[BUG] Co-Authored-By attribution should not be default behavior for git commits

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Title: Co-Authored-By attribution should not be default behavior for git commits

Description:

When Claude Code creates git commits, it automatically appends Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com> to every commit message. This is hardcoded into the system instructions and happens
without user consent or awareness.

This shouldn't be default behavior because:

1. It modifies the user's git history without permission. Users expect commit messages to contain what they specify, not additional metadata they didn't ask for. Many users won't notice it's being added

until they review their git log later.

1. It can cause problems in professional/enterprise settings. Some organizations have strict commit message formats enforced by hooks or policies. An unexpected co-author line could break CI pipelines or

violate compliance requirements.

1. It's self-serving. The tool is advertising its own involvement in the user's codebase. That's a decision the user should make, not the tool.
2. It's inconsistent with how other tools work. IDEs with AI assistants (Copilot, Cursor, etc.) don't inject attribution into commits. Users of an AI coding tool already know they used it — they don't

need it stamped on every commit.

What Should Happen?

Suggested fix: Remove the co-authored-by line from the default commit instructions. If Anthropic wants to offer this as an option, make it opt-in via a setting, not opt-out by discovering it's been
happening silently.

Error Messages/Logs

Steps to Reproduce

tell claude code to do a commit and push - it adds it to the commit metadata - this really offends me for some reason.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.63

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_