Model demos are easy. Operational AI is harder because behavior drifts, inputs change, and the cost of a wrong answer is rarely zero.
Evaluation harnesses—fixed cases, scoring criteria, regression suites, and sampling of live traffic—are how you know whether a change improved the system.
We design AI features the same way we design other critical paths: with observability, fallbacks, and a human path when confidence is low. The model is a component. The system includes everything around it.