diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2ce0142..d255d41 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,10 +9,10 @@ on:
 jobs:
   check:
     name: Lint and validate
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
 
       - name: Lint
         run: make lint
@@ -22,13 +22,13 @@ jobs:
 
   link-check:
     name: Check links
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
 
       - name: Check links
-        uses: lycheeverse/lychee-action@v2
+        uses: lycheeverse/lychee-action@e7477775783ea5526144ba13e8db5eec57747ce8 # v2.9.0
         with:
           args: >-
             --exclude-loopback
diff --git a/Makefile b/Makefile
index 9a0cfd2..7c52f6a 100644
--- a/Makefile
+++ b/Makefile
@@ -4,6 +4,9 @@ lint:
 validate:
 	bash scripts/validate-workspace.sh
 
+validate-workflows:
+	bash scripts/validate-workflow-policy.sh .
+
 lint-fix:
 	npx rumdl check --fix .
 
@@ -15,4 +18,4 @@ check-links:
 
 ci: lint validate check-links
 
-.PHONY: lint validate lint-fix format check-links ci
+.PHONY: lint validate validate-workflows lint-fix format check-links ci
diff --git a/scripts/setup-github-repo.sh b/scripts/setup-github-repo.sh
index 67d2783..dadb879 100755
--- a/scripts/setup-github-repo.sh
+++ b/scripts/setup-github-repo.sh
@@ -153,5 +153,5 @@ echo "  Org-level labels: bug, enhancement, question, duplicate, needs-repro, ne
 echo "          stale, good first issue, wontfix, invalid, security, needs-human-review"
 echo ""
 echo "  Next required step"
-echo "    Run sdk-sync before opening implementation PRs so .github/workflows/semantic-pr.yml"
+echo "    Run sdk-sync before opening implementation PRs so .github/workflows/semantic-pull-request.yml"
 echo "    and other managed community files are present."
diff --git a/scripts/validate-workflow-policy.sh b/scripts/validate-workflow-policy.sh
new file mode 100644
index 0000000..bd6bd15
--- /dev/null
+++ b/scripts/validate-workflow-policy.sh
@@ -0,0 +1,60 @@
+#!/usr/bin/env bash
+# Validates Altertable's GitHub Actions supply-chain and runtime policy.
+#
+# Usage: ./scripts/validate-workflow-policy.sh [repository-root]
+
+set -euo pipefail
+
+REPOSITORY_ROOT="${1:-.}"
+REQUIRED_UBUNTU_RUNNER="ubuntu-24.04"
+WORKFLOWS_DIRECTORY="$REPOSITORY_ROOT/.github/workflows"
+
+fail() {
+  echo "ERROR: $*" >&2
+  exit 1
+}
+
+[[ -d "$WORKFLOWS_DIRECTORY" ]] || exit 0
+
+while IFS= read -r -d '' workflow; do
+  while IFS= read -r runner; do
+    [[ "$runner" == "$REQUIRED_UBUNTU_RUNNER" ]] || fail \
+      "$workflow must use $REQUIRED_UBUNTU_RUNNER instead of $runner"
+  done < <(sed -nE 's/^[[:space:]]*runs-on:[[:space:]]*(ubuntu-(latest|[0-9]+\.[0-9]+))[[:space:]]*(#.*)?$/\1/p' "$workflow")
+
+  while IFS= read -r action_reference; do
+    action_reference="${action_reference%%[[:space:]]#*}"
+    case "$action_reference" in
+      ./*) continue ;;
+      docker://*) fail "$workflow must pin container actions by digest: $action_reference" ;;
+    esac
+
+    [[ "$action_reference" =~ ^[^@]+@[0-9a-f]{40}$ ]] || fail \
+      "$workflow has an action that is not pinned to a commit SHA: $action_reference"
+  done < <(sed -nE \
+    -e 's/^[[:space:]]*-[[:space:]]*uses:[[:space:]]*([^[:space:]#]+).*/\1/p' \
+    -e 's/^[[:space:]]*uses:[[:space:]]*([^[:space:]#]+).*/\1/p' \
+    "$workflow")
+done < <(find "$WORKFLOWS_DIRECTORY" -type f \( -name '*.yml' -o -name '*.yaml' \) -print0)
+
+if grep -R -qE 'uses:[[:space:]]*actions/setup-node@' "$WORKFLOWS_DIRECTORY"; then
+  [[ -f "$REPOSITORY_ROOT/.node-version" ]] || fail \
+    "$REPOSITORY_ROOT uses actions/setup-node but has no .node-version"
+  grep -R -qE 'node-version-file:[[:space:]]*\.node-version([[:space:]]|$)' "$WORKFLOWS_DIRECTORY" || fail \
+    "$REPOSITORY_ROOT must configure actions/setup-node with node-version-file: .node-version"
+  if grep -R -qE '^[[:space:]]*node-version:[[:space:]]*[^[:space:]#]' "$WORKFLOWS_DIRECTORY"; then
+    fail "$REPOSITORY_ROOT must not hard-code node-version in workflows; use .node-version"
+  fi
+fi
+
+if grep -R -qE 'uses:[[:space:]]*oven-sh/setup-bun@' "$WORKFLOWS_DIRECTORY"; then
+  [[ -f "$REPOSITORY_ROOT/.bun-version" ]] || fail \
+    "$REPOSITORY_ROOT uses oven-sh/setup-bun but has no .bun-version"
+  grep -R -qE 'bun-version-file:[[:space:]]*\.bun-version([[:space:]]|$)' "$WORKFLOWS_DIRECTORY" || fail \
+    "$REPOSITORY_ROOT must configure oven-sh/setup-bun with bun-version-file: .bun-version"
+  if grep -R -qE '^[[:space:]]*bun-version:[[:space:]]*[^[:space:]#]' "$WORKFLOWS_DIRECTORY"; then
+    fail "$REPOSITORY_ROOT must not hard-code bun-version in workflows; use .bun-version"
+  fi
+fi
+
+echo "Workflow policy passed: $REPOSITORY_ROOT"
diff --git a/scripts/validate-workspace.sh b/scripts/validate-workspace.sh
index 7d1f6d3..56234eb 100755
--- a/scripts/validate-workspace.sh
+++ b/scripts/validate-workspace.sh
@@ -26,7 +26,7 @@ require_file scripts/spec-status.sh
 require_file scripts/ecosystem-status.sh
 require_file scripts/subscribe-repos.sh
 require_file schemas/heartbeat-state.example.json
-require_file skills/sdk-sync/templates/.github/workflows/semantic-pr.yml
+require_file skills/sdk-sync/templates/.github/workflows/semantic-pull-request.yml
 
