diff --git a/AGENTS.md b/AGENTS.md
index d330961793a..1b22e46a869 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -250,6 +250,7 @@ The proxy takes ~15-20 seconds to fully start (it runs Prisma migrations on boot
 
 See `CLAUDE.md` and the `Makefile` for standard commands. Key notes:
 
+- If `poetry install` fails with "pyproject.toml changed significantly since poetry.lock was last generated", run `poetry lock` first to regenerate the lock file.
 - `psycopg-binary` must be installed (`poetry run pip install psycopg-binary`) because the pytest-postgresql plugin requires it and the lock file only includes `psycopg` (no binary).
 - The `--timeout` pytest flag is NOT available; don't pass it.
 - Unit tests: `poetry run pytest tests/test_litellm/ -x -vv -n 4`