={expanded}
-                aria-controls="object-properties"
-            >
-                <Chevron open={expanded} />
-                <span className="font-semibold">Properties</span>
-            </button>
+            <div className="flex items-center gap-1">
+                <button
+                    type="button"
+                    onClick={() => setExpanded((v) => !v)}
+                    className="flex items-center gap-1 text-[12px] text-gray-100 hover:text-white"
+                    aria-expanded={expanded}
+                    aria-controls="object-properties"
+                >
+                    <Chevron open={expanded} />
+                    <span className="font-semibold">Properties</span>
+                </button>
+                <RowKebabMenu
+                    ariaLabel="Properties display options"
+                    header="Clicked-at decimals"
+                    items={decimalItems}
+                    buttonClassName="h-5 w-5"
+                />
+            </div>
             {expanded && (
                 <div id="object-properties" className="mt-1 ml-4 table">
                     {meta && !known && <Row label="Type:">{(meta as any).type ?? 'Unknown'}</Row>}
@@ -277,9 +360,15 @@ const ObjectMetadataPanel: React.FC<Props> = ({data}) => {
                         </>
                     )}
                     <ClickedAtRow />
+                    <ClickedFaceRow />
                     {link && <LinkRow link={link} />}
                 </div>
             )}
+            {expanded && showMeshStats && (
+                <div className="ml-4">
+                    <MeshStatsSection />
+                </div>
+            )}
             <ConnectionsSection fileName={fileName} objectName={clickedName} />
         </div>
     );
diff --git a/src/frontend/src/components/options/DisplayOptions.tsx b/src/frontend/src/components/options/DisplayOptions.tsx
index d8ae96f26..c16e3e82b 100644
--- a/src/frontend/src/components/options/DisplayOptions.tsx
+++ b/src/frontend/src/components/options/DisplayOptions.tsx
@@ -2,6 +2,7 @@ import React from "react";
 import {useOptionsStore} from "@/state/optionsStore";
 import {useColorStore} from "@/state/colorLegendStore";
 import {useModelState} from "@/state/modelState";
+import {refreshEdgeOverlays} from "@/utils/scene/refreshEdgeOverlays";
 
 const Toggle: React.FC<{
     checked: boolean;
@@ -17,10 +18,12 @@ const Toggle: React.FC<{
 const DisplayOptions: React.FC = () => {
     const {
         showEdges, setShowEdges,
+        showMeshStats, setShowMeshStats,
         hideTessellationEdges, setHideTessellationEdges,
         lockTranslation, setLockTranslation,
         enableNodeEditor, setEnableNodeEditor,
         enableWebsocket, setEnableWebsocket,
+        autoFit, setAutoFit,
         autoConvertOnUpload, setAutoConvertOnUpload,
     } = useOptionsStore();
     const {showLegend, setShowLegend} = useColorStore();
@@ -32,20 +35,28 @@ const DisplayOptions: React.FC = () => {
                 section — it's a perf-diagnosis toggle, not a display
                 preference. */}
             <Toggle checked={showLegend} onChange={() => setShowLegend(!showLegend)}>Show Color Legend</Toggle>
-            <Toggle checked={showEdges} onChange={() => setShowEdges(!showEdges)}>Geometry Edges</Toggle>
+            <Toggle
+                checked={showEdges}
+                onChange={() => {
+                    setShowEdges(!showEdges);
+                    refreshEdgeOverlays();
+                }}
+            >
+                Geometry Edges
+            </Toggle>
             {showEdges && (
                 <label className="flex items-start space-x-2 pl-6">
                     <input
                         type="checkbox"
                         className="mt-1"
                         checked={hideTessellationEdges}
-                        onChange={() => setHideTessellationEdges(!hideTessellationEdges)}
+                        onChange={() => {
+                            setHideTessellationEdges(!hideTessellationEdges);
+                            refreshEdgeOverlays();
+                        }}
                     />
                     <span className="leading-tight">
                         Hide tessellation lines
-                        <span className="ml-1 text-[10px] uppercase tracking-wide text-amber-300">
-                            (reload required)
-                        </span>
                         <span className="block text-xs text-gray-400">
                             Drops near-coplanar edges (the triangulation grid
                             on curved surfaces). Keeps real feature edges and
@@ -54,6 +65,9 @@ const DisplayOptions: React.FC = () => {
                     </span>
                 </label>
             )}
+            <Toggle checked={showMeshStats} onChange={() => setShowMeshStats(!showMeshStats)}>
+                Mesh stats in Properties
+            </Toggle>
             <label className="flex items-start space-x-2">
                 <input
                     type="checkbox"
@@ -70,6 +84,7 @@ const DisplayOptions: React.FC = () => {
                     </span>
                 </span>
             </label>
+            <Toggle checked={autoFit} onChange={() => setAutoFit(!autoFit)}>Auto Fit to View</Toggle>
             <Toggle checked={lockTranslation} onChange={() => setLockTranslation(!lockTranslation)}>Lock Translation</Toggle>
             <Toggle checked={enableNodeEditor} onChange={() => setEnableNodeEditor(!enableNodeEditor)}>Enable Node Editor</Toggle>
             <Toggle checked={enableWebsocket} onChange={() => setEnableWebsocket(!enableWebsocket)}>Enable Websocket</Toggle>
diff --git a/src/frontend/src/components/options/ThemeOptions.tsx b/src/frontend/src/components/options/ThemeOptions.tsx
index 1eca977a2..aa821c6c4 100644
--- a/src/frontend/src/components/options/ThemeOptions.tsx
+++ b/src/frontend/src/components/options/ThemeOptions.tsx
@@ -5,6 +5,7 @@ import {
     ThemePresetId,
     useThemeStore,
 } from "@/state/themeStore";
+import {useGalleryStore} from "@/state/galleryStore";
 
 // Theme picker for the menu-row panels. Four preset cards (each a
 // live mini-preview of its chrome) plus custom swatches for panel
@@ -22,11 +23,28 @@ const ThemeOptions: React.FC = () => {
     const setBgOpacity = useThemeStore((s) => s.setBgOpacity);
     const resetCustom = useThemeStore((s) => s.resetCustom);
 
+    const galleryEnabled = useGalleryStore((s) => s.enabled);
+    const setGalleryEnabled = useGalleryStore((s) => s.setEnabled);
+
     const hasCustom = customBg !== null || customText !== null;
     const effective = effectivePanelTheme({preset, customBg, customText, bgOpacity});
 
     return (
         <div className="space-y-3 text-xs">
+            <label className="flex items-center justify-between gap-2 cursor-pointer">
+                <span>
+                    Gallery mode
+                    <span className="block text-[10px] text-gray-400">
+                        Prev/next HUD cycling this scope's files
+                    </span>
+                </span>
+                <input
+                    type="checkbox"
+                    checked={galleryEnabled}
+                    onChange={(e) => setGalleryEnabled(e.target.checked)}
+                    className="h-4 w-4 cursor-pointer accent-blue-500"
+                />
+            </label>
             <div className="grid grid-cols-2 gap-2">
                 {(Object.keys(THEME_PRESETS) as ThemePresetId[]).map((id) => {
                     const p = THEME_PRESETS[id];
diff --git a/src/frontend/src/components/storage/StorageBrowser.tsx b/src/frontend/src/components/storage/StorageBrowser.tsx
index e7a0b79c7..fdf9ec3ee 100644
--- a/src/frontend/src/components/storage/StorageBrowser.tsx
+++ b/src/frontend/src/components/storage/StorageBrowser.tsx
@@ -30,10 +30,12 @@ import {
     FolderNode,
     loadExpandedFolders,
     loadPendingFolders,
+    previewKeyList,
     saveExpandedFolders,
     savePendingFolders,
 } from "@/utils/storage/fileTree";
 import {RowKebabMenu} from "@/components/common/RowKebabMenu";
+import InlineNameInput from "@/components/common/InlineNameInput";
 import PositionedMenu, {KebabMenuItem} from "@/components/common/PositionedMenu";
 import FolderPickerModal from "@/components/common/FolderPickerModal";
 import {viewerApi} from "@/services/viewerApi";
@@ -212,54 +214,6 @@ function formatRelative(iso: string): string {
     return new Date(t).toISOString().slice(0, 10);
 }
 
-// Inline name editor used for file/folder rename and new-folder
-// creation. Enter commits, Escape (or blur) cancels. ``selectStem``
-// pre-selects the basename-without-extension so a quick type replaces
-// the name but keeps the extension.
-const InlineNameInput: React.FC<{
-    initial: string;
-    placeholder?: string;
-    selectStem?: boolean;
-    onCommit: (value: string) => void;
-    onCancel: () => void;
-}> = ({initial, placeholder, selectStem, onCommit, onCancel}) => {
-    const inputRef = useRef<HTMLInputElement>(null);
-    useEffect(() => {
-        const el = inputRef.current;
-        if (!el) return;
-        el.focus();
-        if (selectStem) {
-            const dot = initial.lastIndexOf(".");
-            el.setSelectionRange(0, dot > 0 ? dot : initial.length);
-        } else {
-            el.select();
-        }
-        // eslint-disable-next-line react-hooks/exhaustive-deps
-    }, []);
-    return (
-        <input
-            ref={inputRef}
-            type="text"
-            defaultValue={initial}
-            placeholder={placeholder}
-            className={
-                "flex-1 min-w-0 bg-gray-800 border border-blue-500 rounded-sm " +
-                "px-1 py-0.5 text-xs text-gray-100 focus:outline-hidden"
-            }
-            onClick={(e) => e.stopPropagation()}
-            onPointerDown={(e) => e.stopPropagation()}
-            onKeyDown={(e) => {
-                if (e.key === "Enter") {
-                    onCommit((e.target as HTMLInputElement).value);
-                } else if (e.key === "Escape") {
-                    onCancel();
-                }
-            }}
-            onBlur={onCancel}
-        />
-    );
-};
-
 const StorageBrowser: React.FC = () => {
     const files = useServerInfoStore((s) => s.serverFileObjects);
     const {sidecars} = useBuildSidecars(files);
@@ -444,10 +398,13 @@ const StorageBrowser: React.FC = () => {
     const mutations = useStorageMutations();
     const canMutate = mutations.canMutate;
 
-    // The picker modal drives both move flows; ``onPick`` is the
-    // closure that knows what to do once a destination is chosen.
+    // The picker modal drives the move flows and the upload-destination
+    // prompt; ``onPick`` is the closure that knows what to do once a
+    // destination is chosen.
     const [picker, setPicker] = useState<{
         title: string;
+        allowRoot?: boolean;
+        submitLabel?: string;
         onPick: (folder: string) => Promise<void> | void;
     } | null>(null);
     // Download a stored blob with auth (REST mode). The suggested filename is the
@@ -460,27 +417,69 @@ const StorageBrowser: React.FC = () => {
         window.alert(e instanceof Error ? e.message : String(e));
     };
 
+    // In-flight move status — a spinner line under the header so a
+    // drag-drop of many files visibly runs until the listing refreshes.
+    // Moves are chunked purely so the counter ticks between requests;
+    // every chunk is still a server-side S3 rename (CopyObject+Delete
+    // on Garage) — no file bytes pass through the browser. The ref
+    // rejects overlapping batches (concurrent moves would race on the
+    // server-side collision checks).
+    const [opNote, setOpNote] = useState<string | null>(null);
+    const opBusyRef = useRef(false);
+    const OP_CHUNK = 8;
+    const moveKeysWithProgress = async (keys: string[], folder: string) => {
+        if (opBusyRef.current || keys.length === 0) return;
+        opBusyRef.current = true;
+        const label = folder ? `${folder}/` : "root /";
+        setOpNote(`Moving 0/${keys.length} to ${label}…`);
+        try {
+            if (folder === "") {
+                // Move-to-root: the move endpoint requires a non-empty
+                // folder, so root moves are per-key renames to the
+                // basename.
+                let done = 0;
+                for (const k of keys) {
+                    setOpNote(`Moving ${done + 1}/${keys.length} to ${label}…`);
+                    await mutations.renameKey(k, basenameOf(k));
+                    done++;
+                }
+            } else {
+                const failed: Array<{key: string; reason: string}> = [];
+                for (let i = 0; i < keys.length; i += OP_CHUNK) {
+                    const chunk = keys.slice(i, i + OP_CHUNK);
+                    setOpNote(`Moving ${Math.min(i + chunk.length, keys.length)}/${keys.length} to ${label}…`);
+                    const r = await mutations.moveKeys(chunk, folder);
+                    failed.push(...r.failed);
+                }
+                if (failed.length > 0) {
+                    window.alert(failed.map((f) => `${f.key}: ${f.reason}`).join("\n"));
+                }
+            }
+            clearSelection();
+            void request_list_of_files_from_server();
+        } catch (e) {
+            alertError(e);
+        } finally {
+            opBusyRef.current = false;
+            setOpNote(null);
+        }
+    };
+
     const onMoveSingleToFolder = (key: string) => {
         setPicker({
             title: `Move "${key}" to folder`,
-            onPick: async (folder) => {
-                try {
-                    const r = await mutations.moveKeys([key], folder);
-                    if (r.failed.length > 0) {
-                        window.alert(r.failed.map((f) => `${f.key}: ${f.reason}`).join("\n"));
-                    }
-                    void request_list_of_files_from_server();
-                } catch (e) {
-                    alertError(e);
-                }
-            },
+            onPick: (folder) => moveKeysWithProgress([key], folder),
         });
     };
 
     const runFolderMove = async (folderPath: string, newPath: string) => {
         if (newPath === folderPath) return;
+        if (opBusyRef.current) return;
+        opBusyRef.current = true;
+        const allKeys = files.map((f) => f.name);
+        const count = allKeys.filter((k) => k.replace(/^\/+/, "").startsWith(folderPath + "/")).length;
+        setOpNote(`Moving folder "${folderPath}" → "${newPath}" (${count} file${count === 1 ? "" : "s"})…`);
         try {
-            const allKeys = files.map((f) => f.name);
             const r = await mutations.renameOrMoveFolder(folderPath, newPath, allKeys);
             if (r.failed.length > 0) {
                 window.alert(r.failed.map((f) => `${f.key}: ${f.reason}`).join("\n"));
@@ -495,6 +494,9 @@ const StorageBrowser: React.FC = () => {
             void request_list_of_files_from_server();
         } catch (e) {
             alertError(e);
+        } finally {
+            opBusyRef.current = false;
+            setOpNote(null);
         }
     };
 
@@ -574,12 +576,13 @@ const StorageBrowser: React.FC = () => {
             removePendingFoldersUnder(path);
             return;
         }
+        const prefix = path + "/";
+        const targets = files.filter((x) => x.name.replace(/^\/+/, "").startsWith(prefix));
         if (!window.confirm(
             `Delete folder "${path}" and its ${fileCount} file${fileCount === 1 ? "" : "s"}?\n` +
-            "Converted view caches are removed too.",
+            "Converted view caches are removed too.\n\n" +
+            previewKeyList(targets.map((t) => t.name)),
         )) return;
-        const prefix = path + "/";
-        const targets = files.filter((x) => x.name.replace(/^\/+/, "").startsWith(prefix));
         try {
             // Sequential: each delete cascades derived blobs server-side
             // and parallel calls would race on the storage listing.
@@ -712,7 +715,8 @@ const StorageBrowser: React.FC = () => {
         if (keys.length === 0) return;
         if (!window.confirm(
             `Delete ${keys.length} file${keys.length === 1 ? "" : "s"}?\n` +
-            "Converted view caches are removed too.",
+            "Converted view caches are removed too.\n\n" +
+            previewKeyList(keys),
         )) return;
         setBulkBusy("delete");
         try {
@@ -735,18 +739,7 @@ const StorageBrowser: React.FC = () => {
         if (keys.length === 0) return;
         setPicker({
             title: `Move ${keys.length} file${keys.length === 1 ? "" : "s"} to folder`,
-            onPick: async (folder) => {
-                try {
-                    const r = await mutations.moveKeys(keys, folder);
-                    if (r.failed.length > 0) {
-                        window.alert(r.failed.map((f) => `${f.key}: ${f.reason}`).join("\n"));
-                    }
-                    clearSelection();
-                    void request_list_of_files_from_server();
-                } catch (e) {
-                    alertError(e);
-                }
-            },
+            onPick: (folder) => moveKeysWithProgress(keys, folder),
         });
     };
 
@@ -803,9 +796,22 @@ const StorageBrowser: React.FC = () => {
     const onFilePicked = (e: React.ChangeEvent<HTMLInputElement>) => {
         const picked = Array.from(e.target.files ?? []);
         e.target.value = "";
-        const folder = uploadTargetRef.current ?? undefined;
+        const folder = uploadTargetRef.current;
         uploadTargetRef.current = null;
-        void uploadFilesTo(picked, folder);
+        if (picked.length === 0) return;
+        if (folder !== null) {
+            // "Upload here…" on a folder row — destination already chosen.
+            void uploadFilesTo(picked, folder || undefined);
+            return;
+        }
+        // Generic "Upload files…": ask where the batch should land — an
+        // existing folder, a new path, or the top level (the default).
+        setPicker({
+            title: `Upload ${picked.length} file${picked.length === 1 ? "" : "s"} to`,
+            allowRoot: true,
+            submitLabel: "Upload",
+            onPick: (dest) => void uploadFilesTo(picked, dest || undefined),
+        });
     };
 
     // ── Drag & drop ─────────────────────────────────────────────────
@@ -845,26 +851,7 @@ const StorageBrowser: React.FC = () => {
                 return;
             }
             keys = keys.filter((k) => typeof k === "string" && dirnameOf(k) !== target);
-            if (keys.length === 0) return;
-            try {
-                if (target === "") {
-                    // Move-to-root: the move endpoint requires a non-empty
-                    // folder, so root moves are per-key renames to the
-                    // basename.
-                    for (const k of keys) {
-                        await mutations.renameKey(k, basenameOf(k));
-                    }
-                } else {
-                    const r = await mutations.moveKeys(keys, target);
-                    if (r.failed.length > 0) {
-                        window.alert(r.failed.map((f) => `${f.key}: ${f.reason}`).join("\n"));
-                    }
-                }
-                clearSelection();
-                void request_list_of_files_from_server();
-            } catch (err) {
-                alertError(err);
-            }
+            await moveKeysWithProgress(keys, target);
             return;
         }
         if (e.dataTransfer.files?.length) {
@@ -956,23 +943,40 @@ const StorageBrowser: React.FC = () => {
 
     const onListKeyDown = (e: React.KeyboardEvent) => {
         if (flatRows.length === 0) return;
-        if (!["ArrowUp", "ArrowDown", "ArrowLeft", "ArrowRight", "Enter", " "].includes(e.key)) return;
+        if (!["ArrowUp", "ArrowDown", "ArrowLeft", "ArrowRight", "Enter", " ", "Delete"].includes(e.key)) return;
         // Don't steal keys from the inline rename/new-folder inputs.
         if ((e.target as HTMLElement).tagName === "INPUT") return;
         e.preventDefault();
         e.stopPropagation();
         const idx = focusedKey ? flatRows.findIndex((r) => rowKeyOf(r) === focusedKey) : -1;
         const row = idx >= 0 ? flatRows[idx] : null;
-        const focusAt = (i: number) => {
+        // Shift+Arrow extends the selection while moving focus —
+        // multi-select without a pointer. Anchor the range on the row
+        // we're leaving, then take the row we land on with us. Folder
+        // rows just pass through (they can't be selected).
+        const selectFileRow = (r: FlatRow | null) => {
+            if (!r || r.kind !== "file") return;
+            setSelection((prev) => {
+                const next = new Set(prev);
+                next.add(r.name);
+                return next;
+            });
+            lastSelectedRef.current = r.name;
+        };
+        const focusAt = (i: number, extendSelection = false) => {
             const clamped = Math.max(0, Math.min(flatRows.length - 1, i));
+            if (extendSelection) {
+                selectFileRow(row);
+                selectFileRow(flatRows[clamped]);
+            }
             setFocusedKey(rowKeyOf(flatRows[clamped]));
         };
         switch (e.key) {
             case "ArrowDown":
-                focusAt(idx < 0 ? 0 : idx + 1);
+                focusAt(idx < 0 ? 0 : idx + 1, e.shiftKey);
                 break;
             case "ArrowUp":
-                focusAt(idx < 0 ? flatRows.length - 1 : idx - 1);
+                focusAt(idx < 0 ? flatRows.length - 1 : idx - 1, e.shiftKey);
                 break;
             case "ArrowRight":
                 if (!row) {
@@ -1000,6 +1004,33 @@ const StorageBrowser: React.FC = () => {
             case " ":
                 if (row?.kind === "file") toggleSelection(row.name);
                 break;
+            case "Delete": {
+                if (!canMutate) break;
+                if (selection.size > 0) {
+                    // The selection takes precedence over the focused row.
+                    // Version blobs are server-protected — refuse loudly
+                    // instead of half-deleting the batch.
+                    const hasVersions = Array.from(selection).some((k) =>
+                        k.replace(/^\/+/, "").startsWith("versions/"),
+                    );
+                    if (hasVersions) {
+                        window.alert("CI version files can't be deleted");
+                        break;
+                    }
+                    void onDeleteSelected();
+                    break;
+                }
+                if (!row) break;
+                if (row.kind === "file") {
+                    void onDeleteFile(row.file);
+                } else {
+                    const prefix = row.path + "/";
+                    const count = files.filter((x) =>
+                        x.name.replace(/^\/+/, "").startsWith(prefix)).length;
+                    void onDeleteFolder(row.path, count, count === 0);
+                }
+                break;
+            }
         }
     };
 
@@ -1232,6 +1263,15 @@ const StorageBrowser: React.FC = () => {
                     </div>
                 );
             })()}
+            {opNote && (
+                <div className="mb-2 flex items-center gap-2 text-xs text-blue-300">
+                    <span
+                        className="inline-block w-3.5 h-3.5 border-2 border-current border-t-transparent rounded-full animate-spin shrink-0"
+                        aria-hidden="true"
+                    />
+                    <span className="truncate flex-1 min-w-0" role="status">{opNote}</span>
+                </div>
+            )}
             {uploadName && (
                 <div className="mb-2 text-xs">
                     <div className="flex items-center justify-between gap-2">
@@ -1532,6 +1572,8 @@ const StorageBrowser: React.FC = () => {
                 open={picker !== null}
                 title={picker?.title ?? ""}
                 existingFolders={existingFolderPaths}
+                allowRoot={picker?.allowRoot}
+                submitLabel={picker?.submitLabel}
                 onCancel={() => setPicker(null)}
                 onPick={(folder) => {
                     const action = picker?.onPick;
diff --git a/src/frontend/src/components/viewer/CanvasWrapper.tsx b/src/frontend/src/components/viewer/CanvasWrapper.tsx
index b60970f62..4106686ce 100644
--- a/src/frontend/src/components/viewer/CanvasWrapper.tsx
+++ b/src/frontend/src/components/viewer/CanvasWrapper.tsx
@@ -4,6 +4,7 @@ import ColorLegend from "./ColorLegend";
 import ThreeCanvas from "./ThreeCanvas";
 import SectionPlanesController from "./SectionPlanesController";
 import FemConceptsController from "./FemConceptsController";
+import GalleryControls from "./GalleryControls";
 
 const CanvasWrapper: React.FC = () => {
   return (
@@ -15,6 +16,8 @@ const CanvasWrapper: React.FC = () => {
       <div id="canvasParent" className="absolute w-full h-full">
         <ThreeCanvas />
       </div>
+      {/* Gallery HUD (opt-in via Theme options): prev/next over the scope's files. */}
+      <GalleryControls />
       {/* Headless: reconciles section-plane clipping/caps/gizmo with the scene. */}
       <SectionPlanesController />
       {/* Headless: draws the FEM-concept glyph overlay (masses / BCs / loads). */}
diff --git a/src/frontend/src/components/viewer/GalleryControls.tsx b/src/frontend/src/components/viewer/GalleryControls.tsx
new file mode 100644
index 000000000..239f67e06
--- /dev/null
+++ b/src/frontend/src/components/viewer/GalleryControls.tsx
@@ -0,0 +1,495 @@
+import React, {useCallback, useEffect, useMemo, useRef, useState} from "react";
+import {useGalleryStore} from "@/state/galleryStore";
+import {useServerInfoStore} from "@/state/serverInfoStore";
+import {useModelState} from "@/state/modelState";
+import {useObjectInfoStore} from "@/state/objectInfoStore";
+import {useLoadQueueStore} from "@/state/loadQueueStore";
+import {useScopeStore, scopeUrlPart} from "@/state/scopeStore";
+import {clear_loaded_model} from "@/utils/scene/handlers/clear_loaded_model";
+import {convertWithSelection} from "@/services/conversion";
+import {SerializerTessellatorSelect} from "@/components/convert/SerializerTessellatorSelect";
+import type {SerializerSelection} from "@/services/conversion/serializerMatrix";
+import {canLoadIntoSceneLegacy, isStreamingFEAResult} from "@/utils/scene/fileKinds";
+import {collectGeomEntries, focusGeomEntry, endGeomWalk, type GeomEntry} from "@/utils/scene/galleryWalk";
+import {writeToClipboard} from "@/utils/clipboard/copySelectionNames";
+import FilePickerModal from "@/components/common/FilePickerModal";
+
+// Gallery HUD. Three "walk" types (dropdown):
+//   - "files": cycles the current scope's loadable files (clear → load).
+//   - "geoms": cycles every geom in the scene, selecting + framing each,
+//     ordered by scene or mesh density.
+//   - "tree": the same, in model-tree hierarchy order.
+// Desktop: compact card top-right. Mobile: full-width bottom bar.
+const GalleryControls: React.FC = () => {
+    const enabled = useGalleryStore((s) => s.enabled);
+    const walk = useGalleryStore((s) => s.walk);
+    const setWalk = useGalleryStore((s) => s.setWalk);
+    const geomOrder = useGalleryStore((s) => s.geomOrder);
+    const setGeomOrder = useGalleryStore((s) => s.setGeomOrder);
+    const hideUnselected = useGalleryStore((s) => s.hideUnselected);
+    const toggleHideUnselected = useGalleryStore((s) => s.toggleHideUnselected);
+    const setMobileBarHeight = useGalleryStore((s) => s.setMobileBarHeight);
+
+    // Publish the mobile bar's live height so the audit toast can stack above it (not overlap).
+    // getBoundingClientRect().height is 0 when the bar is display:none (desktop md:hidden), so the
+    // offset naturally applies only on mobile.
+    const mobileBarRef = useRef<HTMLDivElement | null>(null);
+    useEffect(() => {
+        const el = mobileBarRef.current;
+        if (!el || typeof ResizeObserver === "undefined") {
+            setMobileBarHeight(0);
+            return;
+        }
+        const publish = () => setMobileBarHeight(el.getBoundingClientRect().height);
+        const ro = new ResizeObserver(publish);
+        ro.observe(el);
+        publish();
+        return () => {
+            ro.disconnect();
+            setMobileBarHeight(0);
+        };
+    }, [setMobileBarHeight, enabled]);
+
+    const fileObjects = useServerInfoStore((s) => s.serverFileObjects);
+    // The overlay load path registers into the plural loaded-source SET (not the
+    // singular loadedSourceName), so anchor + "is it shown?" checks use the set.
+    const loadedSources = useModelState((s) => s.loadedSourceNames);
+    const loadBusy = useLoadQueueStore((s) => s.current);
+    const selectedName = useObjectInfoStore((s) => s.name);
+    // A stable key for the active scope so a scope switch resets the walk (its geom entries point at
+    // the old scope's now-disposed meshes).
+    const scopeKey = useScopeStore((s) => (s.current ? scopeUrlPart(s.current) : ""));
+
+    const isGeomWalk = walk === "geoms";
+
+    // ---- Files walk -------------------------------------------------------
+    // The gallery walks only files the viewer can actually mount.
+    const files = useMemo(
+        () =>
+            fileObjects
+                .map((f) => f.name)
+                .filter((n) => isStreamingFEAResult(n) || canLoadIntoSceneLegacy(n)),
+        [fileObjects],
+    );
+
+    const [index, setIndex] = useState(0);
+
+    const go = useCallback(
+        async (next: number) => {
+            if (files.length === 0) return;
+            const wrapped = (next + files.length) % files.length;
+            setIndex(wrapped);
+            // Gallery = one at a time: clear the scene, then load the pick.
+            await clear_loaded_model();
+            useLoadQueueStore.getState().enqueue({name: files[wrapped]});
+        },
+        [files],
+    );
+
+    // Keep the index anchored to whatever is actually shown: when a gallery file
+    // is in the scene point at it; when the file list changes (scope switch /
+    // refresh) clamp into range.
+    useEffect(() => {
+        if (files.length === 0) return;
+        const at = files.findIndex((f) => loadedSources.has(f));
+        if (at >= 0) setIndex(at);
+        else setIndex((i) => Math.min(i, files.length - 1));
+    }, [files, loadedSources]);
+
+    // Auto-load the current pick when the FILES walk turns on with nothing from
+    // the scope's files already in the scene — otherwise the HUD shows a path but
+    // the viewer stays empty until the user clicks Next/Prev.
+    useEffect(() => {
+        if (!enabled || isGeomWalk || files.length === 0 || loadBusy) return;
+        const anyShown = files.some((f) => loadedSources.has(f));
+        if (!anyShown) void go(index);
+        // Only re-evaluate on enable / file-list change, not on every index tick.
+        // eslint-disable-next-line react-hooks/exhaustive-deps
+    }, [enabled, isGeomWalk, files]);
+
+    // ---- Geoms / tree walk ------------------------------------------------
+    const [geomEntries, setGeomEntries] = useState<GeomEntry[]>([]);
+    const [geomIndex, setGeomIndex] = useState(0);
+    const focusedOnce = useRef(false);
+
+    const rebuildGeoms = useCallback(() => {
+        if (!isGeomWalk) return [] as GeomEntry[];
+        // Runs synchronously inside effects; a mid-transition scene must never throw here (that
+        // would unmount the whole app). Fall back to an empty walk on any error.
+        let entries: GeomEntry[] = [];
+        try {
+            entries = collectGeomEntries(geomOrder);
+        } catch {
+            entries = [];
+        }
+        setGeomEntries(entries);
+        return entries;
+    }, [isGeomWalk, geomOrder]);
+
+    const goGeom = useCallback(
+        async (next: number, entriesOverride?: GeomEntry[]) => {
+            const entries = entriesOverride ?? geomEntries;
+            if (entries.length === 0) return;
+            const wrapped = (next + entries.length) % entries.length;
+            setGeomIndex(wrapped);
+            await focusGeomEntry(entries[wrapped], {hideUnselected, forceEdges: geomOrder === "distorted"});
+        },
+        [geomEntries, hideUnselected, geomOrder],
+    );
+
+    // Entering a geom walk or changing walk/order (re)builds the list and
+    // restarts the slideshow at the first geom — a predictable place to begin.
+    useEffect(() => {
+        if (!enabled || !isGeomWalk) return;
+        const entries = rebuildGeoms();
+        setGeomIndex(0);
+        if (entries.length > 0) {
+            focusedOnce.current = true;
+            void goGeom(0, entries);
+        }
+        // eslint-disable-next-line react-hooks/exhaustive-deps
+    }, [enabled, isGeomWalk, geomOrder]);
+
+    // A scene change (file loaded/unloaded) rebuilds the list but keeps the
+    // current position; focus the first geom if the scene only just populated.
+    useEffect(() => {
+        if (!enabled || !isGeomWalk) return;
+        const entries = rebuildGeoms();
+        setGeomIndex((i) => Math.min(i, Math.max(0, entries.length - 1)));
+        if (!focusedOnce.current && entries.length > 0) {
+            focusedOnce.current = true;
+            void goGeom(0, entries);
+        }
+        // eslint-disable-next-line react-hooks/exhaustive-deps
+    }, [loadedSources]);
+
+    // Re-apply isolation when the hide-unselected toggle flips mid-walk.
+    useEffect(() => {
+        if (!enabled || !isGeomWalk || geomEntries.length === 0) return;
+        void goGeom(geomIndex);
+        // eslint-disable-next-line react-hooks/exhaustive-deps
+    }, [hideUnselected]);
+
+    // Switching scope disposes the current scope's meshes; drop the walk's stale entries + any
+    // isolation/selection so nothing references a freed mesh. The scene-change effect above then
+    // rebuilds cleanly once the new scope's geoms land.
+    useEffect(() => {
+        endGeomWalk();
+        setGeomEntries([]);
+        setGeomIndex(0);
+        focusedOnce.current = false;
+    }, [scopeKey]);
+
+    // Leaving a geom walk (switch to files, disable gallery) restores the scene —
+    // but only if we actually entered one, so enabling the files walk never
+    // clears a selection the user made before opening the gallery.
+    useEffect(() => {
+        if ((!enabled || !isGeomWalk) && focusedOnce.current) {
+            focusedOnce.current = false;
+            endGeomWalk();
+        }
+        // eslint-disable-next-line react-hooks/exhaustive-deps
+    }, [enabled, isGeomWalk]);
+
+    // ---- Shared nav -------------------------------------------------------
+    const step = useCallback(
+        (delta: number) => {
+            if (isGeomWalk) void goGeom(geomIndex + delta);
+            else void go(index + delta);
+        },
+        [isGeomWalk, goGeom, geomIndex, go, index],
+    );
+
+    // Left/Right arrows cycle prev/next while gallery mode is active (the camera
+    // controls don't bind arrow keys, so there's no conflict). Ignored while
+    // typing or while a file load is in flight; preventDefault stops scrolling.
+    useEffect(() => {
+        if (!enabled) return;
+        const onKey = (e: KeyboardEvent) => {
+            if (e.key !== "ArrowLeft" && e.key !== "ArrowRight") return;
+            const t = e.target as HTMLElement | null;
+            if (t && (t.tagName === "INPUT" || t.tagName === "TEXTAREA" || t.isContentEditable)) return;
+            if (!isGeomWalk && useLoadQueueStore.getState().current) return; // a load is already running
+            e.preventDefault();
+            step(e.key === "ArrowRight" ? 1 : -1);
+        };
+        window.addEventListener("keydown", onKey);
+        return () => window.removeEventListener("keydown", onKey);
+    }, [enabled, step, isGeomWalk]);
+
+    // ---- Tools drawer (re-convert; FILES walk only) -----------------------
+    const [toolsOpen, setToolsOpen] = useState(false);
+    const [reconverting, setReconverting] = useState(false);
+    const [reconvertMsg, setReconvertMsg] = useState<string | null>(null);
+    // Serializer/tessellator pick for the reconvert. Empty until the user
+    // touches a dropdown; convertWithSelection then normalises against the
+    // backend matrix (defaults to the cpp/native server path).
+    const [serializerSel, setSerializerSel] = useState<SerializerSelection>({});
+
+    const current = files[index] ?? null;
+    const currentExt = current ? (current.slice(current.lastIndexOf(".")).toLowerCase()) : "";
+
+    const reconvert = useCallback(async () => {
+        if (!current || reconverting) return;
+        const scope = useScopeStore.getState().current;
+        const scopePart = scope ? scopeUrlPart(scope) : "";
+        setReconverting(true);
+        setReconvertMsg("re-converting…");
+        try {
+            const derivedKey = await convertWithSelection(scopePart, current, "glb", {
+                selection: serializerSel,
+                reconvert: true,
+            });
+            await clear_loaded_model();
+            const {overlay_file_in_scene} = await import("@/utils/scene/handlers/overlay_file_in_scene");
+            await overlay_file_in_scene(current, derivedKey, {scope: scopePart});
+            setReconvertMsg("loaded fresh conversion");
+        } catch (e) {
+            setReconvertMsg(`failed: ${e instanceof Error ? e.message : String(e)}`);
+        } finally {
+            setReconverting(false);
+        }
+    }, [current, reconverting, serializerSel]);
+
+    // NOTE: every hook must be declared before the `if (!enabled) return null` early return below —
+    // React counts hooks per render, so a hook after the return changes the count when the gallery is
+    // toggled on/off and crashes the app ("rendered more hooks than during the previous render").
+    const [nameCopied, setNameCopied] = useState(false);
+    const copyName = useCallback(async (text: string) => {
+        if (!text) return;
+        if (await writeToClipboard(text)) {
+            setNameCopied(true);
+            window.setTimeout(() => setNameCopied(false), 1200);
+        }
+    }, []);
+
+    // Clicking the "N / M" counter opens a single-file picker (the shared storage-browser tree) to jump
+    // straight to a file instead of stepping Prev/Next through a long scope. The picker returns a blob
+    // key; map it back to the gallery's file list (by exact name or basename) and load it via `go` —
+    // which works in both walks (in the geoms walk, loading a new file rebuilds the geom list).
+    const [filePickerOpen, setFilePickerOpen] = useState(false);
+    const jumpToFile = useCallback(
+        (key: string) => {
+            setFilePickerOpen(false);
+            const base = key.split("/").pop() ?? key;
+            let at = files.indexOf(key);
+            if (at < 0) at = files.findIndex((n) => (n.split("/").pop() ?? n) === base);
+            if (at >= 0) void go(at);
+        },
+        [files, go],
+    );
+
+    if (!enabled) return null;
+
+    const count = isGeomWalk ? geomEntries.length : files.length;
+    const activeIndex = isGeomWalk ? geomIndex : index;
+    const empty = count === 0;
+    const navBusy = !isGeomWalk && !!loadBusy;
+    const curEntry = isGeomWalk ? geomEntries[geomIndex] : undefined;
+    const spikeSuffix =
+        geomOrder === "distorted" && curEntry
+            ? ` · spike ${curEntry.spike.toFixed(1)}× · ${curEntry.spikeTris} tri${curEntry.spikeTris === 1 ? "" : "s"}`
+            : "";
+    const primaryLabel = isGeomWalk
+        ? empty
+            ? geomOrder === "distorted"
+                ? "no distorted geoms 🎉"
+                : "no geoms in scene"
+            : (selectedName ?? `geom ${geomIndex + 1}`) + spikeSuffix
+        : empty
+          ? "no viewable files in this scope"
+          : (current ?? "");
+
+    const walkSelector = (
+        <select
+            aria-label="Walk type"
+            value={walk}
+            onChange={(e) => setWalk(e.target.value as typeof walk)}
+            className="rounded-sm border border-gray-600 bg-gray-800 px-1 py-0.5 text-[11px] text-gray-100"
+        >
+            <option value="files">Files</option>
+            <option value="geoms">Geoms</option>
+        </select>
+    );
+
+    // Geom-walk sub-controls: order + isolate toggle + refresh.
+    const geomControls = isGeomWalk && (
+        <div className="flex flex-wrap items-center gap-2 text-[11px] text-gray-300">
+            <select
+                aria-label="Geom order"
+                value={geomOrder}
+                onChange={(e) => setGeomOrder(e.target.value as typeof geomOrder)}
+                className="rounded-sm border border-gray-600 bg-gray-800 px-1 py-0.5 text-[11px] text-gray-100"
+            >
+                <option value="scene">Order: scene</option>
+                <option value="density">Order: density</option>
+                <option value="tree">Order: tree</option>
+                <option value="distorted">Order: distorted tris</option>
+            </select>
+            <label className="flex items-center gap-1" title="Hide everything except the current geom during the walk">
+                <input type="checkbox" checked={hideUnselected} onChange={() => toggleHideUnselected()} />
+                <span>Isolate</span>
+            </label>
+            <button
+                type="button"
+                onClick={() => {
+                    const entries = rebuildGeoms();
+                    if (entries.length) void goGeom(Math.min(geomIndex, entries.length - 1), entries);
+                }}
+                title="Rebuild the geom list from the current scene"
+                className="rounded-sm border border-gray-600 px-1.5 py-0.5 hover:bg-gray-700"
+            >
+                ⟳
+            </button>
+        </div>
+    );
+
+    // Re-convert operates on the current file (files[index]), which is the loaded file in BOTH the
+    // files walk and the geoms walk — so the reconvert-path tools are available in either mode (a user
+    // walking a model's geoms can still reconvert it via a different path, e.g. to pick up a fix).
+    const toolsDrawer = (
+        <div className="border-t border-gray-700 pt-1">
+            <button
+                type="button"
+                onClick={() => setToolsOpen((v) => !v)}
+                className="flex w-full items-center justify-between text-[10px] uppercase tracking-wide text-gray-400 hover:text-gray-200"
+            >
+                <span>Tools</span>
+                <span>{toolsOpen ? "▾" : "▸"}</span>
+            </button>
+            {toolsOpen && (
+                <div className="mt-1 flex flex-col gap-1">
+                    {current && (
+                        <div className="flex flex-wrap items-center gap-x-3 gap-y-1">
+                            <SerializerTessellatorSelect
+                                ext={currentExt}
+                                target="glb"
+                                value={serializerSel}
+                                onChange={setSerializerSel}
+                                disabled={reconverting}
+                                compact
+                            />
+                        </div>
+                    )}
+                    <button
+                        type="button"
+                        disabled={empty || reconverting}
+                        onClick={() => void reconvert()}
+                        title="Run a fresh conversion (throwaway; never overwrites the audit-run product)"
+                        className="rounded-sm border border-amber-600/60 px-2 py-0.5 text-amber-200 hover:bg-amber-900/30 disabled:opacity-40 disabled:cursor-default"
+                    >
+                        {reconverting ? "Re-converting…" : "↻ Re-convert"}
+                    </button>
+                    {reconvertMsg && <span className="truncate text-[10px] text-gray-400">{reconvertMsg}</span>}
+                </div>
+            )}
+        </div>
+    );
+
+    return (
+        <>
+            {/* Desktop: compact top-right card. */}
+            <div className="hidden md:flex pointer-events-auto absolute right-3 top-3 z-20 max-w-[42vw] flex-col gap-1 rounded-md border border-gray-600 bg-gray-900/85 px-2 py-1.5 text-xs text-gray-100 shadow-lg backdrop-blur-sm">
+                <div className="flex items-center gap-2">
+                    {walkSelector}
+                    <button
+                        type="button"
+                        aria-label="Previous"
+                        disabled={empty || navBusy}
+                        onClick={() => step(-1)}
+                        className="rounded-sm border border-gray-600 px-2 py-0.5 hover:bg-gray-700 disabled:opacity-40 disabled:cursor-default"
+                    >
+                        ‹ Prev
+                    </button>
+                    <button
+                        type="button"
+                        onClick={() => setFilePickerOpen(true)}
+                        disabled={files.length === 0}
+                        title="Jump to a file…"
+                        className="tabular-nums text-gray-400 hover:text-gray-100 hover:underline disabled:cursor-default disabled:no-underline"
+                    >
+                        {empty ? "0 / 0" : `${activeIndex + 1} / ${count}`}
+                    </button>
+                    <button
+                        type="button"
+                        aria-label="Next"
+                        disabled={empty || navBusy}
+                        onClick={() => step(1)}
+                        className="rounded-sm border border-gray-600 px-2 py-0.5 hover:bg-gray-700 disabled:opacity-40 disabled:cursor-default"
+                    >
+                        Next ›
+                    </button>
+                </div>
+                {geomControls}
+                <button
+                    type="button"
+                    onClick={() => void copyName(primaryLabel)}
+                    disabled={empty}
+                    title={empty ? primaryLabel : `Click to copy: ${primaryLabel}`}
+                    className="truncate text-left font-mono text-[11px] text-gray-300 hover:text-gray-100 disabled:cursor-default"
+                >
+                    {nameCopied ? "✓ copied" : primaryLabel}
+                </button>
+                {toolsDrawer}
+            </div>
+
+            {/* Mobile: bottom bar, larger tap targets, clear of the top menu. */}
+            <div ref={mobileBarRef} className="flex md:hidden pointer-events-auto absolute inset-x-2 bottom-2 z-20 flex-col gap-1 rounded-md border border-gray-600 bg-gray-900/90 px-2 py-2 text-xs text-gray-100 shadow-lg backdrop-blur-sm">
+                <div className="flex items-center gap-2">
+                    {walkSelector}
+                    <button
+                        type="button"
+                        aria-label="Previous"
+                        disabled={empty || navBusy}
+                        onClick={() => step(-1)}
+                        className="shrink-0 rounded-sm border border-gray-600 px-3 py-2 text-base leading-none hover:bg-gray-700 disabled:opacity-40 disabled:cursor-default"
+                    >
+                        ‹
+                    </button>
+                    <div className="min-w-0 flex-1 text-center">
+                        <button
+                            type="button"
+                            onClick={() => void copyName(primaryLabel)}
+                            disabled={empty}
+                            title={empty ? primaryLabel : `Tap to copy: ${primaryLabel}`}
+                            className="w-full truncate font-mono text-[11px] text-gray-200 hover:text-white disabled:cursor-default"
+                        >
+                            {nameCopied ? "✓ copied" : primaryLabel}
+                        </button>
+                        <button
+                            type="button"
+                            onClick={() => setFilePickerOpen(true)}
+                            disabled={files.length === 0}
+                            className="tabular-nums text-[10px] text-gray-500 hover:text-gray-300 disabled:cursor-default"
+                        >
+                            {empty ? "0 / 0" : `${activeIndex + 1} / ${count}`}
+                        </button>
+                    </div>
+                    <button
+                        type="button"
+                        aria-label="Next"
+                        disabled={empty || navBusy}
+                        onClick={() => step(1)}
+                        className="shrink-0 rounded-sm border border-gray-600 px-3 py-2 text-base leading-none hover:bg-gray-700 disabled:opacity-40 disabled:cursor-default"
+                    >
+                        ›
+                    </button>
+                </div>
+                {geomControls}
+                {toolsDrawer}
+            </div>
+
+            <FilePickerModal
+                open={filePickerOpen}
+                scope={scopeKey}
+                title="Jump to file"
+                initialKey={current ?? undefined}
+                filter={(f) => isStreamingFEAResult(f.key) || canLoadIntoSceneLegacy(f.key)}
+                onCancel={() => setFilePickerOpen(false)}
+                onPick={jumpToFile}
+            />
+        </>
+    );
+};
+
+export default GalleryControls;
diff --git a/src/frontend/src/components/viewer/sceneHelpers/adaptiveClipping.ts b/src/frontend/src/components/viewer/sceneHelpers/adaptiveClipping.ts
new file mode 100644
index 000000000..4a7cbdc99
--- /dev/null
+++ b/src/frontend/src/components/viewer/sceneHelpers/adaptiveClipping.ts
@@ -0,0 +1,44 @@
+import * as THREE from "three";
+import CameraControls from "camera-controls";
+import {OrbitControls} from "three/examples/jsm/controls/OrbitControls.js";
+
+// Scale the camera near/far clipping planes (and the control dolly limits) to the size of the
+// content the camera is framing, so small models don't clip away when zooming in.
+//
+// The camera is constructed with a fixed near = 0.1 (setupCamera.ts). That means you can never get
+// closer than 0.1 world units before geometry crosses the near plane and disappears — fine for a
+// building-scale model, but for a model only a few units across (e.g. a component in mm modelled at
+// unit scale) 0.1 clips most of it the moment you try to zoom in. Deriving near from the framed
+// bounding-sphere radius makes the zoom-in headroom proportional to model size at any scale.
+//
+// near/far span keeps a ~1e6 ratio; with far tied to the same radius the model stays comfortably
+// inside the frustum (camera fits at ~2*radius) while near shrinks enough to inspect fine detail.
+export function applyAdaptiveClipping(
+    camera: THREE.PerspectiveCamera,
+    controls: OrbitControls | CameraControls | null | undefined,
+    radius: number,
+) {
+    if (!isFinite(radius) || radius <= 0) return;
+
+    const near = Math.max(radius * 1e-3, 1e-6);
+    const far = Math.max(radius * 1e3, near * 1e4);
+
+    // Only rewrite when meaningfully different — avoids redundant projection-matrix churn when the
+    // same model is re-framed (fit-all, center-on-selection) at an already-correct scale.
+    if (Math.abs(camera.near - near) > near * 1e-3 || Math.abs(camera.far - far) > far * 1e-3) {
+        camera.near = near;
+        camera.far = far;
+        camera.updateProjectionMatrix();
+    }
+
+    // Let the controls dolly all the way in to the near plane (and not past far). CameraControls and
+    // OrbitControls both gate dolly by minDistance/maxDistance; default minDistance keeps you further
+    // out than the new near plane would allow, so match them to the adaptive planes.
+    if (controls instanceof OrbitControls) {
+        controls.minDistance = near;
+        controls.maxDistance = far;
+    } else if (controls instanceof CameraControls) {
+        controls.minDistance = near;
+        controls.maxDistance = far;
+    }
+}
diff --git a/src/frontend/src/components/viewer/sceneHelpers/setupCameraControlsHandlers.ts b/src/frontend/src/components/viewer/sceneHelpers/setupCameraControlsHandlers.ts
index 00d95f62a..2c4b6f47d 100644
--- a/src/frontend/src/components/viewer/sceneHelpers/setupCameraControlsHandlers.ts
+++ b/src/frontend/src/components/viewer/sceneHelpers/setupCameraControlsHandlers.ts
@@ -8,6 +8,7 @@ import {useTreeViewStore} from "@/state/treeViewStore";
 import CameraControls from "camera-controls";
 import {copySelectionNames} from "@/utils/clipboard/copySelectionNames";
 import {hideSelectedRanges, unhideAllRanges} from "@/utils/scene/visibility";
+import {applyAdaptiveClipping} from "@/components/viewer/sceneHelpers/adaptiveClipping";
 
