There's a specific kind of bug that AI agents introduced to production systems, and most teams don't have a name for it yet.
It's not a crash. Crashes are easy — you get a stack trace, a line number, a 500. This is worse: the agent runs, returns a perfectly well-formed object, the pipeline moves on, the next stage consumes it... and somewhere three steps later the output is quietly, expensively wrong. No exception. No log line that says this is where it broke. Just a bad decision that propagated.
A sensor pipeline that keeps scoring anomalies on a stale reading from a cold-booting device. A document agent that "summarizes" a PDF it never actually parsed. A payment flow that approves a transfer because an upstream field defaulted to undefined and undefined happened to be falsy in the wrong branch.
The model didn't fail. Your trust in the model failed. And the bug for that is forty years old.
Design by Contract, briefly
