Claude Opus 4.6 can work for twelve hours. It can work reliably for seventy minutes. Mythos and likely Fable 5 can work for 16 hours at 50% correctness and 2-3 hours at 80%. Both numbers describe the same model doing the same kind of work, measured by the same organization. The gap between them is ...

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Link :
https://www.nextbigfuture.com/2026/08/twelve-hours-of-ai-work-seventy-minutes-you-can-trust.html