Topic summary
Claude Fable
Extracted from the Wikipedia article Claude Mythos.
In June 2026, Anthropic publicly released Claude Fable 5, a "Mythos-class" model made available for general use with a set of safeguards, alongside Claude Mythos 5, a restricted-access version of the same underlying model with those safeguards lifted in some areas. According to Anthropic, the two models are identical apart from their safeguards; when Fable 5's classifiers flag a request relating to cybersecurity, biology and chemistry, or model distillation, the response is instead handled by the less capable Claude Opus. Mythos 5.1 and Fable 5.1 were released in September 2026.