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

Anthropic released Claude Fable 5.1 and Claude Mythos 5.1, with Fable 5.1 scoring 52.6% on Terminal-Bench-Science 0.1 (up from 24.7% for Fable 5) and cutting cache reads by 75% to $0.25 per million tokens. Fable 5.1 is generally available on the Claude API, AWS, Google Cloud, and Microsoft Foundry, while Mythos 5.1 remains restricted to vetted organizations under Project Glasswing. The release includes a 1M token context window and three breaking API changes, including removal of forced tool use.

Anthropic has released Claude Fable 5.1 and Claude Mythos 5.1, the same model behind two different safeguard layers. Fable 5.1 is generally available on the Claude API, AWS, Google Cloud, and Microsoft Foundry; Mythos 5.1 remains restricted to vetted organizations under Project Glasswing. Fable 5.1 scores 52.6% on Terminal-Bench-Science 0.1 against 24.7% for Fable 5, ships a 1M token context window, and drops cache reads 75% to $0.25 per million tokens while base pricing holds at $10 and $50. Three API changes are breaking, including the removal of forced tool use. The post Anthropic Releases Claude Fable 5.1 and Claude Mythos 5.1: 52.6% on Terminal-Bench-Science and 75% Cheaper Cache Reads https://www.marktechpost.com/2026/09/01/anthropic-releases-claude-fable-5-1-and-claude-mythos-5-1-52-6-on-terminal-bench-science-and-75-cheaper-cache-reads/ appeared first on MarkTechPost https://www.marktechpost.com .