The reusable worker loop a served agent runs. serve_queue claims from a TaskQueue, dispatches by operation to a handler, and completes each task (idempotent, lease-safe; a raising handler reports the exception type only). run_worker is the same loop over an A2A Worker. Both take stop / max_idle_rounds (serve-forever or drain-and-return), an injectable sleep, and a heartbeat hook (wire announce for a live-roster seat). hallpass runs no model loop of its own by design; the handler is where a model or tool call goes, acting with the agent's scoped token. Demo: examples/reference_agent.py. Additive; 320 tests, mypy --strict, ruff, catalog freshness green.