 jq empty repositories.config.json
 
@@ -81,8 +81,12 @@ if grep -R -nE "Close the issue|Close the PR|close the issue|close the PR|will b
   fail "autonomous issue/PR close instruction found"
 fi
 
-if ! grep -q "action-semantic-pull-request@v5" skills/sdk-sync/templates/.github/workflows/semantic-pr.yml; then
-  fail "semantic PR title template does not use the required action"
-fi
+bash scripts/validate-workflow-policy.sh .
+
+template_root="$(mktemp -d)"
+trap 'rm -rf "$template_root"' EXIT
+mkdir -p "$template_root/.github"
+cp -R skills/sdk-sync/templates/.github/workflows "$template_root/.github/workflows"
+bash scripts/validate-workflow-policy.sh "$template_root"
 
 echo "Workspace validation passed"
diff --git a/skills/sdk-release/SKILL.md b/skills/sdk-release/SKILL.md
index 822e582..cfc1787 100644
--- a/skills/sdk-release/SKILL.md
+++ b/skills/sdk-release/SKILL.md
@@ -67,7 +67,7 @@ Use **release-please** GitHub Action for:
 3. GitHub Release creation with release notes.
 4. Triggering registry publish on release.
 
-Because Altertable squash-merges pull requests and release-please derives release notes and version bumps from the merged commit subject, every repository using release-please must validate pull request titles in CI. The required gate is a dedicated GitHub Actions workflow using `amannn/action-semantic-pull-request@v5`, triggered on `pull_request_target` for `opened`, `edited`, and `synchronize`. Allowed title types are:
+Because Altertable squash-merges pull requests and release-please derives release notes and version bumps from the merged commit subject, every repository using release-please must validate pull request titles in CI. The required gate is a dedicated GitHub Actions workflow using `amannn/action-semantic-pull-request@48f256284bd46cdaab1048c3721360e808335d50` (v6.1.1), triggered on `pull_request_target` for `opened`, `edited`, and `synchronize`. Allowed title types are:
 
 - `feat`
 - `fix`
@@ -81,7 +81,7 @@ Because Altertable squash-merges pull requests and release-please derives releas
 - `build`
 - `ci`
 
-Name the workflow clearly (for example `Semantic Pull Request`), keep it separate from language-specific CI when possible, and treat missing PR-title validation as release automation drift that must be patched across affected repositories. The canonical workflow is managed by [sdk-sync](../sdk-sync/SKILL.md) at `skills/sdk-sync/templates/.github/workflows/semantic-pr.yml`.
+Name the workflow clearly (for example `Semantic Pull Request`), keep it separate from language-specific CI when possible, and treat missing PR-title validation as release automation drift that must be patched across affected repositories. The canonical workflow is managed by [sdk-sync](../sdk-sync/SKILL.md) at `skills/sdk-sync/templates/.github/workflows/semantic-pull-request.yml`. It and every repository workflow must follow sdk-sync's GitHub Actions policy: Ubuntu 24.04 LTS, immutable action SHAs, and `.node-version`/`.bun-version` runtime files where those toolchains are used.
 
