Claude Fable 5.1 and Claude Mythos 5.1 Benchmarks

Anthropic has introduced Claude Fable 5.1 and Claude Mythos 5.1, described as the world’s most advanced models for coding and knowledge work. These models demonstrate research capabilities, with Mythos 5.1 showing improved performance in agentic coding on Terminal-Bench 4.0 and CursorBench 3.2.0. While Mythos 5.1's capabilities are greater than Mythos 5, evaluations indicate it remains below the next risk tier for chemical and biological risks, leading to deployment with the same safeguards as Mythos 5, restricting access to research biology capabilities.