[BUG] Claude Code intermittenly fails to include Co-Authored-By in git commit messages

[marcindulak]

Preflight Checklist

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

What's Wrong?

The commit messages often lack the expected Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com> attribution. This behaved erratically as early as in Jnauary 2026, or maybe eariler, but recently the attribution appears to be lacking more often.

What Should Happen?

All commit messages include the attribution.

Error Messages/Logs

No errors printed in the CLI.

Steps to Reproduce

See https://github.com/marcindulak/learning-api-styles-gen-ai-experiments/pull/45/commits.

All commits, except the earliest three and the lastest commit should have the defailt Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com> attribution added, but this is not the case.

This is the .claude/CLAUDE.md file used, and here is the prompt.

Here are the full project level .claude/settings.json

{
  "autoMemoryEnabled": false,
  "env": {
    "CLAUDE_BASH_MAINTAIN_PROJECT_WORKING_DIR": "1",
    "CLAUDE_CODE_DISABLE_AUTO_MEMORY": "1",
    "CLAUDE_CODE_DISABLE_FEEDBACK_SURVEY": "1",
    "CLAUDE_CODE_HIDE_ACCOUNT_INFO": 1,
    "DISABLE_AUTOUPDATER": "1",
    "DISABLE_ERROR_REPORTING": "1",
    "DISABLE_TELEMETRY": "1",
    "IS_DEMO": "1",
    "PIP_CACHE_DIR": ".cache/pip",
    "XDG_CACHE_HOME": ".cache",
    "npm_config_cache": ".cache/npm"
  },
  "model": "opus",
  "permissions": {
    "allow": [
      "Bash(behave *)",
      "Bash(cat *)",
      "Bash(docker *)",
      "Bash(find *)",
      "Bash(grep *)",
      "Bash(ls *)",
      "Bash(sort *)",
      "Bash(wc *)"
    ],
    "ask": [],
    "defaultMode": "default",
    "deny": [
      "Bash(git config *)",
      "Bash(git push *)",
      "Bash(sudo *)",
      "Edit(**/.gitconfig)",
      "Read(./.azure/**)",
      "Read(./.env)",
      "Read(./.terraform/**)",
      "Read(~/.aws/**)",
      "Read(~/.azure/**)",
      "Read(~/.config/gcloud/**)",
      "Read(~/.ssh/**)",
      "Read(~/.terraform.d/**)",
      "Write(**/.gitconfig)"
    ]
  },
  "sandbox": {
    "allowUnsandboxedCommands": false,
    "autoAllowBashIfSandboxed": true,
    "enabled": true,
    "network": {
      "allowAllUnixSockets": true,
      "allowLocalBinding": true
    }
  }
}

and here the user ~/.claude/settings.json

{
  "autoUpdatesChannel": "stable"
}

Claude Model

Opus

Is this a regression?

No, this never worked

Last Working Version

No response

Claude Code Version

2.1.126 (Claude Code)

Platform

Anthropic API

Operating System

Other Linux

Terminal/Shell

Other

Additional Information

See the screenshot below of the example commits that lack attribution.

[github-actions]

Found 3 possible duplicate issues:

1. Auto-mode safety classifier denies the Co-Authored-By trailer that the Bash tool's own system prompt instructs the model to add #53571
2. Content-integrity check non-deterministically blocks the system-prompt-prescribed Co-Authored-By line #56457
3. [Bug] Model classifier rejects claude-opus-4-7 as invalid model #51945

This issue will be automatically closed as a duplicate in 3 days.

• If your issue is a duplicate, please close it and 👍 the existing issue instead
• To prevent auto-closure, add a comment or 👎 this comment

🤖 Generated with Claude Code

[marcindulak]

The issues suggested as duplicate may be different because:

1. I see no errors related to Co-Authored-By, or maybe I don't know where to find them: grep -i "misleading|fabricated" -r ~/.claude/projects/ returns no hits .
2. The problem with missing attribution was present for a long time, and it was not limited to single model. See for example the missing attributions by sonnet-4-5 on 2026-03-08.