Remove/allow disabling the forced "Co-Authored-By: Claude" trailer on git commits

Preflight Checklist

• [x] I have searched existing issues for similar behavior reports
• [x] This report does NOT contain sensitive information (API keys, passwords, etc.)

Type of Behavior Issue

Claude modified files I didn't ask it to modify

What You Asked Claude to Do

The built-in git-commit workflow instructs Claude Code to always append a Co-Authored-By: Claude <noreply@anthropic.com> trailer to every commit it creates, with no way to opt out via configuration.

This is a problem because:

Commit messages in a private/internal repo are not something a third-party default should silently modify without the user opting in.
Telling Claude in-session not to add it only works until the instruction is forgotten or re-derives from the base system prompt in a later session — it's not persistent, because the instruction lives outside the user's editable context (CLAUDE.md, settings, etc.).
There's currently no supported settings.json / CLAUDE.md flag to disable this trailer permanently.
Requested fix: add a setting (e.g. in settings.json, or a CLAUDE.md directive) that disables the Co-Authored-By trailer, honored by the built-in commit workflow, so users don't have to re-instruct the agent every session.

What Claude Actually Did

It adds " Co-Authored-By: Claude <noreply@anthropic.com> trailer " I notes it later and wa sdiappinbted sinc enow it is hard to eliminate now

Expected Behavior

NO extra , not related to my porject stuff

Files Affected

ALL FILES

Permission Mode

Accept Edits was ON (auto-accepting changes)

Can You Reproduce This?

Yes, every time with the same prompt

Steps to Reproduce

_No response_

Claude Model

Sonnet

Relevant Conversation

Impact

Critical - Data loss or corrupted project

Claude Code Version

sonnet 5

Platform

Anthropic API

Additional Context

_No response_