diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
new file mode 100644
index 00000000..adb05a64
--- /dev/null
+++ b/.github/workflows/codeql.yml
@@ -0,0 +1,53 @@
+name: CodeQL
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+  schedule:
+    # Weekly drift scan — Saturdays at 09:37 UTC
+    - cron: '37 9 * * 6'
+
+permissions:
+  contents: read
+  security-events: write
+  packages: read
+  actions: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.head_ref || github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  analyze:
+    name: Analyze (${{ matrix.language }})
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - language: actions
+            build-mode: none
+          - language: javascript-typescript
+            build-mode: none
+          - language: rust
+            build-mode: none
+          # Ruby excluded — only a single Homebrew formula file exists.
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@v4
+        with:
+          languages: ${{ matrix.language }}
+          build-mode: ${{ matrix.build-mode }}
+          queries: security-and-quality
+
+      - name: Perform CodeQL Analysis
+        uses: github/codeql-action/analyze@v4
+        with:
+          category: '/language:${{ matrix.language }}'