undertakingyou Commit Message Drafter
Generate a commit message from the current working tree and print it to the terminal. The user will copy, adjust, and commit themselves — never run git commit.
Gathering context
Run all of these in parallel:
git branch --show-current— the branch name often contains the ticket numbergit status— staged, unstaged, and untracked filesgit diff --staged— staged changes in detailgit diff— unstaged tracked-file changesgit diff --stat— summary of files changed and magnitude (useful for large diffs)
Then for any untracked files shown in git status:
- Skip binary files and generated artifacts (lock files, build output,
.min.js, etc.) - Read the first ~50 lines of each — enough to understand purpose, not the full contents
- If there are more than 10 untracked files, read the most important-looking ones and summarize the rest by filename
If there are no uncommitted changes at all, say so and stop.
Inferring the ticket number
Check the branch name first. If it starts with a pattern like VS-1234, PROJ-567, ABC-89 (letters, hyphen, digits), that's the ticket number. If the branch doesn't contain one (e.g. main, feature/refactor-auth), ask the user — or if they don't use tickets, leave the ticket prefix out entirely.
Composing the message
Format:
<ticket> - <short title>
WHAT:
- <change 1>
- <change 2>
- ...
WHY:
<one or two sentences>
<attribution>
First line
<ticket> - <short title> — a brief imperative-mood summary of the change (e.g. "Disallow createJob from guest org"). Keep it under ~70 characters total. If the branch name reads like a good title after stripping the ticket prefix, use it. Otherwise write one from the diff.
If the conversation makes the context behind this round of changes clear (addressing review comments, fixing CI, etc.), append it: <ticket> - <short title> - <context>. Only include this if the reason is obvious from conversation; don't invent one.
WHAT section
A bulleted list of what changed. Each bullet must be 12 words or fewer — terse, scannable, no filler.
- Group related changes into single bullets ("Add and update tests" not one per file)
- Use plain language, not file paths
- 3–6 bullets for a typical change; fewer is fine
- For very large diffs (20+ files), organize by area of change
WHY section
One or two sentences explaining why this change is valuable or necessary — what a reviewer needs to know that isn't obvious from the diff. If the motivation is unclear, write your best guess and note the uncertainty so the user can adjust.
Attribution
If the session has attribution guidance configured (e.g. a Co-Authored-By line in system instructions), use that. Otherwise, use:
Co-Authored-By: Claude <model name> <noreply@anthropic.com>
where <model name> is the model powering this conversation (e.g. Opus 4.6).
Output
Print the complete commit message inside a fenced code block so the user can copy it. After the block, one sentence like "Adjust as needed and commit when ready." is fine.
If anything is ambiguous (motivation, ticket number, whether certain untracked files should be included), note it briefly after the message.