diff --git a/.github/workflows/test-plugin-install.yml b/.github/workflows/test-plugin-install.yml
index 82054e05..9d1c6756 100644
--- a/.github/workflows/test-plugin-install.yml
+++ b/.github/workflows/test-plugin-install.yml
@@ -69,6 +69,52 @@ jobs:
       - name: Test artifact-path validator
         run: node --test scripts/validate-artifact-paths-test.js
 
+  # Ubuntu coverage stays in the existing jobs above, preserving their check names.
+  validate-platforms:
+    name: Validate tooling (${{ matrix.os }})
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [macos-latest, windows-latest]
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v6
+        with:
+          node-version: '24'
+
+      - name: Test validators and eval runner
+        run: >-
+          node --test
+          scripts/lib/skill-lint-test.js
+          scripts/validate-versions-test.js
+          scripts/run-evals-test.js
+          scripts/validate-reference-links-test.js
+          scripts/validate-commands-test.js
+          scripts/validate-artifact-paths-test.js
+
+      - name: Validate all skills
+        run: node scripts/validate-skills.js
+
+      - name: Validate manifest versions
+        run: node scripts/validate-versions.js
+
+      - name: Validate references/ links in skills
+        run: node scripts/validate-reference-links.js
+
+      - name: Validate commands across all tool directories
+        run: node scripts/validate-commands.js
+
+      - name: Validate spec/plan/todo artifact paths
+        run: node scripts/validate-artifact-paths.js
+
+      - name: Run skill evals (trigger + routing)
+        run: node scripts/run-evals.js --min-rank1 95
+
   test-hooks:
     name: Hook regression tests
     runs-on: ubuntu-latest
@@ -83,7 +129,7 @@ jobs:
 
   validate:
     name: Validate plugin structure
-    needs: [validate-skills, validate-commands]
+    needs: [validate-skills, validate-commands, validate-platforms]
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v6