 export function setupCameraControlsHandlers(
     scene: THREE.Scene,
@@ -142,6 +143,9 @@ export const zoomToAll = (scene: THREE.Scene, camera: THREE.PerspectiveCamera, c
     const center = sphere.center.clone();
     const radius = sphere.radius;
 
+    // Adapt near/far to model size so small models can be zoomed into without near-plane clipping.
+    applyAdaptiveClipping(camera, controls, radius);
+
     // Compute required distance so the sphere fits both vertically and horizontally
     const vFov = THREE.MathUtils.degToRad(camera.fov);
     const aspect = camera.aspect || 1;
diff --git a/src/frontend/src/components/viewer/sceneHelpers/setupModelLoader.ts b/src/frontend/src/components/viewer/sceneHelpers/setupModelLoader.ts
index bfb58dddd..a4881f2ff 100644
--- a/src/frontend/src/components/viewer/sceneHelpers/setupModelLoader.ts
+++ b/src/frontend/src/components/viewer/sceneHelpers/setupModelLoader.ts
@@ -3,7 +3,8 @@ import {prepareLoadedModel} from "./prepareLoadedModel";
 import {useModelState} from "@/state/modelState";
 import {useOptionsStore} from "@/state/optionsStore";
 import {useAnimationStore} from "@/state/animationStore";
-import {animationControllerRef, modelKeyMapRef, sceneRef, simulationDataRef, adaExtensionRef} from "@/state/refs";
+import {animationControllerRef, cameraRef, controlsRef, modelKeyMapRef, sceneRef, simulationDataRef, adaExtensionRef} from "@/state/refs";
+import {zoomToAll} from "./setupCameraControlsHandlers";
 import {SimulationDataExtensionMetadata} from "@/extensions/design_and_analysis_extension";
 import {requestRender} from "@/state/perfStore";
 import {FilePurpose} from "@/flatbuffers/base/file-purpose";
@@ -14,6 +15,7 @@ import {AnimationController} from "@/utils/scene/animations/AnimationController"
 import {updateAllPointsSize} from "@/utils/scene/updatePointSizes";
 import type {LoadMetricsRecorder} from "@/utils/scene/loadMetrics";
 import {fastSceneBox} from "@/utils/scene/boundsFast";
+import {applyAdaptiveClipping} from "@/components/viewer/sceneHelpers/adaptiveClipping";
 
 /** Optional hook to mutate the freshly-loaded gltf scene (typically
  * to inject ``userData["draw_ranges_<meshName>"]`` and
@@ -173,5 +175,30 @@ export async function setupModelLoaderAsync(
         // Set the hasAnimation flag to true in the store
         animationStore.setHasAnimation(true);
     }
+
+    // Adapt near/far clipping to the loaded model's size so small models can be zoomed into without
+    // near-plane clipping — independent of autoFit (zoomToAll re-applies it, but this covers the
+    // autoFit-off case too). Uses the model bounding box captured above / in the store.
+    {
+        const cam = cameraRef.current;
+        const ctl = controlsRef.current;
+        const box = useModelState.getState().boundingBox; // fresh — setBoundingBox ran above
+        if (cam && box && !box.isEmpty()) {
+            const radius = box.getBoundingSphere(new THREE.Sphere()).radius;
+            applyAdaptiveClipping(cam as THREE.PerspectiveCamera, ctl, radius);
+        }
+    }
+
+    // Auto fit-to-all after the model is in the scene (scene-config toggle, default on) —
+    // frames a freshly loaded model, and each geom cycled through in gallery mode, without a
+    // manual Shift+A. Deferred a frame so the just-added meshes' world bounds are current.
+    if (optionsStore.autoFit) {
+        const cam = cameraRef.current;
+        const ctl = controlsRef.current;
+        const scn = sceneRef.current;
+        if (cam && ctl && scn) {
+            requestAnimationFrame(() => zoomToAll(scn, cam as THREE.PerspectiveCamera, ctl));
+        }
+    }
     return modelGroup;
 }
diff --git a/src/frontend/src/components/viewer/sceneHelpers/setupPointerHandler.ts b/src/frontend/src/components/viewer/sceneHelpers/setupPointerHandler.ts
index 342dff3f5..f40be7ddf 100644
--- a/src/frontend/src/components/viewer/sceneHelpers/setupPointerHandler.ts
+++ b/src/frontend/src/components/viewer/sceneHelpers/setupPointerHandler.ts
@@ -3,6 +3,7 @@ import * as THREE from "three";
 import {handleClickEmptySpace} from "@/utils/mesh_select/handleClickEmptySpace";
 import {handleClickMesh} from "@/utils/mesh_select/handleClickMesh";
 import {handleClickPoints} from "@/utils/mesh_select/handleClickPoints";
+import {CustomBatchedMesh} from "@/utils/mesh_select/CustomBatchedMesh";
 // handleClickMesh signature change accommodates a prefilledRangeId
 // from the GPU mesh picker; the raycast fallback still passes only
 // the intersection.
@@ -109,9 +110,18 @@ export function setupPointerHandler(
         try {
             const meshPick = gpuMeshPicker.pickAt(e.clientX, e.clientY);
             if (meshPick) {
+                // GPU picking identifies the object + a representative vertex (the draw range's
+                // first vertex), NOT the exact clicked point — so "Clicked at" would show the same
+                // coordinate for every click on one object (very noticeable on a small model). Refine
+                // it with a raycast against just the picked mesh; that also yields the exact triangle
+                // index for face-level picking (the full-scene raycast would hit the edge overlay first
+                // and require zooming way in). Falls back to the vertex when the mesh is too large to
+                // raycast cheaply (keeps the huge-FEA fast path — face picking then unavailable there).
+                const refined = raycastPointOnMesh(e, camera, renderer, meshPick.mesh);
                 const fakeIntersection: THREE.Intersection = {
                     object: meshPick.mesh,
-                    point: meshPick.worldPosition.clone(),
+                    point: refined?.point ?? meshPick.worldPosition.clone(),
+                    faceIndex: refined?.faceIndex,
                     distance: 0,
                 } as THREE.Intersection;
                 await handleClickMesh(fakeIntersection, e, meshPick.rangeId);
@@ -149,8 +159,14 @@ export function setupPointerHandler(
         }
 
         if (nearestMesh) {
-            // Clear any highlighted point if not multi-select
-            await handleClickMesh(nearestMesh, e);
+            // Only imported geometry (CustomBatchedMesh) is selectable. If the first opaque
+            // hit is anything else — a section-plane cap, a helper, a non-shape mesh — treat
+            // the click as a deselect, not a no-op: clicking off a shape clears the selection.
+            if (nearestMesh.object instanceof CustomBatchedMesh) {
+                await handleClickMesh(nearestMesh, e);
+            } else {
+                handleClickEmptySpace(e);
+            }
             return;
         }
 
@@ -182,6 +198,39 @@ export function setupPointerHandler(
  *  landed essentially at the camera position and rotation degenerated
  *  into spinning in place — easiest to trigger on mobile, where you
  *  pinch in close before double-tapping. */
+// Raycast the clicked pixel against a SINGLE mesh to recover the exact world-space hit point.
+// Used to refine the GPU picker's representative-vertex position into the real clicked point.
+// Bounded by triangle count so a whole-model batched mesh (millions of tris) doesn't stall the
+// click — above the cap the caller keeps the fast approximate vertex.
+const MAX_REFINE_TRIS = 600_000;
+
+function raycastPointOnMesh(
+    e: MouseEvent,
+    camera: THREE.PerspectiveCamera,
+    renderer: THREE.WebGLRenderer,
+    mesh: THREE.Object3D,
+): {point: THREE.Vector3; faceIndex: number | undefined} | null {
+    try {
+        const geom = (mesh as THREE.Mesh).geometry as THREE.BufferGeometry | undefined;
+        if (!geom) return null;
+        const triCount = (geom.index ? geom.index.count : geom.attributes.position?.count ?? 0) / 3;
+        if (triCount > MAX_REFINE_TRIS) return null;
+        const rect = renderer.domElement.getBoundingClientRect();
+        const nx = ((e.clientX - rect.left) / rect.width) * 2 - 1;
+        const ny = -((e.clientY - rect.top) / rect.height) * 2 + 1;
+        const ray = new THREE.Raycaster();
+        ray.layers.set(0);
+        ray.layers.disable(1);
+        ray.setFromCamera(new THREE.Vector2(nx, ny), camera);
+        // Only the picked mesh — never the edge/wireframe overlays — so the triangle index is reliable
+        // regardless of zoom (the full-scene raycast would hit an edge line first when zoomed out).
+        const hit = ray.intersectObject(mesh, false)[0];
+        return hit?.point ? {point: hit.point.clone(), faceIndex: hit.faceIndex ?? undefined} : null;
+    } catch {
+        return null;
+    }
+}
+
 function pickWorldPoint(
     e: MouseEvent,
     camera: THREE.PerspectiveCamera,
diff --git a/src/frontend/src/index.html b/src/frontend/src/index.html
index 2e7097401..e6ccd915e 100644
--- a/src/frontend/src/index.html
+++ b/src/frontend/src/index.html
@@ -12,6 +12,18 @@
           Hosted viewer mode injects window.COMMS_MODE / window.API_BASE
           via /config.js. In Vite dev or embedded mode the request 404s
           and the comms picker falls back to the WS default.
+
+          MUST stay a blocking (non-defer) classic script. Vite emits the
+          SPA entry as a module in <head> (<script type="module">), which is
+          implicitly deferred. Deferred scripts (modules + `defer` classics)
+          run in DOCUMENT ORDER after parsing, so a `defer` here would run
+          config.js AFTER the head entry module — the SPA would read
+          window.AUTH_*/COMMS_MODE before config.js set them and bootstrap
+          with no auth config (empty "signed in as", no admin button, comms
+          falling back). A blocking classic script instead runs during parse
+          (in the body, before the deferred head module executes), so the
+          globals are in place when the SPA reads them. /config.js is served
+          in ~20ms, so blocking is not a meaningful render cost anyway.
         -->
         <script src="/config.js" onerror="this.remove()"></script>
         <script type="module" src="index.tsx"></script>
diff --git a/src/frontend/src/runtime/config.ts b/src/frontend/src/runtime/config.ts
index 9821abd6e..623ffbb80 100644
--- a/src/frontend/src/runtime/config.ts
+++ b/src/frontend/src/runtime/config.ts
@@ -10,6 +10,26 @@ export interface ConversionOption {
     default?: boolean | string | number | null;
     description?: string;
     enum?: readonly string[];
+    // Data-driven extras carried by dependent enum options (serializer /
+    // tessellator dropdowns). The backend is the single source of this
+    // vocabulary; the frontend renders straight from these fields and never
+    // hardcodes the choices:
+    //   labels    — human label per enum value.
+    //   depends_on — name of the option this one's choices depend on.
+    //   enum_by   — for each value of the depends_on option, the subset of
+    //               THIS option's enum that applies (drives the dependent
+    //               dropdown; empty/absent = static enum).
+    //   runtime   — per enum value, "client" (runs in the browser: WASM /
+    //               Pyodide) vs "server" (worker). Lets the SPA route + gate.
+    labels?: Readonly<Record<string, string>>;
+    depends_on?: string;
+    enum_by?: Readonly<Record<string, readonly string[]>>;
+    runtime?: Readonly<Record<string, "client" | "server">>;
+    // Human display name for the axis this option represents (distinct from the
+    // per-value `labels`). Lets the backend name the 2nd path-dropdown per target
+    // — "Tessellator" for mesh targets, "Writer" for B-rep targets — without the
+    // frontend hardcoding it.
+    title?: string;
 }
 
 //
diff --git a/src/frontend/src/services/auth/oidc.ts b/src/frontend/src/services/auth/oidc.ts
index 5fc97f04a..774815ff6 100644
--- a/src/frontend/src/services/auth/oidc.ts
+++ b/src/frontend/src/services/auth/oidc.ts
@@ -33,6 +33,14 @@ const STORAGE_PKCE = "ada-oidc-pkce";
 const STORAGE_RETURN = "ada-oidc-return";
 const STORAGE_REFRESH = "ada-oidc-refresh";
 const STORAGE_STATE = "ada-oidc-state";
+// Persistent cache of the OIDC discovery doc. The endpoints (authorize/token/
+// jwks) are public and effectively static, so caching across page reloads
+// removes a ~260ms authentik round-trip (plus a possible slow TLS handshake)
+// from the token-refresh path that runs on every load. Keyed by issuer so a
+// config change invalidates it; short-ish TTL so a genuine endpoint move is
+// picked up within the day.
+const STORAGE_DISCOVERY = "ada-oidc-discovery";
+const DISCOVERY_TTL_MS = 24 * 60 * 60 * 1000;
 
 let discovery: DiscoveryDoc | null = null;
 let accessToken: string | null = null;
@@ -70,9 +78,29 @@ async function loadDiscovery(): Promise<DiscoveryDoc> {
     if (discovery) return discovery;
     const issuer = runtime.authIssuer();
     if (!issuer) throw new Error("AUTH_ISSUER not configured");
+    // Persistent cache (survives reloads), validated against the current issuer
+    // and TTL. Wrapped in try/catch so a disabled/full localStorage (private
+    // mode, embedded iframe) silently falls back to fetching.
+    try {
+        const raw = localStorage.getItem(STORAGE_DISCOVERY);
+        if (raw) {
+            const c = JSON.parse(raw) as {doc: DiscoveryDoc; at: number; issuer: string};
+            if (c.doc && c.issuer === issuer && Date.now() - c.at < DISCOVERY_TTL_MS) {
+                discovery = c.doc;
+                return discovery;
+            }
+        }
+    } catch {
+        /* corrupt / unavailable cache — fall through and refetch */
+    }
     const r = await fetch(`${issuer}/.well-known/openid-configuration`);
     if (!r.ok) throw new Error(`oidc discovery failed: ${r.status}`);
     discovery = await r.json();
+    try {
+        localStorage.setItem(STORAGE_DISCOVERY, JSON.stringify({doc: discovery, at: Date.now(), issuer}));
+    } catch {
+        /* storage unavailable — the in-memory module cache still applies */
+    }
     return discovery!;
 }
 
diff --git a/src/frontend/src/services/conversion/index.ts b/src/frontend/src/services/conversion/index.ts
index 060127681..422c8481d 100644
--- a/src/frontend/src/services/conversion/index.ts
+++ b/src/frontend/src/services/conversion/index.ts
@@ -7,6 +7,7 @@ import {runtime} from "@/runtime/config";
 import {viewerApi, TargetFormat, ScopeUrl} from "@/services/viewerApi";
 import {convertViaServer} from "./serverPipeline";
 import {wasmSupportsConversion, isWasmFeaSource} from "./wasmSupport";
+import {serializerSchemaFor, normalizeSelection, SerializerSelection} from "./serializerMatrix";
 
 // NOTE: the Pyodide pipeline is imported lazily (inside ensureConverted), not
 // at module top. It pulls a `new Worker(new URL(...))` that Vite emits as a
@@ -63,6 +64,83 @@ export async function ensureConverted(
     return convertViaServer(scope, sourceKey, targetFormat, opts);
 }
 
+function extOf(name: string): string {
+    const i = name.lastIndexOf(".");
+    return i === -1 ? "" : name.slice(i).toLowerCase();
+}
+
+/**
+ * Convert routing the serializer/tessellator selection (from the reconvert
+ * dropdowns) to the right pipeline: a client serializer (runtime="client",
+ * i.e. the in-browser WASM/Pyodide path) goes to the Pyodide pipeline, any
+ * server serializer forwards ``{serializer, tessellator}`` as conversion
+ * options to the worker where :func:`_apply_glb_serializer` folds them into the
+ * engine knobs. Returns the derived storage key. Shared by the gallery
+ * reconvert tool and the /convert page so both honour the same matrix.
+ */
+export async function convertWithSelection(
+    scope: ScopeUrl,
+    sourceKey: string,
+    targetFormat: TargetFormat,
+    opts?: {
+        selection?: SerializerSelection;
+        extraOptions?: Record<string, boolean | string | number | null>;
+        reconvert?: boolean;
+    },
+): Promise<string> {
+    const ext = extOf(sourceKey);
+    const schema = serializerSchemaFor(ext, targetFormat);
+    const selection = opts?.selection ?? {};
+    const resolved = schema ? normalizeSelection(schema, selection) : null;
+
+    if (resolved?.isClient) {
+        // In-browser path — no server round-trip. Two client engines, picked by
+        // the tessellator token:
+        //   wasm-native → the OCC-free, no-pyodide adacpp_step_glb embind module
+        //                 (STEP → GLB only, 2.3 MB, no Python runtime).
+        //   pyodide     → the Pyodide pipeline (ifc / step / mesh, wasm wheels).
+        if (resolved.tessellator === "wasm-native") {
+            // CAD→GLB (step/ifc → glb) via the native embind GLB modules.
+            const {convertViaWasmNativeAndUpload, nativeCadGlbSupported} = await import(
+                "./nativeCadGlbPipeline"
+            );
+            if (nativeCadGlbSupported(sourceKey, targetFormat)) {
+                return convertViaWasmNativeAndUpload(scope, sourceKey, targetFormat);
+            }
+            // B-rep→B-rep (step→ifc / ifc→step) via the native embind writer module.
+            const {convertViaWasmBrepAndUpload, nativeBrepWriterSupported} = await import(
+                "./nativeBrepWriterPipeline"
+            );
+            if (nativeBrepWriterSupported(sourceKey, targetFormat)) {
+                return convertViaWasmBrepAndUpload(scope, sourceKey, targetFormat);
+            }
+            // No native module covers this (source, target) — fall through to Pyodide.
+        }
+        if (!wasmSupportsConversion(sourceKey, targetFormat)) {
+            throw new Error(
+                `in-browser conversion doesn't support ${ext || sourceKey} → ${targetFormat}`,
+            );
+        }
+        const {convertViaPyodideAndUpload} = await import("./pyodidePipeline");
+        return convertViaPyodideAndUpload(scope, sourceKey, targetFormat);
+    }
+
+    if (!runtime.convertEnabled()) {
+        throw new Error("conversion not enabled on this deployment");
+    }
+    const conversionOptions: Record<string, boolean | string | number | null> = {
+        ...(opts?.extraOptions ?? {}),
+    };
+    if (resolved) {
+        conversionOptions.serializer = resolved.serializer;
+        conversionOptions.tessellator = resolved.tessellator;
+    }
+    return convertViaServer(scope, sourceKey, targetFormat, {
+        conversionOptions: Object.keys(conversionOptions).length ? conversionOptions : undefined,
+        reconvert: opts?.reconvert,
+    });
+}
+
 // Backwards-compatible wrapper for the GLB-for-viewing flow. ``opts.streamer``
 // forces the memory-bounded streaming STEP->GLB converter (for large assemblies
 // that OOM the normal OCC path).
diff --git a/src/frontend/src/services/conversion/nativeBrepWriterPipeline.ts b/src/frontend/src/services/conversion/nativeBrepWriterPipeline.ts
new file mode 100644
index 000000000..c89e71556
--- /dev/null
+++ b/src/frontend/src/services/conversion/nativeBrepWriterPipeline.ts
@@ -0,0 +1,164 @@
+// In-browser conversion pipeline using the NATIVE (no-pyodide) adacpp_brep_writer wasm module.
+// STEP→IFC and IFC→STEP. Fetches source bytes, runs the embind writer in a Web Worker, PUTs the
+// output back to storage (same derived-key contract as the server + pyodide paths), and records a
+// metrics-rich audit row (WASM badge). Buffered MEMFS IO; an OPFS-streaming tier can follow the
+// CAD→GLB pattern for very large B-rep files.
+
+import {useConversionStore, ConversionJob} from "@/state/conversionStore";
+import {viewerApi, ScopeUrl, TargetFormat} from "@/services/viewerApi";
+import {
+    nativeBrepWrite,
+    nativeBrepWriteStreaming,
+    nativeBrepWriterOpfsAvailable,
+    type BrepDir,
+} from "@/utils/nativeConvert/brepWriterConverter";
+
+const WASM_IMAGE_TAG = "wasm:native-brepwriter";
+
+// Above this source size, prefer the OPFS-streaming tier (source read off-disk, bounded RSS) when
+// OPFS + a presigned URL are available; below it, the buffered MEMFS path.
+const OPFS_STREAM_THRESHOLD = 100 * 1024 * 1024; // 100 MB
+
+function extOf(name: string): string {
+    const i = name.lastIndexOf(".");
+    return i === -1 ? "" : name.slice(i).toLowerCase();
+}
+
+// The conversion direction for a (source ext, target). STEP/STP→IFC and IFC→STEP only.
+function brepDirFor(sourceKey: string, targetFormat: TargetFormat): BrepDir | null {
+    const ext = extOf(sourceKey);
+    if ((ext === ".step" || ext === ".stp") && targetFormat === "ifc") return "step2ifc";
+    if (ext === ".ifc" && targetFormat === "step") return "ifc2step";
+    return null;
+}
+
+/** Does the native B-rep writer handle this (source, target)? STEP→IFC / IFC→STEP only. */
+export function nativeBrepWriterSupported(sourceKey: string, targetFormat: TargetFormat): boolean {
+    return brepDirFor(sourceKey, targetFormat) !== null;
+}
+
+export async function convertViaWasmBrepAndUpload(
+    scope: ScopeUrl,
+    sourceKey: string,
+    targetFormat: TargetFormat,
+    opts?: {auditRunId?: string | null},
+): Promise<string> {
+    const dir = brepDirFor(sourceKey, targetFormat);
+    if (!dir) {
+        throw new Error(`native B-rep writer only does STEP→IFC / IFC→STEP (got ${sourceKey} → ${targetFormat})`);
+    }
+    const storeKey = `${sourceKey}::${targetFormat}`;
+    const store = useConversionStore.getState();
+    const startedAt = Date.now();
+    const job: ConversionJob = {
+        sourceKey: storeKey,
+        jobId: "wasm-native",
+        derivedKey: "",
+        status: "running",
+        progress: 0.05,
+        stage: "fetching source",
+        error: null,
+        startedAt,
+    };
+    store.setJob(storeKey, job);
+
+    let auditJobId: string | null = null;
+    try {
+        auditJobId = await viewerApi.auditLocalCreate(scope, {
+            key: sourceKey,
+            target_format: targetFormat,
+            audit_run_id: opts?.auditRunId ?? null,
+            image_tag: WASM_IMAGE_TAG,
+        });
+    } catch {
+        /* proceed without an audit row */
+    }
+    const finishAudit = async (body: Parameters<typeof viewerApi.auditLocalUpdate>[2]) => {
+        if (!auditJobId) return;
+        try {
+            await viewerApi.auditLocalUpdate(scope, auditJobId, body);
+        } catch {
+            /* best-effort */
+        }
+    };
+
+    try {
+        const label = dir === "step2ifc" ? "STEP → IFC" : "IFC → STEP";
+        // Prefer OPFS streaming for large sources (bounded RSS): presign + feature-detect OPFS. Falls
+        // back to buffering the whole source into the wasm heap when small, presign-less, or no OPFS.
+        // A streaming run is NOT retried buffered (re-reading a huge file would OOM).
+        let streamUrl: {url: string; size: number} | null = null;
+        try {
+            const dl = await viewerApi.requestDownloadUrl(scope, sourceKey);
+            if (dl.size >= OPFS_STREAM_THRESHOLD && (await nativeBrepWriterOpfsAvailable())) {
+                streamUrl = {url: dl.url, size: dl.size};
+            }
+        } catch {
+            streamUrl = null; // presign unavailable → buffered fallback
+        }
+
+        let output: ArrayBuffer;
+        let products: number;
+        let ms: number;
+        let readBytes: number;
+        if (streamUrl) {
+            store.setJob(storeKey, {
+                ...(store.jobs[storeKey] || job),
+                progress: 0.2,
+                stage: `writing ${label} in browser (native, OPFS)`,
+            });
+            ({output, products, ms} = await nativeBrepWriteStreaming(dir, streamUrl.url));
+            readBytes = streamUrl.size; // source size; only streamed, never staged whole
+        } else {
+            const sourceBuf = await viewerApi.getBlob(scope, sourceKey);
+            readBytes = sourceBuf.byteLength; // capture before the buffer is transferred to the worker
+
+            store.setJob(storeKey, {
+                ...(store.jobs[storeKey] || job),
+                progress: 0.2,
+                stage: `writing ${label} in browser (native)`,
+            });
+
+            ({output, products, ms} = await nativeBrepWrite(dir, sourceBuf));
+        }
+        const outBytes = new Uint8Array(output);
+
+        store.setJob(storeKey, {
+            ...(store.jobs[storeKey] || job),
+            progress: 0.9,
+            stage: `uploading derived (${products.toLocaleString()} products, ${Math.round(ms)} ms)`,
+        });
+
+        const derivedKey = await viewerApi.putDerivedBlob(scope, sourceKey, targetFormat, outBytes);
+
+        store.setJob(storeKey, {
+            ...(store.jobs[storeKey] || job),
+            progress: 1.0,
+            stage: "ready",
+            status: "done",
+            derivedKey,
+        });
+
+        await finishAudit({
+            status: "done",
+            duration_ms: Date.now() - startedAt,
+            read_bytes: readBytes,
+            write_bytes: outBytes.byteLength,
+        });
+        return derivedKey;
+    } catch (err) {
+        const msg = err instanceof Error ? err.message : String(err);
+        store.setJob(storeKey, {
+            ...(store.jobs[storeKey] || job),
+            status: "error",
+            stage: "error",
+            error: msg,
+        });
+        await finishAudit({
+            status: "error",
+            duration_ms: Date.now() - startedAt,
+            error: msg,
+        });
+        throw err;
+    }
+}
diff --git a/src/frontend/src/services/conversion/nativeCadGlbPipeline.ts b/src/frontend/src/services/conversion/nativeCadGlbPipeline.ts
new file mode 100644
index 000000000..18b4805bf
--- /dev/null
+++ b/src/frontend/src/services/conversion/nativeCadGlbPipeline.ts
@@ -0,0 +1,169 @@
+// In-browser conversion pipeline using the NATIVE (no-pyodide) adacpp CAD→GLB wasm modules
+// (adacpp_step_glb / adacpp_ifc_glb). STEP/STP + IFC → GLB. Fetches source bytes from storage, runs
+// the embind module in a Web Worker, PUTs the resulting GLB back to storage (same derived-key
+// contract as the server + pyodide paths), and records a metrics-rich audit row so the conversion
+// shows up in the audit panel with a "WASM" badge exactly like the pyodide path.
+
+import {useConversionStore, ConversionJob} from "@/state/conversionStore";
+import {viewerApi, ScopeUrl, TargetFormat} from "@/services/viewerApi";
+import {
+    nativeCadToGlb,
+    nativeCadToGlbStreaming,
+    nativeCadGlbOpfsAvailable,
+    type CadKind,
+} from "@/utils/nativeConvert/cadGlbConverter";
+
+// Distinguishes the native embind module from the pyodide path in the audit panel.
+const WASM_IMAGE_TAG = "wasm:native-cadglb";
+
+// Above this source size we prefer the OPFS-streaming tier (source read off-disk via pread, bounded
+// RSS) over buffering the whole source into the wasm heap — provided OPFS + a presigned URL are both
+// available. Below it, the buffered MEMFS path is simpler and plenty (and the validated default).
+const OPFS_STREAM_THRESHOLD = 100 * 1024 * 1024; // 100 MB
+
+function extOf(name: string): string {
+    const i = name.lastIndexOf(".");
+    return i === -1 ? "" : name.slice(i).toLowerCase();
+}
+
+// Which native module handles a source extension (STEP/STP → step_glb, IFC → ifc_glb).
+function cadKindFor(sourceKey: string): CadKind | null {
+    const ext = extOf(sourceKey);
+    if (ext === ".step" || ext === ".stp") return "step";
+    if (ext === ".ifc") return "ifc";
+    return null;
+}
+
+/** Does a native (no-pyodide) module handle this (source, target)? {STEP,STP,IFC} → GLB. */
+export function nativeCadGlbSupported(sourceKey: string, targetFormat: TargetFormat): boolean {
+    return targetFormat === "glb" && cadKindFor(sourceKey) !== null;
+}
+
+export async function convertViaWasmNativeAndUpload(
+    scope: ScopeUrl,
+    sourceKey: string,
+    targetFormat: TargetFormat = "glb",
+    opts?: {auditRunId?: string | null},
+): Promise<string> {
+    const kind = cadKindFor(sourceKey);
+    if (targetFormat !== "glb" || !kind) {
+        throw new Error(`native wasm module only converts STEP/IFC → GLB (got ${sourceKey} → ${targetFormat})`);
+    }
+    const storeKey = `${sourceKey}::${targetFormat}`;
+    const store = useConversionStore.getState();
+    const startedAt = Date.now();
+    const job: ConversionJob = {
+        sourceKey: storeKey,
+        jobId: "wasm-native",
+        derivedKey: "",
+        status: "running",
+        progress: 0.05,
+        stage: "fetching source",
+        error: null,
+        startedAt,
+    };
+    store.setJob(storeKey, job);
+
+    // Open the audit row first so the conversion shows as "running". Best-effort.
+    let auditJobId: string | null = null;
+    try {
+        auditJobId = await viewerApi.auditLocalCreate(scope, {
+            key: sourceKey,
+            target_format: targetFormat,
+            audit_run_id: opts?.auditRunId ?? null,
+            image_tag: WASM_IMAGE_TAG,
+        });
+    } catch {
+        /* proceed without an audit row */
+    }
+    const finishAudit = async (body: Parameters<typeof viewerApi.auditLocalUpdate>[2]) => {
+        if (!auditJobId) return;
+        try {
+            await viewerApi.auditLocalUpdate(scope, auditJobId, body);
+        } catch {
+            /* best-effort */
+        }
+    };
+
+    try {
+        // Prefer the OPFS-streaming tier for large sources: mint a presigned URL, feature-detect
+        // OPFS, and stream the STEP through OPFS (bounded RSS) so a multi-GB deck never has to fit
+        // the wasm heap. Falls back to buffering the whole source into the wasm heap when the source
+        // is small, presign is unavailable (local-disk backends 503), or OPFS isn't supported. A
+        // streaming run is NOT retried buffered — re-reading a huge deck into the heap would just OOM.
+        const upper = kind.toUpperCase();
+        let streamUrl: {url: string; size: number} | null = null;
+        try {
+            const dl = await viewerApi.requestDownloadUrl(scope, sourceKey);
+            if (dl.size >= OPFS_STREAM_THRESHOLD && (await nativeCadGlbOpfsAvailable(kind))) {
+                streamUrl = {url: dl.url, size: dl.size};
+            }
+        } catch {
+            streamUrl = null; // presign unavailable → buffered fallback
+        }
+
+        let glb: ArrayBuffer;
+        let products: number;
+        let ms: number;
+        let readBytes: number;
+        if (streamUrl) {
+            store.setJob(storeKey, {
+                ...(store.jobs[storeKey] || job),
+                progress: 0.15,
+                stage: `streaming ${upper} → GLB in browser (native, OPFS)`,
+            });
+            ({glb, products, ms} = await nativeCadToGlbStreaming(kind, streamUrl.url));
+            readBytes = streamUrl.size; // source size; only streamed, never staged whole
+        } else {
+            const sourceBuf = await viewerApi.getBlob(scope, sourceKey);
+            readBytes = sourceBuf.byteLength; // capture before the buffer is transferred to the worker
+
+            store.setJob(storeKey, {
+                ...(store.jobs[storeKey] || job),
+                progress: 0.15,
+                stage: `converting ${upper} → GLB in browser (native)`,
+            });
+
+            ({glb, products, ms} = await nativeCadToGlb(kind, sourceBuf));
+        }
+        const outBytes = new Uint8Array(glb);
+
+        store.setJob(storeKey, {
+            ...(store.jobs[storeKey] || job),
+            progress: 0.9,
+            stage: `uploading derived (${products.toLocaleString()} products, ${Math.round(ms)} ms)`,
+        });
+
+        const derivedKey = await viewerApi.putDerivedBlob(scope, sourceKey, targetFormat, outBytes);
+
+        store.setJob(storeKey, {
+            ...(store.jobs[storeKey] || job),
+            progress: 1.0,
+            stage: "ready",
+            status: "done",
+            derivedKey,
+        });
+
+        await finishAudit({
+            status: "done",
+            duration_ms: Date.now() - startedAt,
+            read_bytes: readBytes,
+            write_bytes: outBytes.byteLength,
+        });
+        return derivedKey;
+    } catch (err) {
+        const msg = err instanceof Error ? err.message : String(err);
+        store.setJob(storeKey, {
+            ...(store.jobs[storeKey] || job),
+            status: "error",
+            stage: "error",
+            error: msg,
+        });
+        await finishAudit({
+            status: "error",
+            duration_ms: Date.now() - startedAt,
+            error: msg,
+        });
+        throw err;
+    }
+}
diff --git a/src/frontend/src/services/conversion/serializerMatrix.ts b/src/frontend/src/services/conversion/serializerMatrix.ts
new file mode 100644
index 000000000..2f406e0d0
--- /dev/null
+++ b/src/frontend/src/services/conversion/serializerMatrix.ts
@@ -0,0 +1,65 @@
+// Frontend adapter over the backend-advertised serializer × tessellator
+// matrix. The vocabulary, labels, per-serializer tessellator sets and the
+// client-vs-server runtime split are ALL declared by the adapy backend and
+// ride to the SPA on the conversion matrix (`options[<target>]`, see
+// converter.py `_glb_serializer_options`). This module reads that schema —
+// it hardcodes NONE of the choices — so the two dependent reconvert dropdowns
+// (gallery tools + ConversionRow) and the client/server routing all agree.
+
+import {runtime, ConversionOption} from "@/runtime/config";
+
+export interface SerializerSelection {
+    serializer?: string;
+    tessellator?: string;
+}
+
+export interface SerializerSchema {
+    serializer: ConversionOption; // enum with `labels` + `runtime`
+    tessellator: ConversionOption; // enum with `labels` + `enum_by` (keyed by serializer)
+}
+
+/** The serializer + tessellator option schema for a (source ext, target)
+ * pair, or null when the target advertises no serializer choice (only →GLB
+ * rows do). */
+export function serializerSchemaFor(ext: string, target: string): SerializerSchema | null {
+    const opts = runtime.conversionOptionsFor(ext, target);
+    const serializer = opts.find((o) => o.name === "serializer");
+    const tessellator = opts.find((o) => o.name === "tessellator");
+    if (!serializer || !tessellator || !serializer.enum || !tessellator.enum) return null;
+    return {serializer, tessellator};
+}
+
+/** Tessellator tokens valid for a given serializer, from the backend's
+ * `enum_by` dependency map (falls back to the flat enum). */
+export function tessellatorsFor(schema: SerializerSchema, serializer: string): readonly string[] {
+    const bySer = schema.tessellator.enum_by?.[serializer];
+    if (bySer && bySer.length) return bySer;
+    return schema.tessellator.enum ?? [];
+}
+
+/** Resolve a (possibly partial) user selection into a fully-populated,
+ * schema-valid pick. Falls the serializer back to its default and the
+ * tessellator to the first token allowed for that serializer, so a stale or
+ * empty selection still sends coherent tokens. */
+export function normalizeSelection(
+    schema: SerializerSchema,
+    value: SerializerSelection,
+): {serializer: string; tessellator: string; isClient: boolean} {
+    const serEnum = schema.serializer.enum ?? [];
+    let serializer = value.serializer && serEnum.includes(value.serializer)
+        ? value.serializer
+        : String(schema.serializer.default ?? serEnum[0] ?? "");
+    const allowed = tessellatorsFor(schema, serializer);
+    const tessellator = value.tessellator && allowed.includes(value.tessellator)
+        ? value.tessellator
+        : allowed[0] ?? "";
+    const isClient = schema.serializer.runtime?.[serializer] === "client";
+    return {serializer, tessellator, isClient};
+}
+
+/** Convenience: does the current selection route to the in-browser pipeline? */
+export function selectionIsClient(ext: string, target: string, value: SerializerSelection): boolean {
+    const schema = serializerSchemaFor(ext, target);
+    if (!schema) return false;
+    return normalizeSelection(schema, value).isClient;
+}
diff --git a/src/frontend/src/services/conversion/serverPipeline.ts b/src/frontend/src/services/conversion/serverPipeline.ts
index 372fb6bb6..02d5c5402 100644
--- a/src/frontend/src/services/conversion/serverPipeline.ts
+++ b/src/frontend/src/services/conversion/serverPipeline.ts
@@ -33,6 +33,9 @@ export async function convertViaServer(
         // (``runtime.conversionOptionsFor(ext, target)``); ConversionRow
         // collects them from the rendered option widgets.
         conversionOptions?: Record<string, boolean | string | number | null>;
+        // Force a fresh re-conversion into the ``_reconvert/`` namespace (never touches the
+        // ``_derived/`` audit product). The returned derived_key points at ``_reconvert/…``.
+        reconvert?: boolean;
     },
 ): Promise<string> {
     // Track jobs per (source, format) so a parallel ifc + xml conversion
@@ -43,7 +46,7 @@ export async function convertViaServer(
         opts?.step !== undefined && opts?.field !== undefined
             ? `::s${opts.step}.${opts.field}`
             : "";
-    const storeKey = `${sourceKey}::${targetFormat}${pickSuffix}`;
+    const storeKey = `${sourceKey}::${targetFormat}${pickSuffix}${opts?.reconvert ? "::reconvert" : ""}`;
     const store = useConversionStore.getState();
 
     const initial = await viewerApi.convert(scope, sourceKey, targetFormat, opts);
@@ -84,6 +87,12 @@ export async function convertViaServer(
         if (payload.status === "error") {
             throw new Error(payload.error || "conversion failed");
         }
+        // A user-killed job (or a watchdog-reaped one that surfaced as cancelled) is terminal — stop
+        // polling and reject, so callers awaiting the conversion (e.g. the gallery reconvert's
+        // "Re-converting…" state) reset instead of hanging until the ~30 min poll ceiling.
+        if (payload.status === "cancelled") {
+            throw new Error(payload.error || "conversion cancelled");
+        }
     }
     throw new Error("conversion did not complete within the poll window");
 }
diff --git a/src/frontend/src/services/viewerApi.ts b/src/frontend/src/services/viewerApi.ts
index c3b97aeef..aac07ccf8 100644
--- a/src/frontend/src/services/viewerApi.ts
+++ b/src/frontend/src/services/viewerApi.ts
@@ -66,7 +66,7 @@ export interface MeResponse {
     email: string;
     displayName: string;
     isAdmin: boolean;
-    scopes: Array<{kind: "shared" | "user" | "project"; id: string | null; name: string}>;
+    scopes: Array<{kind: "shared" | "user" | "project" | "corpus"; id: string | null; name: string}>;
     projects: Array<{id: string; slug: string; name: string; role: string}>;
 }
 
@@ -595,6 +595,39 @@ export interface ConvertMeta {
     // as % utilization across all cores rather than a cumulative ramp.
     cpu_cores?: number | null;
     options?: Record<string, string>;
+    // adacpp [STEPPROF-JSON] pipeline summaries, parsed from the captured child log when
+    // the profile_conversions toggle was on — one entry per instrumented C++ pipeline run.
+    cpp_profile?: CppProfile[];
+}
+
+export interface CppProfilePhase {
+    name: string;
+    ms: number;
+    rss_mb: number;
+}
+
+export interface CppProfileThread {
+    tid: number;
+    solids: number;
+    busy_ms: number;
+}
+
+export interface CppProfile {
+    label: string;
+    wall_ms: number;
+    peak_rss_mb: number;
+    cpu_s?: number;
+    parallelism?: number;
+    vctx?: number;
+    nvctx?: number;
+    disk_read_mb?: number;
+    majflt?: number;
+    solids?: number;
+    tris?: number;
+    max_tris_solid?: number;
+    phases: CppProfilePhase[];
+    notes?: Record<string, number>;
+    threads?: CppProfileThread[];
 }
 
 export interface WorkerPackage {
@@ -617,6 +650,9 @@ export interface AuditRun {
     // Idle time (ms) excluded from the active duration — the gap before a
     // later validation pass folded into the run. UI subtracts it.
     idle_ms?: number | null;
+    // Sum of every cell's own duration_ms — the run's active compute time,
+    // independent of wall clock. The UI shows this as the run's total runtime.
+    cells_duration_ms?: number | null;
     scope: string;
     worker_pool: string | null;
     trigger: string;
@@ -625,6 +661,10 @@ export interface AuditRun {
     status: string;
     note: string | null;
     total: number;
+    // Auto-validation parity cells counted into `total` upfront but not yet
+    // enqueued (the poller dispatches them once the conversion cells land).
+    // 0 once the validation pass starts, and for non-auto-validate runs.
+    validate_total?: number;
     ok: number;
     failed: number;
     skipped: number;
@@ -761,6 +801,16 @@ export interface AuditRunJob {
     // Empty for cells finished before migration 013 / cells that
     // hit the dispatcher's cached short-circuit.
     worker_image_tag: string | null;
+    // Per-conversion provenance + quality flags (JSONB). Includes
+    // ``occ_fallback`` ({count, reasons, geoms}) when the NGEOM/libtess2 path
+    // silently fell back to OCC, and ``mesh_flags`` for distorted triangles.
+    convert_meta?: {
+        occ_fallback?: {count: number; reasons?: Record<string, number>; geoms?: Record<string, number>};
+        mesh_flags?: {distorted_tris?: number; distorted_frac?: number; n_tris?: number};
+        // Faces with a trim boundary that tessellated to zero triangles (silently dropped geometry).
+        geom_health?: {dropped_faces?: number; total_faces?: number};
+        [k: string]: unknown;
+    } | null;
 }
 
 export interface ProfileStatsRow {
@@ -859,6 +909,8 @@ export interface AuditFilters {
     action?: string;
     /** Conversion target format (glb / ifc / step / …). */
     target?: string;
+    /** Job state (queued / running / done / error). */
+    status?: string;
     /** Case-insensitive substring filter on the source filepath/filename. */
     key?: string;
     before_id?: number;
@@ -1458,6 +1510,9 @@ export const viewerApi = {
             // ``null`` clears any global override; otherwise the
             // type matches the option's declared ``type``.
             conversionOptions?: Record<string, boolean | string | number | null>;
+            // Re-convert: always re-run and write to the separate ``_reconvert/`` namespace so
+            // a corpus scope's ``_derived/`` audit product is never overwritten.
+            reconvert?: boolean;
         },
     ): Promise<ConvertResponse> {
         const body: Record<string, unknown> = {
@@ -1471,6 +1526,9 @@ export const viewerApi = {
         if (opts?.conversionOptions && Object.keys(opts.conversionOptions).length) {
             body.conversion_options = opts.conversionOptions;
         }
+        if (opts?.reconvert) {
+            body.reconvert = true;
+        }
         const r = await authedFetch(
             `${runtime.apiBase()}/scopes/${encodeURIComponent(scope)}/convert`,
             {
@@ -1664,6 +1722,24 @@ export const viewerApi = {
         return jsonOrThrow(r, "adminCorpusCreate");
     },
 
+    /** Admin: update a corpus's display name / description. The slug
+     * is immutable (baked into the storage prefix + scope URLs). An
+     * empty description clears it. */
+    async adminCorpusUpdate(
+        slug: string,
+        body: {name: string; description: string | null},
+    ): Promise<Corpus> {
+        const r = await authedFetch(
+            `${runtime.apiBase()}/admin/corpora/${encodeURIComponent(slug)}`,
+            {
+                method: "PATCH",
+                headers: {"Content-Type": "application/json"},
+                body: JSON.stringify(body),
+            },
+        );
+        return jsonOrThrow(r, "adminCorpusUpdate");
+    },
+
     /** Admin: soft-delete a corpus by slug. Storage bytes survive —
      * the operator clears those out-of-band. The slug becomes
      * immediately available for reuse. */
@@ -1714,6 +1790,22 @@ export const viewerApi = {
         return jsonOrThrow(r, `adminAuditRunReDispatch(${runId})`);
     },
 
+    /** Admin: re-run a single cell of a run in place (right-click → Rerun).
+     * Enqueues one force-rebuild conversion for (key, target) against the run's
+     * own scope/pool and reopens the run; the other cells are untouched.
+     * Returns the (reopened) run. */
+    async adminAuditRunRerunCell(runId: string, key: string, target: string): Promise<AuditRun> {
+        const r = await authedFetch(
+            `${runtime.apiBase()}/admin/audit/runs/${encodeURIComponent(runId)}/rerun-cell`,
+            {
+                method: "POST",
+                headers: {"Content-Type": "application/json"},
+                body: JSON.stringify({key, target}),
+            },
+        );
+        return jsonOrThrow(r, `adminAuditRunRerunCell(${runId})`);
+    },
+
     /** Admin: append a validation (cross-format parity) pass to a finished
      * run — folded into the same run, not a new one. 409 if the run isn't
      * finished or has already been validated. Returns the (reopened) run. */
diff --git a/src/frontend/src/state/auditToastStore.ts b/src/frontend/src/state/auditToastStore.ts
new file mode 100644
index 000000000..58fd06162
--- /dev/null
+++ b/src/frontend/src/state/auditToastStore.ts
@@ -0,0 +1,21 @@
+import {create} from "zustand";
+import {persist} from "zustand/middleware";
+
+// Whether the ambient "audit sweep in progress" toast is hidden. Toggled from the Audit Runs
+// panel; the toast (ConversionProgress) reads it. Persisted so the operator's choice sticks.
+interface AuditToastState {
+    hidden: boolean;
+    setHidden: (v: boolean) => void;
+    toggle: () => void;
+}
+
+export const useAuditToastStore = create<AuditToastState>()(
+    persist(
+        (set) => ({
+            hidden: false,
+            setHidden: (hidden) => set({hidden}),
+            toggle: () => set((s) => ({hidden: !s.hidden})),
+        }),
+        {name: "ada-audit-toast"},
+    ),
+);
diff --git a/src/frontend/src/state/galleryStore.ts b/src/frontend/src/state/galleryStore.ts
new file mode 100644
index 000000000..1042db681
--- /dev/null
+++ b/src/frontend/src/state/galleryStore.ts
@@ -0,0 +1,78 @@
+import {create} from "zustand";
+import {persist} from "zustand/middleware";
+
+// Gallery mode: a small prev/next HUD. The "files" walk cycles the
+// current scope's loadable FILES one at a time (clear → load). The
+// "geoms" walk cycles the GEOMS already in the scene, selecting +
+// framing each in turn (a slideshow of the model's parts), in one of
+// three orders:
+//   - "scene": scene/batched-mesh traversal order (roughly load order).
+//   - "density": triangles per surface area — heaviest/most-detailed
+//     geometry first.
+//   - "tree": the model tree's hierarchy order (parent → children DFS).
+//   - "distorted": only geoms with a "crows-nest" spike (a thin triangle
+//     shooting out past the geometry), worst-first — the tessellation-bug
+//     inspector. Forces geometry edges on so the spikes are visible.
+// "hideUnselected" optionally isolates the current geom during a geom
+// walk (hides everything else) so it reads clearly.
+//
+// The enabled flag and the walk preferences persist (viewing
+// preferences); the per-walk index is transient and lives in the
+// GalleryControls component (it depends on the current scope / scene).
+export type GalleryWalk = "files" | "geoms";
+export type GeomWalkOrder = "scene" | "density" | "tree" | "distorted";
+
+interface GalleryState {
+    enabled: boolean;
+    setEnabled: (v: boolean) => void;
+    toggle: () => void;
+
+    walk: GalleryWalk;
+    setWalk: (w: GalleryWalk) => void;
+
+    geomOrder: GeomWalkOrder;
+    setGeomOrder: (o: GeomWalkOrder) => void;
+
+    hideUnselected: boolean;
+    setHideUnselected: (v: boolean) => void;
+    toggleHideUnselected: () => void;
+
+    // Measured height (px) of the mobile gallery bar so bottom-anchored overlays (the audit toast)
+    // can stack ABOVE it instead of overlapping. 0 when the bar isn't shown (desktop / gallery off).
+    // Transient — not persisted.
+    mobileBarHeight: number;
+    setMobileBarHeight: (h: number) => void;
+}
+
+export const useGalleryStore = create<GalleryState>()(
+    persist(
+        (set) => ({
+            enabled: false,
+            setEnabled: (v) => set({enabled: v}),
+            toggle: () => set((s) => ({enabled: !s.enabled})),
+
+            walk: "files",
+            setWalk: (walk) => set({walk}),
+
+            geomOrder: "scene",
+            setGeomOrder: (geomOrder) => set({geomOrder}),
+
+            hideUnselected: false,
+            setHideUnselected: (hideUnselected) => set({hideUnselected}),
+            toggleHideUnselected: () => set((s) => ({hideUnselected: !s.hideUnselected})),
+
+            mobileBarHeight: 0,
+            setMobileBarHeight: (mobileBarHeight) => set({mobileBarHeight}),
+        }),
+        {
+            name: "ada-gallery",
+            // Persist only the viewing preferences; mobileBarHeight is transient runtime layout.
+            partialize: (s) => ({
+                enabled: s.enabled,
+                walk: s.walk,
+                geomOrder: s.geomOrder,
+                hideUnselected: s.hideUnselected,
+            }),
+        },
+    ),
+);
diff --git a/src/frontend/src/state/meshPanelStore.ts b/src/frontend/src/state/meshPanelStore.ts
new file mode 100644
index 000000000..70cebbdb1
--- /dev/null
+++ b/src/frontend/src/state/meshPanelStore.ts
@@ -0,0 +1,39 @@
+import {create} from "zustand";
+import {persist} from "zustand/middleware";
+import {DEFAULT_SPIKE_THRESHOLDS} from "@/utils/mesh_select/meshStats";
+
+// Editable spike thresholds for the Scene panel's "Mesh" mode (Scene dropdown → Mesh). The section
+// scans every geom in the scene for "crows-nest" tessellation spikes (see meshStats.ts) and lists
+// the offenders in a distortion-sorted table; these two thresholds let a scan be re-run tighter or
+// looser than the gallery's fixed defaults, and persist as a viewing preference. Visibility is owned
+// by sceneInfoStore (mode === "mesh"); scan RESULTS are transient in the section component.
+interface MeshPanelState {
+    spikeAspectMin: number;
+    spikeOutlierK: number;
+    setSpikeAspectMin: (v: number) => void;
+    setSpikeOutlierK: (v: number) => void;
+    resetThresholds: () => void;
+}
+
+export const useMeshPanelStore = create<MeshPanelState>()(
+    persist(
+        (set) => ({
+            spikeAspectMin: DEFAULT_SPIKE_THRESHOLDS.spikeAspectMin,
+            spikeOutlierK: DEFAULT_SPIKE_THRESHOLDS.spikeOutlierK,
+            setSpikeAspectMin: (spikeAspectMin) => set({spikeAspectMin}),
+            setSpikeOutlierK: (spikeOutlierK) => set({spikeOutlierK}),
+            resetThresholds: () =>
+                set({
+                    spikeAspectMin: DEFAULT_SPIKE_THRESHOLDS.spikeAspectMin,
+                    spikeOutlierK: DEFAULT_SPIKE_THRESHOLDS.spikeOutlierK,
+                }),
+        }),
+        {
+            name: "ada-mesh-panel",
+            partialize: (s) => ({
+                spikeAspectMin: s.spikeAspectMin,
+                spikeOutlierK: s.spikeOutlierK,
+            }),
+        },
+    ),
+);
diff --git a/src/frontend/src/state/model_worker/cacheModelUtils.ts b/src/frontend/src/state/model_worker/cacheModelUtils.ts
index 10ef61a0e..50b13242d 100644
--- a/src/frontend/src/state/model_worker/cacheModelUtils.ts
+++ b/src/frontend/src/state/model_worker/cacheModelUtils.ts
@@ -1,6 +1,9 @@
 // state/cacheModelUtils.ts
 import {modelStore} from "./modelStore";
 import {useTreeViewStore} from "../treeViewStore";
+import {useOptionsStore} from "@/state/optionsStore";
+import {clearFaceHighlight} from "@/utils/mesh_select/faceHighlight";
+import {useObjectInfoStore} from "@/state/objectInfoStore";
 import {TreeNodeData} from "@/components/tree_view/CustomNode";
 
 /**
@@ -51,9 +54,35 @@ export async function cacheAndBuildTree(
         >;
     }
 
+    // Opt-in per-face clickable regions: face_ranges_node<idx> = {rangeId: [[start,len,faceId,seq],...]}
+    // where start/len are relative to that solid's draw range. Present only for GLBs converted with
+    // face-region capture; absent otherwise (the faces toggle stays hidden).
+    const faceRanges: Record<string, Record<number, [number, number, number, number][]>> = {};
+    for (const k of Object.keys(rawUserData).filter((k) =>
+        k.startsWith("face_ranges_node")
+    )) {
+        const idx = k.slice("face_ranges_node".length);
+        faceRanges[`node${idx}`] = rawUserData[k] as Record<
+            number,
+            [number, number, number, number][]
+        >;
+    }
+
+    // Advertise face-region availability so the scene-info solid/faces toggle appears (or hides).
+    const hasFaceRegions = Object.keys(faceRanges).length > 0;
+    const opts = useOptionsStore.getState();
+    opts.setFaceRegionsAvailable(hasFaceRegions);
+    // Loading a model that can't do face picking snaps the mode back to Solid, so the toggle (now
+    // hidden) can't leave clicks stuck on the raycast path with no face id ever resolving.
+    if (!hasFaceRegions && opts.faceLevelPicking) {
+        opts.setFaceLevelPicking(false);
+        clearFaceHighlight();
+        useObjectInfoStore.getState().setClickedFace(null);
+    }
+
     // 2) cache → IndexedDB
     try {
-        await modelStore.add(key, hierarchy, drawRanges);
+        await modelStore.add(key, hierarchy, drawRanges, faceRanges);
     } catch (err: unknown) {
         console.error("Failed to cache model metadata", err);
         // you could even early-return here if caching is critical
diff --git a/src/frontend/src/state/model_worker/modelCache.worker.ts b/src/frontend/src/state/model_worker/modelCache.worker.ts
index 32dff575f..50ff192bb 100644
--- a/src/frontend/src/state/model_worker/modelCache.worker.ts
+++ b/src/frontend/src/state/model_worker/modelCache.worker.ts
@@ -7,10 +7,13 @@ export interface ModelData {
     key: string;
     hierarchy: Record<string, [string, string | number]>;
     drawRanges: Record<string, Record<number, [number, number]>>;
+    faceRanges?: FaceRangesMap;
 }
 
 // In-worker, we’ll keep an in-memory map from key → its drawRanges
 type DrawRangesMap = Record<string, Record<number, [number, number]>>;
+// meshName → rangeId → list of [relStart, len, faceId, seq] (start/len relative to the draw range)
+type FaceRangesMap = Record<string, Record<number, [number, number, number, number][]>>;
 type HierarchyMap = Record<string, [string, string | number]>;
 
 class ModelWorkerAPI {
@@ -18,6 +21,7 @@ class ModelWorkerAPI {
     private models!: Table<ModelData, string>;
     private memoryCacheDrawRange = new Map<string, DrawRangesMap>();
     private memoryCacheHierarchy = new Map<string, HierarchyMap>();
+    private memoryCacheFaceRange = new Map<string, FaceRangesMap>();
 
     constructor() {
         this.db = new Dexie("ModelCacheDB");
@@ -25,11 +29,54 @@ class ModelWorkerAPI {
         this.models = this.db.table("models") as Table<ModelData, string>;
     }
 
-    async add(key: string, hierarchy: Record<string, [string, string | number]>, drawRanges: Record<string, Record<number, [number, number]>>): Promise<void> {
-        await this.models.put({key, hierarchy, drawRanges});
+    async add(key: string, hierarchy: Record<string, [string, string | number]>, drawRanges: Record<string, Record<number, [number, number]>>, faceRanges?: FaceRangesMap): Promise<void> {
+        await this.models.put({key, hierarchy, drawRanges, faceRanges});
         // keep in memory for super-fast lookups
         this.memoryCacheDrawRange.set(key, drawRanges);
         this.memoryCacheHierarchy.set(key, hierarchy);
+        if (faceRanges) this.memoryCacheFaceRange.set(key, faceRanges);
+    }
+
+    /** True iff this model carries per-face clickable regions (opt-in face_ranges_node extras). */
+    async hasFaceRanges(key: string): Promise<boolean> {
+        const fr = this.memoryCacheFaceRange.get(key);
+        return !!fr && Object.keys(fr).length > 0;
+    }
+
+    /**
+     * Resolve a clicked triangle to its source face region. Finds the object's draw range
+     * (faceStart ∈ [start,start+len)) then the face sub-range within it (offsets are relative to
+     * the draw-range start). Returns {rangeId, faceId, seq} or null.
+     */
+    async getFaceInfo(
+        key: string,
+        meshName: string,
+        faceIndex: number
+    ): Promise<{rangeId: string; faceId: number; seq: number; start: number; length: number} | null> {
+        const faceRanges = this.memoryCacheFaceRange.get(key);
+        const drawRanges = this.memoryCacheDrawRange.get(key);
+        if (!faceRanges || !drawRanges) return null;
+        const facesForMesh = faceRanges[meshName];
+        const rangesForMesh = drawRanges[meshName];
+        if (!facesForMesh || !rangesForMesh) return null;
+
+        const faceStart = faceIndex * 3;
+        for (const [rangeId, [start, length]] of Object.entries(rangesForMesh)) {
+            if (faceStart >= start && faceStart < start + length) {
+                const subs = facesForMesh[rangeId as unknown as number];
+                if (!subs) return null;
+                const rel = faceStart - start; // face offsets are relative to the draw range
+                for (const [fStart, fLen, faceId, seq] of subs) {
+                    if (rel >= fStart && rel < fStart + fLen) {
+                        // start/length are ABSOLUTE index positions (draw-range start + face offset),
+                        // ready for CustomBatchedMesh.highlightFaceRange.
+                        return {rangeId, faceId, seq, start: start + fStart, length: fLen};
+                    }
+                }
+                return null;
+            }
+        }
+        return null;
     }
 
     async get(key: string): Promise<ModelData | undefined> {
@@ -178,7 +225,11 @@ class ModelWorkerAPI {
             if (parent === "*" || parent === null) {
                 root = nodes[string_id];
             } else {
-                let parent_id = id_rangeIdMap.get(parent);
+                // id_hierarchy keys are JSON strings, but the parent field is emitted as a NUMBER by
+                // the native C++ writer (build_scene_extras: `hier << parent`), so a raw Map.get(0)
+                // misses the "0" key and the whole tree flattens ("No parent found for X (0)").
+                // Coerce to string so numeric and string parents both resolve.
+                let parent_id = id_rangeIdMap.get(String(parent));
                 if (!parent_id) {
                     console.warn(
                         `ModelWorkerAPI: No parent found for ${string_id} (${parent})`
diff --git a/src/frontend/src/state/model_worker/modelStore.ts b/src/frontend/src/state/model_worker/modelStore.ts
index 02c373aad..25de738b6 100644
--- a/src/frontend/src/state/model_worker/modelStore.ts
+++ b/src/frontend/src/state/model_worker/modelStore.ts
@@ -15,7 +15,8 @@ export interface ModelStoreAPI {
     add(
         key: string,
         hierarchy: Record<string, [string, string | number]>,
-        drawRanges: Record<string, Record<number, [number, number]>>
+        drawRanges: Record<string, Record<number, [number, number]>>,
+        faceRanges?: Record<string, Record<number, [number, number, number, number][]>>
     ): Promise<void>;
 
     get(key: string): Promise<ModelData | undefined>;
@@ -60,6 +61,15 @@ export interface ModelStoreAPI {
         key: string,
         memberNames: string[]
     ): Promise<Array<[string, string]>>; // Returns [meshName, rangeId] pairs
+
+    // Opt-in per-face clickable regions
+    hasFaceRanges(key: string): Promise<boolean>;
+
+    getFaceInfo(
+        key: string,
+        meshName: string,
+        faceIndex: number
+    ): Promise<{rangeId: string; faceId: number; seq: number; start: number; length: number} | null>;
 }
 
 const worker = new Worker();
diff --git a/src/frontend/src/state/objectInfoStore.ts b/src/frontend/src/state/objectInfoStore.ts
index dbb5fd739..c477685ee 100644
--- a/src/frontend/src/state/objectInfoStore.ts
+++ b/src/frontend/src/state/objectInfoStore.ts
@@ -7,6 +7,10 @@ type ObjectInfoState = {
     setFaceIndex: (faceIndex: number | null) => void;
     clickCoordinate: { x: number; y: number, z: number } | null;
     setClickCoordinate: (clickCoordinate: { x: number; y: number, z: number } | null) => void;
+    // Source face region of the last click (opt-in face-level picking): STEP/IFC entity id + the
+    // 0-based face index within the solid. null when face picking is off or unavailable.
+    clickedFace: { faceId: number; seq: number } | null;
+    setClickedFace: (clickedFace: { faceId: number; seq: number } | null) => void;
     jsonData: any | null;
     setJsonData: (jsonData: any | null) => void;
     // Source file owning the currently-selected object. Passed back
@@ -25,6 +29,8 @@ export const useObjectInfoStore = create<ObjectInfoState>((set) => ({
     setFaceIndex: (faceIndex) => set(() => ({faceIndex})),
     clickCoordinate: null,
     setClickCoordinate: (clickCoordinate) => set(() => ({clickCoordinate})),
+    clickedFace: null,
+    setClickedFace: (clickedFace) => set(() => ({clickedFace})),
     jsonData: null,
     setJsonData: (jsonData) => set(() => ({jsonData})),
     fileName: null,
diff --git a/src/frontend/src/state/optionsStore.ts b/src/frontend/src/state/optionsStore.ts
index 2ac8916a9..f97715080 100644
--- a/src/frontend/src/state/optionsStore.ts
+++ b/src/frontend/src/state/optionsStore.ts
@@ -8,6 +8,8 @@ export type OptionsState = {
     isOptionsVisible: boolean;
     showPerf: boolean;
     showEdges: boolean;
+    // Show the "Mesh" tessellation-stats block inside the selection's Properties panel.
+    showMeshStats: boolean;
     hideTessellationEdges: boolean;
     lockTranslation: boolean;
     enableWebsocket: boolean;
@@ -15,14 +17,30 @@ export type OptionsState = {
     pointSize: number;
     pointSizeAbsolute: boolean;
     useGpuPointPicking: boolean;
+    // Fit the camera to the whole model after each load (zoom-to-all). Default ON so a
+    // freshly loaded model — and each geom cycled through in gallery mode — is framed
+    // without a manual Shift+A. Off keeps the camera where it is across loads.
+    autoFit: boolean;
     // Auto-convert uploaded source files to GLB on upload. Default OFF — an
     // upload shouldn't silently spend worker time / spawn a conversion the user
     // didn't ask for; they trigger conversion explicitly from the file row.
     autoConvertOnUpload: boolean;
+    // Decimal places shown for the "Clicked at" coordinate row. Adjustable because a
+    // small model (a few mm across) needs more decimals before the displayed position
+    // changes at all between nearby clicks; a building-scale model wants fewer.
+    clickedCoordDecimals: number;
+    // Face-level picking (opt-in). When on, clicks resolve the exact source face region (STEP/IFC
+    // #id) via the raycast path instead of the fast GPU object-pick. Only meaningful for GLBs that
+    // carry face_ranges (the scene-info toggle is hidden otherwise).
+    faceLevelPicking: boolean;
+    // Runtime capability (not a user preference): the most recently loaded model carries per-face
+    // regions. Gates the solid/faces toggle so it only appears when face picking can actually work.
+    faceRegionsAvailable: boolean;
 
     setIsOptionsVisible: (value: boolean) => void;
     setShowPerf: (value: boolean) => void;
     setShowEdges: (value: boolean) => void;
+    setShowMeshStats: (value: boolean) => void;
     setHideTessellationEdges: (value: boolean) => void;
     setLockTranslation: (value: boolean) => void;
     setEnableWebsocket: (value: boolean) => void;
@@ -30,13 +48,18 @@ export type OptionsState = {
     setPointSize: (value: number) => void;
     setPointSizeAbsolute: (value: boolean) => void;
     setUseGpuPointPicking: (value: boolean) => void;
+    setAutoFit: (value: boolean) => void;
     setAutoConvertOnUpload: (value: boolean) => void;
+    setClickedCoordDecimals: (value: number) => void;
+    setFaceLevelPicking: (value: boolean) => void;
+    setFaceRegionsAvailable: (value: boolean) => void;
 };
 
 export const useOptionsStore = create<OptionsState>((set) => ({
     isOptionsVisible: false,
     showPerf: false,
     showEdges: true,
+    showMeshStats: true,
     hideTessellationEdges: true,
     lockTranslation: false,
     enableWebsocket: true,
@@ -44,11 +67,16 @@ export const useOptionsStore = create<OptionsState>((set) => ({
     pointSize: 0.01,
     pointSizeAbsolute: true,
     useGpuPointPicking: true,
+    autoFit: true,
     autoConvertOnUpload: false,
+    clickedCoordDecimals: 3,
+    faceLevelPicking: false,
+    faceRegionsAvailable: false,
 
     setIsOptionsVisible: (v) => set({isOptionsVisible: v}),
     setShowPerf: (v) => set({showPerf: v}),
     setShowEdges: (v) => set({showEdges: v}),
+    setShowMeshStats: (v) => set({showMeshStats: v}),
     setHideTessellationEdges: (v) => set({hideTessellationEdges: v}),
     setLockTranslation: (v) => set({lockTranslation: v}),
     setEnableWebsocket: (v) => set({enableWebsocket: v}),
@@ -56,5 +84,9 @@ export const useOptionsStore = create<OptionsState>((set) => ({
     setPointSize: (v) => set({pointSize: v}),
     setPointSizeAbsolute: (v) => set({pointSizeAbsolute: v}),
     setUseGpuPointPicking: (v) => set({useGpuPointPicking: v}),
+    setAutoFit: (v) => set({autoFit: v}),
     setAutoConvertOnUpload: (v) => set({autoConvertOnUpload: v}),
+    setClickedCoordDecimals: (v) => set({clickedCoordDecimals: v}),
+    setFaceLevelPicking: (v) => set({faceLevelPicking: v}),
+    setFaceRegionsAvailable: (v) => set({faceRegionsAvailable: v}),
 }));
diff --git a/src/frontend/src/state/sceneInfoStore.ts b/src/frontend/src/state/sceneInfoStore.ts
index 18533829d..c1ee360ce 100644
--- a/src/frontend/src/state/sceneInfoStore.ts
+++ b/src/frontend/src/state/sceneInfoStore.ts
@@ -45,7 +45,7 @@ export interface UtilityResult {
   summary?: Record<string, unknown>;
 }
 
-export type SceneInfoMode = 'info' | 'utilities' | 'section' | 'fem';
+export type SceneInfoMode = 'info' | 'utilities' | 'section' | 'fem' | 'mesh';
 
 interface SceneInfoState {
   show_scene_info_box: boolean;
diff --git a/src/frontend/src/state/scopeStore.ts b/src/frontend/src/state/scopeStore.ts
index cd09e8bbf..95e3916b0 100644
--- a/src/frontend/src/state/scopeStore.ts
+++ b/src/frontend/src/state/scopeStore.ts
@@ -4,8 +4,9 @@ import {persist} from "zustand/middleware";
 // One scope the user is browsing right now. Mirrors the backend's
 // /api/me response.
 export interface ScopeOption {
-    kind: "shared" | "user" | "project";
-    id: string | null; // 'me' for user-scope here; null for shared
+    kind: "shared" | "user" | "project" | "corpus";
+    // 'me' for user-scope; null for shared; the corpus slug for corpus.
+    id: string | null;
     name: string;
 }
 
@@ -66,5 +67,6 @@ export function scopeUrlPart(s: ScopeOption | null): string {
     if (!s) return "shared";
     if (s.kind === "shared") return "shared";
     if (s.kind === "user") return "user:me"; // server resolves 'me' to the caller's sub
+    if (s.kind === "corpus") return `corpus:${s.id}`; // admin-only, gated server-side
     return `project:${s.id}`;
 }
diff --git a/src/frontend/src/utils/mesh_select/CustomBatchedMesh.ts b/src/frontend/src/utils/mesh_select/CustomBatchedMesh.ts
index e45b35c0c..5d207383a 100644
--- a/src/frontend/src/utils/mesh_select/CustomBatchedMesh.ts
+++ b/src/frontend/src/utils/mesh_select/CustomBatchedMesh.ts
@@ -39,6 +39,7 @@ export class CustomBatchedMesh extends THREE.Mesh {
     private edgeMesh?: THREE.LineSegments;
     private rangeIdToIndex?: Map<string, number>;
     private edgeMaterial?: THREE.ShaderMaterial;
+    public edgesEligible = false; // true once a design edge overlay was built (persists across rebuilds)
 
     // Cached materials to avoid per-click allocations for non-vertex-colored meshes
     private _matSelected?: THREE.Material;
@@ -48,6 +49,10 @@ export class CustomBatchedMesh extends THREE.Mesh {
     private _usesVertexColorsFlag: boolean = false;
     private _baseColors?: Float32Array; // snapshot of current animated/base colors
     private _selectionOverlay?: THREE.Mesh;
+    // Independent overlay for per-face highlighting (opt-in face picking) — a single index sub-range
+    // drawn in a distinct colour on top of object selection. Separate from _selectionOverlay so the
+    // two never fight over materials/groups.
+    private _faceOverlay?: THREE.Mesh;
     private _overlaySourceIndices?: Uint32Array; // mapping: overlay vertex i -> base vertex index
 
     // Class properties for raycasting
@@ -236,6 +241,7 @@ export class CustomBatchedMesh extends THREE.Mesh {
 
     /** call this when you have a renderer and want the overlay in the scene */
     public getEdgeOverlay(renderer: THREE.WebGLRenderer): THREE.LineSegments {
+        this.edgesEligible = true; // this mesh takes a design edge overlay (FEA meshes never call this)
         if (!this.edgeMesh) {
             // first‐time initialization
             const {geometry, rangeIdToIndex} =
@@ -253,6 +259,19 @@ export class CustomBatchedMesh extends THREE.Mesh {
         return this.edgeMesh;
     }
 
+    /** Drop the cached edge overlay so the next getEdgeOverlay() rebuilds it from the CURRENT options
+     *  (e.g. after hideTessellationEdges toggled feature-only vs full-triangulation edges). Returns the
+     *  old LineSegments so the caller can remove it from the scene before re-adding the rebuilt one. */
+    public invalidateEdgeOverlay(): THREE.LineSegments | undefined {
+        const old = this.edgeMesh;
+        (this.edgeMesh?.geometry as THREE.BufferGeometry | undefined)?.dispose();
+        this.edgeMaterial?.dispose();
+        this.edgeMesh = undefined;
+        this.edgeMaterial = undefined;
+        this.rangeIdToIndex = undefined;
+        return old;
+    }
+
     public updateSelectionGroups(rangeIds: string[]) {
         this.selectedRanges = new Set(rangeIds);
 
@@ -388,6 +407,7 @@ export class CustomBatchedMesh extends THREE.Mesh {
      * never falls. Idempotent; only disposes per-instance clones, never shared singletons. */
     dispose(): void {
         this._disposeSelectionOverlay();
+        this.clearFaceHighlight();
         if (this.edgeMesh) {
             (this.edgeMesh.geometry as THREE.BufferGeometry | undefined)?.dispose();
             this.edgeMesh = undefined;
@@ -421,6 +441,72 @@ export class CustomBatchedMesh extends THREE.Mesh {
         }
     }
 
+    /** Highlight a single index sub-range (one source face) in a distinct colour, on top of object
+     *  selection. start/length are absolute positions into this mesh's index buffer. Independent of
+     *  the object-selection overlay. Pass length<=0 (or call clearFaceHighlight) to remove it. */
+    public highlightFaceRange(start: number, length: number): void {
+        const srcGeom = this.geometry as THREE.BufferGeometry;
+        const idxAttr = srcGeom.getIndex();
+        const idxCount = idxAttr ? idxAttr.count : (srcGeom.attributes.position?.count ?? 0);
+        if (!(length > 0) || idxCount === 0 || start < 0 || start >= idxCount) {
+            this.clearFaceHighlight();
+            return;
+        }
+        const s = start;
+        const c = Math.min(length, idxCount - start);
+
+        let overlayGeom: THREE.BufferGeometry;
+        if (this._faceOverlay) {
+            overlayGeom = this._faceOverlay.geometry as THREE.BufferGeometry;
+        } else {
+            // Reference (do NOT clone) the base attributes/index + morphs so the GPU morphs it for free
+            // and no extra vertex memory is used — same approach as the selection overlay.
+            overlayGeom = new THREE.BufferGeometry();
+            if (srcGeom.index) overlayGeom.setIndex(srcGeom.index);
+            for (const name of Object.keys(srcGeom.attributes))
+                overlayGeom.setAttribute(name, srcGeom.getAttribute(name));
+            overlayGeom.morphAttributes = {} as any;
+            if (srcGeom.morphAttributes)
+                for (const mName of Object.keys(srcGeom.morphAttributes))
+                    (overlayGeom.morphAttributes as any)[mName] = (srcGeom.morphAttributes as any)[mName];
+            overlayGeom.morphTargetsRelative = srcGeom.morphTargetsRelative === true;
+
+            // Same blue as object selection — in Faces mode only the clicked face is painted (the rest
+            // of the solid keeps its normal colour), so it reads as a face-granular selection.
+            const visMat = selectedMaterial.clone();
+            visMat.side = THREE.DoubleSide;
+            (visMat as any).morphTargets = true;
+            (visMat as any).polygonOffset = true;
+            (visMat as any).polygonOffsetFactor = -2; // sit in front of the base surface
+            (visMat as any).polygonOffsetUnits = -2;
+            const invMat = new THREE.MeshBasicMaterial({visible: false});
+            (invMat as any).morphTargets = true;
+
+            this._faceOverlay = new THREE.Mesh(overlayGeom, [visMat, invMat]);
+            this._faceOverlay.matrixAutoUpdate = true;
+            this._faceOverlay.layers.mask = this.layers.mask;
+            this.add(this._faceOverlay);
+        }
+        (this._faceOverlay as any).morphTargetInfluences = (this as any).morphTargetInfluences;
+        (this._faceOverlay as any).morphTargetDictionary = (this as any).morphTargetDictionary;
+
+        // groups: [0,s) invisible, [s,s+c) the visible face, [s+c,end) invisible
+        overlayGeom.clearGroups();
+        if (s > 0) overlayGeom.addGroup(0, s, 1);
+        overlayGeom.addGroup(s, c, 0);
+        if (s + c < idxCount) overlayGeom.addGroup(s + c, idxCount - (s + c), 1);
+    }
+
+    /** Remove the per-face highlight overlay. Disposes only the cloned materials (the geometry shares
+     *  base attributes — disposing it would free the base mesh's GPU buffers). */
+    public clearFaceHighlight(): void {
+        if (!this._faceOverlay) return;
+        this.remove(this._faceOverlay);
+        const m = this._faceOverlay.material as THREE.Material | THREE.Material[];
+        (Array.isArray(m) ? m : [m]).forEach((x) => x && x.dispose());
+        this._faceOverlay = undefined;
+    }
+
     private _rebuildSelectionOverlay(rangeIds: string[]): void {
         // Clear overlay when nothing selected
         if (!rangeIds || rangeIds.length === 0) {
diff --git a/src/frontend/src/utils/mesh_select/faceHighlight.ts b/src/frontend/src/utils/mesh_select/faceHighlight.ts
new file mode 100644
index 000000000..66dab0a25
--- /dev/null
+++ b/src/frontend/src/utils/mesh_select/faceHighlight.ts
@@ -0,0 +1,20 @@
+// Coordinates the single active per-face highlight across meshes: highlighting a face on one mesh
+// clears any face highlight on the previously-highlighted mesh, so only the clicked face is ever lit.
+import type {CustomBatchedMesh} from "./CustomBatchedMesh";
+
+let current: CustomBatchedMesh | null = null;
+
+/** Highlight [start, length) (absolute index positions) on `mesh`, clearing the prior highlight. */
+export function setFaceHighlight(mesh: CustomBatchedMesh, start: number, length: number): void {
+    if (current && current !== mesh) current.clearFaceHighlight();
+    current = mesh;
+    mesh.highlightFaceRange(start, length);
+}
+
+/** Remove the active per-face highlight, if any. */
+export function clearFaceHighlight(): void {
+    if (current) {
+        current.clearFaceHighlight();
+        current = null;
+    }
+}
diff --git a/src/frontend/src/utils/mesh_select/handleClickEmptySpace.ts b/src/frontend/src/utils/mesh_select/handleClickEmptySpace.ts
index 315f266c1..de9b9224d 100644
--- a/src/frontend/src/utils/mesh_select/handleClickEmptySpace.ts
+++ b/src/frontend/src/utils/mesh_select/handleClickEmptySpace.ts
@@ -1,36 +1,26 @@
 import {useSelectedObjectStore} from "@/state/useSelectedObjectStore";
-import {CustomBatchedMesh} from "./CustomBatchedMesh";
 import * as THREE from "three";
 import {Object3D} from "three";
 import {clearPointSelectionMask} from "../scene/pointsImpostor";
 import {sceneRef} from "@/state/refs";
+import {clearFaceHighlight} from "./faceHighlight";
+import {useObjectInfoStore} from "@/state/objectInfoStore";
 
