diff --git a/AGENTS.md b/AGENTS.md
index ffe3a1f..1b899b8 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -16,6 +16,9 @@ This is the **project-orchestrator (PO)** repo. See `README.md` for what the PO
 
 - **Always commit and push** every change to this repo (`git add -A && git commit && git push
   origin main`) — including memory updates. Don't wait to be asked.
+- **No co-author / session trailers in commit messages.** Do not append `Co-Authored-By:` or
+  `Claude-Session:` (or any similar agent-attribution) lines to commits — here or in any other repo
+  worked on from this environment. Keep commit messages clean.
 - Git identity is set locally on this repo (`mfowler.email@protonmail.com` / `mfowler`); it was not
   configured globally in this environment.
 - Push credentials for `git.autonomic.zone` come from the active cc-ci project