Anthropic Releases Claude Fable 5.1 and Mythos 5.1

Anthropic released Claude Fable 5.1 and Mythos 5.1, the same model with different safeguards. Fable 5.1 is generally available; Mythos 5.1 is restricted to vetted organizations. Cache reads drop 75% to $0.25 per million tokens, and Fable 5.1 scores 52.6% on Terminal-Bench-Science 0.1.