Retry storms turned 1 timeout into 340 duplicate calls billed in 90 seconds
Infinite tool loop ran 1,200 iterations before I noticed at 2am
Partial stream cleanup stopped half-written DB writes corrupting records
Trap every error class with a circuit breaker and a hard iteration cap
Five Claude API errors quietly drained my account before I built guards around them. None of them threw a loud crash. They just kept billing while I slept. Here is exactly what broke, what it cost, and the traps I now run on every project.
