DarwinX Evolves the Harness Instead of the Weights: +7.7 Points on Terminal-Bench 2.1 to 83.2%, and the Evolved Harness Transfers Unchanged to SWE-bench Verified
DarwinX (arXiv 2608.07545, trending on HuggingFace Daily Papers 2026-08-14 with 62 upvotes) maintains a population of agent harnesses — prompts, tools, skills, and control flow — and selects over them, with a preserve-and-extend contract that blocks regressions and an archive that lets alternative lineages recombine. Reported results: Terminal-Bench 2.1 up 7.7 points to 83.2% (84.7% on a stronger base model), 68.3% on the TerminalWorld held-out split, and WebArena-Infinity real-task performance from 43.5% to 93.0% audit-clean. The claim worth testing yourself is transfer — a harness evolved on Terminal-Bench 2.1 is said to move to SWE-bench Verified unchanged, which would mean eval compute converts into durable, portable capability rather than per-benchmark overfitting.
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