Anthropic Launches Claude Fable 5.1 with Significant Benchmark Improvements

Anthropic released Claude Fable 5.1 and Claude Mythos 5.1 on September 1, marking the first update to the series since Fable 5. The new models are designed for programming and knowledge-based tasks. Fable 5.1 achieved a 52.6% pass rate on the Terminal-Bench-Science 0.1 benchmark, more than doubling the 24.7% score of its predecessor. While Fable 5.1 is available to all Claude users, Mythos 5.1 remains restricted to professionals verified through Anthropic's cybersecurity and life sciences programs. Pricing for Fable 5.1 is set at $10 per million input token