diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 7b4b41b..c3ebea1 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -173,3 +173,65 @@ jobs:
       - name: Cargo build --release (verifies the binary links)
         working-directory: src-tauri
         run: cargo build --release
+
+  cross-platform:
+    name: Cross-platform (${{ matrix.label }})
+    runs-on: ${{ matrix.os }}
+    timeout-minutes: 45
+    # Compile + link the Tauri binary against each platform's webview so a
+    # macOS-only Tauri API (like the title_bar_style / RunEvent::Opened blockers
+    # PR #197 fixed) can't silently regress cross-platform builds on main.
+    # Promoted from the retired cross-platform-spike.yml — see
+    # docs/CROSS-PLATFORM-HARDENING.md item 9. Compile/link-only by design;
+    # bundling + signing stay out of CI (tracked as P2 in that doc).
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - os: ubuntu-latest
+            label: Linux
+          - os: windows-latest
+            label: Windows
+    steps:
+      - uses: actions/checkout@v6
+
+      - uses: pnpm/action-setup@v6
+        with:
+          version: 10
+
+      - uses: actions/setup-node@v6
+        with:
+          node-version: 22
+          cache: pnpm
+
+      # Linux WebKitGTK toolchain (Tauri v2 → webkit2gtk-4.1). Windows ships
+      # WebView2 with the runner image, so no system deps there.
+      - name: Install Linux system deps
+        if: matrix.os == 'ubuntu-latest'
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y \
+            libwebkit2gtk-4.1-dev \
+            libappindicator3-dev \
+            librsvg2-dev \
+            patchelf \
+            libxdo-dev \
+            libssl-dev
+
+      - uses: dtolnay/rust-toolchain@stable
+
+      - name: Cache cargo registry + target
+        uses: Swatinem/rust-cache@v2
+        with:
+          workspaces: src-tauri
+
+      - name: Install frontend deps
+        run: pnpm install --frozen-lockfile
+
+      # `--no-bundle` compiles + links the binary against the platform webview
+      # (WebView2 / WebKitGTK) without producing installers, so the macOS-only
+      # bundle targets in tauri.conf.json are never exercised. `--debug` skips
+      # release LTO so the job finishes in CI-friendly time while still proving
+      # the link step.
+      - name: tauri build (compile + link only)
+        run: pnpm tauri build --debug --no-bundle
diff --git a/.github/workflows/cross-platform-spike.yml b/.github/workflows/cross-platform-spike.yml
deleted file mode 100644
index 3977c0c..0000000
--- a/.github/workflows/cross-platform-spike.yml
+++ /dev/null
@@ -1,75 +0,0 @@
-name: Cross-platform spike
-
-# GTM-SCALE-PLAN.md §3 (unlock 2) / §10 item 7.
-# Validates that Markup *compiles and links* the webview on Windows + Linux —
-# the gating question for the "go cross-platform" bet. This is a SPIKE, not a
-# release pipeline: it builds the binary with `--no-bundle` (no installers, no
-# signing) and does NOT touch the macOS release flow. Rendering/IME/file-watch
-# behaviour still needs manual testing on real machines — those go into the
-# "cross-platform hardening" to-do, not here.
-#
-# Triggers: manual (workflow_dispatch) + push to spike/** so the branch self-tests.
-
-on:
-  workflow_dispatch: {}
-  push:
-    branches: ["spike/**"]
-
-permissions:
-  contents: read
-
-env:
-  CARGO_TERM_COLOR: always
-
-jobs:
-  build:
-    name: tauri build (${{ matrix.os }})
-    runs-on: ${{ matrix.os }}
-    timeout-minutes: 45
-    strategy:
-      fail-fast: false
-      matrix:
-        os: [ubuntu-latest, windows-latest]
-    steps:
-      - uses: actions/checkout@v6
-
-      - uses: pnpm/action-setup@v6
-        with:
-          version: 10
-
-      - uses: actions/setup-node@v6
-        with:
-          node-version: 22
-          cache: pnpm
-
-      # Linux WebKitGTK toolchain (Tauri v2 → webkit2gtk-4.1). Windows ships
-      # WebView2 with the runner image, so no system deps there.
-      - name: Install Linux system deps
-        if: matrix.os == 'ubuntu-latest'
-        run: |
-          sudo apt-get update
-          sudo apt-get install -y \
-            libwebkit2gtk-4.1-dev \
-            libappindicator3-dev \
-            librsvg2-dev \
-            patchelf \
-            libxdo-dev \
-            libssl-dev
-
-      - uses: dtolnay/rust-toolchain@stable
-
-      - name: Cache cargo registry + target
-        uses: Swatinem/rust-cache@v2
-        with:
-          workspaces: src-tauri
-
-      - name: Install frontend deps
-        run: pnpm install --frozen-lockfile
-
-      # `--no-bundle` compiles + links the binary against the platform webview
-      # (WebView2 / WebKitGTK) without producing installers — the macOS-only
-      # bundle targets in tauri.conf.json are therefore never exercised.
-      # `--debug` skips release LTO so the spike finishes in CI-friendly time
-      # while still proving the link step.
-      - name: tauri build (compile + link only)
-        run: pnpm tauri build --debug --no-bundle
diff --git a/docs/CROSS-PLATFORM-HARDENING.md b/docs/CROSS-PLATFORM-HARDENING.md
index a776fc0..e029030 100644
--- a/docs/CROSS-PLATFORM-HARDENING.md
+++ b/docs/CROSS-PLATFORM-HARDENING.md
@@ -1,8 +1,10 @@
 # Cross-platform hardening to-do (Windows + Linux)
 
