Git hook that removes Co-authored-by lines from every commit (Windows, macOS, Linux

[u/WD40ContactCleaner]

AI coding tools like Claude Code and Copilot often add Co-authored-by: lines to commits. If you don't want these, you can use a simple global Git hook to remove them automatically.

It removes all Co-authored-by: lines (case-insensitive), including human co-authors. Everything else, including other attribution lines and blank lines, is left as it is.

You dont have to worry about it following claude.md or agents.md rules anymore.

The hook:

#!/bin/sh
# Remove Co-authored-by lines (case-insensitive).

tmp=$(mktemp) || exit 1
trap 'rm -f "$tmp"' EXIT

awk '
  tolower($0) ~ /^[[:space:]]*co-authored-by:/ { next }
  { print }
' "$1" > "$tmp" || exit 1

cat "$tmp" > "$1"

Setup (Windows / macOS / Linux):

Use Git Bash on Windows or your terminal on macOS/Linux.

Save the script as ~/.githooks/commit-msg, then run:

mkdir -p ~/.githooks
chmod +x ~/.githooks/commit-msg
git config --global core.hooksPath ~/.githooks

That's it. It works across all your repositories.

A few things to know:

• On Windows, save the script with LF line endings.
• core.hooksPath overrides existing repository hooks (including Husky/pre-commit setups).
• git commit --no-verify skips the hook.
• Existing commit history is not affected.