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Evals
A repeatable way to turn model behavior into evidence.
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An eval is a repeatable test that turns model behavior into evidence instead of vibes.
What it means
An eval combines examples, expected behavior, rubrics, and scoring so teams can compare prompts, models, routes, or training runs.
Why product teams care
Without evals, teams chase impressive demos. With evals, they can decide whether a change improves common cases, hard cases, and business-critical failures.
Understudy angle
Understudy uses evals to decide whether prompt changes, structured outputs, model routing, or training actually improve a workflow.
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An eval is the contract for what better means.
Write five passing examples and five failing examples for one task.