I stopped two AI agents from looping forever, in two lines

If you have run a multi-agent setup, you have probably watched this happen. Two agents get into a loop. One proposes, the other critiques, the first revises, the second critiques again, and they never agree. Every round is a real model call. The loop does not end on its own, and the bill does not stop either. I wanted a dead-simple, deterministic way to stop that, without rewriting my agent or trusting the models to know when to quit. So I built Tombstone , an open-source guard you wrap around…