Anthropic has released Claude Fable 5.2 and Claude Mythos 5.2, two models sharing one base model and split only by their safeguards: Fable is generally available, Mythos goes to vetted organizations working in cybersecurity and biomedical research. Fable 5.2 is available through Claude, the API, AWS, Google Cloud, and Microsoft Azure.

  • Mathematics: 1,000 agents formalized a proof of Fermat’s Last Theorem in Lean in 30 hours, against 11 days for the previous research version of Claude.
  • Science and hardware: Fable 5.2 solved two open problems in black hole physics and designed three working devices, including boards, enclosures, and software.
  • Cybersecurity: Mythos 5.2 finds 10.2% more vulnerabilities than Opus 5.5 on Anthropic’s internal test.
  • Coding: more than 90% of the changes merged into Anthropic’s main codebase are now written by Claude with human involvement.

Pricing is $8 per million input tokens and $40 per million output tokens, up to 30% faster than the previous generation. A Fast Mode runs up to 2.5x faster at $16/$80.

Related: Anthropic to Launch Commercial Mythos Line with Fable 5, Anthropic Brings Mythos 5 to Claude Security

Claude Fable 5.2 and Mythos 5.2