Claude Fable 5.2 Lands: 1,000 Agents Formalized Fermat’s Last Theorem in 30 Hours

Anthropic released Claude Fable 5.2 and Claude Mythos 5.2 on Monday, and the headline number is not a benchmark — it is 1,000 agents with nobody directing them formally proving Fermat’s Last Theorem in about 30 hours. The model also built a working operating system from an empty folder, and it got 30 percent faster and 20 percent cheaper than the model it replaces. All of it landed this morning, hours after most of the AI news cycle had already filed its stories. Fable and Mythos are the same model Start with the structure, because it confuses people. Fable and Mythos are the same underlying model. The difference is safeguards. Mythos has the cyber and biology capabilities unlocked; Fable carries the restrictions, which is why Anthropic can offer it to everyone. Researchers who need the raw capability apply through Anthropic’s Cyber and Life Sciences Verification Programs. Both now generate output up to 30 percent faster than Fable 5.1 and Mythos 5.1, and the price came down.

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