diff --git a/skills/uipath-maestro-flow/references/author/references/editing-operations-json.md b/skills/uipath-maestro-flow/references/author/references/editing-operations-json.md
index 65d247ec9..87bd83880 100644
--- a/skills/uipath-maestro-flow/references/author/references/editing-operations-json.md
+++ b/skills/uipath-maestro-flow/references/author/references/editing-operations-json.md
@@ -30,7 +30,7 @@ Before editing the `.flow` file, ensure each of the following is handled. These
 1. **Locate the canonical `.flow` file.** Before any `Edit` / `Write`, find the flow project directory — it is the directory that contains `project.uiproj`. The canonical `.flow` lives **next to** that `project.uiproj`, not at the solution root. Commands like `uip solution new <Name>` + `uip maestro flow init <Name>` create nested paths (`<Name>/<Name>/project.uiproj`); the `.flow` you must edit is `<Name>/<Name>/<Name>.flow`, not `<Name>/<Name>.flow`. Run `find . -name project.uiproj -type f` and pin every `Edit` / `Write` call to the sibling file. `uip maestro flow validate <PATH>.flow` will accept a misplaced file, so validation alone does **not** confirm the right target — only the colocation with `project.uiproj` does.
 2. **Definitions and versions.** For every new node type, run `uip maestro flow registry get <type> --output json`. Copy the returned node definition object **verbatim** into `definitions[]` — one entry per unique `type:typeVersion`. Depending on CLI/plugin version, the node definition may appear as `Data.Node` or as the top-level object containing fields such as `nodeType`, `version`, and `handleConfiguration`; copy that node object, not the surrounding `Result` / `Code` envelope. Then set each node instance's `typeVersion` to the exact copied definition `version` value. The validator matches `type:typeVersion` exactly; `typeVersion: "1.0.0"` does not match a registry definition with `"version": "1.0"`. Never hand-write or paraphrase definitions (see "Every node type needs a `definitions` entry" in [the Author capability index](../CAPABILITY.md)).
 3. **Unique node ID.** Pick a camelCase ID that does not collide with existing node IDs. Prefer meaningful names (`fetchUsers`, `filterActive`) since they become part of every `$vars.<nodeId>.*` expression.
-4. **`sourcePort` and `targetPort` on every edge.** Omitting `targetPort` is the #1 validation error (see "`targetPort` is required on every edge" in [the Author capability index](../CAPABILITY.md)). Use `sourcePort`, never `sourceHandle`; `sourceHandle` is not part of the `.flow` edge schema and produces the vague root error `Invalid input: expected string, received undefined`. Look up ports in the relevant plugin's `planning.md` or in [file-format.md — Standard ports](../../shared/file-format.md).
+4. **`sourcePort` and `targetPort` on every edge.** Omitting `targetPort` is the #1 validation error (see "`targetPort` is required on every edge" in [the Author capability index](../CAPABILITY.md)). Use `sourcePort`, never `sourceHandle`; `sourceHandle` is not part of the `.flow` edge schema and produces a precise schema error such as `[error] [edges[N].sourcePort] Invalid input: expected string, received undefined` (the path tells you exactly which edge entry is missing the `sourcePort` key). Look up ports in the relevant plugin's `planning.md` or in [file-format.md — Standard ports](../../shared/file-format.md).
 5. **Node outputs block.** Every data-producing node needs an `outputs` block on the node instance (not just in `definitions`). Action nodes: `output` + `error`. Trigger nodes: `output`. End/terminate: none. (See "Every node that produces data MUST have `outputs` on the node instance" in [the Author capability index](../CAPABILITY.md).)
 6. **`variables.nodes[]`.** Add entries for the new node's outputs. Optional under today's runtime, but expected for completeness and diff clarity.
 7. **On delete — cascade manually.** Remove the node from `nodes`. Then sweep `edges[]` for any with matching `sourceNodeId`/`targetNodeId`. Then prune `definitions[]` if this was the last user of the type. Then check `bindings_v2.json` — but only remove a connector binding if no remaining node uses the same connector (bindings are shared at the connector level).
diff --git a/skills/uipath-maestro-flow/references/diagnose/references/failure-modes.md b/skills/uipath-maestro-flow/references/diagnose/references/failure-modes.md
index c6e1033f7..e62807054 100644
--- a/skills/uipath-maestro-flow/references/diagnose/references/failure-modes.md
+++ b/skills/uipath-maestro-flow/references/diagnose/references/failure-modes.md
@@ -206,15 +206,22 @@ Local `uip maestro flow validate` returns `Result: Success`. The same flow fails
 
 ### Cause
 
-Multiple. `flow validate` is a JSON schema + cross-reference check; it does not catch:
+Multiple. `flow validate` is a JSON schema + cross-reference check plus a small set of structural rules; it does not catch:
 
 - Missing `=js:` prefix → see [MST-9107](#mst-9107--js-prefix-missing)
 - Reused reference IDs → see [Reused reference ID](#reused-reference-id--cross-connection-id-leakage)
 - Missing top-level `bindings[]` entries on resource nodes → see [Missing `bindings[]` on resource node](#missing-bindings-on-resource-node)
-- Connector input fields with hand-written `inputs.detail` (missing `essentialConfiguration` block) — re-run `uip maestro flow node configure` to populate properly
 - HITL `completed` port unwired → see [HITL `completed` port unwired](#hitl-completed-port-unwired)
 - Stale `layout` data → see [MST-9061](#mst-9061--misshapen-rectangle-nodes-in-studio-web) (cosmetic, not faulting)
 
+The structural rules **do** catch (validate exits non-zero, with a shape hint pointing at `uip maestro flow node configure` as the canonical authoring path):
+
+- Connector `inputs.detail.configuration` missing or empty
+- Connector `inputs.detail.configuration` decoded but lacking the `essentialConfiguration` envelope
+- Connector `inputs.detail.configuration` containing invalid JSON inside the `=jsonString:` prefix
+
+If you see one of those error titles, re-run `uip maestro flow node configure` rather than hand-editing.
+
 ### Fix
 
 Triage via the diagnostic priority ladder in [troubleshooting-guide.md](troubleshooting-guide.md). Match the incident message and faulting element to the patterns above.
diff --git a/skills/uipath-maestro-flow/references/shared/file-format.md b/skills/uipath-maestro-flow/references/shared/file-format.md
index e151c9e81..5b68e5ddf 100644
--- a/skills/uipath-maestro-flow/references/shared/file-format.md
+++ b/skills/uipath-maestro-flow/references/shared/file-format.md
@@ -202,9 +202,9 @@ Each key in `layout.nodes` is a node `id`. `flow tidy` creates an entry for ever
 }
 ```
 
-> **Gotcha**: `targetPort` is required. Omitting it produces `[error] [edges.N.targetPort] expected string, received undefined` at validate time.
+> **Gotcha**: `targetPort` is required. Omitting it produces `[error] [edges[N].targetPort] Invalid input: expected string, received undefined` at validate time.
 >
-> **Gotcha**: the source field is `sourcePort`, not `sourceHandle`. If you write `sourceHandle`, validation fails with the vague root-level error `Invalid input: expected string, received undefined`.
+> **Gotcha**: the source field is `sourcePort`, not `sourceHandle`. If you write `sourceHandle`, validation fails with `[error] [edges[N].sourcePort] Invalid input: expected string, received undefined` — the path identifies the offending edge entry exactly.
 
 ## Definition entry