Anthropic launched Claude Fable 5 on June 9, its most powerful model ever made available to the general public. According to Anthropic's announcement, Fable 5 is a Mythos-class model — the highest capability tier — with state-of-the-art results across software engineering, vision, scientific research, and long-horizon tasks. Stripe, an early tester, reported using it to complete a codebase migration in a day that would have taken a full engineering team over two months by hand. Because Mythos-class models pose elevated cybersecurity and biology risks, Fable 5 ships with new safety classifiers that automatically route sensitive queries to Claude Opus 4.8 instead — a fallback that triggers in under 5% of sessions. A less-restricted version, Claude Mythos 5, remains limited to cybersecurity partners via Project Glasswing. Both models are priced at $10 per million input tokens.