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Fine-Tuning Evaluation & Validation

How to evaluate fine-tuned models — metrics by task type, regression testing, and the complete evaluation pipeline.

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Production9 min readFirst readThe Eval StackFine-Tuning Data Preparation

After this section you can

  • Score the right baselines before training so an improvement claim means something
  • Pick the metric per task type and judge a fine-tune pairwise against its baseline
  • Build ship gates, a forgetting regression suite and a canary for a fine-tuned model
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Fine-Tuning Evaluation & Validation

A fine-tune is only better than something you measured first. Baselines, a metric per task type, a judge used properly, a regression suite for forgetting, and a canary before full traffic.

Key idea

Build the eval before you train. Score the best prompted baseline on a frozen test set, write the ship gates down, and let the candidate pass them on its task and on everything it might have forgotten. Then canary it, because production traffic always holds surprises.

The evaluation frame: baselines first, gates before shipping, canary before everyone
BUILT BEFORE TRAINING · RUN ON EVERY CANDIDATE 1 · Baselines best prompt · large model current system 2 · Train validation split picks the checkpoint 3 · Ship gates task metric · judge regression suite 4 · Canary small traffic share auto-rollback 5 · Rollout watch drift, keep rollback pass Fail: back to the data fix examples, rebalance, retrain Gates and thresholds are written down before the first run, so results cannot move the goalposts.

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