How to Debug AI-Generated Code — 3 Production Failure Patterns

I built a full inventory module with Cursor. looked clean, client approved it. Then it started creating duplicate records on every save. Root cause: the AI correctly wrote the upsert call, but never persisted the record UUID back to state. Every save treated the form as a new record. After debugging multiple of these in production ERP and CRM work, I've found AI-generated code breaks in three predictable patterns - and each has a different debugging approach. Pattern 1: Structural violations AI puts logic in the wrong place. Functions in the parent component that should be in a helper file.