Claude Fable 5

Claude Fable 5 is a Mythos-class model developed by Anthropic and made generally available on 9 June 2026. According to the company its capabilities exceed those of any model Anthropic had previously released for general use, reaching state of the art on nearly all tested benchmarks, including software engineering, knowledge work, vision and scientific research. The model's lead grows with the length and complexity of the task.

Fable 5 shares the same underlying model as Claude Mythos 5, the difference being its safeguards. When safety classifiers detect a request related to cybersecurity, biology and chemistry, or distillation, the response is handled by Claude Opus 4.8 instead. Anthropic reports that more than 95% of sessions involve no fallback. The model is available through the Claude API as claude-fable-5 at 10 USD per million input tokens and 50 USD per million output tokens.