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

Anthropic has released two new models — Claude Fable 5.1 and Claude Mythos 5.1 — as incremental updates to its Claude 5 family. The flagship result is 52.6% on Terminal-Bench-Science, a rigorous coding and scientific reasoning benchmark, while cache read pricing has been cut by 75%, meaningfully lowering costs for applications that rely heavily on prompt caching. These updates matter for developers running high-throughput inference workloads, as the cache pricing drop directly reduces operational costs for production deployments. The benchmark improvements signal stronger performance on multi-step technical reasoning tasks, making these models more competitive for agentic coding and scientific workflows. Developers using the Anthropic API should review updated pricing tiers and benchmark comparisons to decide whether to migrate from earlier Claude 5 versions.