Evaluation (Evals)
Also called: evals
Systematic measurement of whether an AI system does what you need — your tests, not the vendor's.
Evals are the automated test suite for probabilistic software: a fixed set of cases with expected outcomes, run on every change. They are the only way to know whether a prompt tweak or model upgrade helped or quietly broke something. Public benchmarks tell you about the model; evals tell you about your system.
In practice: 200 real tickets with correct answers, run against every prompt change.