GitHub Copilot: 247,000 https://github.com/search?q=is%3Apr+author%3Acopilot-swe-age... - is:pr author:copilot-swe-agent[bot]
Claude: 147,000 https://github.com/search?q=is%3Apr+in%3Abody+%28%22Generate... - is:pr in:body ("Generated with Claude Code" OR "Co-Authored-By: Claude" OR "Co-authored-by: Claude")
OpenAI Codex: ~2,000,000 (over-estimate, there's no obvious author reference here so this is just title or bid containing "codex"): https://github.com/search?q=is%3Apr+%28in%3Abody+OR+in%3Atit... - is:pr (in:body OR in:title) codex
Suggestions for improvements to this methodology are welcome!