# Regression eval

An eval designed to protect a working AI feature against unintended change.

Classic software: a regression test, a deterministic check that known-good output stays the same.
AI: checking a working feature still performs as well after a change, including the vendor updating or retiring the model.
Regression eval: Example: a working chatbot whose tools or documents are rewritten to be more efficient; you need to confirm it works as well as before. Because the output isn't deterministic, exact-match tests aren't enough for the content, so you use eval machinery: a frozen test set, scored, with a threshold you don't drop below, run before and after.

Also called: Regression test

Kind of: Eval

Related: Verified test set, Reward hacking

Source: https://redfinchadvisory.com/lexicon/regression-eval (version 1.0, changed 2026-10-21)