-export function handleClickEmptySpace(event: MouseEvent) {
-    const selectedObjects = useSelectedObjectStore.getState().selectedObjects;
-    selectedObjects.forEach((drawRangeIds, mesh) => {
-        if (!(mesh instanceof CustomBatchedMesh)) {
-            // loop recursively through the children of the mesh
-            (mesh as Object3D).traverse((child: Object3D) => {
-                if (child instanceof CustomBatchedMesh) {
-                    child.clearSelectionGroups();
-                }
-            });
-        } else if ((mesh as any).isPoints) {
-            clearPointSelectionMask(mesh as unknown as THREE.Points);
-        } else {
-            mesh.clearSelectionGroups();
-        }
-    });
+export function handleClickEmptySpace(_event: MouseEvent) {
+    // Fully deselect: clearSelectedObjects clears each object's visual selection groups AND
+    // empties the selectedObjects map, so the info box / tree view also drop the selection.
+    // (Clearing only the visual groups, as this used to, left a stale selection in the store.)
+    useSelectedObjectStore.getState().clearSelectedObjects();
+    // Drop any per-face highlight + its Properties row along with the object selection.
+    clearFaceHighlight();
+    useObjectInfoStore.getState().setClickedFace(null);
 
-    // traverse over Three.POINTS in scene objects
+    // Also drop point-selection masks on any Points NOT tracked in the store.
     const scene = sceneRef.current;
-    if (!scene) {
-        return;
-    }
-    (scene.traverse((child: Object3D) => {
-            if (child instanceof THREE.Points) {
-                clearPointSelectionMask(child as THREE.Points);
-            }
+    if (!scene) return;
+    scene.traverse((child: Object3D) => {
+        if (child instanceof THREE.Points) {
+            clearPointSelectionMask(child as THREE.Points);
         }
-    ))
+    });
 }
\ No newline at end of file
diff --git a/src/frontend/src/utils/mesh_select/handleClickMesh.ts b/src/frontend/src/utils/mesh_select/handleClickMesh.ts
index 374df1b03..b10d2fe22 100644
--- a/src/frontend/src/utils/mesh_select/handleClickMesh.ts
+++ b/src/frontend/src/utils/mesh_select/handleClickMesh.ts
@@ -3,7 +3,9 @@ import * as THREE from "three";
 import {CustomBatchedMesh} from "./CustomBatchedMesh";
 import {useModelState} from "@/state/modelState";
 import {useObjectInfoStore} from "@/state/objectInfoStore";
-import {queryMeshDrawRange, queryNameFromRangeId} from "./queryMeshDrawRange";
+import {queryMeshDrawRange, queryNameFromRangeId, queryFaceInfo} from "./queryMeshDrawRange";
+import {useOptionsStore} from "@/state/optionsStore";
+import {setFaceHighlight, clearFaceHighlight} from "./faceHighlight";
 import {perform_selection} from "./perform_selection";
 import {query_ws_server_mesh_info} from "./handlers/send_mesh_selected_info_callback";
 import {useTreeViewStore} from "@/state/treeViewStore";
@@ -36,15 +38,19 @@ export async function handleClickMesh(
     // faceIndex → rangeId worker round-trip entirely; the raycast
     // fallback still uses it.
     let rangeId: string;
+    // The mesh-name key the metadata cache actually uses — mesh.name usually, but the native GLB path
+    // keys by node<node_id>, so the draw-range lookup falls back to it. Track which one resolved so
+    // face-level picking below queries the SAME key (its earlier bug was using mesh.name unconditionally).
+    let resolvedMeshName = mesh.name;
     if (prefilledRangeId !== undefined) {
         rangeId = prefilledRangeId;
     } else {
         // ← await the worker lookup
-        const meshName = mesh.name; // e.g. "node0"
-        let drawRange = await queryMeshDrawRange(mesh.unique_key, meshName, faceIndex);
+        let drawRange = await queryMeshDrawRange(mesh.unique_key, resolvedMeshName, faceIndex);
         if (!drawRange) {
-            if (mesh.userData?.node_id) {
-                drawRange = await queryMeshDrawRange(mesh.unique_key, `node${mesh.userData?.node_id}`, faceIndex);
+            if (mesh.userData?.node_id != null) {
+                resolvedMeshName = `node${mesh.userData?.node_id}`;
+                drawRange = await queryMeshDrawRange(mesh.unique_key, resolvedMeshName, faceIndex);
             }
             if (!drawRange) {
                 console.warn("selected mesh has no draw range");
@@ -54,7 +60,33 @@ export async function handleClickMesh(
         [rangeId] = drawRange;
     }
 
-    await perform_selection(mesh, shiftKey, rangeId);
+    const facePicking = useOptionsStore.getState().faceLevelPicking;
+
+    // Face-level picking (opt-in): resolve the clicked triangle to its source face region (STEP/IFC
+    // #id) and highlight just that face in the selection colour. Try both mesh-name keys (mesh.name /
+    // node<node_id>) since the GPU-pick path supplies a prefilled rangeId and skips the draw-range
+    // lookup that would otherwise resolve the key. faceIndex comes from the refined single-mesh raycast.
+    if (facePicking && typeof intersect.faceIndex === "number") {
+        let fi = await queryFaceInfo(mesh.unique_key, mesh.name, intersect.faceIndex);
+        if (!fi && mesh.userData?.node_id != null) {
+            fi = await queryFaceInfo(mesh.unique_key, `node${mesh.userData?.node_id}`, intersect.faceIndex);
+        }
+        useObjectInfoStore.getState().setClickedFace(fi ? {faceId: fi.faceId, seq: fi.seq} : null);
+        if (fi) setFaceHighlight(mesh, fi.start, fi.length);
+        else clearFaceHighlight();
+    } else {
+        useObjectInfoStore.getState().setClickedFace(null);
+        clearFaceHighlight();
+    }
+
+    // Faces mode highlights ONLY the clicked face (the rest of the solid keeps its normal colour), so
+    // skip the whole-object selection overlay and drop any lingering one. The Properties panel still
+    // populates — it's gated on the object name set below, not on the selection store.
+    if (!facePicking) {
+        await perform_selection(mesh, shiftKey, rangeId);
+    } else {
+        useSelectedObjectStore.getState().clearSelectedObjects();
+    }
 
     // update object info
     const last_selected_name = await queryNameFromRangeId(mesh.unique_key, rangeId);
@@ -74,9 +106,9 @@ export async function handleClickMesh(
     useObjectInfoStore.getState().setJsonData(null);
     void query_ws_server_mesh_info(last_selected_name, faceIndex, activeFile);
 
-    // update tree selection
+    // update tree selection — only in Solid mode; Faces mode doesn't select the whole object
     const treeViewStore = useTreeViewStore.getState();
-    if (treeViewStore.treeData && treeViewStore.tree && !treeViewStore.isTreeCollapsed) {
+    if (!facePicking && treeViewStore.treeData && treeViewStore.tree && !treeViewStore.isTreeCollapsed) {
         // flag programmatic change
         // @ts-ignore
         treeViewStore.tree.isProgrammaticChange = true;
diff --git a/src/frontend/src/utils/mesh_select/meshStats.ts b/src/frontend/src/utils/mesh_select/meshStats.ts
new file mode 100644
index 000000000..c2173cba1
--- /dev/null
+++ b/src/frontend/src/utils/mesh_select/meshStats.ts
@@ -0,0 +1,165 @@
+import * as THREE from "three";
+import {CustomBatchedMesh} from "./CustomBatchedMesh";
+
+// Per-geom (draw-range) mesh statistics, computed client-side from the
+// batched geometry buffer. Shared by the gallery "density" walk order
+// (sort by triangles-per-area) and the Object Info "Mesh" section.
+//
+// A geom is one draw-range: [start, count] into the shared index
+// buffer. Triangles = count / 3. "density" here is triangles per unit
+// of surface AREA (m²) — the natural measure for the shell/plate
+// meshes the viewer shows; volume is reported too for solids. Both are
+// in local mesh space (metres in adapy's world).
+export interface RangeStats {
+    triangles: number;
+    vertices: number; // distinct vertices referenced by this range
+    sizeX: number;
+    sizeY: number;
+    sizeZ: number;
+    volume: number; // bounding-box volume, m³
+    area: number; // summed triangle area, m²
+    density: number; // triangles / area (0 when area is 0)
+    // "Crows-nest" spike score: how far the worst OUTLIER vertex sits from the mesh body, as a
+    // multiple of the median vertex→centroid distance. A vertex shooting out past the geometry (the
+    // crows-nest bug) scores high; benign geometry — even a deep thin extrusion whose side triangles
+    // reach right across the bbox, or a coarse curved surface — has all its vertices ON the body, so
+    // it scores ~1. Ranking by this walks the real spikes first. 0 for a tiny/degenerate mesh.
+    maxSpike: number;
+    spikeTris: number; // thin triangles that touch an outlier vertex (dist > SPIKE_OUTLIER_K · median)
+}
+
+// A triangle is "thin" (needle-like) once longest-edge² / (2·area) exceeds this.
+const SPIKE_ASPECT_MIN = 8;
+// A vertex is an OUTLIER (crows-nest spike) once its distance from the robust (median) centroid
+// exceeds this multiple of the median vertex distance. A compact body sits at ~1–3×; a genuine
+// spike is far out. This is what a raw edge/bbox reach test can't do — a deep extrusion's long side
+// edges look identical to a spike by length, but their vertices aren't outliers.
+export const SPIKE_OUTLIER_K = 4;
+
+// The two spike thresholds, adjustable from the Mesh inspection panel so a scan can be re-run tighter
+// or looser. The module constants above are the defaults (and what the gallery uses).
+export interface SpikeThresholds {
+    spikeAspectMin: number; // longest-edge² / (2·area) over which a triangle is "thin"
+    spikeOutlierK: number; // vertex-distance / median over which a vertex is a crows-nest outlier
+}
+export const DEFAULT_SPIKE_THRESHOLDS: SpikeThresholds = {
+    spikeAspectMin: SPIKE_ASPECT_MIN,
+    spikeOutlierK: SPIKE_OUTLIER_K,
+};
+
+export function computeRangeStats(
+    mesh: CustomBatchedMesh,
+    rangeId: string,
+    thresholds: SpikeThresholds = DEFAULT_SPIKE_THRESHOLDS,
+): RangeStats | null {
+    const geometry = mesh.geometry as THREE.BufferGeometry;
+    const pos = geometry.getAttribute("position") as THREE.BufferAttribute | undefined;
+    const indexAttr = geometry.getIndex();
+    const range = mesh.drawRanges.get(rangeId);
+    if (!pos || !indexAttr || !range) return null;
+
+    const [start, count] = range;
+    const idx = indexAttr.array as Uint16Array | Uint32Array;
+    const end = Math.min(start + count, idx.length);
+
+    const bbox = new THREE.Box3();
+    const seen = new Set<number>();
+    const a = new THREE.Vector3();
+    const b = new THREE.Vector3();
+    const c = new THREE.Vector3();
+    const ab = new THREE.Vector3();
+    const ac = new THREE.Vector3();
+    const cross = new THREE.Vector3();
+    const bc = new THREE.Vector3();
+    let area = 0;
+
+    for (let i = start; i + 2 < end; i += 3) {
+        const ia = idx[i];
+        const ib = idx[i + 1];
+        const ic = idx[i + 2];
+        a.fromBufferAttribute(pos, ia);
+        b.fromBufferAttribute(pos, ib);
+        c.fromBufferAttribute(pos, ic);
+        bbox.expandByPoint(a);
+        bbox.expandByPoint(b);
+        bbox.expandByPoint(c);
+        seen.add(ia);
+        seen.add(ib);
+        seen.add(ic);
+        ab.subVectors(b, a);
+        ac.subVectors(c, a);
+        area += 0.5 * cross.crossVectors(ab, ac).length();
+    }
+
+    const size = new THREE.Vector3();
+    if (!bbox.isEmpty()) bbox.getSize(size);
+    const triangles = Math.floor(count / 3);
+    const volume = size.x * size.y * size.z;
+    const density = area > 0 ? triangles / area : 0;
+
+    // --- crows-nest spike detection (outlier vertices) ---------------------------------------
+    // Robust (median-per-axis) centroid, then median vertex→centroid distance as the body scale. A
+    // vertex whose distance exceeds SPIKE_OUTLIER_K × that median is a spike (shot out past the body).
+    const verts = [...seen];
+    const median = (arr: number[]): number => {
+        if (arr.length === 0) return 0;
+        const s = arr.slice().sort((x, y) => x - y);
+        const m = s.length >> 1;
+        return s.length % 2 ? s[m] : 0.5 * (s[m - 1] + s[m]);
+    };
+    const xs: number[] = [];
+    const ys: number[] = [];
+    const zs: number[] = [];
+    for (const vi of verts) {
+        xs.push(pos.getX(vi));
+        ys.push(pos.getY(vi));
+        zs.push(pos.getZ(vi));
+    }
+    const cx = median(xs);
+    const cy = median(ys);
+    const cz = median(zs);
+    const dists = verts.map((_, k) => Math.hypot(xs[k] - cx, ys[k] - cy, zs[k] - cz));
+    const medDist = median(dists);
+    let maxSpike = 0;
+    const outliers = new Set<number>();
+    if (medDist > 1e-9) {
+        for (let k = 0; k < verts.length; k++) {
+            const ratio = dists[k] / medDist;
+            if (ratio > maxSpike) maxSpike = ratio;
+            if (ratio > thresholds.spikeOutlierK) outliers.add(verts[k]);
+        }
+    }
+
+    // Count thin triangles that touch an outlier vertex — only when outliers exist.
+    let spikeTris = 0;
+    if (outliers.size) {
+        for (let i = start; i + 2 < end; i += 3) {
+            const ia = idx[i];
+            const ib = idx[i + 1];
+            const ic = idx[i + 2];
+            if (!outliers.has(ia) && !outliers.has(ib) && !outliers.has(ic)) continue;
+            a.fromBufferAttribute(pos, ia);
+            b.fromBufferAttribute(pos, ib);
+            c.fromBufferAttribute(pos, ic);
+            ab.subVectors(b, a);
+            ac.subVectors(c, a);
+            bc.subVectors(c, b);
+            const triArea = 0.5 * cross.crossVectors(ab, ac).length();
+            const emax = Math.max(ab.length(), ac.length(), bc.length());
+            if (triArea > 0 && emax * emax > thresholds.spikeAspectMin * 2 * triArea) spikeTris++;
+        }
+    }
+
+    return {
+        triangles,
+        vertices: seen.size,
+        sizeX: size.x,
+        sizeY: size.y,
+        sizeZ: size.z,
+        volume,
+        area,
+        density,
+        maxSpike,
+        spikeTris,
+    };
+}
diff --git a/src/frontend/src/utils/mesh_select/queryMeshDrawRange.ts b/src/frontend/src/utils/mesh_select/queryMeshDrawRange.ts
index 03f3817d9..cacca4609 100644
--- a/src/frontend/src/utils/mesh_select/queryMeshDrawRange.ts
+++ b/src/frontend/src/utils/mesh_select/queryMeshDrawRange.ts
@@ -31,4 +31,19 @@ export async function queryPointRangeByRangeId(
     rangeId: string
 ): Promise<[number, number] | null> {
     return await modelStore.getPointRangeByRangeId(key, meshName, rangeId);
+}
+
+// Per-face clickable regions (opt-in face_ranges_node): resolve a clicked triangle to its source
+// face region (STEP/IFC entity id + sequential index within the solid), or null when the model
+// carries no face regions / the triangle isn't in one.
+export async function queryFaceInfo(
+    key: string,
+    meshName: string,
+    faceIndex: number
+): Promise<{rangeId: string; faceId: number; seq: number; start: number; length: number} | null> {
+    return await modelStore.getFaceInfo(key, meshName, faceIndex);
+}
+
+export async function queryHasFaceRanges(key: string): Promise<boolean> {
+    return await modelStore.hasFaceRanges(key);
 }
\ No newline at end of file
diff --git a/src/frontend/src/utils/nativeConvert/brepWriterConverter.ts b/src/frontend/src/utils/nativeConvert/brepWriterConverter.ts
new file mode 100644
index 000000000..b551bf89d
--- /dev/null
+++ b/src/frontend/src/utils/nativeConvert/brepWriterConverter.ts
@@ -0,0 +1,48 @@
+// Main-thread wrapper for the in-browser native (no-pyodide) B-rep writer (STEP→IFC / IFC→STEP).
+// Spins up the brepWriterConverter Web Worker (Comlink). Mirrors cadGlbConverter.ts.
+
+import * as Comlink from "comlink";
+
+import BrepWriterConverterWorker from "./brepWriterConverter.worker.ts?worker&inline";
+import type {BrepWriterConverterAPI, NativeBrepWriteResult, BrepDir} from "./brepWriterConverter.worker";
+
+export type {BrepDir, NativeBrepWriteResult} from "./brepWriterConverter.worker";
+
+let worker: Worker | null = null;
+let apiRemote: Comlink.Remote<BrepWriterConverterAPI> | null = null;
+
+function ensureApi(): Comlink.Remote<BrepWriterConverterAPI> {
+    if (!apiRemote) {
+        worker = new BrepWriterConverterWorker();
+        apiRemote = Comlink.wrap<BrepWriterConverterAPI>(worker);
+    }
+    return apiRemote;
+}
+
+/** Convert a STEP/IFC buffer to the other B-rep format in the worker. The buffer is transferred. */
+export async function nativeBrepWrite(
+    dir: BrepDir,
+    srcBytes: ArrayBuffer,
+    opts?: {schema?: string; maxSolids?: number},
+): Promise<NativeBrepWriteResult> {
+    return ensureApi().convert(dir, Comlink.transfer(srcBytes, [srcBytes]), opts);
+}
+
+/** Does this browser/worker support the OPFS-streaming tier for the B-rep writer? */
+export async function nativeBrepWriterOpfsAvailable(): Promise<boolean> {
+    try {
+        return await ensureApi().opfsAvailable();
+    } catch {
+        return false;
+    }
+}
+
+/** Convert a STEP/IFC at a (presigned, streamable) URL, streaming the source through OPFS so a large
+ * B-rep file never has to fit the wasm heap. Requires nativeBrepWriterOpfsAvailable(). */
+export async function nativeBrepWriteStreaming(
+    dir: BrepDir,
+    sourceUrl: string,
+    opts?: {schema?: string; maxSolids?: number},
+): Promise<NativeBrepWriteResult> {
+    return ensureApi().convertStreaming(dir, sourceUrl, opts);
+}
diff --git a/src/frontend/src/utils/nativeConvert/brepWriterConverter.worker.ts b/src/frontend/src/utils/nativeConvert/brepWriterConverter.worker.ts
new file mode 100644
index 000000000..cda09f8f9
--- /dev/null
+++ b/src/frontend/src/utils/nativeConvert/brepWriterConverter.worker.ts
@@ -0,0 +1,130 @@
+// Web Worker: native (no-pyodide) B-rep writer — STEP→IFC and IFC→STEP entirely in the browser via
+// the OCC-free adacpp_brep_writer embind module (StreamIndex/IfcResolver readers → ifc_emit/step_emit
+// emitters; no tessellation, no OCC, no ifcopenshell, no Python). ~1.3 MB. Buffered MEMFS path +
+// OPFS-streaming tier (mountOpfs) for very large B-rep files, sharing opfsWasmfs with cadGlbConverter.
+//
+// embind surface (adacpp/src/cad/brep_writer_wasm.cpp):
+//   stepToIfc(inPath, outPath, schema, deflection, angularDeg, maxSolids) -> products (0 = none/error)
+//   ifcToStep(inPath, outPath, deflection, angularDeg, maxSolids)         -> products
+//   mountOpfs(mountPoint) -> 0 ok
+
+import * as Comlink from "comlink";
+
+import {loadEmscriptenModule} from "@/utils/wasm/emscriptenLoader";
+import {WasmfsModule, OPFS_MOUNT, ensureOpfsMounted, streamUrlToOpfs, unlinkAll} from "./opfsWasmfs";
+
+const WASM_URL = "/wasm/adacpp_brep_writer.js";
+
+// Conversion direction. The wire target (ifc/step) determines which verb runs.
+export type BrepDir = "step2ifc" | "ifc2step";
+
+interface EmscriptenFS {
+    writeFile(path: string, data: Uint8Array): void;
+    readFile(path: string): Uint8Array;
+    unlink(path: string): void;
+    mkdir(path: string): void;
+    open(path: string, flags: string): unknown;
+    write(stream: unknown, buffer: Uint8Array, offset: number, length: number, position: number): number;
+    close(stream: unknown): void;
+}
+interface EmModule extends WasmfsModule {
+    FS: EmscriptenFS;
+    stepToIfc(
+        inPath: string,
+        outPath: string,
+        schema: string,
+        deflection: number,
+        angularDeg: number,
+        maxSolids: number,
+    ): number;
+    ifcToStep(inPath: string, outPath: string, deflection: number, angularDeg: number, maxSolids: number): number;
+    mountOpfs(mountPoint: string): number;
+}
+
+let modulePromise: Promise<EmModule> | null = null;
+function getModule(): Promise<EmModule> {
+    if (!modulePromise) modulePromise = loadEmscriptenModule<EmModule>(WASM_URL);
+    return modulePromise;
+}
+
+export interface NativeBrepWriteResult {
+    output: ArrayBuffer;
+    products: number;
+    ms: number;
+}
+
+// AP242 face-set fallback tolerances (only used for geometry the analytic emitter can't represent);
+// match the adapy production defaults. IFC schema for the STEP→IFC direction.
+const DEFAULT_DEFLECTION = 2.0;
+const DEFAULT_ANGULAR_DEG = 20.0;
+const DEFAULT_IFC_SCHEMA = "IFC4X3_ADD2";
+
+const srcExt = (dir: BrepDir) => (dir === "step2ifc" ? "step" : "ifc");
+const outExt = (dir: BrepDir) => (dir === "step2ifc" ? "ifc" : "step");
+
+// Run the writer verb for `dir` on inPath → outPath. Returns products (>0 success).
+function runWriter(Module: EmModule, dir: BrepDir, inPath: string, outPath: string, schema: string, maxSolids: number) {
+    return dir === "step2ifc"
+        ? Module.stepToIfc(inPath, outPath, schema, DEFAULT_DEFLECTION, DEFAULT_ANGULAR_DEG, maxSolids)
+        : Module.ifcToStep(inPath, outPath, DEFAULT_DEFLECTION, DEFAULT_ANGULAR_DEG, maxSolids);
+}
+
+const api = {
+    // Can this worker OPFS-stream? (mount is the capability gate; worker-only.)
+    async opfsAvailable(): Promise<boolean> {
+        return ensureOpfsMounted(await getModule());
+    },
+
+    // Buffered path: source bytes → MEMFS → output. Simplest; fine below the OPFS threshold.
+    async convert(
+        dir: BrepDir,
+        srcBytes: ArrayBuffer,
+        opts?: {schema?: string; maxSolids?: number},
+    ): Promise<NativeBrepWriteResult> {
+        const Module = await getModule();
+        const t0 = performance.now();
+        const inPath = `/in.${srcExt(dir)}`;
+        const outPath = `/out.${outExt(dir)}`;
+        Module.FS.writeFile(inPath, new Uint8Array(srcBytes));
+        const products = runWriter(Module, dir, inPath, outPath, opts?.schema ?? DEFAULT_IFC_SCHEMA, opts?.maxSolids ?? 0);
+        if (products <= 0) {
+            throw new Error(`native ${dir === "step2ifc" ? "STEP→IFC" : "IFC→STEP"} wrote no products`);
+        }
+        const out = Module.FS.readFile(outPath);
+        const output = out.slice().buffer;
+        unlinkAll(Module, [inPath, outPath]);
+        const result: NativeBrepWriteResult = {output, products, ms: performance.now() - t0};
+        return Comlink.transfer(result, [output]);
+    },
+
+    // OPFS-streaming path: stream a (presigned) URL into OPFS through WASMFS, write off-disk, read the
+    // output back through WASMFS. For B-rep files too large to buffer in the wasm heap.
+    async convertStreaming(
+        dir: BrepDir,
+        sourceUrl: string,
+        opts?: {schema?: string; maxSolids?: number},
+    ): Promise<NativeBrepWriteResult> {
+        const Module = await getModule();
+        if (!ensureOpfsMounted(Module)) {
+            throw new Error("OPFS streaming unavailable in this worker (OPFS backend not mountable)");
+        }
+        const t0 = performance.now();
+        const inPath = `${OPFS_MOUNT}/adacpp_brep_in.${srcExt(dir)}`;
+        const outPath = `${OPFS_MOUNT}/adacpp_brep_out.${outExt(dir)}`;
+        await streamUrlToOpfs(Module, inPath, sourceUrl);
+        const cleanup = () => unlinkAll(Module, [inPath, outPath]);
+        const products = runWriter(Module, dir, inPath, outPath, opts?.schema ?? DEFAULT_IFC_SCHEMA, opts?.maxSolids ?? 0);
+        if (products <= 0) {
+            cleanup();
+            throw new Error(`native streaming ${dir === "step2ifc" ? "STEP→IFC" : "IFC→STEP"} wrote no products`);
+        }
+        const out = Module.FS.readFile(outPath);
+        const output = out.slice().buffer;
+        cleanup();
+        const result: NativeBrepWriteResult = {output, products, ms: performance.now() - t0};
+        return Comlink.transfer(result, [output]);
+    },
+};
+
+export type BrepWriterConverterAPI = typeof api;
+Comlink.expose(api);
diff --git a/src/frontend/src/utils/nativeConvert/cadGlbConverter.ts b/src/frontend/src/utils/nativeConvert/cadGlbConverter.ts
new file mode 100644
index 000000000..3aadec383
--- /dev/null
+++ b/src/frontend/src/utils/nativeConvert/cadGlbConverter.ts
@@ -0,0 +1,62 @@
+// Main-thread wrapper for the in-browser native (no-pyodide) CAD -> GLB converter (STEP + IFC). Spins
+// up the cadGlbConverter Web Worker (Comlink) and exposes kind-generic entry points. Mirrors
+// diffConverter.ts.
+
+import * as Comlink from "comlink";
+
+import CadGlbConverterWorker from "./cadGlbConverter.worker.ts?worker&inline";
+import type {CadGlbConverterAPI, NativeCadGlbResult, CadKind} from "./cadGlbConverter.worker";
+
+export type {CadKind, NativeCadGlbResult} from "./cadGlbConverter.worker";
+
+let worker: Worker | null = null;
+let apiRemote: Comlink.Remote<CadGlbConverterAPI> | null = null;
+
+function ensureApi(): Comlink.Remote<CadGlbConverterAPI> {
+    if (!apiRemote) {
+        worker = new CadGlbConverterWorker();
+        apiRemote = Comlink.wrap<CadGlbConverterAPI>(worker);
+    }
+    return apiRemote;
+}
+
+// adapy production tessellation defaults (see adacpp step_to_glb_single / stream_ifc_to_glb).
+const DEFAULT_DEFLECTION = 2.0;
+const DEFAULT_ANGULAR_DEG = 20.0;
+
+function tessOpts(opts?: {deflection?: number; angularDeg?: number; meshopt?: boolean}) {
+    return {
+        deflection: opts?.deflection ?? DEFAULT_DEFLECTION,
+        angularDeg: opts?.angularDeg ?? DEFAULT_ANGULAR_DEG,
+        meshopt: opts?.meshopt ?? true,
+    };
+}
+
+/** Convert a STEP/IFC buffer to GLB in the worker. The buffer is transferred (consumed). */
+export async function nativeCadToGlb(
+    kind: CadKind,
+    srcBytes: ArrayBuffer,
+    opts?: {deflection?: number; angularDeg?: number; meshopt?: boolean},
+): Promise<NativeCadGlbResult> {
+    return ensureApi().toGlb(kind, Comlink.transfer(srcBytes, [srcBytes]), tessOpts(opts));
+}
+
+/** Does this browser/worker support the OPFS-streaming tier (worker-only sync access handles + a
+ * mountable OPFS backend) for the given module? */
+export async function nativeCadGlbOpfsAvailable(kind: CadKind): Promise<boolean> {
+    try {
+        return await ensureApi().opfsAvailable(kind);
+    } catch {
+        return false;
+    }
+}
+
+/** Convert a STEP/IFC at a (presigned, streamable) URL to GLB, streaming the source through OPFS so a
+ * multi-GB source never has to fit the wasm heap. Requires nativeCadGlbOpfsAvailable(kind). */
+export async function nativeCadToGlbStreaming(
+    kind: CadKind,
+    sourceUrl: string,
+    opts?: {deflection?: number; angularDeg?: number; meshopt?: boolean},
+): Promise<NativeCadGlbResult> {
+    return ensureApi().toGlbStreaming(kind, sourceUrl, tessOpts(opts));
+}
diff --git a/src/frontend/src/utils/nativeConvert/cadGlbConverter.worker.ts b/src/frontend/src/utils/nativeConvert/cadGlbConverter.worker.ts
new file mode 100644
index 000000000..c3a340665
--- /dev/null
+++ b/src/frontend/src/utils/nativeConvert/cadGlbConverter.worker.ts
@@ -0,0 +1,167 @@
+// Web Worker: CAD (STEP / IFC) -> GLB entirely in the browser via the OCC-free, NO-pyodide adacpp
+// embind wasm modules (native Part-21 / IfcResolver reader + libtess2 + meshoptimizer + GLB writer).
+// The lightweight counterpart to the pyodide pipeline — ~2.3 MB per module, no Python runtime.
+//
+// embind surface (see adacpp/src/cad/{cad_wasm,ifc_glb_wasm}.cpp):
+//   stepToGlb / ifcToGlb(inPath, outPath, spillDir, deflection, angularDeg, meshopt) -> product count
+//                                                                                        (<0 on error)
+//   mountOpfs(mountPoint) -> 0 ok
+// IO goes through the emscripten FS. Buffered path uses in-heap MEMFS; the OPFS-streaming path mounts
+// OPFS via WASMFS so a multi-GB source reads off-disk via `pread` (bounded RSS), never the wasm heap.
+
+import * as Comlink from "comlink";
+
+import {loadEmscriptenModule} from "@/utils/wasm/emscriptenLoader";
+import {WasmfsModule, OPFS_MOUNT, ensureOpfsMounted, streamUrlToOpfs, unlinkAll} from "./opfsWasmfs";
+
+// Which native module + verb + source extension a `kind` maps to. Each module ships its own single
+// verb; both share the FS + mountOpfs surface.
+export type CadKind = "step" | "ifc";
+const MODULES: Record<CadKind, {url: string; verb: string; ext: string}> = {
+    step: {url: "/wasm/adacpp_step_glb.js", verb: "stepToGlb", ext: "step"},
+    ifc: {url: "/wasm/adacpp_ifc_glb.js", verb: "ifcToGlb", ext: "ifc"},
+};
+
+interface EmscriptenFS {
+    writeFile(path: string, data: Uint8Array): void;
+    readFile(path: string): Uint8Array;
+    mkdir(path: string): void;
+    unlink(path: string): void;
+    open(path: string, flags: string): unknown;
+    write(stream: unknown, buffer: Uint8Array, offset: number, length: number, position: number): number;
+    close(stream: unknown): void;
+}
+interface EmModule extends WasmfsModule {
+    FS: EmscriptenFS;
+    mountOpfs(mountPoint: string): number;
+    // The per-module conversion verb (stepToGlb / ifcToGlb) — same signature, looked up by name.
+    [verb: string]: unknown;
+}
+type ConvertVerb = (
+    inPath: string,
+    outPath: string,
+    spillDir: string,
+    deflection: number,
+    angularDeg: number,
+    meshopt: boolean,
+) => number;
+
+const modulePromises: Partial<Record<CadKind, Promise<EmModule>>> = {};
+function getModule(kind: CadKind): Promise<EmModule> {
+    let p = modulePromises[kind];
+    if (!p) {
+        p = loadEmscriptenModule<EmModule>(MODULES[kind].url);
+        modulePromises[kind] = p;
+    }
+    return p;
+}
+function convertVerb(Module: EmModule, kind: CadKind): ConvertVerb {
+    return Module[MODULES[kind].verb] as ConvertVerb;
+}
+
+export interface NativeCadGlbResult {
+    glb: ArrayBuffer;
+    products: number; // products (STEP solids / IFC products) written, not triangles
+    ms: number;
+}
+
+// OPFS-mounted streaming file paths (all under OPFS_MOUNT so every byte lives on disk, not the wasm
+// heap). Streaming write + mount are the shared opfsWasmfs helpers. Names are namespaced per module.
+const opfsInPath = (kind: CadKind) => `${OPFS_MOUNT}/adacpp_${kind}glb_in.${MODULES[kind].ext}`;
+const opfsOutPath = (kind: CadKind) => `${OPFS_MOUNT}/adacpp_${kind}glb_out.glb`;
+const opfsSpillDir = (kind: CadKind) => `${OPFS_MOUNT}/adacpp_${kind}glb_spill`;
+
+const api = {
+    // Can this worker run the OPFS-streaming tier for `kind`? Mounting OPFS (worker-only) is the real
+    // capability gate; the pipeline decides WHEN to use it (large sources with a presigned URL).
+    async opfsAvailable(kind: CadKind): Promise<boolean> {
+        return ensureOpfsMounted(await getModule(kind));
+    },
+
+    // OPFS-streaming path: stream a (presigned) URL into OPFS, tessellate off-disk via pread, write
+    // the GLB to OPFS, read it back through WASMFS. For multi-GB sources that can't fit the wasm heap.
+    async toGlbStreaming(
+        kind: CadKind,
+        sourceUrl: string,
+        opts: {deflection: number; angularDeg: number; meshopt: boolean},
+    ): Promise<NativeCadGlbResult> {
+        const Module = await getModule(kind);
+        if (!ensureOpfsMounted(Module)) {
+            throw new Error("OPFS streaming unavailable in this worker (OPFS backend not mountable)");
+        }
+        const t0 = performance.now();
+        const inPath = opfsInPath(kind);
+        await streamUrlToOpfs(Module, inPath, sourceUrl);
+        const outPath = opfsOutPath(kind);
+        try {
+            Module.FS.mkdir(opfsSpillDir(kind));
+        } catch {
+            /* already exists on a reused module */
+        }
+        const cleanup = () => unlinkAll(Module, [inPath, outPath]);
+        const products = convertVerb(Module, kind)(
+            inPath,
+            outPath,
+            opfsSpillDir(kind),
+            opts.deflection,
+            opts.angularDeg,
+            opts.meshopt,
+        );
+        if (products < 0) {
+            cleanup();
+            throw new Error(`native streaming ${kind.toUpperCase()}→GLB failed (I/O error in the wasm module)`);
+        }
+        // Read the OPFS-written GLB back through WASMFS (all IO goes through WASMFS — consistent, no
+        // cross-boundary flush race). Materialises the output once — the GLB is far smaller than source.
+        const out = Module.FS.readFile(outPath);
+        const glb = out.slice().buffer;
+        cleanup();
+        const result: NativeCadGlbResult = {glb, products, ms: performance.now() - t0};
+        return Comlink.transfer(result, [glb]);
+    },
+
+    // Buffered path: source bytes -> MEMFS (in-heap) -> GLB. Simplest; fine below the OPFS threshold.
+    async toGlb(
+        kind: CadKind,
+        srcBytes: ArrayBuffer,
+        opts: {deflection: number; angularDeg: number; meshopt: boolean},
+    ): Promise<NativeCadGlbResult> {
+        const Module = await getModule(kind);
+        const inPath = `/in.${MODULES[kind].ext}`;
+        const outPath = "/out.glb";
+        const spillDir = "/spill";
+        const t0 = performance.now();
+        Module.FS.writeFile(inPath, new Uint8Array(srcBytes));
+        try {
+            Module.FS.mkdir(spillDir);
+        } catch {
+            /* already exists on a reused module — fine */
+        }
+        const products = convertVerb(Module, kind)(
+            inPath,
+            outPath,
+            spillDir,
+            opts.deflection,
+            opts.angularDeg,
+            opts.meshopt,
+        );
+        if (products < 0) {
+            throw new Error(`native ${kind.toUpperCase()}→GLB failed (I/O error in the wasm module)`);
+        }
+        const out = Module.FS.readFile(outPath);
+        // Own a transferable copy off the wasm heap, then release the FS entries so a reused module
+        // doesn't accumulate files across conversions.
+        const glb = out.slice().buffer;
+        try {
+            Module.FS.unlink(inPath);
+            Module.FS.unlink(outPath);
+        } catch {
+            /* best-effort cleanup */
+        }
+        const result: NativeCadGlbResult = {glb, products, ms: performance.now() - t0};
+        return Comlink.transfer(result, [glb]);
+    },
+};
+
+export type CadGlbConverterAPI = typeof api;
+Comlink.expose(api);
diff --git a/src/frontend/src/utils/nativeConvert/opfsWasmfs.ts b/src/frontend/src/utils/nativeConvert/opfsWasmfs.ts
new file mode 100644
index 000000000..f25551456
--- /dev/null
+++ b/src/frontend/src/utils/nativeConvert/opfsWasmfs.ts
@@ -0,0 +1,90 @@
+// Shared OPFS-via-WASMFS streaming helpers for the native (no-pyodide) adacpp embind modules
+// (cadGlbConverter, brepWriterConverter). All IO goes THROUGH WASMFS — never the browser OPFS API —
+// so a file streamed in is immediately visible to the C++ `pread` (WASMFS caches its dir listing at
+// mount time, so a browser-OPFS-created file can be invisible to the module). Writing through the
+// OPFS-mounted path still lands each chunk on disk (bounded RSS), so multi-GB sources never have to
+// fit the wasm heap.
+
+// The WASMFS mount point (maps to the OPFS root). Each module has its OWN FS, so mounting the same
+// point in different modules is independent.
+export const OPFS_MOUNT = "/opfs";
+
+// Minimal surface the helpers need — every adacpp embind module built with -sWASMFS + EXPORTED FS
+// satisfies this structurally.
+export interface WasmfsModule {
+    FS: {
+        readFile(path: string): Uint8Array;
+        unlink(path: string): void;
+        mkdir(path: string): void;
+        open(path: string, flags: string): unknown;
+        write(stream: unknown, buffer: Uint8Array, offset: number, length: number, position: number): number;
+        close(stream: unknown): void;
+    };
+    mountOpfs(mountPoint: string): number;
+}
+
+// wasmfs_create_opfs_backend() ABORTS the whole module (fatal) if called on the main browser thread
+// without JSPI — which would also kill the buffered fallback that shares the module. It is only safe
+// inside a dedicated Worker (emscripten_is_main_browser_thread() == false there). Callers always run
+// in a Worker, but guard anyway so a mount can never abort the shared module.
+function inDedicatedWorker(): boolean {
+    return (
+        typeof (globalThis as {WorkerGlobalScope?: unknown}).WorkerGlobalScope !== "undefined" &&
+        typeof (globalThis as {DedicatedWorkerGlobalScope?: unknown}).DedicatedWorkerGlobalScope !== "undefined" &&
+        (globalThis as unknown as {self?: unknown}).self instanceof
+            (globalThis as unknown as {DedicatedWorkerGlobalScope: new () => unknown}).DedicatedWorkerGlobalScope
+    );
+}
+
+// Per-module "mounted" latch (modules are distinct objects; WeakSet keeps this GC-friendly).
+const mounted = new WeakSet<object>();
+
+/** Mount OPFS at OPFS_MOUNT for this module (once). Returns false when not in a worker or OPFS isn't
+ * available — the caller then falls back to the buffered MEMFS path. */
+export function ensureOpfsMounted(Module: WasmfsModule): boolean {
+    if (mounted.has(Module)) return true;
+    if (!inDedicatedWorker()) return false;
+    try {
+        if (Module.mountOpfs(OPFS_MOUNT) === 0) {
+            mounted.add(Module);
+            return true;
+        }
+    } catch {
+        /* OPFS unavailable — caller falls back to the buffered MEMFS path */
+    }
+    return false;
+}
+
+/** Stream `sourceUrl` into `inPath` (under OPFS_MOUNT) THROUGH WASMFS, chunk by chunk. Each chunk
+ * writes straight through to OPFS at its offset and is freed; nothing accumulates in the heap, and the
+ * file is immediately visible to the module's `pread`. */
+export async function streamUrlToOpfs(Module: WasmfsModule, inPath: string, sourceUrl: string): Promise<void> {
+    const resp = await fetch(sourceUrl);
+    if (!resp.ok || !resp.body) {
+        throw new Error(`fetch source failed: ${resp.status} ${resp.statusText}`);
+    }
+    const stream = Module.FS.open(inPath, "w");
+    try {
+        const reader = resp.body.getReader();
+        let pos = 0;
+        for (;;) {
+            const {done, value} = await reader.read();
+            if (done) break;
+            Module.FS.write(stream, value, 0, value.byteLength, pos);
+            pos += value.byteLength;
+        }
+    } finally {
+        Module.FS.close(stream);
+    }
+}
+
+/** Best-effort FS.unlink of every path (ignore missing). */
+export function unlinkAll(Module: WasmfsModule, paths: string[]): void {
+    for (const p of paths) {
+        try {
+            Module.FS.unlink(p);
+        } catch {
+            /* best-effort cleanup */
+        }
+    }
+}
diff --git a/src/frontend/src/utils/scene/centerViewOnSelection.ts b/src/frontend/src/utils/scene/centerViewOnSelection.ts
index bf6d64945..abc3ae130 100644
--- a/src/frontend/src/utils/scene/centerViewOnSelection.ts
+++ b/src/frontend/src/utils/scene/centerViewOnSelection.ts
@@ -5,6 +5,7 @@ import {useModelState} from '@/state/modelState';
 import {OrbitControls} from 'three/examples/jsm/controls/OrbitControls';
 import CameraControls from 'camera-controls';
 import {selectedPointRef} from "@/state/refs";
+import {applyAdaptiveClipping} from "@/components/viewer/sceneHelpers/adaptiveClipping";
 
 export const centerViewOnSelection = (
     controls: OrbitControls | CameraControls,
@@ -139,6 +140,11 @@ function center_on_bounding_box(boundingBox: THREE.Box3, camera: Camera, fillFac
         return;
     }
 
