diff --git a/.github/workflows/README.md b/.github/workflows/README.md
index 7042cac9a..d11f74df3 100644
--- a/.github/workflows/README.md
+++ b/.github/workflows/README.md
@@ -129,6 +129,36 @@ Runs code quality checks.
 4. `node` - Run Node lint and format checks via `make lint:node` and `make fmt:check:node`
 5. `c` - Run C SDK lint and format checks via `make lint:c` and `make fmt:check:c`
 
+### `codeql.yml`
+
+Runs CodeQL code scanning (advanced setup) across all analyzed languages.
+
+**Why advanced setup:** CodeQL *default setup* does not analyze pull requests
+from forks, so the `code_scanning` ruleset rule ("Require code scanning
+results") permanently blocks fork PRs. Advanced setup runs on `pull_request`,
+so fork PRs in this public repo are scanned and the gate is satisfiable without
+an admin bypass.
+
+**Bootstrap guard:** GitHub rejects advanced CodeQL uploads while default setup
+is enabled. The workflow is dormant until repository variable
+`CODEQL_ADVANCED_SETUP_ENABLED` is set to `true`.
+
+**Triggers:**
+- Push to `main`
+- Pull requests against `main` (including fork PRs)
+- Manual dispatch
+- Weekly schedule (Mondays 03:31 UTC)
+
+**Jobs:**
+1. `analyze` - Matrix over `actions`, `c-cpp`, `go`, `javascript-typescript`, `python`, `rust`. All use `build-mode: none` (source-only, no compile) except `go`, which requires `autobuild` (Go's extractor must observe a build). Uses `github/codeql-action@v4`.
+
+**Activation sequence:**
+1. Merge this workflow while `CODEQL_ADVANCED_SETUP_ENABLED` is unset or `false`, so default setup remains the active scanner.
+2. Disable CodeQL default setup.
+3. Set repository variable `CODEQL_ADVANCED_SETUP_ENABLED=true`.
+4. Trigger a new push, pull request update, or manual dispatch and verify CodeQL analysis uploads successfully.
+5. Roll back by setting `CODEQL_ADVANCED_SETUP_ENABLED=false` and re-enabling default setup.
+
 ### `e2e-test.yml`
 
 Runs VM-based E2E integration tests on an ephemeral AWS EC2 self-hosted runner.
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
new file mode 100644
index 000000000..24af84a70
--- /dev/null
+++ b/.github/workflows/codeql.yml
@@ -0,0 +1,75 @@
+# CodeQL advanced setup.
+#
+# Replaces CodeQL "default setup", which does not analyze pull requests from
+# forks. Advanced setup runs on `pull_request`, so fork PRs are scanned and the
+# "Require code scanning results" ruleset rule can be satisfied without an admin
+# bypass.
+#
+# GitHub rejects advanced CodeQL uploads while default setup is enabled, so keep
+# this workflow dormant until repository variable CODEQL_ADVANCED_SETUP_ENABLED
+# is set to "true" after default setup is disabled.
+#
+# Languages use `build-mode: none` (source-only analysis, no compile step) where
+# CodeQL supports it. Go does not support `none` — its extractor must observe a
+# build — so Go uses `autobuild` (the same mode default setup used successfully
+# for this repo).
+name: CodeQL
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+  workflow_dispatch:
+  schedule:
+    # Weekly full scan of the default branch (Mondays 03:31 UTC).
+    - cron: "31 3 * * 1"
+
+# Cancel in-progress analysis when a PR is updated.
+concurrency:
+  group: codeql-${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
+jobs:
+  analyze:
+    if: vars.CODEQL_ADVANCED_SETUP_ENABLED == 'true'
+    name: Analyze (${{ matrix.language }})
+    runs-on: ubuntu-latest
+    permissions:
+      # Required to upload code scanning results.
+      security-events: write
+      # Required by the CodeQL action to read the repository and Actions runs.
+      contents: read
+      actions: read
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - language: actions
+            build-mode: none
+          - language: c-cpp
+            build-mode: none
+          - language: go
+            build-mode: autobuild
+          - language: javascript-typescript
+            build-mode: none
+          - language: python
+            build-mode: none
+          - language: rust
+            build-mode: none
+    steps:
+      - name: Checkout
+        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
+        with:
+          persist-credentials: false
+
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@8aad20d150bbac5944a9f9d289da16a4b0d87c1e # v4.36.2
+        with:
+          languages: ${{ matrix.language }}
+          build-mode: ${{ matrix.build-mode }}
+
+      - name: Perform CodeQL analysis
+        uses: github/codeql-action/analyze@8aad20d150bbac5944a9f9d289da16a4b0d87c1e # v4.36.2
+        with:
+          category: "/language:${{ matrix.language }}"