docker:27-cli is Alpine with no Node.js, but actions/checkout@v4 is a JS action that needs a Node runtime in the job container — it failed at Checkout with exit 127. node:22-bookworm-slim already has Node (same reason the test job's node:22-alpine works); Docker CLI and openssh-client are added via apt instead. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>