I Fixed the "AI Commit Messages" Problem in 20 Lines of Python

You've probably seen that trending post — "I Asked AI to Write My Commit Messages and It Was Embarrassing." Same. But instead of accepting embarrassing output, I fixed it. Here's the thing: the problem isn't AI writing commit messages. The problem is how you ask it. One clear system prompt + the actual diff = surprisingly good results. The Setup No new packages. No API key. If you have Claude Code , you're already set. #!/usr/bin/env python3 import subprocess SYSTEM = ( " You are a git commit message generator. " " Output ONLY the commit message — no explanation, no markdown, no quotes. " " Follow Conventional Commits: type(scope): subject. " " Types: feat, fix, docs, style, refactor, test, chore. " " Subject: imperative, lowercase, max 72 chars. " ) diff = subprocess . check_output ([ " git " , " diff " , " --staged " ], text = True ) if not diff . strip (): print ( " Nothing staged. Run `git add` first. " ) raise SystemExit ( 1 ) msg = subprocess . check_output ( [ " claude " , " -p " , SYSTEM + " \n\n " + diff ], text = True , ). strip () print ( msg ) That's it. 20 lines. Uses the claude CLI under the hood — no API key, no config, just your existing Claude Code OAuth session. Why It Works The system prompt does the heavy lifting. Three constraints: Output ONLY the commit message — no preamble, no explanation Follow Conventional Commits — feat , fix , chore , etc. max 72 chars — keeps it readable in git log The diff is the context. You're not asking "write a commit message". You're asking "given these exact changes, what happened?" That's a much more answerable question. Usage # No setup needed if you have Claude Code. Just: git add . python /path/to/git_commit.py # → feat(server): add AI commit message generator via Claude CLI Or wire it into a git alias: git config --global alias.ai '!python /path/to/git_commit.py' # git ai The Results Before: update stuff fix bug WIP added the thing After: feat(api): add generate_commit_message tool to MCP server fix(auth): ha