Claude Mythos 5.1

Claude Mythos 5.1 is Anthropic's trusted-access deployment of the Claude Fable 5.1 weights (cataloged publicly as Fable 5.1). It is targeted for demanding reasoning and long-horizon agentic work with text and image input, tool use, multilingual support, and a 1M-token context window. Benchmarks below are sourced from Anthropic's official Claude Fable/Mythos 5.1 scorecard. It is not generally available via the public Claude API as a cataloged model id.