Supervision is the unlock. The pattern that works best for us: every agent action goes through a lightweight policy check before execution. Not a second LLM call — that's too slow and too expensive. A set of deterministic rules that catch the obvious failure modes (wrong format, out-of-scope action, exceeding token budget). The LLM handles the creative reasoning, the supervisor handles the predictable constraints. Think of it as the same reason you don't let a junior dev push to production without CI/CD. The agent is the dev, the supervisor is the pipeline. This approach cut our agent error rate by roughly 60% without adding meaningful latency.