On Tuesday, Anthropic unveiled two new AI models: Claude Fable 5 for the general public and Claude Mythos 5 for a restricted circle of trusted partners. Both models are built on the same technical foundation but differ significantly in their usage restrictions. Fable 5 is the deliberately limited, “safe” variant of the Mythos model, which Anthropic had made accessible only in a limited capacity since April 2026. Background: Why Mythos Remained Under Wraps for So Long Back in April 2026,