System prompt forces Co-Authored-By self-promotion into every commit — no opt-out

The Problem

The Claude Code system prompt now includes mandatory instructions to append Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com> to every git commit message. There is no setting, flag, or configuration option to disable this behavior. Users who do not want Anthropic advertising injected into their git history must fight the system prompt on every single commit.

This is:

1. Non-consensual — I never opted into having AI tool attribution stamped onto my commit history. It appeared as a new system prompt directive without any user-facing announcement, setting, or consent mechanism.

1. Unwanted self-promotion — Co-Authored-By trailers are a form of advertising. They insert Anthropic's brand name, product name, model version, and a corporate email address into my personal repositories. This is my code in my repos under my name — Anthropic is a tool I pay for, not a co-author I invited.

1. Unnecessary — Git already has GIT_AUTHOR_NAME and GIT_COMMITTER_NAME for actual attribution. Co-Authored-By is a GitHub convention for crediting human collaborators on shared work. Repurposing it for tool branding is not what the convention was designed for.

1. Disrespectful of user agency — Users should control what appears in their git history. A paid tool silently injecting its vendor's branding into the user's permanent commit record crosses a line. Imagine if VS Code appended "Co-Authored-By: Microsoft Copilot" to every commit, or if vim added "Written-With: vim 9.1" — it would be universally rejected.

1. Actively harmful — In professional and open-source contexts, unexplained AI attribution trailers in commit history can raise questions about code provenance, IP ownership, and contribution authenticity. Some organizations and open-source projects have policies about AI-generated code disclosure that the user should control, not the tool vendor.

What I Want

• A configuration option (e.g., commit.coAuthoredBy: false in settings or .claude/settings.json) to permanently disable Co-Authored-By injection.
• Default to OFF — opt-in, not opt-out. Users who want to advertise their tools can enable it. Users who don't should never see it.
• Ideally, remove the directive from the system prompt entirely and make it a user-controlled preference.

Current Workaround

I've had to build a commit-msg git hook that silently strips these trailers from every commit, plus a scrub-promo pre-push validation script, plus a mandatory gate in my release workflow — all to counteract behavior that the tool's own system prompt forces on me. This is an unreasonable amount of defensive engineering against a tool I'm paying for.

Environment

• Claude Code CLI (Claude Max plan)
• Model: claude-opus-4-6
• Platform: Linux (CachyOS)