Error-Handling

A single agent error rarely stays a single error. The bad output goes into the context, the next step reasons on top of it, and the mistake compounds down the trajectory — one wrong step becoming N wrong steps. This is the cascade, why it’s structurally different from a fleet-wide blast radius, and the three interruption points that stop a local mistake from eating the whole run.

An agent burned ~$200 overnight retrying an HTTP 400 — a request that was defined to fail. No component was buggy; each layer retried “reasonably.” The teardown: why retryability is a property of the error and not a default, how three nested retry caps multiply into 75 doomed attempts per item, and why per-step caps never bound a bill. With the two-line fix and a circuit breaker.