Repos split on AI co-author trailers in commits

A study of the 10,000 most-starred repos found a split: about 400 tell coding agents not to add Co-Authored-By, while roughly 330 ask for an Assisted-by line or an AI co-author trailer. Two-thirds of the rules sit in CLAUDE.md and AGENTS.md, which load in every session.

• 465 repos ban AI co-author trailers, 283 without naming a specific agent
• 137 repos require Assisted-by, and 30 more use it instead of Co-Authored-By
• Repos with such a rule have a median of 4 instruction files vs 2 overall
• Claude Code and Cursor add the trailer by default; a setting turns it off