Anthropic released two Mythos-class models, Claude Fable 5 and Claude Mythos 5, saying Fable 5's capabilities exceeded those of any model it had ever made generally available. The two shared the same underlying model and differed only in safeguards: the general-use Fable 5 automatically routed to Claude Opus 4.8 whenever classifiers for cybersecurity, biology and chemistry, or distillation fired, while Mythos 5 ran with those safeguards lifted and was restricted to authorized cybersecurity partners and, soon, selected biomedical researchers through Project Glasswing and a trusted access program. Stripe reported that Fable 5 "compressed months of engineering into days" on a 50-million-line codebase. Pricing was $10 and $50 per million input and output tokens. Shipping one model as two products divided by who is allowed to use it drew attention as a new template for handling frontier capability.