Anthropic launched Claude Fable 5.1 and the restricted Mythos 5.1, calling them the world's most advanced models for coding and knowledge work. Fable 5.1 scores 55.8% on Terminal-Bench 4.0 (vs. 42.0% for Fable 5) and more than doubles Fable 5 on Terminal-Bench-Science 0.1 at 52.6%. Cache reads are 75% cheaper, cutting typical cost about 25% and highly agentic workloads by up to 45%. It is already live in Cursor (73.4% on CursorBench 3.2) and GitHub Copilot.

Key Takeaways

  • ✓Fable 5.1 is built for long-running coding, deep codebase research, and complex agentic workflows, with fewer false refusals
  • ✓Cheaper cache reads cut agentic cost by up to 45%, and lower-effort settings can match prior peak quality
  • ✓Mythos 5.1 is trusted-access only, paired with Enterprise Frontier Safeguards for ZDR-plus monitoring
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Up NextClaude Fable 5.1 and Mythos 5.1 Launch for Coding and Knowledge Work
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