Anthropic brings Mythos to the masses with Claude Fable 5, its most powerful generally available model ever

Anthropic today launched two new AI models — Claude Fable 5 and Claude Mythos 5 — marking the company’s first broad release of the powerful “Mythos-class” AI capabilities it previously made available only to participating organizations in its restricted cybersecurity program, Project Glasswing, which it announced two months ago.The company says Fable 5, which is the version most users and developers will get starting today, exceeds every Claude model it has previously made generally available — featuring stronger performance across software engineering, knowledge work, vision, scientific research and long-running tasks. It smashes the existing benchmarks and comes atop on nearly all of them, though the prior Claude Mythos Preview version of the model still takes the top spots on computer use and multidisciplinary reasoning (see benchmark chart below and here). The new Claude Mythos 5, by contrast, is a more restricted, upgraded version of the prior, similarly restricted Mythos Preview model. As such, it has certain safeguards lifted for approved users, including Anthropic's cybersecurity partners in its Project Glasswing effort, and select biology researchers. The key difference is that the general purpose Fable 5 wraps the same underlying Mythos-class capability in new safeguards. Anthropic says requests involving certain high-risk areas — including cybersecurity, biology and chemistry, and model distillation — are automatically routed to Claude Opus 4.8, Anthropic's previously flagship general model, instead, with users notified when that happens. The company says more than 95% of Fable sessions run entirely on Fable’s own responses, with no fallback, and that internal and external red-teaming efforts found no “universal jailbreaks” after more than 1,000 hours of testing.Anthropic says Fable 5 is available to the general public today through its website, apps, and API, but that Mythos 5 will initially only be made available to users who already have acce