Anthropic introduced Claude Fable 5.1 and restricted-access Mythos 5.1, calling them the world’s most advanced models for coding and knowledge work. Fable 5.1 more than doubles Fable 5 on a science terminal benchmark, cuts cache-read cost by 75%, and is already live in GitHub Copilot and Cursor.

Key Takeaways

  • ✓Scores 52.6% on Terminal-Bench-Science 0.1 (more than double Fable 5) and 55.8% on Terminal-Bench 4.0 versus 42.0%
  • ✓Cache reads are 75% cheaper, cutting typical cost ~25% and highly agentic workloads up to 45%
  • ✓Fable 5.1 is generally available today; Mythos 5.1 is trusted-access only, with Enterprise Frontier Safeguards rolling out this fall
ADSponsored