tl;dr: Anthropic released Claude Fable 5.1 and Mythos 5.1, claiming state-of-the-art performance on coding, agentic, and scientific research benchmarks, with Mythos 5.1 restricted to vetted cybersecurity and life sciences users. Notable results include designing protein binders with ~50% hit rates, generating a higher-resolution Venus elevation map, and speeding up open-source bio ML models up to 2.5x. Pricing drops ~25% (up to 45% for agentic workloads) via 75%-cheaper cache reads, and a new Enterprise Frontier Safeguards system offers zero-data-retention privacy while keeping misuse protections.