 > Output of the GTM-SCALE-PLAN.md §3 (unlock 2) / §10 item 7 **spike**.
-> The spike workflow ([`.github/workflows/cross-platform-spike.yml`](../.github/workflows/cross-platform-spike.yml))
-> runs `tauri build --no-bundle` on `ubuntu-latest` + `windows-latest`.
+> The cross-platform compile/link check (`tauri build --no-bundle` on
+> `ubuntu-latest` + `windows-latest`) now runs in CI as the `cross-platform`
+> matrix job in [`ci.yml`](../.github/workflows/ci.yml) — see item 9. (It began
+> as the standalone `cross-platform-spike.yml`, now retired.)
 > This file enumerates what the spike found and what's left before a real
 > Win/Linux beta (GTM §5 P1).
 >
@@ -71,9 +73,16 @@ Ordered by user-visible impact.
 
 ### P4 — CI & process
 
-9. **Promote the spike into real CI** once green: add Win/Linux to the matrix in
-   `ci.yml` (build + Rust tests), and a bundling smoke. Retire
-   `cross-platform-spike.yml` or fold it in.
+9. **✅ Promote the spike into real CI** — *done.* The Win/Linux
+   `tauri build --debug --no-bundle` compile/link check now runs on every
+   `pull_request` (and push to `main`) as the `cross-platform` matrix job in
+   [`ci.yml`](../.github/workflows/ci.yml), and `cross-platform-spike.yml` has
+   been retired (folded in). The checks **`Cross-platform (Linux)`** and
+   **`Cross-platform (Windows)`** are required for merge in `main`'s branch
+   protection, so a macOS-only Tauri API can't silently regress cross-platform
+   builds again. Kept **compile/link-only** — Rust tests on Win/Linux and a
+   bundling smoke are deliberately out of scope (bundling is P2 item 3) to keep
+   CI time reasonable.
 10. **Maintenance load**: GTM §9 risk — staff the matrix and lean on the
     contributor community so cross-platform doesn't rot.
 
diff --git a/docs/marketing/alternativeto-entry.md b/docs/marketing/alternativeto-entry.md
index 04f1df1..72d2483 100644
--- a/docs/marketing/alternativeto-entry.md
+++ b/docs/marketing/alternativeto-entry.md
@@ -65,5 +65,7 @@ Tag Markup as an alternative to:
 - Honest framing: on macOS, Tauri renders via the system WebView (WKWebView) — it's
   native, not Electron. Say "native (Tauri/Rust)", don't claim "no webview".
 - Add a screenshot or two from `marketing/MarkupScreenshots-mac/` during submission.
-- Re-list platforms to include Windows/Linux the day those builds ship — the
-  cross-platform spike (`.github/workflows/cross-platform-spike.yml`) is the gate.
+- Re-list platforms to include Windows/Linux the day those builds ship — CI
+  already compile-checks both (`cross-platform` job in
+  `.github/workflows/ci.yml`); the remaining bundling/signing gates are tracked
+  in `docs/CROSS-PLATFORM-HARDENING.md`.