Fable 5 is Anthropic's most advanced AI model, launched in June 2026 as their first "Mythos-class" model made available to the public.

It outperforms every previous Claude model on nearly all benchmarks, with exceptional capabilities in software engineering, scientific research, and complex reasoning tasks. The longer and more complex your task, the bigger the gap between Fable 5 and other models.

Builders use it through Claude.ai or the API for tasks like multi-file code refactoring, deep research synthesis, and analyzing complex documents. Some queries trigger conservative safeguards and fall back to Claude Opus 4.8, but this happens in less than 5% of sessions.

Pricing is $10 per million input tokens and $50 per million output tokens. There's also a more powerful version called Claude Mythos 5 with fewer restrictions, currently available only to select cyberdefenders and infrastructure providers.