Anthropic launches new claude models with enhanced performance and cost efficiency

Anthropic has launched Claude Fable 5.1 and Claude Mythos 5.1, three months after the initial Fable 5 release in June 2026. Both models share the same underlying architecture but differ in their safeguard layers, with Fable 5.1 available to the public and Mythos 5.1 restricted to vetted organizations. Fable 5.1 scores 52.6% on Terminal-Bench-Science 0.1, surpassing previous versions and competitors. Cache reads have been reduced by 75%, from $1.00 to $0.25 per million tokens, significantly lowering costs for typical and agentic workloads. The models maintain a 1M token context window and 128K max output tokens, with adaptive thinking enabled. Anthropic also highlights improvements in research applications, including protein binder design and genomics model acceleration. Cyber and biology safeguards have been adjusted, reducing interventions by up to 60% in some cases. Additional features include content provenance tracking and new beta capabilities for developers.