Harness learning: a 4B model trained to rewrite agent code beat its 35B teacher on average
A 4B-parameter model trained to rewrite an agent's code beat its 35B teacher on average (0.62 vs 0.56) on 21 unseen puzzle families, per a 28 September 2026 arXiv preprint. A fixed hand-built harness still averaged 0.69, and the commercial tools found so far tune prompt text only.
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