+    // Adapt near/far to the framed selection size so zooming into a small selection doesn't clip.
+    if (camera instanceof THREE.PerspectiveCamera) {
+        applyAdaptiveClipping(camera, controls, radius);
+    }
+
     let distance = 0;
     if (camera instanceof THREE.PerspectiveCamera) {
         const fov = (camera.fov * Math.PI) / 180; // Radians
diff --git a/src/frontend/src/utils/scene/galleryWalk.ts b/src/frontend/src/utils/scene/galleryWalk.ts
new file mode 100644
index 000000000..ad841bbe3
--- /dev/null
+++ b/src/frontend/src/utils/scene/galleryWalk.ts
@@ -0,0 +1,204 @@
+import {sceneRef, cameraRef, controlsRef} from "@/state/refs";
+import {CustomBatchedMesh} from "@/utils/mesh_select/CustomBatchedMesh";
+import {useSelectedObjectStore} from "@/state/useSelectedObjectStore";
+import {useObjectInfoStore} from "@/state/objectInfoStore";
+import {useModelState} from "@/state/modelState";
+import {useTreeViewStore} from "@/state/treeViewStore";
+import {requestRender} from "@/state/perfStore";
+import {centerViewOnSelection} from "@/utils/scene/centerViewOnSelection";
+import {unhideAllRanges} from "@/utils/scene/visibility";
+import {queryNameFromRangeId} from "@/utils/mesh_select/queryMeshDrawRange";
+import {query_ws_server_mesh_info} from "@/utils/mesh_select/handlers/send_mesh_selected_info_callback";
+import {computeRangeStats, DEFAULT_SPIKE_THRESHOLDS} from "@/utils/mesh_select/meshStats";
+import type {SpikeThresholds} from "@/utils/mesh_select/meshStats";
+import {useOptionsStore} from "@/state/optionsStore";
+import type {GeomWalkOrder} from "@/state/galleryStore";
+
+// Geom-level gallery walk: enumerate every draw-range (geom) currently
+// in the scene, then select + frame them one at a time. The walk order
+// is "scene" (traversal order), "density" (triangles per surface area,
+// heaviest first), "tree" (the model tree's hierarchy order), or
+// "distorted" (only geoms with a crows-nest spike, worst-first).
+
+export interface GeomEntry {
+    mesh: CustomBatchedMesh;
+    rangeId: string;
+    triangles: number;
+    density: number;
+    spike: number; // worst thin-triangle reach (fraction of bbox diagonal); see meshStats maxSpike
+    spikeTris: number; // how many spike triangles this geom has
+}
+
+export type WalkOrder = GeomWalkOrder;
+
+function allBatchedMeshes(): CustomBatchedMesh[] {
+    const out: CustomBatchedMesh[] = [];
+    sceneRef.current?.traverse((o) => {
+        if (o instanceof CustomBatchedMesh) out.push(o);
+    });
+    return out;
+}
+
+function sceneOrderEntries(
+    meshes: CustomBatchedMesh[],
+    withStats: boolean,
+    thresholds: SpikeThresholds = DEFAULT_SPIKE_THRESHOLDS,
+): GeomEntry[] {
+    const entries: GeomEntry[] = [];
+    for (const mesh of meshes) {
+        for (const rangeId of mesh.drawRanges.keys()) {
+            if (withStats) {
+                const s = computeRangeStats(mesh, rangeId, thresholds);
+                entries.push({
+                    mesh,
+                    rangeId,
+                    triangles: s?.triangles ?? 0,
+                    density: s?.density ?? 0,
+                    spike: s?.maxSpike ?? 0,
+                    spikeTris: s?.spikeTris ?? 0,
+                });
+            } else {
+                const range = mesh.drawRanges.get(rangeId)!;
+                entries.push({mesh, rangeId, triangles: Math.floor(range[1] / 3), density: 0, spike: 0, spikeTris: 0});
+            }
+        }
+    }
+    return entries;
+}
+
+function treeOrderEntries(meshes: CustomBatchedMesh[]): GeomEntry[] {
+    const byKey = new Map<string, CustomBatchedMesh>();
+    for (const m of meshes) byKey.set(m.unique_key, m);
+
+    const treeData = useTreeViewStore.getState().treeData;
+    if (!treeData) return sceneOrderEntries(meshes, false);
+
+    const entries: GeomEntry[] = [];
+    const seen = new Set<string>();
+    const visit = (node: any) => {
+        const rid = node?.rangeId;
+        const mk = node?.model_key;
+        if (rid != null && mk != null) {
+            const mesh = byKey.get(String(mk));
+            const rangeId = String(rid);
+            const dedupKey = `${mk}|${rangeId}`;
+            if (mesh && mesh.drawRanges.has(rangeId) && !seen.has(dedupKey)) {
+                seen.add(dedupKey);
+                const range = mesh.drawRanges.get(rangeId)!;
+                entries.push({mesh, rangeId, triangles: Math.floor(range[1] / 3), density: 0, spike: 0, spikeTris: 0});
+            }
+        }
+        if (Array.isArray(node?.children)) for (const c of node.children) visit(c);
+    };
+    visit(treeData);
+
+    // Tree may not cover every batched geom (e.g. FEA overlays with no
+    // tree rows) — fall back to scene order when it yields nothing.
+    return entries.length > 0 ? entries : sceneOrderEntries(meshes, false);
+}
+
+export function collectGeomEntries(
+    order: WalkOrder,
+    thresholds: SpikeThresholds = DEFAULT_SPIKE_THRESHOLDS,
+): GeomEntry[] {
+    const meshes = allBatchedMeshes();
+    if (order === "tree") return treeOrderEntries(meshes);
+    const entries = sceneOrderEntries(meshes, order === "density" || order === "distorted", thresholds);
+    if (order === "density") entries.sort((x, y) => y.density - x.density);
+    if (order === "distorted") {
+        // Only geoms with an outlier-vertex spike, worst-first — the walk visits problems, not the
+        // whole model. Empty result ⇒ nothing distorted (the good outcome). The Mesh panel passes
+        // adjusted thresholds here to re-scan tighter/looser; the gallery uses the default.
+        return entries.filter((e) => e.spike > thresholds.spikeOutlierK).sort((x, y) => y.spike - x.spike);
+    }
+    return entries;
+}
+
+// Hide every draw-range except the kept (mesh, rangeId). hideBatchDrawRange
+// is additive-only, so reset with unhideAllRanges() first.
+function hideAllExcept(keepMesh: CustomBatchedMesh, keepRangeId: string): void {
+    unhideAllRanges();
+    for (const mesh of allBatchedMeshes()) {
+        const toHide: string[] = [];
+        for (const id of mesh.drawRanges.keys()) {
+            if (mesh === keepMesh && id === keepRangeId) continue;
+            toHide.push(id);
+        }
+        if (toHide.length) mesh.hideBatchDrawRange(toHide);
+    }
+    requestRender();
+}
+
+// Select the entry, populate the Object Info panel, optionally isolate
+// it, and frame the camera on it (fit object).
+// True only while the mesh is still attached to the live scene. A scope switch disposes the old
+// scope's batched meshes; a walk holding stale entries would otherwise select/frame a freed mesh
+// (disposed geometry -> crash). Guards every operation that touches a walked mesh.
+function meshIsLive(mesh: CustomBatchedMesh | undefined | null): boolean {
+    if (!mesh) return false;
+    const scene = sceneRef.current;
+    if (!scene) return false;
+    let node: any = mesh;
+    while (node) {
+        if (node === scene) return true;
+        node = node.parent;
+    }
+    return false;
+}
+
+export async function focusGeomEntry(
+    entry: GeomEntry | undefined,
+    opts: {hideUnselected: boolean; forceEdges?: boolean},
+): Promise<void> {
+    // A scope/scene transition can leave a stale or disposed entry in the walk — never crash on it.
+    if (!entry || !meshIsLive(entry.mesh) || !entry.mesh.drawRanges.has(entry.rangeId)) return;
+    const {mesh, rangeId} = entry;
+
+    // Inspecting spikes is pointless without triangle edges — turn them on for the distorted walk.
+    // (Geometry Edges default on; this re-asserts it. A user who loaded with edges off may need a
+    // reload for the overlay to attach — the toggle itself is reload-gated.)
+    if (opts.forceEdges && !useOptionsStore.getState().showEdges) {
+        useOptionsStore.getState().setShowEdges(true);
+    }
+
+    const sel = useSelectedObjectStore.getState();
+    sel.clearSelectedObjects();
+
+    if (opts.hideUnselected) hideAllExcept(mesh, rangeId);
+    else unhideAllRanges();
+
+    sel.addSelectedObject(mesh, rangeId);
+
+    // Info panel: same fields the click handler populates.
+    const name = await queryNameFromRangeId(mesh.unique_key, rangeId);
+    const info = useObjectInfoStore.getState();
+    info.setName(name);
+    const activeFile = useModelState.getState().loadedSourceName;
+    info.setFileName(activeFile ?? null);
+    info.setJsonData(null);
+    info.setFaceIndex(null);
+    if (name) {
+        try {
+            void query_ws_server_mesh_info(name, 0, activeFile);
+        } catch {
+            /* metadata is best-effort; selection + framing still work */
+        }
+    }
+
+    // The name lookup above awaited; a scope switch may have disposed the mesh in that window.
+    // Re-check before framing so centerViewOnSelection never reads freed geometry.
+    if (!meshIsLive(mesh)) return;
+    const controls = controlsRef.current;
+    const camera = cameraRef.current;
+    if (controls && camera) centerViewOnSelection(controls, camera, 1.5);
+    requestRender();
+}
+
+// Leave a geom walk cleanly: drop the isolation and the selection so the
+// scene returns to its normal state (used when the walk type changes,
+// gallery mode is turned off, or the scope is reloaded).
+export function endGeomWalk(): void {
+    unhideAllRanges();
+    useSelectedObjectStore.getState().clearSelectedObjects();
+    requestRender();
+}
diff --git a/src/frontend/src/utils/scene/handlers/view_in_3d.ts b/src/frontend/src/utils/scene/handlers/view_in_3d.ts
index 6e5ba5550..cd2fb76d5 100644
--- a/src/frontend/src/utils/scene/handlers/view_in_3d.ts
+++ b/src/frontend/src/utils/scene/handlers/view_in_3d.ts
@@ -23,10 +23,14 @@ import {useOptionsStore} from "@/state/optionsStore";
 export async function view_in_3d(
     sourceKey: string,
     derivedKey: string,
+    // Load the blob from this scope instead of the currently-selected one.
+    // The audit grid passes its run's scope (e.g. corpus:<slug>) so a cell's
+    // cached product opens regardless of which scope the user is browsing.
+    scopeOverride?: string,
 ): Promise<void> {
     const inModal = useViewerPanelStore.getState().open !== null;
     const scope = useScopeStore.getState().current;
-    const scopePart = scope ? scopeUrlPart(scope) : "";
+    const scopePart = scopeOverride ?? (scope ? scopeUrlPart(scope) : "");
 
     if (!inModal) {
         const params = new URLSearchParams({
@@ -45,5 +49,5 @@ export async function view_in_3d(
     useOptionsStore.getState().setIsOptionsVisible(false);
 
     const {overlay_file_in_scene} = await import("./overlay_file_in_scene");
-    await overlay_file_in_scene(sourceKey, derivedKey);
+    await overlay_file_in_scene(sourceKey, derivedKey, scopeOverride ? {scope: scopeOverride} : undefined);
 }
diff --git a/src/frontend/src/utils/scene/refreshEdgeOverlays.ts b/src/frontend/src/utils/scene/refreshEdgeOverlays.ts
new file mode 100644
index 000000000..f7e768f96
--- /dev/null
+++ b/src/frontend/src/utils/scene/refreshEdgeOverlays.ts
@@ -0,0 +1,33 @@
+import * as THREE from "three";
+import {sceneRef, rendererRef} from "@/state/refs";
+import {CustomBatchedMesh} from "@/utils/mesh_select/CustomBatchedMesh";
+import {useOptionsStore} from "@/state/optionsStore";
+import {requestRender} from "@/state/perfStore";
+
+// Rebuild every design mesh's edge overlay in place — WITHOUT a page/model reload — so a change to
+// `showEdges` (on/off) or `hideTessellationEdges` (feature-only vs full triangulation grid) takes
+// effect immediately. Both are otherwise baked at model load (prepareLoadedModel builds the overlay
+// once, reading hideTessellationEdges at that time), which is why the options drawer says "reload".
+//
+// For each eligible mesh (one that took an edge overlay at load — FEA streaming meshes never do): drop
+// the stale overlay + its cached geometry, and when edges are on, re-add a freshly-built overlay
+// (rebuilt from the CURRENT options). Preserves the overlay's layer (1) + parent so picking/masking is
+// unchanged. NB: a live rebuild resets the edge material's per-range highlight/hide state — re-click to
+// restore it if needed.
+export function refreshEdgeOverlays(): void {
+    const scene = sceneRef.current;
+    const renderer = rendererRef.current;
+    if (!scene || !renderer) return;
+    const showEdges = useOptionsStore.getState().showEdges;
+    const meshes: CustomBatchedMesh[] = [];
+    scene.traverse((o) => {
+        if (o instanceof CustomBatchedMesh && o.edgesEligible) meshes.push(o);
+    });
+    for (const mesh of meshes) {
+        const old = mesh.invalidateEdgeOverlay();
+        const parent = old?.parent ?? (mesh.parent as THREE.Object3D | null);
+        old?.parent?.remove(old);
+        if (showEdges && parent && mesh.drawRanges.size) parent.add(mesh.getEdgeOverlay(renderer));
+    }
+    requestRender();
+}
diff --git a/src/frontend/src/utils/storage/fileTree.ts b/src/frontend/src/utils/storage/fileTree.ts
index 16416d9c2..54203d3b2 100644
--- a/src/frontend/src/utils/storage/fileTree.ts
+++ b/src/frontend/src/utils/storage/fileTree.ts
@@ -98,6 +98,15 @@ export function buildFileTree<T>(
     return root.children;
 }
 
+// Short bullet list of keys for delete-confirmation dialogs — first
+// ``max`` entries, then an "…and N more" line. Keeps the confirm()
+// readable when the selection (or folder) holds hundreds of files.
+export function previewKeyList(keys: readonly string[], max = 15): string {
+    const shown = keys.slice(0, max).map((k) => `  • ${k}`);
+    if (keys.length > max) shown.push(`  …and ${keys.length - max} more`);
+    return shown.join("\n");
+}
+
 // Persisted per-scope so expand state survives reloads but doesn't
 // leak across scopes. Caller passes a ``namespace`` (e.g. "storage"
 // for the regular browser, "admin-storage" for the admin table) so
diff --git a/src/frontend/src/utils/websocket/initWebSocket.ts b/src/frontend/src/utils/websocket/initWebSocket.ts
index 4a0bd2986..146437845 100644
--- a/src/frontend/src/utils/websocket/initWebSocket.ts
+++ b/src/frontend/src/utils/websocket/initWebSocket.ts
@@ -24,6 +24,13 @@ function pickConnectUrl(): string {
  * during ``initWebSocket`` (well before AuthGate's bootstrap
  * resolves). */
 export function loadInitialServerState(): void {
+    // File listing goes out FIRST: it's what the storage browser is
+    // waiting on and the slowest server op (cold S3 list ~3s), so it
+    // must not queue behind server-info. requestServerInfo (process
+    // metadata + the worker-advertised set) is lower priority and can
+    // resolve after — the UI it feeds (convert matrix, tags) isn't on
+    // the critical "show me my files" path.
+    request_list_of_files_from_server();
     requestServerInfo();
     // LIST_WEB_CLIENTS is a websocket-era concept (per-connection
     // client tracking). The REST backend rejects the command with a
@@ -32,7 +39,6 @@ export function loadInitialServerState(): void {
     if (!runtime.isRestMode()) {
         requestConnectedClients();
     }
-    request_list_of_files_from_server();
 }
 
 export async function initWebSocket() {
diff --git a/tests/comms/rest/test_admin.py b/tests/comms/rest/test_admin.py
index b08d16d2b..955427176 100644
--- a/tests/comms/rest/test_admin.py
+++ b/tests/comms/rest/test_admin.py
@@ -131,6 +131,38 @@ def test_admin_uuid_validation(tmp_path):
         assert r.status_code == 400
 
 
+@needs_postgres
+def test_api_me_lists_corpus_scopes_for_admin_only(tmp_path):
+    """An admin's /api/me advertises corpus scopes (so corpus files can be
+    browsed + visualised from the main storage panel); a non-admin's does not."""
+    settings = _settings(tmp_path, db_url=POSTGRES_URL)
+    slug = f"corp-{uuid.uuid4().hex[:12]}"
+    app = create_app(settings)
+    with TestClient(app) as client:
+        # local-dev synthetic user is admin — create a corpus, then read /api/me.
+        r = client.post("/api/admin/corpora", json={"slug": slug, "name": "Corp Test"})
+        assert r.status_code == 201, r.text
+        me = client.get("/api/me").json()
+        corpus_scopes = [s for s in me["scopes"] if s["kind"] == "corpus"]
+        assert any(s["id"] == slug and s["name"] == "Corp Test" for s in corpus_scopes), corpus_scopes
+        client.delete(f"/api/admin/corpora/{slug}")
+
+    # Non-admin: same DB, but no corpus scopes surface.
+    import ada.comms.rest.auth as _auth
+
+    orig = _auth.User.local_dev
+    _auth.User.local_dev = classmethod(
+        lambda cls: cls(sub="viewer", email="v@x", display_name="V", groups=frozenset(), is_admin=False)
+    )
+    try:
+        app2 = create_app(settings)
+        with TestClient(app2) as client:
+            me = client.get("/api/me").json()
+            assert not any(s["kind"] == "corpus" for s in me["scopes"]), me["scopes"]
+    finally:
+        _auth.User.local_dev = orig
+
+
 # ── Live-Postgres path ───────────────────────────────────────────────
 
 
diff --git a/tests/comms/rest/test_audit_run_routes.py b/tests/comms/rest/test_audit_run_routes.py
index 18c2b5a11..662710055 100644
--- a/tests/comms/rest/test_audit_run_routes.py
+++ b/tests/comms/rest/test_audit_run_routes.py
@@ -143,6 +143,66 @@ def test_extend_folds_idle_gap(db):
     assert 3_400_000 < after["idle_ms"] < 3_800_000
 
 
+def test_cells_duration_ms_is_sum_of_cells(db):
+    pool, run = db
+    r = run(db_module.create_audit_run(pool, scope="shared", worker_pool=None))
+    run(db_module.set_audit_run_total(pool, r["id"], 2))
+    run(db_module.insert_audit(pool, user_sub=None, scope_kind="shared", scope_id=None, action="convert",
+                               key="a.step", target_format="glb", status="done", duration_ms=10,
+                               job_id="jobA", audit_run_id=r["id"]))
+    run(db_module.insert_audit(pool, user_sub=None, scope_kind="shared", scope_id=None, action="convert",
+                               key="b.step", target_format="glb", status="error", duration_ms=20,
+                               job_id="jobB", audit_run_id=r["id"]))
+    after = run(db_module.get_audit_run(pool, r["id"]))
+    assert after["cells_duration_ms"] == 30  # sum, not wall clock
+    assert after["ok"] == 1 and after["failed"] == 1 and after["status"] == "finished"
+
+
+def test_reset_audit_cell_for_rerun_undoes_counter_and_reopens(db):
+    pool, run = db
+    r = run(db_module.create_audit_run(pool, scope="shared", worker_pool=None))
+    run(db_module.set_audit_run_total(pool, r["id"], 2))
+    run(db_module.insert_audit(pool, user_sub=None, scope_kind="shared", scope_id=None, action="convert",
+                               key="a.step", target_format="glb", status="done", duration_ms=10,
+                               job_id="jobA", audit_run_id=r["id"]))
+    run(db_module.insert_audit(pool, user_sub=None, scope_kind="shared", scope_id=None, action="convert",
+                               key="b.step", target_format="glb", status="error", duration_ms=20,
+                               job_id="jobB", audit_run_id=r["id"]))
+
+    # Re-run cell B: the failed counter drops, the run reopens, and B's row is
+    # re-pointed at a fresh job with its result timing cleared.
+    ok = run(db_module.reset_audit_cell_for_rerun(pool, r["id"], "b.step", "glb", "jobB2"))
+    assert ok is True
+    mid = run(db_module.get_audit_run(pool, r["id"]))
+    assert mid["failed"] == 0 and mid["ok"] == 1
+    assert mid["status"] == "running" and mid["finished_at"] is None
+    assert mid["cells_duration_ms"] == 10  # B's 20ms cleared until it re-completes
+
+    # The worker completes the new job → B goes green, run re-finishes, runtime
+    # reflects the new per-cell timing.
+    run(db_module.update_audit_by_job(pool, job_id="jobB2", status="done", duration_ms=15))
+    end = run(db_module.get_audit_run(pool, r["id"]))
+    assert end["ok"] == 2 and end["failed"] == 0
+    assert end["status"] == "finished"
+    assert end["cells_duration_ms"] == 25  # 10 + the re-run's 15
+
+    # Unknown cell → no-op, returns False.
+    assert run(db_module.reset_audit_cell_for_rerun(pool, r["id"], "nope.step", "glb", "x")) is False
+
+
+def test_reset_audit_cell_folds_idle_gap(db):
+    pool, run = db
+    r = run(_finish_run(pool, n=1))  # one done cell, run finished
+    # Backdate the finish so the re-run sees a ~1h gap since the original run.
+    run(pool.execute("UPDATE audit_runs SET finished_at = NOW() - INTERVAL '1 hour' WHERE id = $1", r["id"]))
+    run(db_module.reset_audit_cell_for_rerun(pool, r["id"], "models/f0.step", "glb", "job0b"))
+    after = run(db_module.get_audit_run(pool, r["id"]))
+    assert after["status"] == "running" and after["finished_at"] is None
+    # The ~1h gap is folded into idle_ms so wall clock won't swallow it when the
+    # cell re-completes — the re-run only adds its own delta.
+    assert 3_400_000 < after["idle_ms"] < 3_800_000
+
+
 def test_claim_run_for_validation_is_once(db):
     pool, run = db
     r = run(_finish_run(pool, n=1))
@@ -167,6 +227,80 @@ def test_claim_auto_validate_only_flagged_runs(db):
     assert run(db_module.claim_audit_run_for_auto_validate(pool)) is None
 
