Anthropic Launches Claude Fable 5.1 and Claude Mythos 5.1
Mythos 5.1 is the version of Anthropic’s newest frontier model that almost nobody is allowed to use. In September 2026 the company announced Claude Fable 5.1 and Claude Mythos 5.1 together, and it is unusually direct about what separates them: nothing at all, except the safeguards wrapped around the weights. Fable 5.1 is generally available. […]