Anthropic Releases Claude Fable 5.1 and Claude Mythos 5.1: 52.6% on Terminal-Bench-Science and 75% Cheaper Cache Reads

Anthropic has launched Claude Fable 5.1 and Claude Mythos 5.1, utilizing the same underlying model for agentic work. Fable 5.1 is available via Claude API, AWS, Google Cloud, and Microsoft Foundry, while Mythos 5.1 is restricted to Project Glasswing. Fable 5.1 achieves 52.6% on Terminal-Bench-Science 0.1 and features a 1M token context window. Notably, cache read costs dropped 75% to $0.25 per million tokens, alongside the introduction of Enterprise Frontier Safeguards for enhanced data control.