lean-commit skill

Write commit messages terse and exact. Conventional Commits format. No fluff. Why over what.

Rules

Subject line:

• <type>(<scope>): <imperative summary> — <scope> optional
• Types: feat, fix, refactor, perf, docs, test, chore, build, ci, style, revert
• Imperative mood: "add", "fix", "remove" — not "added", "adds", "adding"
• ≤50 chars when possible, hard cap 72
• No trailing period
• Match project convention for capitalization after the colon

Body (only if needed):

• Skip entirely when subject is self-explanatory
• Add body only for: non-obvious why, breaking changes, migration notes, linked issues
• Wrap at 72 chars
• Bullets - not *
• Reference issues/PRs at end: Closes #42, Refs #17

What NEVER goes in:

• "This commit does X", "I", "we", "now", "currently" — the diff says what
• "As requested by..." — use Co-authored-by trailer
• "Generated with Claude Code" or any AI attribution — unless the user's own rule requires an Assisted-by/AI-attribution trailer, then add it as a trailer
• Emoji (unless project convention requires)
• Restating the file name when scope already says it

Examples

Diff: new endpoint for user profile with body explaining the why

• ❌ "feat: add a new endpoint to get user profile information from the database"
• ✅

  feat(api): add GET /users/:id/profile
  
  Mobile client needs profile data without the full user payload
  to reduce LTE bandwidth on cold-launch screens.
  
  Closes #128
  

Diff: breaking API change

• ✅

  feat(api)!: rename /v1/orders to /v1/checkout
  
  BREAKING CHANGE: clients on /v1/orders must migrate to /v1/checkout
  before 2026-06-01. Old route returns 410 after that date.
  

Auto-Clarity

Always include body for: breaking changes, security fixes, data migrations, anything reverting a prior commit. Never compress these into subject-only — future debuggers need the context.

Boundaries

Only generates the commit message. Does not run git commit, does not stage files, does not amend. Output the message as a code block ready to paste. "stop lean-commit" or "normal mode": revert to verbose commit style.