Definition
Plain language
A separate model or program that grades whether an answer is correct.
As stated in the literature
A model or deterministic checker that scores candidate outputs, used to provide reward signals or filter rollouts in training and evaluation.
Also called: verifiers
Why it matters: Verifiers are how systems turn a noisy generator into a reliable end-to-end pipeline, and a strong verifier often matters more than a stronger generator.
For example, a code generator might produce 10 candidate solutions and a verifier runs each against the test suite to pick the one that passes.
Heard on the show
“Human labels get expensive fast, automatic verifiers only exist for things like math and code, and renting a frontier model as a teacher costs real money.”Episode 242 — Making a Vision Model Better by Showing It Blurry Images