 Commit message prefixes:
 
diff --git a/skills/sdk-sync/SKILL.md b/skills/sdk-sync/SKILL.md
index c1f928b..4ea1a14 100644
--- a/skills/sdk-sync/SKILL.md
+++ b/skills/sdk-sync/SKILL.md
@@ -15,6 +15,17 @@ All files in the [`templates/`](./templates/) folder are the source of truth and
 
 Managed files include community docs, issue/PR templates, funding metadata, and release automation guardrails. Language-specific CI workflows are owned by each SDK repo, but the semantic PR title workflow is shared because release-please depends on squash-merge titles.
 
+## GitHub Actions policy
+
+Apply this policy to every workflow in each repository, including language-specific CI, release, security, and semantic-title workflows:
+
+- Linux jobs use `ubuntu-24.04`, the current GitHub-hosted Ubuntu LTS image; do not use `ubuntu-latest` or an older Ubuntu image. macOS and Windows jobs retain their platform-specific pinned image where required.
+- Every third-party `uses:` reference is pinned to a 40-character commit SHA with its reviewed release tag in a comment. Local reusable workflows remain relative references.
+- A repository that uses `actions/setup-node` commits a root `.node-version`; every Node setup reads it through `node-version-file: .node-version` rather than hard-coding a workflow value.
+- A repository that uses `oven-sh/setup-bun` commits a root `.bun-version`; every Bun setup reads it through `bun-version-file: .bun-version` rather than hard-coding a workflow value.
+
+`.node-version` and `.bun-version` are repository-owned runtime contracts, not shared templates: preserve the version that the repository supports and make its workflows consume that file. During an audit, run `bash scripts/validate-workflow-policy.sh <repository-root>` after fetching the target repository. Resolve any intentionally dynamic matrix runner or runtime version to an explicit, pinned value before opening the sync PR.
+
 ### Template variables
 
 Templated files contain `{variable}` placeholders. Render them with repo-specific values during sync:
@@ -41,8 +52,9 @@ Templated files contain `{variable}` placeholders. Render them with repo-specifi
 1. Read `repositories.config.json` and iterate over the `sdks` array (do not include the `workspace` entry).
 2. Clone or fetch all SDK repos from the `sdks` array.
 3. For each managed file, compare the repo's version against the source of truth.
-4. Treat a missing `.github/workflows/semantic-pr.yml` as release automation drift for every repo that uses release-please.
-5. Report drift:
+4. Audit every `.github/workflows/*.{yml,yaml}` against the GitHub Actions policy and record runner, action-pin, and runtime-version-file drift.
+5. Treat a missing `.github/workflows/semantic-pull-request.yml` as release automation drift for every repo that uses release-please.
+6. Report drift:
 
 ```text
 DRIFT REPORT
@@ -50,7 +62,7 @@ DRIFT REPORT
 altertable-lakehouse-ruby:
   ✗ SECURITY.md — missing
   ✗ CONTRIBUTING.md — outdated (missing Conventional Commits section)
-  ✗ .github/workflows/semantic-pr.yml — missing
+  ✗ .github/workflows/semantic-pull-request.yml — missing
   ✓ LICENSE — ok
 
 altertable-py:
@@ -65,6 +77,7 @@ For each repo with drift:
 
 1. Copy verbatim files from `templates/` directly.
 2. Render templated files from `templates/` with repo-specific variables (see **Template variables** above).
+3. For workflow-policy drift, update only the affected repository-owned workflow(s) and root runtime version file(s); do not overwrite language-specific workflow logic with a shared template.
 
 ### Phase 3: Open PRs
 
diff --git a/skills/sdk-sync/templates/.github/workflows/semantic-pr.yml b/skills/sdk-sync/templates/.github/workflows/semantic-pull-request.yml
similarity index 61%
rename from skills/sdk-sync/templates/.github/workflows/semantic-pr.yml
rename to skills/sdk-sync/templates/.github/workflows/semantic-pull-request.yml
index 28320d2..970e6d8 100644
--- a/skills/sdk-sync/templates/.github/workflows/semantic-pr.yml
+++ b/skills/sdk-sync/templates/.github/workflows/semantic-pull-request.yml
@@ -10,13 +10,18 @@ on:
 permissions:
   pull-requests: read
 
+concurrency:
+  group: semantic-pr-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
 jobs:
-  semantic-pr:
+  main:
     name: Validate PR title
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
+    timeout-minutes: 5
     steps:
-      - name: Validate title
-        uses: amannn/action-semantic-pull-request@v5
+      - name: Validate pull request title
+        uses: amannn/action-semantic-pull-request@48f256284bd46cdaab1048c3721360e808335d50 # v6.1.1
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         with: