AI Agent Circuit Breakers: The Reliability Pattern Production Teams Are Missing

On April 29, 2026, a developer published a detailed post-mortem of how they woke up to a $437 API bill. Their agent — a nightly pipeline built to summarize and categorize documents — had entered a retry loop around 11 PM and never stopped. By 7 AM, it had made thousands of identical tool calls, all failing, all billing. The fix took twenty minutes. The loop had run for eight hours. No alert fired. No threshold tripped. Nothing stopped it. This scenario is becoming a reliable rite of passage for