Commit Messages

Use this skill to generate clear, conventional commit messages that explain the "why" not just the "what". Follow this guide when writing commit messages or helping users structure their commits.

When to Use

• User asks for help writing a commit message
• User wants to understand conventional commit format
• User needs to split a large commit into smaller ones
• User asks about commit best practices

Philosophy

• Why > What - The diff shows what changed; the message explains why
• Atomic commits - One logical change per commit
• Future readers - Write for someone debugging at 2am in 6 months
• Searchable - Make it easy to find with git log --grep

Format

Follow Conventional Commits:

type(scope): subject

body (optional)

footer (optional)

Types

Type	When to Use	Example
feat	New feature for the user	feat(auth): add password reset flow
fix	Bug fix for the user	fix(cart): correct quantity calc
docs	Documentation only changes	docs: update API examples
style	Formatting, white-space (not CSS)	style: format with biome
refactor	Code change that neither fixes nor adds	refactor: extract validation utils
perf	Performance improvement	perf: memoize expensive calculation
test	Adding or updating tests	test: add auth integration tests
build	Build system or dependencies	build: upgrade to node 22
ci	CI configuration	ci: add playwright to pipeline
chore	Other changes that don't modify src/test files	chore: update .gitignore

Rules

Subject Line

Rule	Good	Bad
Imperative mood	add user profile	added user profile
No capitalization	fix login bug	Fix login bug
No period	update readme	update readme.
Be specific	fix redirect loop on session expiry	fix bug
Max 50 chars (72 hard limit)	Keep it concise	Don't write essays

Scope (optional)

• Component or area: feat(auth):, fix(api):, test(cart):
• Keep consistent within project
• Omit if change spans multiple areas

Body (when needed)

• Wrap at 72 characters
• Explain why this change was necessary
• Include context that isn't obvious from the diff
• Reference issues: Fixes #123 or Relates to #456

Breaking Changes

feat(api)!: change authentication endpoint

BREAKING CHANGE: /auth/login now requires email instead of username.
Migration: Update all clients to send email field.

Commit Scope Assessment

Before writing the message, assess whether the staged changes should be one commit or multiple.

Signs to Split

Signal	Action
Changes to unrelated files	Split by feature/area
Multiple types (feat + fix)	Separate commits
"and" in your subject line	Probably two commits
> 10 files changed	Consider splitting
Mix of refactor + feature	Refactor first, then feature

Good Split Example

Instead of:

feat: add user profile and fix login redirect and update tests

Split into:

fix(auth): prevent redirect loop on session expiry
feat(profile): add user profile page
test(auth): add session expiry tests

Examples

Good

feat(cart): add quantity selector to cart items

Allow users to update item quantities directly from the cart
instead of navigating back to the product page.

Closes #234

fix(auth): prevent redirect loop on expired session

Session expiry was triggering a redirect to login, which then
redirected back to the protected route, causing an infinite loop.

Now we clear the redirect URL when session expires.

refactor: extract validation logic to shared utilities

Consolidates duplicate Zod schemas from three API routes into
a single source of truth in lib/validation.

No behavior changes.

perf(search): debounce search input to reduce API calls

Search was firing on every keystroke, causing 10+ requests
for a typical query. Now waits 300ms after typing stops.

Reduces search API calls by ~80% based on local testing.

Bad

Message	Problem
fixed stuff	Too vague - what stuff?
Updated the code	Obvious - adds no value
WIP	Not ready to commit
fix: Fix the bug	Redundant, no detail
misc changes	Meaningless
feat: add new feature	What feature?
refactor code	What code? Why?

Output Format

When generating commit messages, provide the complete message ready to use:

type(scope): clear subject line

Optional body explaining the motivation for this change.
Include context that helps future readers understand why
this was done, not just what was done.

Fixes #123

If the commit should be split, recommend splitting with specific guidance:

**Recommendation: Split this commit**

The staged changes include multiple unrelated changes:

1. [Change type 1] - [files affected]
2. [Change type 2] - [files affected]

**Suggested commits:**

1. First commit:

type(scope): first change

2. Second commit:

type(scope): second change

**To split:** Use `git reset HEAD` then stage files for each commit separately.