Anthropic Debuts Claude Fable 5.1 and Mythos 5.1 With Split Safeguards

Anthropic announced Claude Fable 5.1 and Claude Mythos 5.1 on September 1, 2026. The two releases are configurations of the same underlying model with different levels of safeguards: Fable 5.1 is generally available, while Mythos 5.1 is restricted to Anthropic's trusted access programs, with safeguards designed to support work in cybersecurity and the life sciences. Anthropic described the pair as its most advanced models for coding and knowledge work, and said their research capabilities offer…