Authors fast, cheap, maintainable GitHub Actions workflows applying 2026 best practices: caching with `hashFiles` + `restore-keys`, parallelization via matrix + artifacts, reusability (composite actions for steps, reusable workflows for jobs), security (SHA-pinned actions, least-privilege `GITHUB_TOKEN`, concurrency), trackable errors (named steps, step summaries, annotations, and stdout/stderr that always reaches the run log so agents can act on failures), and feedback for comment-triggered runs (👀 acknowledgement reaction on start, 🚀/👎 outcome reaction plus a run-linked comment at the end). Two modes: `scaffold` (default) generates workflow YAML; `review` audits an existing workflow against the same rules. Use when creating CI/CD pipelines, optimizing slow workflows, deduping copy-pasted YAML across repos, or auditing workflow security. Triggers on "github action", "github workflow", "ci pipeline", "create workflow", "speed up ci", "review my workflow", "/github-actions-author".