Practitioner: No serious lab actually trains on the test set today

nrehiew_ · x · 2026-10-29

The author argues that among today's serious players (frontier labs), virtually no one literally trains on the test set. Benchmark performance mainly indicates whether a model was post-trained for the specific capability the benchmark measures.

He adds that training on test was more common in the past, especially for papers—since nobody actually used those models, benchmarks were the only evaluation. Today the cost/benefit of a good or bad model is too high, so no lab would release a model trained on test just to make the model card look good.

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