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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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Production6 min readFirst readFine-Tuning Data Preparation

After this section you can

  • Baseline before training so an improvement claim means something
  • Pick the metric a given task type cannot game
  • Build a regression suite that catches catastrophic forgetting before a canary does
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Fine-Tuning Evaluation & Validation

No eval, no fine-tune. The evaluation pipeline from frozen test set to canary rollout, metrics by task type, catastrophic-forgetting checks, and LLM-as-judge done properly.

THE CENTRAL IDEA

“The fine-tuned model feels better” is not a result — it is the placebo effect with a GPU bill. The eval suite is built before training, the ship gates are written down before results exist, and the test set is frozen so nobody — human or training script — can overfit to it. Evaluation is not the last step of fine-tuning; it is the frame the entire project hangs on. Teams that skip it don’t find out the fine-tune failed — their customers do.

The evaluation pipeline — three measurements, one gate, then the real world
Frozen test set held out before training touched once per candidate Task metrics F1 · exact match · pass rate LLM-as-judge vs base & frontier, pairwise Regression suite MMLU · GSM8K · safety Ship gate thresholds set before training Canary 5% online judge on samples · SLOs Full rollout monitor drift · keep rollback pass Back to data fix examples, retrain fail

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