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Anthropic · model release

Claude Fable 5.1 and Mythos 5.1

Anthropic updates Fable to 5.1, a stronger and cheaper top model, with Mythos 5.1 for vetted users.

In detail

Anthropic released Claude Fable 5.1, generally available, and Claude Mythos 5.1, the same model with different safeguards, available only through trusted access programmes. It estimated Fable 5.1 would cost about 25% less than Fable 5 for typical workloads.

Sources

  1. Introducing Claude Fable 5.1 and Claude Mythos 5.1 · Anthropic · Primary source
  2. Claude Developer Platform release notes · Anthropic · Primary source

Last checked 11 November 2026.

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