diff --git a/CLAUDE.md b/CLAUDE.md
index 8231f06dc..127309ee6 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -97,6 +97,7 @@ Key rules:
 - **All flags must be explicit** — omitting `--login` or `--repo` triggers interactive prompts that crash in Claude Code (no TTY)
 - **Use `--output simple`** for machine-readable output (no table borders)
 - **`tea pr reject` does not work on your own PRs** — use `tea comment` instead
+- **Never delete protected branches:** `main`, `maintenance`, `server`, `client` are protected on Gitea. Do not use `tea pr clean`, `git push --delete`, or `git branch -D` on these branches.
 
 ### File conventions
 - Decisions: domain files in `decisions/` (see `decisions/README.md` for index)