Anthropic launches Claude Fable 5.2

Anthropic launched Claude Fable 5.2 on 9 November and announced Claude Mythos 5.2, which will initially be available only to vetted organizations. The releases follow Fable 5.1 and Mythos 5.1, which came out in September 2026.

Anthropic says both new models improve on their respective predecessors in coding, reasoning and vision, and generate responses faster. The company also says Fable 5.2 can handle difficult software engineering problems and long-running projects, including by coordinating teams of software agents that carry out tasks. The Verge covered the announcement.

What Anthropic says the models did

In prerelease testing, Anthropic says, the models helped its engineers complete software migrations the company described as otherwise infeasible. It also says the models designed 3 working electronic devices from scratch, solved 2 open problems in black-hole physics and made substantial progress on robotics evaluations.

Anthropic says the models also formalized the proof of Fermat’s Last Theorem in 30 hours, expressing the proof in a formal language.