act

act is the second line of defence for GitHub Actions workflows, behind the actionlint skill. actionlint is static — it proves a workflow parses and its expressions and types are sound. act is dynamic — it runs the workflow locally in Docker to see whether it actually works.

Use it as a proposal, not a gate: once actionlint is clean on the staged workflows, offer to run them through act and surface real failures — but never block the commit on act. Its local run can't cover everything, and the local environment is fragile.

When in doubt, ask the operator