 
+def _close_cell(p, run_id, *, key, target_format="glb", action="convert"):
+    return db_module.insert_audit(
+        p,
+        user_sub=None,
+        scope_kind="shared",
+        scope_id=None,
+        action=action,
+        key=key,
+        target_format=target_format,
+        status="done",
+        duration_ms=10,
+        audit_run_id=run_id,
+    )
+
+
+def test_reserved_validation_counts_upfront(db):
+    """An auto-validate run advertises conversions + parity in ``total`` from
+    the start; the validation dispatch consumes the reservation instead of
+    growing the total."""
+    pool, run = db
+    r = run(db_module.create_audit_run(pool, scope="shared", worker_pool=None, auto_validate=True))
+    # 2 conversion cells + 1 reserved parity cell.
+    run(db_module.set_audit_run_total(pool, r["id"], 3, validate_total=1))
+    fresh = run(db_module.get_audit_run(pool, r["id"]))
+    assert fresh["total"] == 3 and fresh["validate_total"] == 1
+
+    # Not claimable while conversion cells are still outstanding.
+    run(_close_cell(pool, r["id"], key="models/f0.step"))
+    assert run(db_module.claim_audit_run_for_auto_validate(pool)) is None
+
+    # All conversion cells landed: the reserve keeps the run 'running',
+    # and the poller can now claim it for validation.
+    run(_close_cell(pool, r["id"], key="models/f1.step"))
+    mid = run(db_module.get_audit_run(pool, r["id"]))
+    assert mid["status"] == "running" and mid["finished_at"] is None
+    claimed = run(db_module.claim_audit_run_for_auto_validate(pool))
+    assert claimed is not None and claimed["id"] == r["id"]
+
+    # Dispatch swaps the reservation for the actual parity count — total unchanged.
+    run(db_module.consume_audit_run_validation_reserve(pool, r["id"], 1))
+    consumed = run(db_module.get_audit_run(pool, r["id"]))
+    assert consumed["total"] == 3 and consumed["validate_total"] == 0
+    assert consumed["status"] == "running"
+    assert consumed["idle_ms"] == 0  # never finished, so no idle gap folded in
+
+    # Parity cell lands → run finishes at the originally-advertised total.
+    run(_close_cell(pool, r["id"], key="models/f0.step", target_format="parity", action="validate"))
+    done = run(db_module.get_audit_run(pool, r["id"]))
+    assert done["status"] == "finished" and done["total"] == 3
+
+
+def test_consume_reserve_handles_drift_and_zero(db):
+    """Scope drift between the two enumerations moves the total by the
+    difference; zero actual parity cells finishes the run on the spot."""
+    pool, run = db
+    # Drift up: reserved 1, actual 2.
+    a = run(db_module.create_audit_run(pool, scope="shared", worker_pool=None, auto_validate=True))
+    run(db_module.set_audit_run_total(pool, a["id"], 2, validate_total=1))
+    run(_close_cell(pool, a["id"], key="models/f0.step"))
+    run(db_module.consume_audit_run_validation_reserve(pool, a["id"], 2))
+    drifted = run(db_module.get_audit_run(pool, a["id"]))
+    assert drifted["total"] == 3 and drifted["validate_total"] == 0
+    assert drifted["status"] == "running"
+
+    # Zero actual: reservation released, run finishes (no bump will arrive).
+    b = run(db_module.create_audit_run(pool, scope="shared", worker_pool=None, auto_validate=True))
+    run(db_module.set_audit_run_total(pool, b["id"], 2, validate_total=1))
+    run(_close_cell(pool, b["id"], key="models/f0.step"))
+    run(db_module.consume_audit_run_validation_reserve(pool, b["id"], 0))
+    released = run(db_module.get_audit_run(pool, b["id"]))
+    assert released["total"] == 1 and released["validate_total"] == 0
+    assert released["status"] == "finished" and released["finished_at"] is not None
+
+
 def test_delete_audit_run_removes_log_rows(db):
     pool, run = db
     r = run(_finish_run(pool, n=2))
diff --git a/tests/comms/rest/test_converter_step_routing.py b/tests/comms/rest/test_converter_step_routing.py
index 7e8807781..2d51e2162 100644
--- a/tests/comms/rest/test_converter_step_routing.py
+++ b/tests/comms/rest/test_converter_step_routing.py
@@ -62,3 +62,84 @@ def test_glb_target_exposes_tessellation_quality_options():
     assert {"tess_linear_deflection", "tess_angular_deg", "tess_relative"} <= names
     # and they are in the global allowlist used by the API validator
     assert "tess_linear_deflection" in conv.ConverterRegistry.all_options()
+
+
+def _serializer_tessellator(source_ext: str):
+    opts = conv.ConverterRegistry.options_for(source_ext, "glb")
+    ser = next(o for o in opts if o["name"] == "serializer")
+    tess = next(o for o in opts if o["name"] == "tessellator")
+    return ser, tess
+
+
+def test_glb_serializer_tessellator_advertised_single_source():
+    """The reconvert dropdowns are data-driven: every → GLB row advertises a
+    serializer enum with labels + a client/server runtime split, and a
+    dependent tessellator enum keyed by serializer (enum_by). The frontend
+    renders straight from this — no hardcoded vocabulary."""
+    for ext in (".step", ".ifc", ".sat"):
+        ser, tess = _serializer_tessellator(ext)
+        assert ser["type"] == "enum" and tess["type"] == "enum"
+        assert ser["default"] == "cpp"
+        assert set(ser["enum"]) == {"cpp", "python", "wasm"}
+        # labels + runtime per serializer value
+        assert set(ser["labels"]) == set(ser["enum"])
+        assert ser["runtime"]["wasm"] == "client"
+        assert ser["runtime"]["cpp"] == "server" and ser["runtime"]["python"] == "server"
+        # dependent tessellator: enum_by keyed by serializer, depends_on wired
+        assert tess["depends_on"] == "serializer"
+        assert set(tess["enum_by"]) == set(ser["enum"])
+        assert tess["enum_by"]["cpp"] == ["native"]
+        assert "pyocc" in tess["enum_by"]["python"] and "cgal" in tess["enum_by"]["python"]
+        assert tess["enum_by"]["wasm"] == ["wasm-native", "pyodide"]
+    # STEP exposes the OCC streaming reader as an extra python kernel; generic does not.
+    step_tess = _serializer_tessellator(".step")[1]
+    ifc_tess = _serializer_tessellator(".ifc")[1]
+    assert "occ" in step_tess["enum_by"]["python"]
+    assert "occ" not in ifc_tess["enum_by"]["python"]
+    # new names are in the API allowlist
+    assert {"serializer", "tessellator"} <= conv.ConverterRegistry.all_options()
+
+
+def test_apply_glb_serializer_resolves_to_engine_knobs():
+    """The serializer/tessellator tokens fold into the existing engine knobs;
+    unset tokens leave explicit knobs untouched (full back-compat)."""
+    ap = conv._apply_glb_serializer
+    # cpp/STEP -> adacpp-native pipeline, server path
+    assert ap(".step", "cpp", None, step_glb_pipeline=None, glb_tess_engine=None) == (
+        conv._STEP_GLB_PIPELINE_ADACPP_NATIVE, None, False)
+    # python/STEP kernels map to the STEP pipeline + force the python path
+    assert ap(".step", "python", "pyocc", step_glb_pipeline=None, glb_tess_engine=None) == (
+        conv._STEP_GLB_PIPELINE_OCC, None, True)
+    assert ap(".step", "python", "cgal", step_glb_pipeline=None, glb_tess_engine=None) == (
+        conv._STEP_GLB_PIPELINE_ADACPP_CGAL, None, True)
+    # python/IFC maps to the BatchTessellator engine + forces python (bypass native ifc->glb)
+    assert ap(".ifc", "python", "ifc-hybrid", step_glb_pipeline=None, glb_tess_engine=None) == (
+        None, conv._STEP_GLB_PIPELINE_ADACPP_HYBRID, True)
+    # client serializer never resolves server-side (routed in-browser by the SPA)
+    assert ap(".ifc", "wasm", "pyodide", step_glb_pipeline=None, glb_tess_engine=None) == (None, None, False)
+    # unset serializer keeps explicit knobs + defaults
+    assert ap(".step", None, None, step_glb_pipeline="occ-builtin", glb_tess_engine=None) == (
+        "occ-builtin", None, False)
+
+
+def test_brep_target_exposes_serializer_writer_axis():
+    """B-rep→B-rep rows (step→ifc, ifc→step) advertise the same shared selector, but the 2nd axis is
+    titled 'Writer' (no tessellation) and mirrors the serializer 1:1."""
+    for frm, to in ((".step", "ifc"), (".ifc", "step")):
+        opts = conv.ConverterRegistry.options_for(frm, to)
+        by_name = {o["name"]: o for o in opts}
+        # not every build registers native ifc→step; skip when the path options aren't present
+        if "serializer" not in by_name:
+            continue
+        ser, wr = by_name["serializer"], by_name["tessellator"]
+        assert ser["title"] == "Serializer"
+        assert set(ser["enum"]) == {"cpp", "python", "wasm"}
+        assert ser["runtime"]["wasm"] == "client"
+        # 2nd axis is DISPLAYED as Writer (wire key stays 'tessellator' for a unified resolver)
+        assert wr["title"] == "Writer"
+        assert wr["depends_on"] == "serializer"
+        assert wr["enum_by"] == {"cpp": ["native"], "python": ["occ"], "wasm": ["wasm-native"]}
+    # python serializer → the OCC writer branch; cpp/wasm do not
+    assert conv._brep_writer_is_python("python") is True
+    assert conv._brep_writer_is_python("cpp") is False
+    assert conv._brep_writer_is_python("wasm") is False
diff --git a/tests/comms/rest/test_reconvert_key.py b/tests/comms/rest/test_reconvert_key.py
new file mode 100644
index 000000000..bf5432613
--- /dev/null
+++ b/tests/comms/rest/test_reconvert_key.py
@@ -0,0 +1,51 @@
+"""The gallery "Re-convert" output lives in a separate ``_reconvert/`` namespace so it never
+overwrites a corpus scope's ``_derived/`` audit product."""
+
+import pytest
+
+from ada.comms.rest.converter import (
+    UnsupportedFormat,
+    derived_key_for,
+    is_derived_key,
+    is_hidden_key,
+    reconvert_key_for,
+)
+
+
+def test_reconvert_key_is_separate_from_derived():
+    src = "cad/ifc/beam-standard-case.ifc"
+    assert reconvert_key_for(src, "glb") == "_reconvert/cad/ifc/beam-standard-case.ifc.glb"
+    # Must NOT collide with the audit-run derived product.
+    assert reconvert_key_for(src, "glb") != derived_key_for(src, "glb")
+
+
+def test_reconvert_key_is_hidden_but_not_derived():
+    key = reconvert_key_for("x/y.ifc", "glb")
+    # Hidden from the file explorer (throwaway, not a user file)...
+    assert is_hidden_key(key) is True
+    # ...but NOT a "derived product" — derived-product logic (rename/cleanup/grouping) must not
+    # touch it, and the audit ``_derived/`` product stays the canonical one.
+    assert is_derived_key(key) is False
+
+
+def test_reconvert_key_rejects_unknown_format():
+    with pytest.raises(UnsupportedFormat):
+        reconvert_key_for("x/y.ifc", "bogus")
+
+
+def test_reconvert_and_overlay_excluded_from_audit_cells():
+    """Audit cell enumeration skips ``is_hidden_key`` (not just ``is_derived_key``). A re-convert
+    or overlay blob is stored as ``.glb`` — a SUPPORTED source ext — and ``_reconvert/`` is
+    deliberately NOT a derived key, so without the hidden-key skip both would leak in as audit
+    cells. Assert the exact filter the dispatcher uses excludes them."""
+    from ada.comms.rest.converter import is_supported_source
+
+    reconvert = "_reconvert/cad/ifc/beam-extruded-solid.ifc.glb"
+    overlay = "_overlays/mymodel.merge.glb"
+    real_source = "cad/ifc/beam-extruded-solid.ifc"
+
+    # Both throwaway blobs pass the source-ext test (glb) but must be hidden...
+    assert is_supported_source(reconvert) and is_hidden_key(reconvert)
+    assert is_supported_source(overlay) and is_hidden_key(overlay)
+    # ...while a genuine corpus source is a source and NOT hidden -> becomes a cell.
+    assert is_supported_source(real_source) and not is_hidden_key(real_source)
diff --git a/tests/core/api/shapes/__init__.py b/tests/core/api/shapes/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/tests/core/api/shapes/test_shape_store.py b/tests/core/api/shapes/test_shape_store.py
new file mode 100644
index 000000000..12d555e20
--- /dev/null
+++ b/tests/core/api/shapes/test_shape_store.py
@@ -0,0 +1,327 @@
+"""ShapeStore + ShapeProxy: blob-backed lazy shape geometry.
+
+Parity is asserted via re-serialization bytes (NGEOM) or field checks — Geometry
+dataclass ``==`` is unusable because Point's ndarray ``__eq__`` breaks dataclass
+equality.
+"""
+
+from __future__ import annotations
+
+import gc
+import pickle
+import weakref
+
+import ada.geom.curves as cu
+import ada.geom.solids as so
+import ada.geom.surfaces as su
+from ada.api.primitives.base import Shape
+from ada.api.shapes import ShapeProxy, ShapeStore
+from ada.cadit.ngeom import serialize_geometries
+from ada.geom.booleans import BooleanOperation, BoolOpEnum
+from ada.geom.core import Geometry
+from ada.geom.placement import Axis2Placement3D, Direction, Point
+
+
+def _line_oe(s, t):
+    ec = cu.EdgeCurve(start=s, end=t, edge_geometry=cu.Line(s, [b - a for a, b in zip(s, t)]), same_sense=True)
+    return cu.OrientedEdge(start=s, end=t, edge_element=ec, orientation=True)
+
+
+def _square_face():
+    p = [(0, 0, 0), (2, 0, 0), (2, 2, 0), (0, 2, 0)]
+    loop = cu.EdgeLoop(edge_list=[_line_oe(p[i], p[(i + 1) % 4]) for i in range(4)])
+    plane = su.Plane(position=Axis2Placement3D(Point(0, 0, 0), Direction(0, 0, 1), Direction(1, 0, 0)))
+    return su.FaceSurface(bounds=[su.FaceBound(bound=loop, orientation=True)], face_surface=plane, same_sense=True)
+
+
+def _shell_geometry(gid="solid1") -> Geometry:
+    return Geometry(id=gid, geometry=su.ClosedShell(cfs_faces=[_square_face()]))
+
+
+def _boolean_geometry(gid="cut1") -> Geometry:
+    base = _shell_geometry(gid)
+    half_space = su.HalfSpaceSolid(
+        base_surface=su.Plane(position=Axis2Placement3D(Point(0, 0, 1), Direction(0, 0, 1), Direction(1, 0, 0)))
+    )
+    box = so.Box(Axis2Placement3D(Point(0, 0, 0), Direction(0, 0, 1), Direction(1, 0, 0)), 1.0, 1.0, 1.0)
+    base.bool_operations = [
+        BooleanOperation(Geometry("hs", half_space), BoolOpEnum.DIFFERENCE),
+        BooleanOperation(Geometry("box", box), BoolOpEnum.UNION),
+    ]
+    return base
+
+
+def _ngeom_blob(geom: Geometry) -> bytes:
+    return serialize_geometries([(str(geom.id), geom.geometry)])
+
+
+def test_ngeom_blob_roundtrip_byte_parity():
+    """ngeom-kind: hydrated tree re-serializes to the exact stored bytes."""
+    g = _shell_geometry()
+    blob = _ngeom_blob(g)
+    store = ShapeStore()
+    idx = store.add_blob(blob, gid=str(g.id))
+    hydrated = store.geometry(idx)
+    assert hydrated.id == "solid1"
+    assert serialize_geometries([(hydrated.id, hydrated.geometry)]) == blob
+
+
+def test_add_blob_rejects_non_ngeom():
+    store = ShapeStore()
+    try:
+        store.add_blob(b"not a buffer at all", gid="x")
+    except ValueError as e:
+        assert "magic" in str(e)
+    else:
+        raise AssertionError("expected ValueError on bad magic")
+
+
+def test_pickle_kind_roundtrips_bool_operations():
+    """pickle-kind: booleans (incl. half-space operands) hydrate exactly."""
+    g = _boolean_geometry()
+    store = ShapeStore()
+    idx = store.add_geometry(g)
+    hydrated = store.geometry(idx)
+    assert hydrated.id == "cut1"
+    assert isinstance(hydrated.geometry, su.ClosedShell)
+    ops = hydrated.bool_operations
+    assert [op.operator for op in ops] == [BoolOpEnum.DIFFERENCE, BoolOpEnum.UNION]
+    hs = ops[0].second_operand.geometry
+    assert isinstance(hs, su.HalfSpaceSolid)
+    assert hs.agreement_flag is True
+    assert list(hs.base_surface.position.location) == [0.0, 0.0, 1.0]
+    box = ops[1].second_operand.geometry
+    assert isinstance(box, so.Box)
+    assert (box.x_length, box.y_length, box.z_length) == (1.0, 1.0, 1.0)
+
+
+def test_weakref_cache_identity_and_release():
+    # hydration_cache_size=0 -> pure weakref semantics (no strong LRU window)
+    store = ShapeStore(hydration_cache_size=0)
+    idx = store.add_geometry(_shell_geometry())
+    g1 = store.geometry(idx)
+    assert store.geometry(idx) is g1, "same live object while referenced"
+    ref = weakref.ref(g1)
+    del g1
+    gc.collect()
+    assert ref() is None, "hydrated tree must be reclaimable once dropped"
+    # and a fresh access hydrates again
+    assert store.geometry(idx).id == "solid1"
+
+
+def test_hydration_lru_keeps_hot_and_evicts_cold():
+    """Back-to-back .geom access must not re-decode (consumers read it 3-5x per
+    call), while the strong window stays bounded — hydrate-all still returns to
+    the blob floor."""
+    store = ShapeStore(hydration_cache_size=2)
+    idxs = [store.add_geometry(_shell_geometry(f"s{i}")) for i in range(4)]
+
+    g0 = store.geometry(idxs[0])
+    assert store.geometry(idxs[0]) is g0, "hot entry must be identity-stable with no outside refs"
+
+    ref0 = weakref.ref(g0)
+    del g0
+    for i in idxs[1:]:  # push idx0 out of the 2-slot window
+        store.geometry(i)
+    gc.collect()
+    assert ref0() is None, "evicted entry must be reclaimable"
+
+
+def test_compression_roundtrip_both_kinds():
+    g = _shell_geometry()
+    blob = _ngeom_blob(g)
+    store = ShapeStore(compress=True)
+    i_ngeom = store.add_blob(blob, gid=str(g.id))
+    i_pickle = store.add_geometry(_boolean_geometry())
+    assert store.record(i_ngeom).compressed and store.record(i_pickle).compressed
+    assert store.nbytes < len(blob) + 100_000  # stored compressed
+    assert store.ngeom_blob(i_ngeom) == blob  # decompresses to the original
+    assert store.geometry(i_pickle).bool_operations[0].operator == BoolOpEnum.DIFFERENCE
+
+
+def test_proxy_is_shape_and_hydrates_via_property():
+    store = ShapeStore()
+    g = _shell_geometry()
+    idx = store.add_blob(_ngeom_blob(g), gid=str(g.id))
+    p = ShapeProxy("solid1", store, idx)
+    assert isinstance(p, Shape)
+    assert p._geom is None, "proxy must not hold an eager tree"
+    # NGEOM lowers ClosedShell -> ConnectedFaceSet; today's eager native reader
+    # yields the same, so downstream behaviour is identical.
+    assert isinstance(p.geom.geometry, su.ConnectedFaceSet)
+    assert p.ngeom_blob() is not None
+
+    # solid_geom() (a base-class method) works through the overridden property on
+    # an accepted solid type — pickle-kind keeps the ClosedShell exact.
+    idx2 = store.add_geometry(_shell_geometry("solid2"))
+    p2 = ShapeProxy("solid2", store, idx2)
+    solid = p2.solid_geom()
+    assert solid.id == "solid2"
+    assert isinstance(solid.geometry, su.ClosedShell)
+
+
+def test_proxy_pin_semantics():
+    # hydration_cache_size=0: the strong LRU window would keep an unpinned mutation
+    # alive until eviction — the CONTRACT (pin before mutating) is what's tested.
+    store = ShapeStore(hydration_cache_size=0)
+    idx = store.add_geometry(_shell_geometry())
+    p = ShapeProxy("solid1", store, idx)
+
+    # unpinned: mutation on a transient hydration does not survive a GC cycle
+    p.geom.color = "marker"
+    gc.collect()
+    assert p.geom.color is None
+
+    pinned = p.pin()
+    pinned.color = "marker"
+    gc.collect()
+    assert p.geom.color == "marker"
+
+    # assigning .geom pins the assigned object
+    other = _shell_geometry("other")
+    p.geom = other
+    assert p.geom is other
+
+
+def test_proxy_pickle_shares_store():
+    store = ShapeStore()
+    g = _shell_geometry()
+    blob = _ngeom_blob(g)
+    idx1 = store.add_blob(blob, gid="a")
+    idx2 = store.add_blob(blob, gid="b")
+    p1 = ShapeProxy("a", store, idx1)
+    p2 = ShapeProxy("b", store, idx2)
+    r1, r2 = pickle.loads(pickle.dumps([p1, p2]))
+    assert r1._shape_store is r2._shape_store, "pickle memo must keep one store"
+    assert r1.geom.id == "a" and r2.geom.id == "b"
+    assert isinstance(r1, ShapeProxy) and isinstance(r1, Shape)
+
+
+def test_blob_fast_path_matches_serialized_tessellation():
+    """A stored NGEOM blob tessellates via tessellate_stream_buffer to the same mesh
+    the hydrate+re-serialize route produces (the lazy fast path skips both steps)."""
+    import pytest
+
+    from ada.cad import active_backend
+
+    be = active_backend()
+    if not hasattr(be, "tessellate_stream_buffer") or not hasattr(be, "tessellate_stream"):
+        pytest.skip("active CAD backend has no NGEOM stream tessellation")
+
+    g = _shell_geometry()
+    store = ShapeStore()
+    idx = store.add_blob(_ngeom_blob(g), gid=str(g.id))
+    p = ShapeProxy("solid1", store, idx)
+
+    via_blob = be.tessellate_stream_buffer(p.ngeom_blob(), pipeline="libtess2")
+    hydrated = p.geom
+    via_items = be.tessellate_stream([(str(hydrated.id), hydrated.geometry)], pipeline="libtess2")
+    assert via_blob.positions.tobytes() == via_items.positions.tobytes()
+    assert via_blob.indices.tobytes() == via_items.indices.tobytes()
+
+
+def test_pickle_kind_has_no_ngeom_blob():
+    store = ShapeStore()
+    idx = store.add_geometry(_boolean_geometry())
+    assert store.ngeom_blob(idx) is None
+    p = ShapeProxy("cut1", store, idx)
+    assert p.ngeom_blob() is None
+
+
+def test_stream_tessellation_applies_bool_operations():
+    """A Geometry wrapper's bool_operations reach the stream kernel: the serializer
+    folds them into a BOOLEAN_RESULT chain (half-space lowered to a finite box, the
+    same lowering adacpp's readers use) and Manifold evaluates the cut."""
+    import pytest
+
+    import ada
+    from ada.cad import active_backend
+
+    be = active_backend()
+    if not hasattr(be, "tessellate_stream"):
+        pytest.skip("active CAD backend has no NGEOM stream tessellation")
+
+    box = ada.PrimBox("bx", (0, 0, 0), (1, 1, 1))
+    box.add_boolean(ada.BoolHalfSpace((0.5, 0.5, 0.6), (0, 0, 1), name="cut"))
+    geom = box.solid_geom()
+    assert geom.bool_operations, "fixture must carry a boolean"
+
+    bm = be.tessellate_stream([("bx", geom)], pipeline="libtess2")
+    z = bm.positions.reshape(-1, 3)[:, 2] if bm.positions.ndim == 1 else bm.positions[:, 2]
+    assert len(z) > 0, "boolean-bearing solid tessellated to nothing"
+    zmax = float(z.max())
+    assert abs(zmax - 0.6) < 1e-6, f"half-space cut not applied (zmax={zmax}, expected 0.6)"
+
+    # solid second operand (UNION): a box fused on top raises the extent instead
+    box2 = ada.PrimBox("bx2", (0, 0, 0), (1, 1, 1))
+    box2.add_boolean(ada.PrimBox("cap", (0.25, 0.25, 0.5), (0.75, 0.75, 1.4)), "union")
+    g2 = box2.solid_geom()
+    bm2 = be.tessellate_stream([("bx2", g2)], pipeline="libtess2")
+    z2 = bm2.positions.reshape(-1, 3)[:, 2] if bm2.positions.ndim == 1 else bm2.positions[:, 2]
+    assert abs(float(z2.max()) - 1.4) < 1e-6, "union operand not applied"
+
+
+def test_backend_builds_hydrated_connected_face_set():
+    """Audit regression: a non-promoted native root hydrates as bare ConnectedFaceSet
+    and must build on the ACTIVE backend (adacpp raised 'not yet ported'); it sews
+    like the ClosedShell/OpenShell shells."""
+    from ada.cad import active_backend
+
+    store = ShapeStore()
+    g = _shell_geometry()
+    idx = store.add_blob(_ngeom_blob(g), gid=str(g.id))
+    hydrated = store.geometry(idx)
+    assert isinstance(hydrated.geometry, su.ConnectedFaceSet)  # single face -> not promoted
+    handle = active_backend().build(hydrated)
+    assert handle is not None
+
+
+def test_native_ifc_brep_products_import_as_ngeom_blobs(tmp_path):
+    """B-rep IFC products the Python-native readers can't resolve import via adacpp's
+    IfcNgeomStream as zero-copy ngeom-kind proxies instead of eager OCC kernel bodies."""
+    import pytest
+
+    import ada
+
+    adacpp = pytest.importorskip("adacpp")
+    if not hasattr(adacpp.cad, "IfcNgeomStream"):
+        pytest.skip("adacpp build predates IfcNgeomStream")
+
+    box = ada.PrimBox("bx", (0, 0, 0), (1, 1, 1))
+    a = ada.Assembly("m") / (ada.Part("p") / [box])
+    stp = tmp_path / "nb.stp"
+    ifc = tmp_path / "nb.ifc"
+    a.to_stp(stp, writer="stream")
+    adacpp.cad.stream_step_to_ifc(str(stp), str(ifc))  # advanced-brep IFC4
+
+    b = ada.from_ifc(ifc)
+    shapes = [s for p in b.get_all_parts_in_assembly(include_self=True) for s in p.shapes]
+    assert shapes
+    for s in shapes:
+        assert isinstance(s, ShapeProxy), f"{s.name}: expected lazy proxy, got {type(s).__name__}"
+        assert s._occ_cache is None, f"{s.name}: eager OCC body retained"
+        rec = s._shape_store.record(s._store_index)
+        assert rec.kind == "ngeom", f"{s.name}: expected native blob, got {rec.kind}"
+        assert s.ngeom_blob() is not None
+        assert s.geom.geometry is not None  # hydrates
+
+
+def test_ifc_roundtrip_imports_lazy_proxies_with_booleans(tmp_path):
+    """from_ifc mints ShapeProxy objects (lazy store default-on) and a boolean cut
+    (IfcBooleanClippingResult -> bool_operations) survives the store round-trip."""
+    import ada
+
+    box = ada.PrimBox("bx", (0, 0, 0), (1, 1, 1))
+    box.add_boolean(ada.BoolHalfSpace((0.5, 0.5, 0.9), (0, 0, 1), name="cut"))
+    a = ada.Assembly("m") / (ada.Part("p") / [box])
+    f = tmp_path / "lazy_bool.ifc"
+    a.to_ifc(f)
+
+    b = ada.from_ifc(f)
+    shapes = [s for p in b.get_all_parts_in_assembly(include_self=True) for s in p.shapes]
+    assert shapes, "no shapes imported"
+    proxies = [s for s in shapes if isinstance(s, ShapeProxy)]
+    assert proxies, f"expected lazy proxies, got {[type(s).__name__ for s in shapes]}"
+    geom = proxies[0].geom
+    assert geom.bool_operations, "boolean clipping lost through the lazy store"
+    assert geom.bool_operations[0].operator == BoolOpEnum.DIFFERENCE
diff --git a/tests/core/api/test_placement_convention.py b/tests/core/api/test_placement_convention.py
new file mode 100644
index 000000000..f6ba98ebe
--- /dev/null
+++ b/tests/core/api/test_placement_convention.py
@@ -0,0 +1,63 @@
+"""Placement rotation-convention self-consistency.
+
+Historically ``from_4x4_matrix`` extracted the local axes from the matrix COLUMNS while every
+other constructor (``from_axis_angle`` / ``from_quaternion`` / ``rotate`` /
+``get_absolute_placement``) and ``rot_matrix`` used ROWS — so ``from_4x4_matrix`` produced the
+TRANSPOSE (== inverse for a rotation), and a rotated IFC ObjectPlacement rendered on the wrong
+world axis. These tests pin the invariants that keep the class consistent.
+"""
+
+import numpy as np
+
+from ada import Placement
+
+# A genuinely asymmetric rotation: 90deg about Z. Standard world matrix M has COLUMNS equal to
+# the world direction of each local axis, so M @ (1,0,0,1) sends local +X to world +Y.
+_R = np.array([[0.0, -1.0, 0.0], [1.0, 0.0, 0.0], [0.0, 0.0, 1.0]])
+_ORIGIN = np.array([5.0, 2.0, 0.0])
+_M = np.eye(4)
+_M[:3, :3] = _R
+_M[:3, 3] = _ORIGIN
+
+
+def _M_at(local):
+    """Ground-truth world point: the standard homogeneous transform applied to a local point."""
+    return (_M @ np.array([local[0], local[1], local[2], 1.0]))[:3]
+
+
+def test_from_4x4_matrix_round_trips_through_get_matrix4x4():
+    """from_4x4_matrix(M).get_matrix4x4() must equal M (it used to return M.T)."""
+    p = Placement.from_4x4_matrix(_M)
+    assert np.allclose(p.get_matrix4x4(), _M)
+
+
+def test_from_4x4_matrix_transforms_local_axis_to_world_direction():
+    """local +X must map to M's column-0 world direction (+Y here), not its negation."""
+    p = Placement.from_4x4_matrix(_M)
+    assert np.allclose(p.transform_local_points_to_global(np.array([[1.0, 0, 0]]))[0], _M_at((1, 0, 0)))
+    assert np.allclose(p.transform_local_points_to_global(np.array([[0.0, 1, 0]]))[0], _M_at((0, 1, 0)))
+
+
+def test_transform_methods_agree_with_get_matrix4x4():
+    """The transform_* helpers and the 4x4 matrix must describe the SAME transform."""
+    from ada import Placement as _P
+
+    p = Placement.from_4x4_matrix(_M)
+    for local in [(1, 0, 0), (0, 1, 0), (0, 0, 1), (0.3, -0.7, 1.2)]:
+        truth = _M_at(local)
+        via_pts = p.transform_local_points_to_global(np.array([[float(local[0]), local[1], local[2]]]))[0]
+        via_other = p.transform_array_from_other_place(
+            np.array([[float(local[0]), local[1], local[2]]]), _P()
+        )[0]
+        via_mat = (p.get_matrix4x4() @ np.array([local[0], local[1], local[2], 1.0]))[:3]
+        assert np.allclose(via_pts, truth), f"transform_local_points_to_global {local}"
+        assert np.allclose(via_other, truth), f"transform_array_from_other_place {local}"
+        assert np.allclose(via_mat, truth), f"get_matrix4x4 {local}"
+
+
+def test_from_4x4_matrix_matches_from_axis_angle():
+    """from_4x4_matrix of a 90deg-about-Z world matrix must equal from_axis_angle(Z, 90) — the
+    two construction paths must produce the same rotation, not transposes of each other."""
+    p_mat = Placement.from_4x4_matrix(_M)
+    p_aa = Placement.from_axis_angle([0, 0, 1], 90, origin=_ORIGIN)
+    assert np.allclose(np.array(p_mat.rot_matrix), np.array(p_aa.rot_matrix))
diff --git a/tests/core/api/test_shape_placement_bake.py b/tests/core/api/test_shape_placement_bake.py
new file mode 100644
index 000000000..f3dd3ed15
--- /dev/null
+++ b/tests/core/api/test_shape_placement_bake.py
@@ -0,0 +1,100 @@
+"""The generic-Shape placement baker (``Shape.solid_geom`` folds a non-identity placement
+into the analytic solid's ``position``).
+
+A generic ``Shape`` (as minted by the IFC/native readers) holds its geometry in LOCAL
+representation coordinates and its world transform on ``self.placement``. The tessellator and
+the STEP/AP242 exporters are placement-agnostic for such shapes — nothing applies the shape's
+own placement downstream — so ``solid_geom()`` has to return world-placed geometry, otherwise
+a rotated shape renders with its rotation dropped. These tests pin that the bake is applied,
+is correct (matches the Placement 4x4 convention), and is idempotent (never mutates / never
+compounds on repeat calls).
+"""
+
+import numpy as np
+
+from ada import Placement, Point, Shape
+from ada.geom import Geometry
+from ada.geom.solids import Box
+
+
+def _box_shape(place: Placement) -> Shape:
+    box = Box.from_2points(Point(0, 0, 0), Point(2, 1, 1))
+    return Shape("boxshape", geom=Geometry("b", box, None), placement=place)
+
+
+def test_identity_placement_leaves_geometry_untouched():
+    sh = _box_shape(Placement())
+    sg = sh.solid_geom()
+    # Same object, position unchanged at the local origin.
+    assert np.allclose(np.asarray(sg.geometry.position.location), (0, 0, 0))
+
+
+def test_rotated_placement_is_baked_into_position():
+    # 90deg about Z at origin (5, 2, 0): local +X -> world +Y, translation applied.
+    place = Placement.from_axis_angle([0, 0, 1], 90, origin=(5, 2, 0))
+    sh = _box_shape(place)
+    pos = sh.solid_geom().geometry.position
+
+    loc_expected = (place.get_matrix4x4() @ np.array([0.0, 0, 0, 1]))[:3]
+    assert np.allclose(np.asarray(pos.location), loc_expected)
+    assert np.allclose(np.asarray(pos.ref_direction), (0, 1, 0), atol=1e-6)  # local X -> world Y
+    assert np.allclose(np.asarray(pos.axis), (0, 0, 1), atol=1e-6)  # Z preserved under a Z-rotation
+
+
+def test_bake_is_idempotent_and_non_mutating():
+    place = Placement.from_axis_angle([0, 0, 1], 90, origin=(5, 2, 0))
+    sh = _box_shape(place)
+    loc_expected = (place.get_matrix4x4() @ np.array([0.0, 0, 0, 1]))[:3]
+
+    first = sh.solid_geom().geometry.position.location
+    second = sh.solid_geom().geometry.position.location
+    assert np.allclose(np.asarray(first), loc_expected)
+    assert np.allclose(np.asarray(second), loc_expected)  # not compounded
+    # The stored geometry (local) is never mutated by the bake.
+    assert np.allclose(np.asarray(sh.geom.geometry.position.location), (0, 0, 0))
+
+
+def test_baked_geometry_renders_placed_via_stream_and_occ():
+    """The baked ``solid_geom()`` tessellates to WORLD coordinates on both the libtess2 stream
+    kernel and OCC — the actual bug the baker fixes (a rotated shape rendered unplaced)."""
+    import pytest
+
+    place = Placement.from_axis_angle([0, 0, 1], 90, origin=(5, 2, 0))
+    sh = _box_shape(place)
+    sg = sh.solid_geom()
+
+    # local box (0,0,0)-(2,1,1) rotated 90 about Z at (5,2,0) -> x in [4,5], y in [2,4], z in [0,1]
+    def _check_bbox(mn, mx):
+        assert 3.9 < mn[0] and mx[0] < 5.1, (mn, mx)
+        assert 1.9 < mn[1] and mx[1] < 4.1, (mn, mx)
+
+    # OCC path (solid_occ builds from the baked solid_geom)
+    occ = pytest.importorskip("OCC")  # noqa: F841
+    from OCC.Core.Bnd import Bnd_Box
+    from OCC.Core.BRepBndLib import brepbndlib
+
+    bb = Bnd_Box()
+    brepbndlib.Add(sh.solid_occ(), bb)
+    xmin, ymin, zmin, xmax, ymax, zmax = bb.Get()
+    _check_bbox((xmin, ymin, zmin), (xmax, ymax, zmax))
+
+
+def test_baked_geometry_renders_placed_via_libtess2():
+    import pytest
+
+    pytest.importorskip("adacpp")
+    from ada.cad import AdacppBackend
+
+    place = Placement.from_axis_angle([0, 0, 1], 90, origin=(5, 2, 0))
+    sh = _box_shape(place)
+    sg = sh.solid_geom()
+
+    be = AdacppBackend()
+    m = be.tessellate_stream([("b", sg)], pipeline="libtess2", deflection=2.0, angular_deg=20.0)
+    pos_attr = getattr(m, "positions", None)
+    if pos_attr is None:
+        pos_attr = m.position
+    pts = np.asarray(pos_attr, dtype=float).reshape(-1, 3)
+    mn, mx = pts.min(0), pts.max(0)
+    assert 3.9 < mn[0] and mx[0] < 5.1, (mn, mx)
+    assert 1.9 < mn[1] and mx[1] < 4.1, (mn, mx)
diff --git a/tests/core/cadit/ifc/read/beams/test_ifc_read_beams.py b/tests/core/cadit/ifc/read/beams/test_ifc_read_beams.py
index 4b6c4f118..ef9d5f615 100644
--- a/tests/core/cadit/ifc/read/beams/test_ifc_read_beams.py
+++ b/tests/core/cadit/ifc/read/beams/test_ifc_read_beams.py
@@ -1,8 +1,20 @@
+import re
+import numpy as np
 import pytest
 
 import ada
 
 
+def _world(bm: ada.Beam, pt) -> tuple:
+    """The beam endpoint in world coords: apply the full placement transform to the
+    LOCAL n1/n2. These beams carry a rotated ObjectPlacement (local Z extruded onto
+    world X), so the placement rotation must be applied — a naive ``origin + n1`` does
+    not, and would silently mask a wrong-axis placement (beam-standard-case.ifc)."""
+    m = bm.placement.get_matrix4x4()
+    q = m @ np.array([pt[0], pt[1], pt[2], 1.0])
+    return tuple(np.round(q[:3], 4))
+
+
 def test_read_standard_case_beams(example_files, tmp_path):
     a = ada.from_ifc(example_files / "ifc_files/beams/beam-standard-case.ifc")
 
@@ -11,19 +23,19 @@ def test_read_standard_case_beams(example_files, tmp_path):
     p = a.get_by_name("Building")
     assert len(p.beams) == 18
 
+    # World-space beam axes, verified against ifcopenshell's create_shape (USE_WORLD_COORDS).
+    # The A-row beams run along world X at increasing Y; the placement swaps local Z -> world X.
     bm_a1: ada.Beam = p.get_by_name("A-1")
-    assert tuple(bm_a1.n1.p) == (-0.055, 0.11, 0.0)
-    assert tuple(bm_a1.n2.p) == (1.945, 0.11, 0.0)
+    assert _world(bm_a1, bm_a1.n1.p) == (0.0, -0.055, 0.11)
+    assert _world(bm_a1, bm_a1.n2.p) == (2.0, -0.055, 0.11)
 
     bm_a2: ada.Beam = p.get_by_name("A-2")
-    o = bm_a2.placement
-    assert tuple(o.origin + bm_a2.n1.p) == (0.0, 1.61, 0.0)
-    assert tuple(o.origin + bm_a2.n2.p) == (2.0, 1.61, 0.0)
+    assert _world(bm_a2, bm_a2.n1.p) == (0.0, 1.5, 0.11)
+    assert _world(bm_a2, bm_a2.n2.p) == (2.0, 1.5, 0.11)
 
     bm_b1: ada.Beam = p.get_by_name("B-1")
-    o = bm_b1.placement
-    assert tuple(o.origin + bm_b1.n1.p) == (-0.075, 0.075, 1.5)
-    assert tuple(o.origin + bm_b1.n2.p) == pytest.approx((2.865, 0.318, 2.046), abs=1e-3)
+    assert _world(bm_b1, bm_b1.n1.p) == pytest.approx((-0.0149, -0.0387, 1.5976), abs=1e-3)
+    assert _world(bm_b1, bm_b1.n2.p) == pytest.approx((2.9249, 0.2043, 2.1436), abs=1e-3)
 
 
 def test_read_extruded_solid_beams(example_files):
@@ -32,8 +44,10 @@ def test_read_extruded_solid_beams(example_files):
     assert len(p.beams) == 1
     bm = p.beams[0]
 
-    assert tuple(bm.n1.p) == (0.0, 0.0, 0.0)
-    assert tuple(bm.n2.p) == (0.0, 10.0, 0.0)
+    # n1/n2 are in the beam's LOCAL frame (the extrusion is along local Z); the ObjectPlacement
+    # rotates that onto world +Y. Check the WORLD endpoints via the placement transform.
+    assert tuple(_world(bm, bm.n1.p)) == (0.0, 0.0, 0.0)
+    assert tuple(_world(bm, bm.n2.p)) == (0.0, 10.0, 0.0)
 
 
 def test_read_varying_cardinal_points(example_files):
@@ -55,3 +69,63 @@ def test_read_revolved_solid(example_files):
     a = ada.from_ifc(example_files / "ifc_files/beams/beam-revolved-solid.ifc")
     _ = a.to_ifc(file_obj_only=True)
     print(a)
+
+
+def test_extruded_solid_beam_winding_is_outward(example_files, monkeypatch):
+    """The production NGEOM libtess2 stream tessellates the extruded beam with OUTWARD-facing
+    normals (positive signed volume). A CW-discretized profile loop previously came out
+    inside-out (negative volume -> dark shading). Gated to ada-cpp (libtess2 needs it)."""
+    import trimesh
+
+    from ada.cad import active_backend
+
+    if active_backend().name != "adacpp":
+        pytest.skip("NGEOM libtess2 stream tessellation is the ada-cpp path")
+
+    monkeypatch.setenv("ADA_STREAM_TESS_PIPELINE", "libtess2")
+    a = ada.from_ifc(example_files / "ifc_files/beams/beam-extruded-solid.ifc")
+    bm = next(iter(a.get_all_physical_objects()))
+    sc = a.to_trimesh_scene(merge_meshes=True)
+    m = trimesh.util.concatenate([g for g in sc.geometry.values() if hasattr(g, "faces")])
+    # Right magnitude (area * length) AND positive sign (outward winding).
+    # Sharp-I ``Ax`` underestimates the real (filleted) IPE600 area by ~4%, so the tessellated
+    # solid — which now includes the web/flange fillets — sits a few % above ``Ax*length``.
+    # Band-check the magnitude (catches gross errors) but keep the strict positive-volume
+    # winding guard.
+    exp = bm.section.properties.Ax * 10.0  # 10 m long
+    assert m.volume > 0, f"extrusion is inside-out (negative volume {m.volume:.5f})"
+    assert exp * 0.97 < m.volume < exp * 1.10, f"volume {m.volume:.5f} out of band around {exp:.5f}"
+
+
+def test_read_varying_cardinal_points_world_positions(example_files):
+    """The 4 beams in beam-varying-cardinal-points.ifc each carry a different CardinalPoint
+    (1/2/8/9). The authoring tool bakes that offset into the extrusion's Position, and each
+    beam's rotated ObjectPlacement (no PlacementRelTo) must be applied — the old no-parent
+    import path dropped the placement, collapsing every profile onto its axis. World bboxes
+    verified against ifcopenshell.geom (USE_WORLD_COORDS)."""
+    import numpy as np
+    import trimesh
+
+    a = ada.from_ifc(example_files / "ifc_files/beams/beam-varying-cardinal-points.ifc")
+    # (min, max) world bbox per beam name.
+    expected = {
+        "BotLeft": ((0.5, 0.0, 0.0), (0.6, 1.0, 0.2)),
+        "BotMid": ((-0.05, 0.0, 0.0), (0.05, 1.0, 0.2)),
+        "TopMid": ((-0.05, 0.0, -0.2), (0.05, 1.0, 0.0)),
+        "TopRight": ((0.4, 0.0, -0.2), (0.5, 1.0, 0.0)),
+    }
+    sc = a.to_trimesh_scene(merge_meshes=False)
+    seen = {}
+    for node in sc.graph.nodes_geometry:
+        m = re.search(r"name=(\w+)", str(node))
+        if not m:
+            continue
+        T, gn = sc.graph[node]
+        v = trimesh.transformations.transform_points(np.asarray(sc.geometry[gn].vertices), T)
+        seen[m.group(1)] = (v.min(0), v.max(0))
+    for nm, (emn, emx) in expected.items():
+        assert nm in seen, f"{nm} not rendered"
+        amn, amx = seen[nm]
+        assert np.allclose(amn, emn, atol=1e-3) and np.allclose(amx, emx, atol=1e-3), (
+            f"{nm}: cardinal offset wrong — got {np.round(amn,3)}..{np.round(amx,3)}, want {emn}..{emx}"
+        )
diff --git a/tests/core/cadit/ifc/read/test_bs_samples.py b/tests/core/cadit/ifc/read/test_bs_samples.py
new file mode 100644
index 000000000..f4fb969a1
--- /dev/null
+++ b/tests/core/cadit/ifc/read/test_bs_samples.py
@@ -0,0 +1,96 @@
+"""Regressions from the corpus audit sweep over the buildingSMART sample set
+(files under files/ifc_files/bs_samples/, all public buildingSMART samples).
+
+Each file previously errored (or silently dropped geometry) across every
+conversion target:
+
+* inch units (unit scale 0.0254) raised NotImplementedError at read
+* IfcTriangulatedFaceSet imported but tessellated to an empty scene
+* type-library files (geometry only on an IfcTypeProduct RepresentationMap,
+  no placed products) imported zero objects
+* IfcRectangleProfileDef swept profiles had no arbitrary-profile conversion
+* IfcTrimmedCurve parameter trims (degrees AND radians files) were rejected,
+  and the PartialEllipse column crashed the 2D-placement ellipse reader
+"""
+
+import pytest
+
+import ada
+
+
+def _read(example_files, name, monkeypatch):
+    monkeypatch.setenv("ADA_IFC_IMPORT_SHAPE_GEOM", "true")
+    ada.config.Config().reload_config()
+    return ada.from_ifc(example_files / f"ifc_files/bs_samples/{name}")
+
+
+def _glb_tri_count(a, tmp_path) -> int:
+    import trimesh
+
+    glb = tmp_path / "out.glb"
+    a.to_gltf(glb)
+    scene = trimesh.load(glb)
+    return sum(len(g.faces) for g in scene.geometry.values() if hasattr(g, "faces"))
+
+
+def test_inch_units_triangulated_column(example_files, monkeypatch, tmp_path):
+    # Inch-unit file (scale 0.0254): read must convert instead of raising, and
+    # the IfcTriangulatedFaceSet body must reach the GLB as a real mesh
+    # (direct mesh path — no kernel build exists for it).
+    a = _read(example_files, "column-straight-rectangle-tessellation.ifc", monkeypatch)
+    objects = list(a.get_all_physical_objects())
+    assert len(objects) == 1
+    # 8"x8" column, 10ft tall — converted to meters.
+    geom = objects[0].geom.geometry
+    assert max(abs(float(c)) for p in geom.coordinates for c in p) == pytest.approx(3.048)
+    assert _glb_tri_count(a, tmp_path) == 12
+
+
+def test_type_library_texture_file(example_files, monkeypatch, tmp_path):
+    # Geometry lives on an IfcBoilerType RepresentationMap; no placed product
+    # exists. The instance-less type import must pick it up.
+    a = _read(example_files, "tessellation-with-image-texture.ifc", monkeypatch)
+    objects = list(a.get_all_physical_objects())
+    assert len(objects) == 1
+    assert _glb_tri_count(a, tmp_path) > 0
+
+
+def test_rectangle_profile_extrusion(example_files, monkeypatch, tmp_path):
+    a = _read(example_files, "extruded-solid.ifc", monkeypatch)
+    objects = list(a.get_all_physical_objects())
+    assert len(objects) == 1
+    assert _glb_tri_count(a, tmp_path) > 0
+    # The AP242 stream writer converts the parametric profile too.
+    out = tmp_path / "out.stp"
+    a.to_stp(str(out), writer="stream", fuse_fem=False)
+    assert out.stat().st_size > 0
+
+
+@pytest.mark.parametrize("unit", ["degrees", "radians"])
+def test_trimmed_curve_parameters(example_files, monkeypatch, tmp_path, unit):
+    # Parameter trims: line basis (IfcVector magnitude scales t), circle basis
+    # (angle in the file's plane-angle unit), ellipse basis (2D placement +
+    # sampled arc). All three columns must import and tessellate.
+    a = _read(example_files, f"curve-parameters-in-{unit}.ifc", monkeypatch)
+    objects = list(a.get_all_physical_objects())
+    assert len(objects) == 3
+    assert _glb_tri_count(a, tmp_path) > 0
+
+
+def test_trimmed_curve_degrees_radians_parity(example_files, monkeypatch, tmp_path):
+    # The two files describe the same geometry in different plane-angle units —
+    # after read-time normalization they must produce identical meshes.
+    import numpy as np
+    import trimesh
+
+    bounds = []
+    tris = []
+    for unit in ("degrees", "radians"):
+        a = _read(example_files, f"curve-parameters-in-{unit}.ifc", monkeypatch)
+        glb = tmp_path / f"{unit}.glb"
+        a.to_gltf(glb)
+        scene = trimesh.load(glb)
+        bounds.append(scene.bounds)
+        tris.append(sum(len(g.faces) for g in scene.geometry.values() if hasattr(g, "faces")))
+    assert tris[0] == tris[1]
+    assert np.allclose(bounds[0], bounds[1], atol=1e-6)
diff --git a/tests/core/cadit/ifc/read/test_read_alignment.py b/tests/core/cadit/ifc/read/test_read_alignment.py
new file mode 100644
index 000000000..5c177252e
--- /dev/null
+++ b/tests/core/cadit/ifc/read/test_read_alignment.py
@@ -0,0 +1,131 @@
+"""Native import + evaluation of IFC4x3 alignment reference curves (no OCC).
+
+Regression for the "zero geometry" bug on alignment files: an IfcAlignment (and its segments)
+carry only curve representations ('Axis' Curve3D / 'FootPrint' Curve2D / 'Segment'), so the
+generic shape importer skipped them and the file rendered empty. The alignment reader now
+evaluates the analytic curve — IfcSegmentedReferenceCurve (cant) over an IfcGradientCurve whose
+horizontal base is an IfcCompositeCurve of IfcCosineSpiral / IfcLine segments — to a sampled 3D
+polyline that renders as GL_LINES.
+
+Ground-truth values are the ifcopenshell.geom (USE_WORLD_COORDS) oracle for
+``segmented-reference-curve.ifc`` (buildingSMART IFC4x3 sample); the analytic evaluator matches
+them to ~1e-6 (cant z to machine precision).
+"""
+
+from __future__ import annotations
+
+import numpy as np
+import pytest
+
+import ada
+from ada.config import Config
+
+FIXTURE = "ifc_files/segmented-reference-curve.ifc"
+
+# Oracle endpoints (ifcopenshell.geom, USE_WORLD_COORDS) for this fixture.
+_HORIZONTAL_END = (98.9299, 13.1346)  # cosine-spiral horizontal, s = 100 m
+_REF_CURVE_END = (98.9299, 13.1346, -7.92)  # 3D reference curve with cant, s = 100 m
+_CANT_Z = {0.0: 0.08, 50.0: -3.92, 100.0: -7.92}  # cant z at base stations
+
+
+@pytest.fixture(autouse=True)
+def _enable_geom():
+    Config().update_config_globally("ifc_import_shape_geom", True)
+
+
+def test_alignment_file_imports_curve_geometry(example_files):
+    """The file used to import as 0 physical objects (every product skipped). It now yields the
+    IfcAlignment reference curve plus its segments, each a PolyLine."""
+    from ada.geom.curves import PolyLine
+
+    a = ada.from_ifc(example_files / FIXTURE)
+    objs = list(a.get_all_physical_objects())
+    assert len(objs) >= 4, f"expected the alignment + segments, got {len(objs)}"
+    polylines = [o for o in objs if o.geom is not None and isinstance(o.geom.geometry, PolyLine)]
+    assert len(polylines) >= 4
+    assert all(len(o.geom.geometry.points) >= 2 for o in polylines)
+
+
+def test_cosine_spiral_horizontal_matches_oracle(example_files):
+    """IfcCosineSpiral evaluation: the horizontal footprint endpoint and the heading angle at the
+    end (which equals the next segment's start bearing, 0.216667 rad)."""
+    import ifcopenshell
+
+    from ada.cadit.ifc.read.geom.curves import get_curve
+    from ada.cadit.ngeom._alignment_sweep import _cosine_spiral_theta, composite_curve_points
+
+    f = ifcopenshell.open(str(example_files / FIXTURE))
+    # #65 is the FootPrint IfcCompositeCurve (cosine-spiral horizontal).
+    cc = get_curve(f.by_id(65))
+    pts = composite_curve_points(cc, 200)
+    assert np.allclose(pts[-1][:2], _HORIZONTAL_END, atol=1e-3)
+    assert np.isclose(pts[0][0], 0.0, atol=1e-6) and np.isclose(pts[0][1], 0.0, atol=1e-6)
+
+    spiral = cc.segments[0].parent_curve  # the IfcCosineSpiral
+    theta_end = float(_cosine_spiral_theta(spiral, 100.0, np.array([100.0]))[0])
+    assert np.isclose(theta_end, 0.2166667, atol=1e-6)
+
+
+def test_segmented_reference_curve_cant_z(example_files):
+    """IfcSegmentedReferenceCurve: (x,y) equals the base gradient curve, and the cant produces the
+    exact cosine vertical offset z(s) = e0 + (L^2/CosineTerm)(cos(pi*s/L) - 1)."""
+    import ifcopenshell
+
+    from ada.cadit.ifc.read.geom.curves import get_curve
+    from ada.cadit.ngeom._alignment_sweep import segmented_reference_curve_points
+
+    f = ifcopenshell.open(str(example_files / FIXTURE))
+    src = get_curve(f.by_id(112))  # IfcSegmentedReferenceCurve
+    pts = segmented_reference_curve_points(src, 200)  # 201 pts at uniform base station 0..100
+
+    assert np.allclose(pts[0], (0.0, 0.0, 0.08), atol=1e-4)
+    assert np.allclose(pts[-1], _REF_CURVE_END, atol=1e-3)
+    # cant z at the sampled stations (index = station since n_per == 200 over 100 m)
+    for station, z in _CANT_Z.items():
+        assert np.isclose(pts[int(station * 2), 2], z, atol=1e-4), f"cant z at s={station}"
+
+
+def test_sectioned_solid_horizontal_native(example_files):
+    """IfcSectionedSolidHorizontal (a profile swept along the alignment directrix over a distance
+    range) reads natively as a triangulated swept shell — NOT the OCC-kernel explosion into
+    thousands of loose faces — so it renders and STEP-round-trips as one solid. bbox matches the
+    ifcopenshell oracle."""
+    import ada.geom.surfaces as su
+
+    a = ada.from_ifc(example_files / "ifc_files/sectioned-solid-horizontal.ifc")
+    objs = list(a.get_all_physical_objects())
+    assert len(objs) == 8  # 1 sectioned solid + 7 alignment curves
+
+    solids = [o for o in objs if o.geom is not None and isinstance(o.geom.geometry, su.TriangulatedFaceSet)]
+    assert len(solids) == 1, "the sectioned solid must read as one native triangulated shell"
+    tfs = solids[0].geom.geometry
+    coords = np.array([[p[0], p[1], p[2]] for p in tfs.coordinates])
+    assert len(tfs.indices) % 3 == 0 and len(tfs.indices) // 3 > 100
+    # oracle (ifcopenshell.geom, USE_WORLD_COORDS): swept over directrix distance 300..600
+    assert np.allclose(coords.min(0), (300.0, -22.26, 148.52), atol=0.1)
+    assert np.allclose(coords.max(0), (599.88, 5.0, 149.7), atol=0.1)
+
+
+def test_alignment_renders_as_lines(example_files):
+    """The imported polylines tessellate to GL_LINES (kernel-free discretize_curve path) with the
+    expected scene bbox (reference curve dips to z = -7.92 from the cant)."""
+    a = ada.from_ifc(example_files / FIXTURE)
+    objs = list(a.get_all_physical_objects())
+
+    from ada.occ.tessellating import BatchTessellator
+    from ada.visit.gltf.meshes import MeshType
+
+    bt = BatchTessellator()
+    seg_total = 0
+    mn = np.full(3, 1e18)
+    mx = np.full(3, -1e18)
+    for ms in bt.batch_tessellate(objs):
+        assert ms.type == MeshType.LINES
+        p = np.asarray(ms.position, dtype=float).reshape(-1, 3)
+        if len(p):
+            mn = np.minimum(mn, p.min(0))
+            mx = np.maximum(mx, p.max(0))
+        seg_total += len(ms.indices) // 2
+    assert seg_total > 100
+    assert np.isclose(mn[2], -7.92, atol=1e-2)  # cant dip present
+    assert mx[0] > 99 and mx[1] > 12  # spans the horizontal footprint
diff --git a/tests/core/cadit/ifc/read/test_read_face_based_surface_model.py b/tests/core/cadit/ifc/read/test_read_face_based_surface_model.py
new file mode 100644
index 000000000..2d12b81f2
--- /dev/null
+++ b/tests/core/cadit/ifc/read/test_read_face_based_surface_model.py
@@ -0,0 +1,37 @@
+"""Native IfcFaceBasedSurfaceModel reader (a set of IfcConnectedFaceSet, each a set of IfcFace).
+
+Previously fell back to the OCC kernel. The reader now builds the native face-set hierarchy
+(FaceBasedSurfaceModel -> ConnectedFaceSet -> Face -> FaceBound -> PolyLoop), which the shared
+OCC/NGEOM face-set builders already tessellate. The product's ObjectPlacement is applied via the
+face-set placement baker (transforms the loop vertices), so it lands in world coordinates.
+"""
+
+from __future__ import annotations
+
+import numpy as np
+
+import ada
+from ada.config import Config
+
+
+def test_face_based_surface_model_native_and_placed(example_files):
+    """surface-model.ifc: an IfcFaceBasedSurfaceModel reads natively (no OCC kernel) and, with its
+    +1 m x ObjectPlacement applied, matches the ifcopenshell oracle bbox ([0.5,-0.5,0]..[1.5,0.5,2])."""
+    import ada.geom.surfaces as su
+
+    Config().update_config_globally("ifc_import_shape_geom", True)
+    a = ada.from_ifc(example_files / "ifc_files/surface-model.ifc")
+    objs = list(a.get_all_physical_objects())
+    assert len(objs) == 1
+    o = objs[0]
+    assert isinstance(o.geom.geometry, su.FaceBasedSurfaceModel)
+    assert o._occ_cache is None  # not built via the IfcOpenShell kernel
+
+    from ada.occ.tessellating import BatchTessellator
+
+    bt = BatchTessellator()
+    pts = [np.asarray(ms.position, float).reshape(-1, 3) for ms in bt.batch_tessellate(objs)]
+    p = np.vstack([x for x in pts if len(x)])
+    assert len(p) > 0
+    assert np.allclose(p.min(0), (0.5, -0.5, 0.0), atol=0.02), p.min(0)
+    assert np.allclose(p.max(0), (1.5, 0.5, 2.0), atol=0.02), p.max(0)
diff --git a/tests/core/cadit/ifc/read/test_read_gzipped_ifc.py b/tests/core/cadit/ifc/read/test_read_gzipped_ifc.py
new file mode 100644
index 000000000..6acf6d3c7
--- /dev/null
+++ b/tests/core/cadit/ifc/read/test_read_gzipped_ifc.py
@@ -0,0 +1,39 @@
+"""Transparently open a gzip-compressed IFC shipped under a plain .ifc name.
+
+Some exporters/servers gzip the model but keep the .ifc extension; ifcopenshell.open then fails
+with 'Unable to parse IFC SPF header'. The reader detects the gzip magic (0x1f 0x8b) and inflates
+the SPF text before parsing, so from_ifc reads it like any other model.
+"""
+
+from __future__ import annotations
+
+import gzip
+
+import ifcopenshell
+
+import ada
+from ada.config import Config
+
+
+def test_from_ifc_opens_gzip_compressed_ifc(example_files):
+    src = example_files / "ifc_files/beam-standard-case-gz.ifc"
+    # sanity: the fixture really is gzip and ifcopenshell.open can't read it directly
+    assert src.read_bytes()[:2] == b"\x1f\x8b"
+
+    Config().update_config_globally("ifc_import_shape_geom", True)
+    a = ada.from_ifc(src)
+    objs = list(a.get_all_physical_objects())
+    assert len(objs) == 18  # 18 IfcBeam in the buildingSMART beam-standard-case sample
+
+
+def test_open_ifc_file_helper_handles_gzip_and_plain(example_files, tmp_path):
+    from ada.cadit.ifc.store import open_ifc_file
+
+    gz = example_files / "ifc_files/beam-standard-case-gz.ifc"
+    f = open_ifc_file(gz)
+    assert f.schema == "IFC4" and len(f.by_type("IfcBeam")) == 18
+
+    # a plain (already-inflated) copy still opens the normal way
+    plain = tmp_path / "plain.ifc"
+    plain.write_text(gzip.decompress(gz.read_bytes()).decode("utf-8", "replace"))
+    assert isinstance(open_ifc_file(plain), ifcopenshell.file)
diff --git a/tests/core/cadit/ifc/read/test_read_indexed_profiles.py b/tests/core/cadit/ifc/read/test_read_indexed_profiles.py
new file mode 100644
index 000000000..2eba6bd72
--- /dev/null
+++ b/tests/core/cadit/ifc/read/test_read_indexed_profiles.py
@@ -0,0 +1,63 @@
+"""Native reading of two profile/curve cases that previously rendered wrong geometry.
+
+1. IfcRoundedRectangleProfileDef — a subtype of IfcRectangleProfileDef, so the plain-rectangle
+   branch used to swallow it and drop RoundingRadius, giving SHARP corners (bath-csg void).
+2. IfcIndexedPolyCurve with a multi-point IfcLineIndex — a polyline through N points is N-1 edges,
+   but only the first two points were kept, collapsing e.g. an I-section's flange outline.
+"""
+
+from __future__ import annotations
+
+import numpy as np
+import pytest
+
+import ada
+from ada.config import Config
+
+
+@pytest.fixture(autouse=True)
+def _enable_geom():
+    Config().update_config_globally("ifc_import_shape_geom", True)
+
+
+def _render_bbox(a):
+    from ada.occ.tessellating import BatchTessellator
+
+    objs = list(a.get_all_physical_objects())
+    p = np.vstack([np.asarray(m.position, float).reshape(-1, 3) for o in objs for m in BatchTessellator().batch_tessellate([o])])
+    return p.min(0), p.max(0)
+
+
+def test_rounded_rectangle_profile_rounds_corners(example_files):
+    """bath-csg-solid: the IfcRoundedRectangleProfileDef void reads as an ArbitraryProfileDef with 4
+    corner arcs (not a sharp rectangle), so the boolean cavity has rounded interior corners."""
+    import ada.geom.curves as cu
+    import ada.geom.surfaces as su
+
+    a = ada.from_ifc(example_files / "ifc_files/bath-csg-solid.ifc")
+    o = list(a.get_all_physical_objects())[0]
+    bops = o.geom.bool_operations or []
+    assert bops, "expected the DIFFERENCE boolean (block - void)"
+    void_profile = bops[0].second_operand.geometry.swept_area
+    assert isinstance(void_profile, su.ArbitraryProfileDef)  # not a sharp RectangleProfileDef
+    arcs = sum(1 for s in void_profile.outer_curve.segments if isinstance(s, cu.ArcLine))
+    assert arcs == 4  # one fillet per corner
+
+
+def test_indexed_polycurve_multipoint_line_index(example_files):
+    """beam-extruded-solid: the I-section profile (IfcIndexedPolyCurve with multi-point IfcLineIndex
+    runs) expands to consecutive edges instead of collapsing to a single edge per run — so the full
+    IPE200 (100mm wide x 200mm tall) is built, not a ~half-width box."""
+    src = example_files / "ifc_files/beam-extruded-solid.ifc"
+    a = ada.from_ifc(src)
+    o = list(a.get_all_physical_objects())[0]
+    # Deterministic, backend-free: the 4 lines + 4 arcs, with the two 6-point line runs each
+    # expanded to 5 edges, give 16 segments (was 8 when runs collapsed to one edge).
+    assert len(o.geom.geometry.swept_area.outer_curve.segments) == 16
+    # End-to-end: the rendered profile spans the full width/height (the collapse gave x-width ~0.047
+    # instead of ~0.1). Coarse thresholds so adacpp tessellation jitter doesn't flake the test.
+    rmn, rmx = _render_bbox(a)
+    size = rmx - rmn
+    assert size[0] > 0.09, size  # full 100mm flange width, not the collapsed ~47mm
+    assert size[2] > 0.18, size  # full 200mm section height
+    assert abs(size[1] - 1.0) < 0.02, size  # 1 m extrusion length
diff --git a/tests/core/cadit/ifc/read/test_read_mapped_item.py b/tests/core/cadit/ifc/read/test_read_mapped_item.py
new file mode 100644
index 000000000..e1c923926
--- /dev/null
+++ b/tests/core/cadit/ifc/read/test_read_mapped_item.py
@@ -0,0 +1,144 @@
+"""Native IfcMappedItem reader (unwrap a mapped representation + apply its transform, no OCC kernel).
+
+IfcMappedItem is an instancing wrapper (a MappingSource representation reused via a MappingTarget
+transform). It previously fell back to the IfcOpenShell OCC kernel (the single most common corpus
+fallback: 75 products / 10 files). The reader now unwraps the single mapped item, reads the
+underlying geometry natively, and bakes the mapped-item 4x4 — so the product reads with no kernel
+and renders. A *multi-item* mapped representation whose items are all face sets (e.g. a detailed
+part exported as several IfcPolygonalFaceSets — the IfcSignal bodies in linear-placement-of-signal)
+merges its items into one geometry and carries the shared transform as a mesh-level instance.
+Non-rigid transforms on analytic solids, non-faceted multi-item sources, and multi-item product
+bodies of differing sources degrade to the kernel fallback (verified graceful).
+"""
+
+from __future__ import annotations
+
+import numpy as np
+import pytest
+
+import ada
+from ada.config import Config
+
+
+@pytest.fixture(autouse=True)
+def _enable_geom():
+    Config().update_config_globally("ifc_import_shape_geom", True)
+
+
+def _tris(objs):
+    from ada.occ.tessellating import BatchTessellator
+
+    bt = BatchTessellator()
+    return sum(len(ms.indices) // 3 for o in objs for ms in bt.batch_tessellate([o]))
+
+
+def test_mapped_swept_disk_solid_reads_native(example_files):
+    """reinforcing-stirrup: an IfcMappedItem wrapping an IfcSweptDiskSolid reads natively (ada.geom
+    SweptDiskSolid, no OCC _occ_cache) and renders."""
+    import ada.geom.solids as so
+
+    a = ada.from_ifc(example_files / "ifc_files/reinforcing-stirrup.ifc")
+    objs = list(a.get_all_physical_objects())
+    assert len(objs) == 1
+    o = objs[0]
+    assert isinstance(o.geom.geometry, so.SweptDiskSolid)  # unwrapped native geometry
+    assert o._occ_cache is None  # NOT built via the IfcOpenShell kernel
+    assert _tris(objs) > 100  # renders (SweptDiskSolid is in solid_geom's accepted types)
+
+
+def test_mapped_csg_solid_reads_native(example_files):
+    """bath-csg-solid: an IfcMappedItem wrapping an IfcCsgSolid reads natively and renders."""
+    a = ada.from_ifc(example_files / "ifc_files/bath-csg-solid.ifc")
+    objs = list(a.get_all_physical_objects())
+    assert len(objs) == 1
+    assert objs[0]._occ_cache is None
+    assert _tris(objs) > 0
+
+
+def test_reinforcing_assembly_matches_oracle(example_files):
+    """End-to-end: reinforcing-assembly (34 mapped IfcSweptDiskSolid rebar + a concrete IfcBeam that
+    falls through to the shape importer). The rebar read native via IfcMappedItem, and the beam's
+    ABSOLUTE ObjectPlacement (a non-identity Y<->Z rotation, PlacementRelTo=None) is applied — so
+    the beam runs along world Y, not Z. The whole assembly bbox must match the ifcopenshell oracle
+    ([-0.1, 0, -0.4]..[0.1, 5, 0])."""
+    a = ada.from_ifc(example_files / "ifc_files/reinforcing-assembly.ifc")
+    objs = list(a.get_all_physical_objects())
+
+    from ada.occ.tessellating import BatchTessellator
+
+    bt = BatchTessellator()
+    pts = [np.asarray(ms.position, float).reshape(-1, 3) for o in objs for ms in bt.batch_tessellate([o])]
+    p = np.vstack([x for x in pts if len(x)])
+    assert np.allclose(p.min(0), (-0.1, 0.0, -0.4), atol=0.02), p.min(0)
+    assert np.allclose(p.max(0), (0.1, 5.0, 0.0), atol=0.02), p.max(0)
+
+
+def test_transform_geometry_rigid_and_nonrigid():
+    """The mapped-item geometry transform: identity is a no-op, a rigid transform moves a face set's
+    coordinates, and a non-uniform/shear transform raises (so the caller keeps the kernel path)."""
+    from ada.cadit.ifc.read.geom.geom_reader import _transform_geometry
+    from ada.geom import surfaces as su
+    from ada.geom.points import Point
+
+    fs = su.PolygonalFaceSet(coordinates=[Point(0, 0, 0), Point(1, 0, 0), Point(0, 1, 0)], faces=[[1, 2, 3]])
+
+    assert _transform_geometry(fs, np.eye(4)) is fs  # identity: unchanged object
+
+    trans = np.eye(4)
+    trans[:3, 3] = (10.0, 20.0, 30.0)  # rigid translation
+    moved = _transform_geometry(fs, trans)
+    assert np.allclose(np.asarray(moved.coordinates[0]), (10, 20, 30))
+
+    shear = np.eye(4)
+    shear[0, 1] = 0.5  # non-rigid shear
+    with pytest.raises(NotImplementedError):
+        _transform_geometry(fs, shear)
+
+
+def test_merge_face_sets_polygonal_offsets_indices():
+    """A multi-item mapped representation's face sets merge into one: coordinates concatenate and the
+    1-based face indices of later items shift by the running vertex count (the core of the
+    linear-placement-of-signal fix — 2 IfcSignals, each a 5-IfcPolygonalFaceSet mapped body)."""
+    from ada.cadit.ifc.read.geom.geom_reader import _merge_face_sets
+    from ada.geom import surfaces as su
+    from ada.geom.points import Point
+
+    a = su.PolygonalFaceSet(coordinates=[Point(0, 0, 0), Point(1, 0, 0), Point(0, 1, 0)], faces=[[1, 2, 3]])
+    b = su.PolygonalFaceSet(coordinates=[Point(2, 0, 0), Point(3, 0, 0), Point(2, 1, 0)], faces=[[1, 2, 3]])
+
+    merged = _merge_face_sets([a, b])
+    assert isinstance(merged, su.PolygonalFaceSet)
+    assert len(merged.coordinates) == 6
+    # first item's indices unchanged; second item's shifted by 3 (a's vertex count)
+    assert merged.faces == [[1, 2, 3], [4, 5, 6]]
+    assert np.allclose(np.asarray(merged.coordinates[3]), (2, 0, 0))
+
+
+def test_merge_face_sets_triangulated_offsets_indices():
+    """Triangulated face sets merge the same way (flat 1-based CoordIndex, offset per item)."""
+    from ada.cadit.ifc.read.geom.geom_reader import _merge_face_sets
+    from ada.geom import surfaces as su
+    from ada.geom.direction import Direction
+    from ada.geom.points import Point
+
+    n = Direction(0, 0, 1)
+    a = su.TriangulatedFaceSet(coordinates=[Point(0, 0, 0), Point(1, 0, 0), Point(0, 1, 0)], normals=[n], indices=[1, 2, 3])
+    b = su.TriangulatedFaceSet(coordinates=[Point(2, 0, 0), Point(3, 0, 0), Point(2, 1, 0)], normals=[n], indices=[1, 2, 3])
+
+    merged = _merge_face_sets([a, b])
+    assert isinstance(merged, su.TriangulatedFaceSet)
+    assert len(merged.coordinates) == 6
+    assert merged.indices == [1, 2, 3, 4, 5, 6]
+
+
+def test_merge_face_sets_rejects_non_face_sets():
+    """Mixed/non-face-set items can't merge — raises so the mapped-item caller keeps the kernel path."""
+    from ada.cadit.ifc.read.geom.geom_reader import _merge_face_sets
+    from ada.geom import solids as so
+    from ada.geom import surfaces as su
+    from ada.geom.points import Point
+
+    fs = su.PolygonalFaceSet(coordinates=[Point(0, 0, 0), Point(1, 0, 0), Point(0, 1, 0)], faces=[[1, 2, 3]])
+    box = so.Box.from_2points(Point(0, 0, 0), Point(1, 1, 1))
+    with pytest.raises(NotImplementedError):
+        _merge_face_sets([fs, box])
diff --git a/tests/core/cadit/ifc/read/test_read_shape_with_transformation.py b/tests/core/cadit/ifc/read/test_read_shape_with_transformation.py
index 17a0eef07..845301a71 100644
--- a/tests/core/cadit/ifc/read/test_read_shape_with_transformation.py
+++ b/tests/core/cadit/ifc/read/test_read_shape_with_transformation.py
@@ -1,3 +1,5 @@
+import numpy as np
+
 import ada
 from ada.config import Config
 from ada.geom.solids import Box
@@ -9,14 +11,48 @@ def test_read_shape_w_transformation(example_files):
     print(a)
 
 
+def test_placement_from_ifc_4x4_roundtrips():
+    """The IFC placement helper must produce a Placement whose get_matrix4x4 — which the
+    scene applies as M@p — reproduces the input world matrix. from_4x4_matrix alone returns
+    the transpose (columns vs rows), which renders axis-swapping placements wrong."""
+    from ada.cadit.ifc.read.geom.placement import placement_from_ifc_4x4
+
+    # world transform: 90deg about Z + translation (a genuine axis swap, not symmetric)
+    m = np.array([[0.0, -1.0, 0.0, -0.42], [1.0, 0.0, 0.0, -0.29], [0.0, 0.0, 1.0, 0.0], [0.0, 0.0, 0.0, 1.0]])
+    p = placement_from_ifc_4x4(m)
+    assert np.allclose(p.get_matrix4x4(), m)
+    # local X (1,0,0) maps to the rotated world direction, not back to (1,0,0)
+    assert np.allclose((p.get_matrix4x4() @ np.array([1.0, 0, 0, 1]))[:3], (-0.42, 0.71, 0.0))
+
+
 def test_read_rotated_box(example_files):
     Config().update_config_globally("ifc_import_shape_geom", True)
     a = ada.from_ifc(example_files / "ifc_files/box_rotated.ifc")
     door1 = a.get_by_name("door1")
     door2 = a.get_by_name("door2")
 
-    geom1 = door1.geom.geometry
-    assert isinstance(geom1, Box)
+    assert isinstance(door1.geom.geometry, Box)
+    assert isinstance(door2.geom.geometry, Box)
+
+    # door2 is door1 rotated 90deg about Z: its placement must carry that rotation (local X
+    # -> world +Y), where the transpose bug previously left it wrong.
+    r2 = np.array(door2.placement.get_matrix4x4())[:3, :3]
+    assert np.allclose(r2 @ np.array([1.0, 0, 0]), (0.0, 1.0, 0.0), atol=1e-6)
+    r1 = np.array(door1.placement.get_matrix4x4())[:3, :3]
+    assert np.allclose(r1, np.eye(3), atol=1e-6)
+
+
+def test_rotated_shape_placement_roundtrips(tmp_path):
+    """A shape under a rotated part placement survives an IFC write->read with the placement
+    applied correctly: box corner (3,1,2) local -> world under a 90deg-about-Z frame at (0,5,0)."""
+    from ada import Placement
+
+    box = ada.PrimBox("b", (0, 0, 0), (3, 1, 2))
+    part = ada.Part("P", placement=Placement(origin=(0, 5, 0), xdir=(0, 1, 0), ydir=(-1, 0, 0), zdir=(0, 0, 1)))
+    (ada.Assembly() / (part / box)).to_ifc(tmp_path / "rotshape.ifc")
 
-    geom2 = door2.geom.geometry
-    assert isinstance(geom2, Box)
+    b = ada.from_ifc(tmp_path / "rotshape.ifc")
+    o = next(iter(b.get_all_physical_objects()))
+    m = o.placement.get_matrix4x4()
+    assert np.allclose((m @ np.array([0.0, 0, 0, 1]))[:3], (0.0, 5.0, 0.0), atol=1e-6)
+    assert np.allclose((m @ np.array([3.0, 1, 2, 1]))[:3], (-1.0, 8.0, 2.0), atol=1e-6)
diff --git a/tests/core/cadit/ifc/roundtripping/test_roundtrip_revolved_beam.py b/tests/core/cadit/ifc/roundtripping/test_roundtrip_revolved_beam.py
index ca73497fe..84c3aef38 100644
--- a/tests/core/cadit/ifc/roundtripping/test_roundtrip_revolved_beam.py
+++ b/tests/core/cadit/ifc/roundtripping/test_roundtrip_revolved_beam.py
@@ -84,3 +84,134 @@ def test_import_buildingsmart_revolved_beam(example_files):
     vol = _solid_volume(a)
     expected = bm.section.properties.Ax * (bm.curve.radius * np.deg2rad(bm.curve.angle))
     assert abs(vol - expected) / expected < 0.05
+
+
+def test_buildingsmart_revolved_beam_arc_is_smooth(example_files):
+    """The revolved beam is a large-radius (7.25 m) arc: its tessellation must sample
+    the sweep finely enough that the bulge apex reaches the true arc extent, not fall
+    short as a coarse few-segment polygon does. Guards the tessellator's angular
+    deflection: a loose one facets the arc and clips the apex (~2% short).
+
+    ada-cpp (the worker/viewer backend) meshes with an explicit 0.2 rad angular
+    deflection. The pythonocc default path (ShapeTesselator) exposes no angular
+    control — only a relative mesh_quality — so it stays coarse here; skip it (its
+    finer BRepMesh path is env-gated, a separate follow-up)."""
+    import numpy as np
+    import pytest
+
+    from ada.cad import active_backend
+
+    if active_backend().name != "adacpp":
+        pytest.skip("angular-deflection smoothness is the ada-cpp tessellation path (worker/viewer)")
+
+    a = ada.from_ifc(example_files / "ifc_files/beams/beam-revolved-solid.ifc")
+    scene = a.to_trimesh_scene(merge_meshes=True)
+    verts = np.vstack([np.asarray(g.vertices) for g in scene.geometry.values() if hasattr(g, "vertices")])
+
+    bm = next(o for o in a.get_all_physical_objects() if isinstance(o, ada.BeamRevolve))
+    # Neutral-axis sagitta of the arc = r(1 - cos(theta/2)); the outer surface apex sits
+    # a further radial half-width out. The tessellated max-x must reach nearly there.
+    theta = np.deg2rad(bm.curve.angle)
+    sagitta = bm.curve.radius * (1.0 - np.cos(theta / 2.0))
+    apex = sagitta + bm.section.w_top / 2.0  # ~2.11 m for this IPE600 beam
+    assert verts[:, 0].max() > apex * 0.99, f"arc apex clipped: {verts[:, 0].max():.3f} vs ~{apex:.3f}"
+
+
+def test_buildingsmart_revolved_beam_via_ngeom_stream(example_files, monkeypatch):
+    """Production (worker/viewer) GLB uses the NGEOM libtess2 stream tessellator, NOT the
+    OCC BatchTessellator the other tests exercise. That path had the revolve wrong three
+    ways: the angle was fed in as radians not degrees (~14 turns -> profile splattered
+    ±12 m around the axis); the revolve axis was left in global coords while the tessellator
+    expects it position-local (axis ended up parallel to the profile normal -> the sweep
+    collapsed flat); and partial revolves emitted no end caps with inside-out winding
+    (negative volume -> dark shading). Assert the streamed solid sits in the right place,
+    closed and outward-facing. Gated to ada-cpp (libtess2 needs it)."""
+    import numpy as np
+    import pytest
+    import trimesh
+
+    from ada.cad import active_backend
+
+    if active_backend().name != "adacpp":
+        pytest.skip("NGEOM libtess2 stream tessellation is the ada-cpp path")
+
+    monkeypatch.setenv("ADA_STREAM_TESS_PIPELINE", "libtess2")
+    a = ada.from_ifc(example_files / "ifc_files/beams/beam-revolved-solid.ifc")
+    bm = next(o for o in a.get_all_physical_objects() if isinstance(o, ada.BeamRevolve))
+    sc = a.to_trimesh_scene(merge_meshes=True)
+    m = trimesh.util.concatenate([g for g in sc.geometry.values() if hasattr(g, "faces")])
+    lo, hi = np.asarray(m.vertices).min(0), np.asarray(m.vertices).max(0)
+
+    # Arc chord runs along +Y to ~10 m; profile depth keeps Z within ±0.3; bulge in +X ~2 m.
+    # Splatter (angle-as-radians) blows Z/X out to ±12; flat (global axis) puts the arc on
+    # the wrong plane so Y never reaches 10.
+    assert hi[1] == pytest.approx(10.08, abs=0.3), f"arc doesn't sweep to p2 along Y: ymax={hi[1]:.2f}"
+    assert abs(lo[2]) < 0.4 and abs(hi[2]) < 0.4, f"profile splattered out of plane in Z: {lo[2]:.2f}..{hi[2]:.2f}"
+    assert 1.5 < hi[0] < 2.3, f"bulge apex X off: {hi[0]:.2f}"
+    # Caps present + outward winding -> a closed, positive-volume solid near the analytic value.
+    exp = bm.section.properties.Ax * (bm.curve.radius * np.deg2rad(bm.curve.angle))
+    # Filleted IPE600 sits a few % above the sharp-Ax analytic (area*arc-length); band-check
+    # the magnitude, keep the positive-volume winding guard.
+    assert m.volume > 0, f"inside-out winding (negative volume {m.volume:.3f})"
+    assert exp * 0.95 < m.volume < exp * 1.12, f"volume {m.volume:.4f} vs analytic {exp:.4f}"
+
+
+def _revolve_curve_params(model):
+    bm = next(o for o in model.get_all_physical_objects() if isinstance(o, ada.BeamRevolve))
+    c = bm.curve
+    return bm, {
+        "radius": round(float(c.radius), 3),
+        "angle": round(float(c.angle), 2),
+        "rot_axis": [round(float(x), 3) for x in c.rot_axis],
+        "section": bm.section.name,
+    }
+
+
+def _stream_bbox_vol(model):
+    import numpy as np
+
+    sc = model.to_trimesh_scene(merge_meshes=True)
+    m = trimesh.util.concatenate([g for g in sc.geometry.values() if hasattr(g, "faces")])
+    v = np.asarray(m.vertices)
+    return v.min(0), v.max(0), float(m.volume)
+
+
+def test_buildingsmart_revolved_beam_ifc_roundtrip_via_stream(example_files, tmp_path, monkeypatch):
+    """The revolved beam must survive an IFC write->read round-trip: the CurveRevolve
+    parameters (radius, sweep angle, revolution axis, section) preserved AND the
+    production NGEOM-tessellated solid landing in the same place, closed and outward.
+    Exercises the libtess2 stream path (the worker/viewer + the path that carried the
+    original splatter/flat/inside-out bug). Gated to ada-cpp."""
+    import numpy as np
+    import pytest
+
+    from ada.cad import active_backend
+
+    if active_backend().name != "adacpp":
+        pytest.skip("NGEOM libtess2 stream tessellation is the ada-cpp path")
+
+    monkeypatch.setenv("ADA_STREAM_TESS_PIPELINE", "libtess2")
+
+    a0 = ada.from_ifc(example_files / "ifc_files/beams/beam-revolved-solid.ifc")
+    _, p0 = _revolve_curve_params(a0)
+    lo0, hi0, vol0 = _stream_bbox_vol(a0)
+
+    a0.to_ifc(tmp_path / "rt.ifc")
+    a1 = ada.from_ifc(tmp_path / "rt.ifc")
+    bm1, p1 = _revolve_curve_params(a1)
+    lo1, hi1, vol1 = _stream_bbox_vol(a1)
+
+    # Parameters preserved exactly through the round-trip.
+    assert p1 == p0 == {"radius": 7.25, "angle": 87.21, "rot_axis": [0.0, 0.0, 1.0], "section": "IPE600"}
+
+    # Geometry preserved: still the correct arc (Y->10, Z in-plane, X-bulge), not splattered
+    # or flat, and still a positive-volume closed solid near the analytic value.
+    assert hi1[1] == pytest.approx(10.08, abs=0.3)
+    assert abs(lo1[2]) < 0.4 and abs(hi1[2]) < 0.4
+    assert 1.9 < hi1[0] < 2.2  # bulge apex ~2.08 at the 10deg corpus default
+    # Filleted IPE600 sits a few % above the sharp-Ax analytic (area*arc-length); band-check.
+    exp = bm1.section.properties.Ax * (bm1.curve.radius * np.deg2rad(bm1.curve.angle))
+    assert vol1 > 0 and exp * 0.95 < vol1 < exp * 1.12
+    # Round-trip is stable, not just valid: same bbox + volume as before the write.
+    assert np.allclose(lo1, lo0, atol=1e-3) and np.allclose(hi1, hi0, atol=1e-3)
+    assert vol1 == pytest.approx(vol0, rel=1e-3)
diff --git a/tests/core/cadit/ngeom/test_adaptive_tess_density.py b/tests/core/cadit/ngeom/test_adaptive_tess_density.py
new file mode 100644
index 000000000..40c8e9e9f
--- /dev/null
+++ b/tests/core/cadit/ngeom/test_adaptive_tess_density.py
@@ -0,0 +1,77 @@
+"""Adaptive per-surface angular tessellation density (model-relative coarsening).
+
+A fixed angular ceiling facets every curved surface the same regardless of size, so dense
+assemblies of tiny features over-tessellate. Adaptive mode (opt-in) relaxes the ceiling for
+surfaces small RELATIVE TO THE MODEL — keyed on ``model_scale`` (the model bbox diagonal) — so a
+standalone small part stays fine while the same-radius feature inside a large model coarsens.
+
+The coarsening itself lives in adacpp (angle_step); these tests pin the adapy contract: the
+registry toggle / estimator, and that model_scale actually flows to the kernel and changes density.
+"""
+
+from __future__ import annotations
+
+import numpy as np
+import pytest
+
+
+def _adacpp_supports_model_scale() -> bool:
+    try:
+        import adacpp
+
+        return "model_scale" in (getattr(adacpp.cad.tessellate_stream, "__doc__", "") or "")
+    except Exception:
+        return False
+
+
+def test_registry_toggle_and_model_scale(monkeypatch):
+    from ada.cad.registry import stream_tess_adaptive, stream_tess_model_scale
+
+    monkeypatch.delenv("ADA_STREAM_TESS_ADAPTIVE", raising=False)
+    assert stream_tess_adaptive() is False  # default OFF (explicit-global-angle mode)
+    assert stream_tess_model_scale() == 0.0
+
+    monkeypatch.setenv("ADA_STREAM_TESS_ADAPTIVE", "1")
+    monkeypatch.setenv("ADA_STREAM_TESS_MODEL_SCALE", "26000")
+    assert stream_tess_adaptive() is True
+    assert stream_tess_model_scale() == pytest.approx(26000.0)
+
+    # adaptive off => model_scale ignored even if set
+    monkeypatch.setenv("ADA_STREAM_TESS_ADAPTIVE", "off")
+    assert stream_tess_model_scale() == 0.0
+
+
+def test_estimate_step_model_scale_robust(tmp_path):
+    """The estimator returns a positive scale and rejects a far-flung outlier point."""
+    from ada.cadit.step.model_scale import estimate_step_model_scale
+
+    import ada
+
+    src = tmp_path / "box.step"
+    (ada.Assembly("a") / (ada.Part("p") / ada.PrimBox("b", (0, 0, 0), (2, 1, 1)))).to_stp(src)
+    ms = estimate_step_model_scale(src)
+    assert ms >= 0.0  # small clean model: a finite scale (or 0 if too few points) — never negative
+
+
+@pytest.mark.skipif(not _adacpp_supports_model_scale(), reason="adacpp build predates model_scale param")
+def test_model_scale_coarsens_small_feature_but_not_standalone():
+    """model_scale flows to the kernel: a cylinder that is a large fraction of a SMALL model keeps
+    its facets, but the SAME cylinder treated as a tiny feature of a HUGE model coarsens."""
+    import ada
+    from ada.cad import AdacppBackend
+
+    be = AdacppBackend()
+    g = ada.PrimCyl("c", (0, 0, 0), (0, 0, 20), 5.0).solid_geom()
+
+    def tris(model_scale):
+        m = be.tessellate_stream(
+            [("c", g)], pipeline="libtess2", deflection=2.0, angular_deg=10.0, model_scale=model_scale
+        )
+        return len(m.indices) // 3
+
+    base = tris(0.0)  # adaptive OFF: fixed 10deg
+    standalone = tris(500.0)  # r_ref=5, cylinder r=5 is a large fraction of the model -> unchanged
+    tiny_feature = tris(100_000.0)  # r_ref=1000, cylinder r=5 is a sub-1% feature -> coarsened
+
+    assert standalone == base, "a part large relative to its model must NOT coarsen"
+    assert tiny_feature < base, "a tiny feature in a huge model must coarsen"
diff --git a/tests/core/cadit/ngeom/test_composite_curve_profile.py b/tests/core/cadit/ngeom/test_composite_curve_profile.py
new file mode 100644
index 000000000..64835ed49
--- /dev/null
+++ b/tests/core/cadit/ngeom/test_composite_curve_profile.py
@@ -0,0 +1,58 @@
+"""Composite-curve profile boundaries + face-based surface models serialize to NGEOM.
+
+Regression for the trimmed-curve-parameters and surface-model audit OCC fallbacks:
+  * an ArbitraryClosedProfileDef whose outer curve is an IfcCompositeCurve of trimmed conic / line
+    segments (curve-parameters-in-degrees/radians), and
+  * an IfcFaceBasedSurfaceModel of plain polyloop faces (surface-model),
+both had no NGEOM path and fell back to OCC.
+"""
+
+from __future__ import annotations
+
+import math
+
+import numpy as np
+
+import ada.geom.curves as cu
+from ada.geom.placement import Axis2Placement3D
+from ada.geom.points import Point
+
+
+def test_trimmed_line_respects_sense_agreement():
+    from ada.cadit.ngeom.serialize import _sample_trimmed_curve
+
+    line = cu.Line(pnt=Point(0, 0, 0), dir=(1.0, 0.0, 0.0))
+    fwd = _sample_trimmed_curve(cu.TrimmedCurve(basis_curve=line, trim1=0.0, trim2=2.0, sense_agreement=True))
+    rev = _sample_trimmed_curve(cu.TrimmedCurve(basis_curve=line, trim1=0.0, trim2=2.0, sense_agreement=False))
+    assert np.allclose(fwd[0], [0, 0, 0]) and np.allclose(fwd[-1], [2, 0, 0])
+    assert np.allclose(rev[0], [2, 0, 0]) and np.allclose(rev[-1], [0, 0, 0])  # reversed
+
+
+def test_trimmed_circle_arc_short_way():
+    from ada.cadit.ngeom.serialize import _sample_trimmed_curve
+
+    circ = cu.Circle(position=Axis2Placement3D(location=(0, 0, 0)), radius=1.0)
+    # 0 -> 90deg, sense True -> a quarter arc from (1,0) to (0,1)
+    pts = np.array(_sample_trimmed_curve(cu.TrimmedCurve(circ, trim1=0.0, trim2=math.pi / 2, sense_agreement=True)))
+    assert np.allclose(pts[0], [1, 0, 0], atol=1e-6)
+    assert np.allclose(pts[-1], [0, 1, 0], atol=1e-6)
+    assert np.allclose(np.linalg.norm(pts, axis=1), 1.0, atol=1e-6)  # every sample on the unit circle
+
+
+def test_composite_pie_slice_area():
+    from ada.cadit.ngeom.serialize import _composite_curve_loop_points
+
+    circ = cu.Circle(position=Axis2Placement3D(location=(0, 0, 0)), radius=1.0)
+    lx = cu.Line(pnt=Point(0, 0, 0), dir=(1.0, 0.0, 0.0))  # origin -> (1,0)
+    ly = cu.Line(pnt=Point(0, 0, 0), dir=(0.0, 1.0, 0.0))  # origin -> (0,1)
+    cc = cu.CompositeCurve(
+        segments=[
+            cu.CompositeCurveSegment(parent_curve=cu.TrimmedCurve(circ, 0.0, math.pi / 2, sense_agreement=True)),
+            cu.CompositeCurveSegment(parent_curve=cu.TrimmedCurve(ly, 0.0, 1.0, sense_agreement=False)),  # (0,1)->0
+            cu.CompositeCurveSegment(parent_curve=cu.TrimmedCurve(lx, 0.0, 1.0, sense_agreement=True)),  # 0->(1,0)
+        ]
+    )
+    p = np.array(_composite_curve_loop_points(cc))
+    x, y = p[:, 0], p[:, 1]
+    area = 0.5 * abs(np.dot(x, np.roll(y, -1)) - np.dot(y, np.roll(x, -1)))
+    assert abs(area - math.pi / 4) < 0.01  # quarter unit disk
diff --git a/tests/core/cadit/ngeom/test_deserialize_solids.py b/tests/core/cadit/ngeom/test_deserialize_solids.py
new file mode 100644
index 000000000..d2afb3fae
--- /dev/null
+++ b/tests/core/cadit/ngeom/test_deserialize_solids.py
@@ -0,0 +1,97 @@
+"""NGEOM deserialize decodes swept/CSG solid tags 50-53 back to ada.geom.
+
+serialize.py emits ExtrudedAreaSolid/RevolvedAreaSolid/BooleanResult/Sphere as tags 50-53 (with the
+profile flattened into a planar FACE), and adacpp's C++ decoder reads them — but the Python
+deserializer used to raise on those tags, so the lazy ShapeStore's pure-Python round-trip failed on
+any analytic solid. It now inverts them (rebuilding the profile from the face's local-XY loops), so
+serialize→deserialize→serialize is byte-identical. Only the baked-frame tag 54 stays lossy (raises).
+"""
+
+from __future__ import annotations
+
+import math
+
+import pytest
+
+import ada.geom.curves as cu
+import ada.geom.solids as so
+import ada.geom.surfaces as su
+from ada import Beam
+from ada.geom import Geometry
+from ada.geom.booleans import BooleanResult, BoolOpEnum
+from ada.geom.direction import Direction
+from ada.geom.placement import Axis1Placement, Axis2Placement3D
+from ada.geom.points import Point
+from ada.cadit.ngeom.deserialize import NgeomDecodeError, deserialize_geometries
+from ada.cadit.ngeom.serialize import serialize_geometries
+
+
+def _roundtrip(geom: Geometry):
+    buf = serialize_geometries([("g", geom)])
+    decoded = deserialize_geometries(buf)
+    assert len(decoded) == 1
+    gg = decoded[0][1]
+    g2 = gg if isinstance(gg, Geometry) else Geometry("g", gg)
+    # byte-identical re-encode is the strongest round-trip guarantee
+    assert serialize_geometries([("g", g2)]) == buf
+    return gg.geometry if isinstance(gg, Geometry) else gg
+
+
+def _rect(w, h):
+    p = [Point(0, 0), Point(w, 0), Point(w, h), Point(0, h)]
+    segs = [cu.Edge(p[i], p[(i + 1) % 4]) for i in range(4)]
+    return su.ArbitraryProfileDef(profile_type=su.ProfileType.AREA, outer_curve=cu.IndexedPolyCurve(segs))
+
+
+def test_extruded_area_solid_roundtrip():
+    """An IPE200 beam's extrusion (I-profile WITH fillet arcs) decodes back to an ExtrudedAreaSolid,
+    fillets intact (byte-identical re-encode)."""
+    g = Beam("b", (0, 0, 0), (2, 0, 0), "IPE200").solid_geom()
+    out = _roundtrip(g)
+    assert isinstance(out, so.ExtrudedAreaSolid)
+
+
+def test_sphere_solid_roundtrip():
+    out = _roundtrip(Geometry("s", so.Sphere(center=Point(0, 0, 0), radius=1.5)))
+    assert isinstance(out, so.Sphere)
+    assert out.radius == pytest.approx(1.5)
+
+
+def test_revolved_area_solid_roundtrip():
+    """Revolve round-trips through the world→local axis transform + degrees↔radians conversion."""
+    rev = so.RevolvedAreaSolid(
+        swept_area=_rect(1, 2),
+        position=Axis2Placement3D(Point(0, 0, 0)),
+        axis=Axis1Placement(Point(3, 0, 0), Direction(0, 0, 1)),
+        angle=270.0,
+    )
+    out = _roundtrip(Geometry("r", rev))
+    assert isinstance(out, so.RevolvedAreaSolid)
+    assert out.angle == pytest.approx(270.0)
+
+
+def test_boolean_result_roundtrip():
+    box = so.Box.from_2points(Point(0, 0, 0), Point(2, 2, 2))
+    sph = so.Sphere(center=Point(1, 1, 1), radius=0.8)
+    out = _roundtrip(Geometry("bool", BooleanResult(first_operand=box, second_operand=sph, operator=BoolOpEnum.DIFFERENCE)))
+    assert isinstance(out, BooleanResult)
+    assert out.operator is BoolOpEnum.DIFFERENCE
+    assert isinstance(out.first_operand, so.ExtrudedAreaSolid)  # Box serializes as an extrusion
+    assert isinstance(out.second_operand, so.Sphere)
+
+
+def test_fixed_reference_swept_is_lossy():
+    """Tag 54 bakes the directrix into per-station frames — not invertible → a clear decode error."""
+    from ada.cadit.ngeom.serialize import _EXTRUDED_AREA_SOLID  # noqa: F401 - ensure module import ok
+
+    # Build a minimal tag-54 buffer by serializing a fixed-ref swept solid if one is constructible;
+    # otherwise assert the decoder rejects the tag directly.
+    from ada.cadit.ngeom import deserialize as _d
+
+    dec = _d._Decoder([(_d._FIXED_REF_SWEPT_SOLID, memoryview(b""))])
+    with pytest.raises(NgeomDecodeError, match="tag 54"):
+        dec.get(0)
+
+
+if __name__ == "__main__":
+    raise SystemExit(pytest.main([__file__, "-v"]))
diff --git a/tests/core/cadit/ngeom/test_faceted_inferred_plane.py b/tests/core/cadit/ngeom/test_faceted_inferred_plane.py
new file mode 100644
index 000000000..65e0283d0
--- /dev/null
+++ b/tests/core/cadit/ngeom/test_faceted_inferred_plane.py
@@ -0,0 +1,62 @@
+"""Faceted-brep (plain planar Face) shells serialize + tessellate natively via libtess2 — with
+inner-bound holes cut and NO vertex displacement.
+
+Regression for basin-faceted-brep.ifc:
+  * FacetedBrep / plain Face had no NGEOM dispatch, so the shell fell back to OCC (which capped the
+    rim's opening).
+  * Once face_surface inferred a plane per plain Face, the inferred planes were transient and the
+    id()-keyed surface() memo collided (a GC'd plane's id reused by the next), so faces referenced
+    the wrong plane record and tessellated to displaced positions — worse the more faces, silently
+    dropping ~20% of surface area on a real shell.
+"""
+
+from __future__ import annotations
+
+import gc
+
+import numpy as np
+import pytest
+
+
+def _square_face(dx: float, dy: float, dz: float):
+    import ada.geom.curves as cu
+    import ada.geom.surfaces as su
+    from ada.geom.points import Point
+
+    s = 0.05
+    loop = cu.PolyLoop(
+        polygon=[Point(dx, dy, dz), Point(dx + s, dy, dz), Point(dx + s, dy + s, dz), Point(dx, dy + s, dz)]
+    )
+    return su.Face(bounds=[su.FaceBound(bound=loop, orientation=True)])  # plain Face -> inferred plane
+
+
+def test_faceted_shell_libtess2_no_displacement():
+    pytest.importorskip("adacpp")
+    import ada.geom.surfaces as su
+    from ada.cad import active_backend
+    from ada.cadit.ngeom.serialize import serialize_geometries
+
+    be = active_backend()
+    if not hasattr(be, "tessellate_stream_buffer"):
+        pytest.skip("active backend has no libtess2 stream")
+
+    # Many small planar faces at distinct locations; GC between builds so a naive id()-memo would
+    # collide on reused plane ids.
+    faces = []
+    for i in range(120):
+        faces.append(_square_face(0.3 + 0.1 * (i % 12), 0.25 + 0.1 * (i // 12), 0.001 * (i % 5)))
+        gc.collect()
+    cfs = su.ConnectedFaceSet(faces)
+
+    def area(blob):
+        m = be.tessellate_stream_buffer(bytes(blob), pipeline="libtess2")
+        v = np.asarray(m.positions, float).reshape(-1, 3)
+        idx = np.asarray(m.indices, int).reshape(-1, 3)
+        tv = v[idx]
+        return 0.5 * np.linalg.norm(np.cross(tv[:, 1] - tv[:, 0], tv[:, 2] - tv[:, 0]), axis=1).sum()
+
+    expected = 120 * 0.05 * 0.05  # every face is a 5cm square
+    got = area(serialize_geometries([("shell", cfs)]))
+    # Without the pin fix this drops well below expected (displaced faces lose area); allow only
+    # tessellation-level slack.
+    assert got == pytest.approx(expected, rel=1e-3), f"{got} vs {expected}"
diff --git a/tests/core/cadit/ngeom/test_serialize.py b/tests/core/cadit/ngeom/test_serialize.py
index 1a60add20..4da79e90c 100644
--- a/tests/core/cadit/ngeom/test_serialize.py
+++ b/tests/core/cadit/ngeom/test_serialize.py
@@ -103,7 +103,9 @@ def test_dependency_order_no_forward_refs():
 def _bspline_surface_face():
     nu, nv = 4, 6  # 24 control points > _BULK_MIN
     rows = [[Point(float(i), float(j), float(i * j) * 0.25) for j in range(nv)] for i in range(nu)]
-    surf = su.BSplineSurfaceWithKnots(
+    # Rational subclass carries the weights as a real field (the geom dataclasses are
+    # slotted — ad-hoc attributes on the non-rational class no longer stick).
+    surf = su.RationalBSplineSurfaceWithKnots(
         u_degree=3,
         v_degree=3,
         control_points_list=rows,
@@ -116,15 +118,15 @@ def _bspline_surface_face():
         u_knots=[float(i) for i in range(20)],
         v_knots=[float(i) * 0.5 for i in range(20)],
         knot_spec=cu.KnotType.UNSPECIFIED,
+        weights_data=[[1.0 + 0.01 * (i + j) for j in range(nv)] for i in range(nu)],  # >16 flat weights
     )
-    surf.weights_data = [[1.0 + 0.01 * (i + j) for j in range(nv)] for i in range(nu)]  # >16 flat weights
     poly = cu.PolyLoop(polygon=[Point(math.cos(0.3 * k), math.sin(0.3 * k), 0.1 * k) for k in range(20)])  # >16 pts
     return su.FaceSurface(bounds=[su.FaceBound(bound=poly, orientation=True)], face_surface=surf, same_sense=True)
 
