The first three parts covered thesis, cost, and security. This one covers everything that separates a demo from a production system. None of it is exciting. All of it is why some teams sleep at night.
The production checklist
Trace everything. Langfuse, LangSmith, or OpenTelemetry; pick one and stick with it. When (not if) a workflow misbehaves in production, traces are the difference between debugging and staring into a black box.
Test like it's software, because it is. Unit tests, integration tests, CI. Accept a hard truth too: you will never reach full coverage of model behavior. That's why critical paths get verification loops and everything else gets user feedback loops.
LLMs are not calculators. Force them through tools for arithmetic, with strict JSON schemas on inputs and outputs. Validate at every boundary.
