FrontierSWE v2: 20-hour autonomous tasks, Fable 5.1 best model by 24+ points
nrehiew_ · x · 2026-09-03
nrehiew released FrontierSWE v2, evaluating models on extremely difficult, extremely long-horizon tasks where models work autonomously for up to 20 hours. Fable 5.1 emerged as the best available model by over 24 percentage points. A follow-up notes thread covers lessons on squeezing performance from models on super-long tasks, including the custom Proximus harness, a time-budget-reminding submit tool, and reward-hacking safeguards.
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