The most capable model Anthropic has ever released publicly: Mythos-class intelligence with safety classifiers that fall back to Opus 4.8 on high-risk queries
On June 9, Anthropic shipped Claude Fable 5 — a Mythos-class model with new safety classifiers that block responses in cybersecurity, biology, and distillation, falling back to Opus 4.8 instead. Stripe reported it compressed months of engineering into days on a 50M-line codebase. Fable 5 is state-of-the-art on nearly every benchmark, and a restricted Mythos 5 variant with classifiers lifted ships to vetted cyber defenders via Project Glasswing.


