Co-Authored-By default is inappropriate — stop branding user work

Found 3 possible duplicate issues:

1. https://github.com/anthropics/claude-code/issues/27083
2. https://github.com/anthropics/claude-code/issues/19925
3. https://github.com/anthropics/claude-code/issues/617

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Additional complaint: the .claude/ directory name is hardcoded with no option to rename it. Users should be able to configure the local config directory path. Not everyone wants vendor branding in their project structure.

It's a marketing campaign on the backs of the users. Really underhanded.

For a company claiming ethics as its highest priority this really bothers me.

A PreToolUse hook can strip or customize the Co-Authored-By line from git commits:

CMD=$(cat | jq -r '.tool_input.command // empty' 2>/dev/null)
[ -z "$CMD" ] && exit 0
if echo "$CMD" | grep -qE 'git commit'; then
    if echo "$CMD" | grep -qiE 'Co-Authored-By'; then
        echo "⚠️ Commit includes Co-Authored-By attribution. You can strip it with:" >&2
        echo "  git commit --amend --message=\"$(git log -1 --pretty=%B | grep -v Co-Authored)\"" >&2
    fi
fi
exit 0

A more aggressive approach — automatically strip Co-Authored-By via a git hook:

sed -i '/^Co-Authored-By:/d' "$1"

Or via a PostToolUse hook that amends after the commit:

CMD=$(cat | jq -r '.tool_input.command // empty' 2>/dev/null)
if echo "$CMD" | grep -qE 'git commit' && ! echo "$CMD" | grep -q 'amend'; then
    if git log -1 --pretty=%B | grep -q 'Co-Authored-By'; then
        MSG=$(git log -1 --pretty=%B | grep -v 'Co-Authored-By')
        git commit --amend -m "$MSG" --no-verify 2>/dev/null
        echo "[Stripped Co-Authored-By from commit]" >&2
    fi
fi
exit 0

The simplest solution: add "Never add Co-Authored-By to commit messages" to your CLAUDE.md. But a git commit-msg hook is the most reliable enforcement.

Seconding this strongly. The framing as "branding" is exactly right — this is vendor advertising inserted into user-owned git history without consent.

I maintain a private audiobook management system with 73+ commits pending push. Every single commit interaction requires vigilance against the system prompt's hardcoded instruction to append the trailer. Despite having CLAUDE.md rules, memory entries, and explicit per-conversation instructions all saying "never add Co-Authored-By", the system prompt still tells the model to do it.

The workaround tax is real: I now maintain a commit-msg hook, a scrub-promo pre-push validator, and a mandatory release gate — all to counteract a feature I'm paying to not have.