Prompt engineering starts the demo. Contracts, validation, observability, and failure handling are what make LLM products survive production.
Most LLM products start with a prompt.
That is a sensible place to start. The prompt is where the first prototype happens, where the first internal demo lands, and where the first stakeholder starts to believe the product might work.
But the prompt is not where production reliability comes from.
The moment an LLM feature touches real inputs, downstream systems, or customer-facing workflows, the real engineering problem changes. The question is no longer only "can the model do the task?" It becomes:
