diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
new file mode 100644
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--- /dev/null
+++ b/.github/workflows/codeql.yml
@@ -0,0 +1,98 @@
+name: "CodeQL & Security Audit"
+
+on:
+  push:
+    branches: ["master", "main"]
+  pull_request:
+    branches: ["master", "main"]
+  schedule:
+    # Run every Monday at 08:00 UTC to catch newly disclosed CVEs
+    - cron: "0 8 * * 1"
+
+jobs:
+  # ── CodeQL analysis ──────────────────────────────────────────────────────────
+  codeql:
+    name: CodeQL
+    runs-on: ubuntu-latest
+    permissions:
+      actions: read
+      contents: read
+      security-events: write
+
+    strategy:
+      fail-fast: false
+      matrix:
+        language: ["javascript-typescript"]
+        # Rust is not yet supported by CodeQL; covered by cargo-audit below.
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@v3
+        with:
+          languages: ${{ matrix.language }}
+          queries: security-extended,security-and-quality
+
+      - name: Autobuild
+        uses: github/codeql-action/autobuild@v3
+
+      - name: Perform CodeQL Analysis
+        uses: github/codeql-action/analyze@v3
+        with:
+          category: "/language:${{ matrix.language }}"
+
+  # ── Rust security audit (cargo-audit) ────────────────────────────────────────
+  rust-audit:
+    name: Rust Security Audit
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      security-events: write
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Install Rust stable
+        uses: dtolnay/rust-toolchain@stable
+
+      - name: Cache cargo registry
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+          key: ${{ runner.os }}-cargo-audit-${{ hashFiles('**/Cargo.lock') }}
+
+      - name: Install cargo-audit
+        run: cargo install cargo-audit --locked
+
+      - name: Run cargo audit
+        # --deny warnings treats advisories as errors so the job fails on CVEs
+        run: |
+          if [ -f Cargo.toml ]; then
+            cargo audit --deny warnings
+          else
+            echo "No Cargo.toml at repo root — skipping rust audit"
+          fi
+
+  # ── Shell script lint (ShellCheck) ───────────────────────────────────────────
+  shellcheck:
+    name: ShellCheck
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      security-events: write
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Run ShellCheck
+        uses: ludeeus/action-shellcheck@master
+        with:
+          severity: warning
+          scandir: "."
+          ignore_paths: ".git"