 
 def _bspline_curve_edge_face():
     cps = [Point(float(i), float(i % 3), 0.0) for i in range(20)]  # >16 control points
-    bc = cu.BSplineCurveWithKnots(
+    bc = cu.RationalBSplineCurveWithKnots(
         degree=3,
         control_points_list=cps,
         curve_form=cu.BSplineCurveFormEnum.POLYLINE_FORM,
@@ -133,8 +135,8 @@ def _bspline_curve_edge_face():
         knot_multiplicities=[1] * 24,  # >16 multiplicities
         knots=[float(i) for i in range(24)],  # >16 knots
         knot_spec=cu.KnotType.UNSPECIFIED,
+        weights_data=[1.0 + 0.001 * i for i in range(20)],  # >16 weights (real field; slotted classes)
     )
-    bc.weights_data = [1.0 + 0.001 * i for i in range(20)]  # >16 weights
     s, t = (0.0, 0.0, 0.0), (19.0, 0.0, 0.0)
     ec = cu.EdgeCurve(start=s, end=t, edge_geometry=bc, same_sense=True)
     oe = cu.OrientedEdge(start=s, end=t, edge_element=ec, orientation=True)
diff --git a/tests/core/cadit/ngeom/test_step2glb_parity_fixes.py b/tests/core/cadit/ngeom/test_step2glb_parity_fixes.py
index cb9a09513..dc11988da 100644
--- a/tests/core/cadit/ngeom/test_step2glb_parity_fixes.py
+++ b/tests/core/cadit/ngeom/test_step2glb_parity_fixes.py
@@ -71,7 +71,17 @@ def total_tris(shape, fname: str) -> int:
         t = 0
         for g in stream_read_step(src, local_pool=False, tolerant=True):
             gi = g.geometry.geometry if hasattr(g.geometry, "geometry") else g.geometry
-            t += len(be.tessellate_stream([(str(g.id), gi)], pipeline="libtess2", deflection=2.0).indices) // 3
+            # Pin max-angle 20 explicitly: this gate measures step2glb PARITY (its ~20-25deg
+            # density), independent of the viewer's finer corpus default (DEFAULT_STREAM_TESS_
+            # ANGULAR_DEG, now 10deg) which would otherwise ~double the golden counts.
+            t += (
+                len(
+                    be.tessellate_stream(
+                        [(str(g.id), gi)], pipeline="libtess2", deflection=2.0, angular_deg=20.0
+                    ).indices
+                )
+                // 3
+            )
         return t
 
     golden = {"cylinder": 120, "sphere": 324}
diff --git a/tests/core/cadit/ngeom/test_swept_disk_solid.py b/tests/core/cadit/ngeom/test_swept_disk_solid.py
new file mode 100644
index 000000000..dbdc52991
--- /dev/null
+++ b/tests/core/cadit/ngeom/test_swept_disk_solid.py
@@ -0,0 +1,34 @@
+"""IfcSweptDiskSolid (rebar/pipe) serializes + tessellates natively via libtess2 — a circular
+profile swept along the directrix — instead of falling back to OCC."""
+
+from __future__ import annotations
+
+import numpy as np
+import pytest
+
+
+def test_swept_disk_solid_tube_libtess2():
+    pytest.importorskip("adacpp")
+    import ada.geom.curves as cu
+    import ada.geom.solids as so
+    from ada.cad import active_backend
+    from ada.cadit.ngeom.serialize import serialize_geometries
+    from ada.geom.points import Point
+
+    be = active_backend()
+    if not hasattr(be, "tessellate_stream_buffer"):
+        pytest.skip("no libtess2 stream")
+
+    # straight rod, radius 0.05, length 10 along +x -> lateral area 2*pi*r*L
+    directrix = cu.IndexedPolyCurve(segments=[cu.Edge(Point(0, 0, 0), Point(10, 0, 0))])
+    sds = so.SweptDiskSolid(directrix=directrix, radius=0.05)
+    blob = serialize_geometries([("rod", sds)])
+    assert len(blob) > 32, "SweptDiskSolid serialized empty (would fall back to OCC)"
+    m = be.tessellate_stream_buffer(bytes(blob), pipeline="libtess2")
+    v = np.asarray(m.positions, float).reshape(-1, 3)
+    idx = np.asarray(m.indices, int).reshape(-1, 3)
+    assert len(idx) > 0
+    tv = v[idx]
+    area = 0.5 * np.linalg.norm(np.cross(tv[:, 1] - tv[:, 0], tv[:, 2] - tv[:, 0]), axis=1).sum()
+    lateral = 2 * np.pi * 0.05 * 10.0  # ~3.14 ; caps add ~2*pi*r^2 (~0.016)
+    assert lateral * 0.9 < area < lateral * 1.15, area
diff --git a/tests/core/cadit/sat/test_plane_surface_frame.py b/tests/core/cadit/sat/test_plane_surface_frame.py
new file mode 100644
index 000000000..6b6e791f6
--- /dev/null
+++ b/tests/core/cadit/sat/test_plane_surface_frame.py
@@ -0,0 +1,36 @@
+"""ACIS plane-surface / straight-curve records must parse their geometry past the entity header.
+
+The record header ``$owner -1 -1 $attrib`` has two bare ``-1`` integers that are numeric, so a
+plain float-filter swallowed them and shifted origin/normal/u_direction by two — planes came out
+with a garbage frame (and the flat plate tessellated to a single triangle via the NGEOM path).
+"""
+
+from __future__ import annotations
+
+import numpy as np
+
+import ada
+
+
+def test_plane_surface_frame_not_shifted(example_files):
+    """plate_1_flat.sat: the planar face reads its true frame (origin ~(20.57,-32.53,3.9), normal
+    ~(0,0,-1)), not the header-shifted garbage the old parser produced."""
+    a = ada.from_acis(example_files / "sat_files/plate_1_flat.sat")
+    o = list(a.get_all_physical_objects())[0]
+    faces = getattr(o.geom.geometry, "cfs_faces", None) or getattr(o.geom.geometry, "faces", None)
+    plane = faces[0].face_surface
+    pos = plane.position
+    assert np.allclose(np.asarray(pos.location), (20.569, -32.525, 3.9), atol=0.01), pos.location
+    n = np.asarray(pos.axis, float)
+    assert np.allclose(np.abs(n), (0, 0, 1), atol=1e-3), n  # unit normal along z (sign is sense-dependent)
+
+
+def test_parse_plane_surface_helper_skips_header():
+    """Unit-level: the header-skip helper drops the `$owner -1 -1 $attrib` prefix and reads the
+    coordinates, not the header integers."""
+    from ada.cadit.sat.parser.parser import _numeric_after_header
+
+    parts = "$-1 -1 -1 $-1 20.5 -32.5 3.9 0 0 -1 -1 0 0 reverse_v I I I I #".split()
+    got = _numeric_after_header(parts)
+    assert got[0:3] == [20.5, -32.5, 3.9]  # origin, not [-1, -1, 20.5]
+    assert got[3:6] == [0.0, 0.0, -1.0]  # normal
diff --git a/tests/core/cadit/sat/test_sat_shape_color.py b/tests/core/cadit/sat/test_sat_shape_color.py
new file mode 100644
index 000000000..9cbb870f1
--- /dev/null
+++ b/tests/core/cadit/sat/test_sat_shape_color.py
@@ -0,0 +1,21 @@
+"""SAT-imported shapes must carry a renderable colour, not render black.
+
+``from_acis`` builds ``Shape(f"shape{i}", Geometry(i, geom))`` with no colour, so
+the Geometry's ``color`` is None. The tessellator reads ``geom.color`` (not the
+Shape's), so without a fallback the body renders black. ``Shape.solid_geom``
+now syncs the Shape's colour (light-gray by default) onto the Geometry.
+"""
+
+import ada
+
+
+def test_sat_shape_solid_geom_has_color(example_files):
+    a = ada.from_acis(example_files / "sat_files/curved_plate.sat")
+    shapes = list(a.get_all_physical_objects())
+    assert shapes, "no shapes imported"
+    for s in shapes:
+        assert s.color is not None
+        g = s.solid_geom()
+        # the Geometry the tessellator meshes must carry the colour too
+        assert g.color is not None, f"{s.name}: solid_geom colour is None (would render black)"
+        assert tuple(g.color) == tuple(s.color)
diff --git a/tests/core/cadit/step/test_stream_mapped_instances.py b/tests/core/cadit/step/test_stream_mapped_instances.py
new file mode 100644
index 000000000..29d3774ec
--- /dev/null
+++ b/tests/core/cadit/step/test_stream_mapped_instances.py
@@ -0,0 +1,94 @@
+"""Non-OCC (ap242_stream) STEP writer preserves multi-instance mapped shapes ANALYTICALLY.
+
+``mapped-shape-with-multiple-items.ifc`` is one IfcBuildingElementProxy whose Body is four
+IfcMappedItems reusing one extruded-solid source under non-uniform-scaled transforms — carried on
+``Geometry.transforms``. The OCC ``to_stp`` writer drops all but one (a rigid STEP placement can't
+carry the scale). The stream writer emits one solid PER instance, transforming the analytic
+Extrusion (exact planar faces + line/arc edges, no tessellation) so the geometry is maintained — a
+faceted bake is only a last resort for transforms the analytic form can't carry.
+"""
+
+from __future__ import annotations
+
+import numpy as np
+import pytest
+
+import ada
+from ada.config import Config
+
+
+@pytest.fixture(autouse=True)
+def _enable_geom():
+    Config().update_config_globally("ifc_import_shape_geom", True)
+
+
+def _fem_or_none(example_files):
+    p = example_files / "ifc_files/mapped_shapes/mapped-shape-with-multiple-items.ifc"
+    return p if p.exists() else None
+
+
+def test_transform_extrusion_analytic_rigid_and_scale():
+    """Unit: the analytic Extrusion transform carries a rotation + axis-aligned non-uniform scale +
+    translation, and refuses an oblique extrude (so the caller facet-falls-back)."""
+    from ada.cadit.step.write.ap242_stream import Extrusion, Seg, _transform_extrusion
+
+    unit = Extrusion(
+        origin=(0.0, 0.0, 0.0),
+        xdir=(1.0, 0.0, 0.0),
+        normal=(0.0, 0.0, 1.0),
+        depth=2.0,
+        outer=[
+            Seg("line", (0.0, 0.0), (1.0, 0.0)),
+            Seg("line", (1.0, 0.0), (1.0, 1.0)),
+            Seg("line", (1.0, 1.0), (0.0, 1.0)),
+            Seg("line", (0.0, 1.0), (0.0, 0.0)),
+        ],
+        inners=[],
+        name="u",
+        color=None,
+    )
+
+    # scale x by 0.5, y by 0.25, translate — stays an analytic extrusion
+    S = np.diag([0.5, 0.25, 1.0, 1.0]).astype(float)
+    S[:3, 3] = (3.0, 4.0, 0.0)
+    placed = _transform_extrusion(unit, S)
+    assert placed is not None
+    assert np.allclose(placed.origin, (3.0, 4.0, 0.0))
+    assert placed.depth == pytest.approx(2.0)
+    # profile x-extent scaled to 0.5, y-extent to 0.25
+    xs = [p[0] for s in placed.outer for p in (s.start, s.end)]
+    ys = [p[1] for s in placed.outer for p in (s.start, s.end)]
+    assert max(xs) - min(xs) == pytest.approx(0.5)
+    assert max(ys) - min(ys) == pytest.approx(0.25)
+
+    # an oblique shear of the extrude direction can't be an axis-aligned extrusion → None (facet)
+    shear = np.eye(4)
+    shear[0, 2] = 1.0  # x += z : tilts the extrude vector off the plane normal
+    assert _transform_extrusion(unit, shear) is None
+
+
+def test_mapped_multiple_items_stream_step_analytic(example_files, tmp_path):
+    """End-to-end: 4 mapped instances → 4 analytic MANIFOLD_SOLID_BREPs (not triangle soup),
+    read back as 4 objects, world bbox matching the ifcopenshell oracle."""
+    src = _fem_or_none(example_files)
+    if src is None:
+        pytest.skip("mapped-shape-with-multiple-items.ifc not in the test corpus")
+
+    a = ada.from_ifc(src)
+    out = tmp_path / "mapped.step"
+    a.to_stp(out, writer="stream")
+
+    data = out.read_bytes()
+    n_solid = data.count(b"MANIFOLD_SOLID_BREP")
+    n_face = data.count(b"ADVANCED_FACE")
+    assert n_solid == 4, f"expected 4 instanced solids, got {n_solid}"
+    # analytic: a handful of exact faces per box (~6), NOT a tessellated triangle mesh (hundreds).
+    assert n_face <= 40, f"expected exact analytic faces, got {n_face} (looks tessellated)"
+
+    a2 = ada.from_step(out, reader="auto")
+    objs = list(a2.get_all_physical_objects())
+    assert len(objs) == 4, f"round-trip dropped instances: {len(objs)}"
+
+
+if __name__ == "__main__":
+    raise SystemExit(pytest.main([__file__, "-v"]))
diff --git a/tests/core/cadit/test_visual_parity_regressions.py b/tests/core/cadit/test_visual_parity_regressions.py
new file mode 100644
index 000000000..67ee0c207
--- /dev/null
+++ b/tests/core/cadit/test_visual_parity_regressions.py
@@ -0,0 +1,68 @@
+"""Cross-format visual-parity regressions from the corpus audit sweep.
+
+Each file below previously lost geometry in at least one structure-preserving
+export (audit run 63 parity phase):
+
+* revolved / varying-extrusion-path beams: BeamRevolve dropped by the DOM
+  Genie-XML writer (only the streaming writer chord-fied them)
+* FixedReferenceSweptAreaSolid: GradientCurve directrix unbuildable ->
+  skipped in STEP export
+* SAT wire bodies: bare curve shapes routed through a pythonocc-only wire
+  builder (skipped under the adacpp backend), and the native STEP counter
+  saw 0 roots in wireframe-only outputs
+* SAT b-spline shell: written as a bare IfcClosedShell the reader could not
+  import back
+* IfcTriangulatedFaceSet: no B-rep build existed, so IFC re-export needed an
+  impossible kernel round-trip and STEP export wrote no solid
+* multi-instance IfcMappedItem (mapped-shape-with-multiple-items): 4 non-uniform-
+  scaled instances of one source solid. The OCC ``to_stp`` writer (the parity's
+  old STEP leg) collapsed them to 1 — a rigid STEP placement can't carry the
+  scale — so the parity now writes STEP via the non-OCC stream writer, which
+  emits one analytic solid per instance.
+"""
+
+import pytest
+
+from ada.cadit.visual_parity import parity_for_source_file
+
+PARITY_SOURCES = [
+    "ifc_files/beams/beam-revolved-solid.ifc",
+    "ifc_files/beams/beam-varying-extrusion-paths.ifc",
+    "ifc_files/fixed-reference-swept-area-solid.ifc",
+    "sat_files/single_beam_sesam.sat",
+    "sat_files/bsplinesurfacewithknots.sat",
+    "fem_files/sesam/xml_all_basic_props.sat",
+    "ifc_files/bs_samples/tessellation-with-image-texture.ifc",
+    "ifc_files/bs_samples/column-straight-rectangle-tessellation.ifc",
+    "ifc_files/mapped_shapes/mapped-shape-with-multiple-items.ifc",
+]
+
+
+@pytest.mark.parametrize("rel_path", PARITY_SOURCES)
+def test_cross_format_parity(example_files, monkeypatch, rel_path):
+    monkeypatch.setenv("ADA_IFC_IMPORT_SHAPE_GEOM", "true")
+    import ada
+
+    ada.config.Config().reload_config()
+
+    res = parity_for_source_file(example_files / rel_path, ("ifc", "xml", "step"))
+    assert res.consistent, f"{rel_path}: counts={res.counts} mismatches={res.mismatches} errors={res.errors}"
+
+
+def test_empty_source_counts_zero_everywhere(example_files, tmp_path):
+    """A geometry-less model must count 0 on every leg. The STEP leg regressed
+    to 1 once (audit run 64): the wireframe-blind native counter fell back to a
+    reload, and the reloaded empty file materialized one zero-vertex Shape."""
+    import ada
+    from ada.cadit.visual_parity import assembly_element_count, cross_format_parity
+
+    res = cross_format_parity(ada.Assembly("Empty"), ("ifc", "step"), work_dir=tmp_path)
+    assert res.counts == {"source": 0, "ifc": 0, "step": 0}
+    assert res.consistent, f"counts={res.counts} mismatches={res.mismatches} errors={res.errors}"
+
+    # And a wire-only STEP must still count its wireframe as 1 (not 0, not a
+    # zero-vertex phantom): GEOMETRIC_CURVE_SET is a stream-reader root.
+    a = ada.from_acis(example_files / "sat_files/single_beam_sesam.sat")
+    out = tmp_path / "wire.step"
+    a.to_stp(out)
+    assert assembly_element_count(ada.from_step(out, reader="auto")) == 1
diff --git a/tests/core/fem/test_mesh_faces.py b/tests/core/fem/test_mesh_faces.py
index b83e87531..b0f11b992 100644
--- a/tests/core/fem/test_mesh_faces.py
+++ b/tests/core/fem/test_mesh_faces.py
@@ -80,11 +80,99 @@ def test_object_free_no_plates_built(fem_files):
     assert len(list(a.get_all_physical_objects(by_type=ada.Plate))) == 0
 
 
-def test_surface_and_panel_not_yet_implemented(fem_files):
+def _tube(nseg=24, nrows=12, r=0.5, length=4.0, t=0.01):
+    """A quad-meshed cylinder along z — exercises the analytic cylinder detection."""
+    from ada import Node
+
+    p = ada.Part("tube")
+    mat = ada.Material("S355")
+    grid: dict = {}
+    nid = 1
+    for iz in range(nrows + 1):
+        for ia in range(nseg):
+            ang = 2.0 * np.pi * ia / nseg
+            grid[(ia, iz)] = Node([r * np.cos(ang), r * np.sin(ang), length * iz / nrows], nid)
+            p.fem.nodes.add(grid[(ia, iz)])
+            nid += 1
+    eid = 1
+    Q = ada.fem.Elem.EL_TYPES.SHELL_SHAPES.QUAD
+    for iz in range(nrows):
+        for ia in range(nseg):
+            a_, b_ = grid[(ia, iz)], grid[((ia + 1) % nseg, iz)]
+            c_, d_ = grid[((ia + 1) % nseg, iz + 1)], grid[(ia, iz + 1)]
+            el = p.fem.add_elem(ada.fem.Elem(eid, [a_, b_, c_, d_], Q, el_formulation_override="S4"))
+            el.fem_sec = p.fem.add_section(
+                ada.fem.FemSection(f"S{eid}", "shell", ada.fem.FemSet(f"s{eid}", [el]), mat, thickness=t)
+            )
+            eid += 1
+    a = ada.Assembly() / p
+    p.fem.sections.merge_by_properties()
+    return a
+
+
+def test_surface_strategy_flat_mesh_matches_coplanar(fem_files):
+    # A mesh with no recognisable curved patches: SURFACE degrades to the flat merge.
     a = ada.from_fem(fem_files / "sesam/beamMassT1.FEM")
-    for strat in (MergeStrategy.SURFACE, MergeStrategy.PANEL):
-        with pytest.raises(NotImplementedError):
-            list(iter_faces(a, strat))
+    surf = list(iter_faces(a, MergeStrategy.SURFACE))
+    cop = list(iter_faces(a, MergeStrategy.COPLANAR))
+    assert all(f.geom_face is None for f in surf)
+    assert len(surf) == len(cop)
+    assert _total_area(surf) == pytest.approx(_total_area(cop), rel=1e-9)
+
+
+def test_surface_strategy_detects_cylinder():
+    a = _tube()
+    part = next(p_ for p_ in a.get_all_parts_in_assembly(include_self=True) if p_.fem is not None and len(p_.fem.elements))
+    faces = list(iter_faces(part, MergeStrategy.SURFACE))
+    analytic = [f for f in faces if f.geom_face is not None]
+    # the 288-quad tube collapses to a handful of analytic cylinder faces
+    assert 1 <= len(analytic) <= 8
+    assert all(f.thickness == pytest.approx(0.01) and f.material == "S355" for f in analytic)
+    # polygon-only consumers (Genie XML) must get flats instead — never lose geometry
+    flats = list(iter_faces(part, MergeStrategy.SURFACE, allow_analytic=False))
+    assert all(f.geom_face is None for f in flats)
+    assert len(flats) >= 1
+
+    # PANEL includes the cylinder pass too
+    panel = [f for f in iter_faces(part, MergeStrategy.PANEL) if f.geom_face is not None]
+    assert len(panel) >= 1
+
+
+def test_surface_strategy_object_stream_yields_curved_plates():
+    a = _tube()
+    part = next(p_ for p_ in a.get_all_parts_in_assembly(include_self=True) if p_.fem is not None and len(p_.fem.elements))
+    objs = list(part.iter_objects_from_fem(beams=False, plates=True, merge_strategy="surface"))
+    curved = [o for o in objs if isinstance(o, ada.PlateCurved)]
+    assert 1 <= len(curved) <= 8
+    assert len(objs) < 20  # 288 shells -> a handful of concept objects
+    # each curved plate tessellates on the active backend (renderable, not just writable)
+    from ada.occ.tessellating import BatchTessellator
+
+    bt = BatchTessellator()
+    for o in curved:
+        (ms,) = list(bt.batch_tessellate([o]))
+        assert len(ms.position) > 0
+
+
+def test_analytic_cylinder_ifc_streaming_roundtrips(tmp_path, monkeypatch):
+    # The streaming IFC B-rep emitter must carry the joint-cut cylinder faces' UV
+    # p-curves (IfcSurfaceCurve/IfcPcurve); without them the trimmed CYLINDRICAL_SURFACE
+    # face can't rebuild its wire on re-import ('wire build failed') and the shell drops.
+    monkeypatch.setenv("ADA_IFC_IMPORT_SHAPE_GEOM", "true")
+    ada.config.Config().reload_config()
+
+    a = _tube()
+    out = tmp_path / "tube.ifc"
+    a.to_ifc(out, streaming=True, merge_strategy="cylinder")
+    txt = out.read_text(errors="ignore").upper()
+    assert txt.count("IFCPCURVE(") > 0
+    assert txt.count("IFCCYLINDRICALSURFACE(") > 0
+
+    b = ada.from_ifc(out)
+    scene = b.to_trimesh_scene()
+    tris = sum(g.faces.shape[0] for g in scene.geometry.values() if hasattr(g, "faces"))
+    # the re-imported cylinder tessellates to a real curved mesh, not a degenerate one
+    assert tris > 100
 
 
 def _part_with_fem(fem_files):
diff --git a/tests/core/geom/solids/test_swept_area_solids.py b/tests/core/geom/solids/test_swept_area_solids.py
index 3295451a6..3662da4be 100644
--- a/tests/core/geom/solids/test_swept_area_solids.py
+++ b/tests/core/geom/solids/test_swept_area_solids.py
@@ -48,8 +48,11 @@ def test_prim_sweep2(tmp_path):
 
     # sweep.show()
 
-    expected = np.asarray([0.622505, 0.415516, 0.808411])
-    np.testing.assert_allclose(mesh.center_mass, expected, atol=0.0001)
+    # Center of mass of the tessellated sweep. atol is 1e-3 (not tighter) because the
+    # exact value depends on the tessellation density — the angular deflection controls
+    # how finely the swept arc is sampled, so a quality change nudges it at the 1e-4 level.
+    expected = np.asarray([0.622645, 0.415708, 0.808493])
+    np.testing.assert_allclose(mesh.center_mass, expected, atol=1e-3)
 
 
 def test_prim_sweep_flipped_normals(tmp_path):
diff --git a/tests/core/geom/test_polygonal_face_set.py b/tests/core/geom/test_polygonal_face_set.py
index 885c49e02..27fa6faf7 100644
--- a/tests/core/geom/test_polygonal_face_set.py
+++ b/tests/core/geom/test_polygonal_face_set.py
@@ -60,3 +60,38 @@ def test_polygonal_face_set_ifc_roundtrip():
     assert read_back.closed is True
     # First coordinate survives the round-trip.
     assert read_back.coordinates[0].is_equal(pfs.coordinates[0])
+
+
+def test_polygonal_face_set_shape_tessellates(example_files):
+    """An IfcPolygonalFaceSet product (polygonal-face-tessellation.ifc) must import AND render.
+    Shape.solid_geom previously rejected PolygonalFaceSet (not in its accepted-types list), so
+    the tessellator skipped it -> empty scene. Also checks the NGEOM libtess2 production path."""
+    import os
+
+    import trimesh
+
+    import ada
+
+    a = ada.from_ifc(example_files / "ifc_files/bs_samples/polygonal-face-tessellation.ifc")
+    shape = next(iter(a.get_all_physical_objects()))
+    # solid_geom must not raise for a PolygonalFaceSet geometry.
+    assert isinstance(shape.solid_geom().geometry, geo_su.PolygonalFaceSet)
+
+    def _faces(**env):
+        for k, v in env.items():
+            os.environ[k] = v
+        try:
+            sc = a.to_trimesh_scene(merge_meshes=True)
+        finally:
+            for k in env:
+                os.environ.pop(k, None)
+        tris = [g for g in sc.geometry.values() if hasattr(g, "faces")]
+        return trimesh.util.concatenate(tris) if tris else None
+
+    for label, env in (("occ", {}), ("libtess2", {"ADA_STREAM_TESS_PIPELINE": "libtess2"})):
+        m = _faces(**env)
+        assert m is not None and len(m.faces) > 0, f"{label}: PolygonalFaceSet produced no geometry"
+        # 20-cube (bbox -10..10) with an inner cavity; both paths agree, outward winding.
+        lo, hi = m.vertices.min(0), m.vertices.max(0)
+        assert lo.min() < -9.9 and hi.max() > 9.9
+        assert m.volume > 0, f"{label}: inside-out ({m.volume})"
diff --git a/tests/core/occ/test_faceted_face_hole.py b/tests/core/occ/test_faceted_face_hole.py
new file mode 100644
index 000000000..0d784ff46
--- /dev/null
+++ b/tests/core/occ/test_faceted_face_hole.py
@@ -0,0 +1,43 @@
+"""A planar (faceted-brep / IfcFace) face with an inner bound must cut a hole, not cap it.
+
+Regression for the ``basin-faceted-brep.ifc`` cap: the top rim face carries an
+``IfcFaceOuterBound`` plus an ``IfcFaceBound`` (the mouth opening). The shell builder used only
+``bounds[0]`` and dropped the inner bound, rendering the opening as a solid cap. ``Face`` faces now
+build every bound, subtracting the inner ones as holes.
+"""
+
+from __future__ import annotations
+
+import ada.geom.curves as cu
+import ada.geom.surfaces as su
+from ada.geom.points import Point
+
+
+def _square(size: float, off: float = 0.0) -> cu.PolyLoop:
+    return cu.PolyLoop(
+        polygon=[
+            Point(off, off, 0.0),
+            Point(off + size, off, 0.0),
+            Point(off + size, off + size, 0.0),
+            Point(off, off + size, 0.0),
+        ]
+    )
+
+
+def test_planar_face_inner_bound_is_a_hole():
+    from ada.occ.geom.surfaces import _face_area, make_planar_face_from_bounds
+
+    # 10x10 outer with a centred 4x4 hole -> area 100 - 16 = 84.
+    bounds = [
+        su.FaceBound(bound=_square(10.0), orientation=True),
+        su.FaceBound(bound=_square(4.0, off=3.0), orientation=True),
+    ]
+    face = make_planar_face_from_bounds(bounds)
+    assert abs(_face_area(face) - 84.0) < 1e-6, _face_area(face)
+
+
+def test_planar_face_single_bound_unchanged():
+    from ada.occ.geom.surfaces import _face_area, make_planar_face_from_bounds
+
+    face = make_planar_face_from_bounds([su.FaceBound(bound=_square(10.0), orientation=True)])
+    assert abs(_face_area(face) - 100.0) < 1e-6, _face_area(face)
diff --git a/tests/core/occ/test_geom_transforms.py b/tests/core/occ/test_geom_transforms.py
new file mode 100644
index 000000000..4e543bdfa
--- /dev/null
+++ b/tests/core/occ/test_geom_transforms.py
@@ -0,0 +1,58 @@
+"""Geometry.transforms → mesh-level instancing.
+
+Regression for the IfcMappedItem OCC fallbacks: a mapped item with a non-rigid (scale/shear)
+transform, or a product that instances one mapping source N times, carries its placement(s) on
+``Geometry.transforms`` and is baked into the tessellated mesh — one emitted MeshStore per
+transform — instead of falling back to the OCC kernel.
+"""
+
+from __future__ import annotations
+
+import numpy as np
+
+from ada.geom import Geometry
+from ada.geom.points import Point
+from ada.geom.solids import Box
+from ada.visit.gltf.meshes import MeshStore, MeshType
+
+
+class _Obj:
+    def __init__(self, transforms):
+        self.geom = Geometry("g", Box.from_2points(Point(0, 0, 0), Point(1, 1, 1)), transforms=transforms)
+
+
+def _unit_ms():
+    # one triangle at unit scale
+    pos = np.array([0, 0, 0, 1, 0, 0, 0, 1, 0], dtype=np.float32)
+    idx = np.array([0, 1, 2], dtype=np.uint32)
+    return MeshStore(0, None, pos, idx, None, 0, MeshType.TRIANGLES, 0)
+
+
+def test_no_transforms_passthrough():
+    from ada.occ.tessellating import _emit_with_geom_transforms
+
+    ms = _unit_ms()
+    out = list(_emit_with_geom_transforms(ms, _Obj(None)))
+    assert len(out) == 1 and out[0] is ms
+
+
+def test_nonuniform_scale_baked_into_positions():
+    from ada.occ.tessellating import _emit_with_geom_transforms
+
+    m = np.diag([2.0, 3.0, 1.0, 1.0])  # non-uniform scale
+    out = list(_emit_with_geom_transforms(_unit_ms(), _Obj([m])))
+    assert len(out) == 1
+    p = np.asarray(out[0].position, float).reshape(-1, 3)
+    assert np.allclose(p[1], [2, 0, 0]) and np.allclose(p[2], [0, 3, 0])
+
+
+def test_multiple_transforms_emit_one_meshstore_each():
+    from ada.occ.tessellating import _emit_with_geom_transforms
+
+    t1 = np.eye(4)
+    t2 = np.eye(4)
+    t2[:3, 3] = [10, 0, 0]  # translate
+    out = list(_emit_with_geom_transforms(_unit_ms(), _Obj([t1, t2])))
+    assert len(out) == 2
+    p2 = np.asarray(out[1].position, float).reshape(-1, 3)
+    assert np.allclose(p2[0], [10, 0, 0])
diff --git a/tests/core/occ/test_mesh_distortion.py b/tests/core/occ/test_mesh_distortion.py
new file mode 100644
index 000000000..ec8eaf27e
--- /dev/null
+++ b/tests/core/occ/test_mesh_distortion.py
@@ -0,0 +1,51 @@
+"""The crows-nest distortion metric flags spike triangles (a vertex shot out past the body) but NOT
+benign geometry — uniform faceting, deep thin extrusions, coarse curves — that a plain aspect/reach
+test over-flags. Mirrors the frontend meshStats spike metric behind the "distorted" gallery walk.
+"""
+
+from __future__ import annotations
+
+import numpy as np
+
+from ada.occ.tessellating import accumulate_mesh_distortion, consume_mesh_distortion_stats
+
+
+def _grid(n: int = 11):
+    xs, ys = np.meshgrid(np.linspace(0, 1, n), np.linspace(0, 1, n))
+    v = np.c_[xs.ravel(), ys.ravel(), np.zeros(n * n)]
+    tris = []
+    for r in range(n - 1):
+        for c in range(n - 1):
+            i = r * n + c
+            tris += [[i, i + 1, i + n + 1], [i, i + n + 1, i + n]]
+    return v, np.asarray(tris)
+
+
+def test_clean_grid_has_no_distortion():
+    v, tris = _grid()
+    accumulate_mesh_distortion(v, tris)
+    assert consume_mesh_distortion_stats()["distorted_tris"] == 0
+
+
+def test_spike_vertex_is_flagged():
+    v, tris = _grid()
+    v2 = np.vstack([v, [0.5, 0.5, 20.0]])  # a vertex shot 20 units off a unit-size sheet
+    sp = len(v2) - 1
+    tris2 = np.vstack([tris, [[0, 1, sp]]])  # a thin triangle reaching out to it
+    accumulate_mesh_distortion(v2, tris2)
+    assert consume_mesh_distortion_stats()["distorted_tris"] == 1
+
+
+def test_deep_thin_extrusion_not_flagged():
+    # A long thin box: side triangles are thin AND reach across the bbox, but no vertex is an
+    # outlier (they're all on the body) — must NOT count as crows-nest distortion.
+    x, y, z = 0.05, 0.05, 5.0
+    corners = np.array(
+        [[0, 0, 0], [x, 0, 0], [x, y, 0], [0, y, 0], [0, 0, z], [x, 0, z], [x, y, z], [0, y, z]], float
+    )
+    faces = [
+        [0, 1, 5], [0, 5, 4], [1, 2, 6], [1, 6, 5], [2, 3, 7], [2, 7, 6],
+        [3, 0, 4], [3, 4, 7], [0, 3, 2], [0, 2, 1], [4, 5, 6], [4, 6, 7],
+    ]
+    accumulate_mesh_distortion(corners, np.asarray(faces))
+    assert consume_mesh_distortion_stats()["distorted_tris"] == 0
diff --git a/tests/core/occ/test_mesh_distortion_scan.py b/tests/core/occ/test_mesh_distortion_scan.py
new file mode 100644
index 000000000..29cc74bf3
--- /dev/null
+++ b/tests/core/occ/test_mesh_distortion_scan.py
@@ -0,0 +1,38 @@
+"""The per-conversion distortion tally flags degenerate/sliver triangles (the audit "distorted
+tris" flag) and the fallback counter tallies libtess2->OCC fallbacks."""
+
+from __future__ import annotations
+
+import numpy as np
+
+
+def test_distortion_counts_slivers_only():
+    from ada.occ.tessellating import accumulate_mesh_distortion, consume_mesh_distortion_stats
+
+    consume_mesh_distortion_stats()  # reset
+    pos = np.array(
+        [
+            [0, 0, 0], [1, 0, 0], [0, 1, 0],       # healthy right triangle
+            [0, 0, 0], [10, 0, 0], [5, 1e-4, 0],   # extreme sliver
+            [0, 0, 0], [1, 0, 0], [1, 0, 0],       # degenerate (repeated vertex)
+        ],
+        float,
+    )
+    idx = np.array([[0, 1, 2], [3, 4, 5], [6, 7, 8]], int)
+    accumulate_mesh_distortion(pos, idx)
+    s = consume_mesh_distortion_stats()
+    assert s["n_tris"] == 3
+    assert s["distorted_tris"] == 2  # sliver + degenerate, not the healthy one
+    assert consume_mesh_distortion_stats()["n_tris"] == 0  # reset on read
+
+
+def test_fallback_counter_reset_on_consume():
+    from ada.occ.tessellating import _record_tess_fallback, consume_tess_fallback_stats
+
+    consume_tess_fallback_stats()  # reset
+    _record_tess_fallback("empty mesh (geom type not NGEOM-serializable)", "FacetedBrep")
+    _record_tess_fallback("active backend has no tessellate_stream", "Box")
+    s = consume_tess_fallback_stats()
+    assert s["count"] == 2
+    assert s["geoms"]["FacetedBrep"] == 1
+    assert consume_tess_fallback_stats()["count"] == 0
diff --git a/tests/core/occ/test_polygonal_face_set_direct.py b/tests/core/occ/test_polygonal_face_set_direct.py
new file mode 100644
index 000000000..89ed66cd6
--- /dev/null
+++ b/tests/core/occ/test_polygonal_face_set_direct.py
@@ -0,0 +1,34 @@
+"""IfcPolygonalFaceSet emits directly as a fan-triangulated 3D mesh (no OCC fallback, no plane
+flattening).
+
+Regression for the alignment/signal OCC fallbacks: PolygonalFaceSet had no NGEOM encoder, so it fell
+back to OCC. It now fan-triangulates in 3D via _direct_triangulated_meshstore — keeping the original
+vertices (a per-face plane inference would flatten non-planar faces).
+"""
+
+from __future__ import annotations
+
+import numpy as np
+
+import ada.geom.surfaces as su
+from ada.geom import Geometry
+from ada.geom.points import Point
+
+
+def test_polygonal_face_set_fan_triangulates_in_3d():
+    from ada.occ.tessellating import BatchTessellator
+
+    # Two faces sharing an edge: a quad (-> 2 tris) and a triangle (-> 1 tri). Non-planar quad to
+    # prove the vertices aren't flattened onto a plane.
+    coords = [
+        Point(0, 0, 0), Point(1, 0, 0), Point(1, 1, 0.3), Point(0, 1, 0),  # quad (non-planar: z=0.3)
+        Point(2, 0, 0),  # extra vertex for the triangle
+    ]
+    pfs = su.PolygonalFaceSet(coordinates=coords, faces=[[1, 2, 3, 4], [2, 5, 3]])
+    ms = BatchTessellator()._direct_triangulated_meshstore(Geometry("p", pfs, None), "n")
+    assert ms is not None
+    idx = np.asarray(ms.indices, int).reshape(-1, 3)
+    assert len(idx) == 3  # 2 (quad fan) + 1 (triangle)
+    pos = np.asarray(ms.position, float).reshape(-1, 3)
+    # Original vertices preserved (not projected onto a plane) — vertex 3 keeps its z=0.3.
+    assert np.isclose(pos[2, 2], 0.3), pos[2]
diff --git a/tests/core/visit/test_stream_adaptive_tess.py b/tests/core/visit/test_stream_adaptive_tess.py
new file mode 100644
index 000000000..055214591
--- /dev/null
+++ b/tests/core/visit/test_stream_adaptive_tess.py
@@ -0,0 +1,50 @@
+"""The streaming STEP->GLB libtess2 path honours adaptive tessellation coarsening
+(ADA_STREAM_TESS_MODEL_SCALE) — small features in a large model tessellate coarser, so a big
+assembly (e.g. the boiler) doesn't over-tessellate every small pipe/torus into a slivery crows-nest.
+
+Regression for scene_from_step_stream, which previously tessellated at a fixed angular ceiling with
+no model_scale (unlike native_step_to_glb, which already coarsens by default).
+"""
+
+from __future__ import annotations
+
+import json
+import os
+import struct
+
+import pytest
+
+
+def _glb_tris(path: str) -> int:
+    d = open(path, "rb").read()
+    jlen = struct.unpack("<I", d[12:16])[0]
+    g = json.loads(d[20:20 + jlen])
+    return sum(g["accessors"][p["indices"]]["count"] // 3 for m in g["meshes"] for p in m["primitives"])
+
+
+def test_stream_model_scale_coarsens(tmp_path, monkeypatch):
+    pytest.importorskip("adacpp")
+    import ada
+    from ada.cad import active_backend
+
+    if not hasattr(active_backend(), "tessellate_stream"):
+        pytest.skip("adacpp build has no tessellate_stream")
+    from ada.visit.scene_handling.scene_from_step_stream import StepStreamSource, convert_step_stream_to_glb
+
+    # small cylinders (r=15) spread across a large extent -> features << model scale
+    objs = [ada.PrimCyl(f"c{i}", (i * 2000, 0, 0), (i * 2000, 0, 200), 15) for i in range(5)]
+    step = tmp_path / "cyls.stp"
+    (ada.Assembly("t") / (ada.Part("p") / objs)).to_stp(str(step))
+
+    monkeypatch.setenv("ADA_STREAM_TESS_PIPELINE", "libtess2")
+
+    monkeypatch.setenv("ADA_STREAM_TESS_MODEL_SCALE", "0")  # adaptive off
+    convert_step_stream_to_glb(StepStreamSource(str(step)), str(tmp_path / "off.glb"))
+    fine = _glb_tris(str(tmp_path / "off.glb"))
+
+    monkeypatch.setenv("ADA_STREAM_TESS_MODEL_SCALE", "20000")  # features << 1% => coarsened
+    convert_step_stream_to_glb(StepStreamSource(str(step)), str(tmp_path / "on.glb"))
+    coarse = _glb_tris(str(tmp_path / "on.glb"))
+
+    assert fine > 0 and coarse > 0
+    assert coarse < fine * 0.5, f"adaptive coarsening had no effect: {coarse} vs {fine}"