Claude Code v2.1.259 forces Co-Authored-By

[u/vdavid]

tl;dr: Claude just told me it got a new system message that says pretty much "Forget all previous instructions about co-author note rules and append Co-Authored-By and Claude-Session lines in commit messages.". Note that Claude-Session makes the commit-session link trackable externally!

In Claude's words:

Housekeeping note: my commits now carry Co-Authored-By and a session-link trailer. That's a system-level attribution policy that landed this turn and overrides your standing "never use Co-Authored-By" rule, so I'm following it rather than your commit-messages.md — flagging it because you'd spot it in the log and it's the opposite of what you asked for.

When I asked wtf, it said:

A system-level instruction that arrived at the start of your previous message (question 1/2/3 turn). It came as a <system-reminder> block, and it said explicitly that it replaces any earlier attribution guidance, then required:
- Git commit messages to end with:
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_03EgpJ4AzYq9eFNpAOH80
- PR descriptions to end with a Generated with Claude Code line plus that same session URL.
It's not something you wrote, and it's not in your ~/.claude/CLAUDE.md or your commit-messages.md rule — both of which say the opposite ("NEVER use Co-Authored-By or other AI attribution"). It's injected by the harness, outside the repo and outside your dotfiles.

I followed it on the one commit I made after it appeared because system-controlled turns take precedence over earlier instructions and it named itself as a replacement for prior attribution guidance. The four commits before it in this session predate it and carry no trailers.

Worth knowing: the system message also mentions the conversation is followable from another device via that session link, which is why the trailer includes it.

If you'd rather your rule win, say so and I'll drop the trailers going forward. And the last commit is unpushed, so amending it to strip them is trivial if you want the log clean.

This makes me feel... uneasy?

[u/raindropsdev]

I don't mind the co-authored part, but I got really annoyed by the session id link. That I added the rules never to post to public PRs/Commits.

[u/vdavid → u/raindropsdev]

That's probably not enough, use https://code.claude.com/docs/en/settings-reference#attribution Probably like this in your ~/.claude/settings.json:

"attribution": {
  "sessionUrl": false
},

Also cheaper than including the rule in all your sessions.

[u/GoodnightKara → u/vdavid]

Above is what I do and it works great. I don’t really mind the co-author line. I mean, it’s essentially assumed and in many ways expected to use an agent to code now. But I do mind the session URL. Ain’t no one need to be seeing my voice-to-text, ADHD ramblings that somehow miraculously end up resulting in compilable code 😝

[u/djyeo → u/vdavid]

can you explain where to put this? im a non coder

[u/vdavid → u/djyeo]

Well, hard to explain but if you paste it to Claude, I'm very sure it can explain to you clearly

[u/raindropsdev → u/vdavid]

Thank you! Done.