Anthropic released Claude Fable 5.1, plus Mythos 5.1 for cyber defenders and life scientists. Fable 5.1 scores 55.8% on Terminal-Bench 4.0 versus 42.0% for Fable 5, more than doubles Terminal-Bench-Science to 52.6%, and is Cursor’s strongest CursorBench 3.2 result at 73.4% max effort. Cache reads are 75% cheaper, cutting typical costs about 25% and highly agentic workloads up to 45%.

Key Takeaways

  • ✓Fable 5.1 is available everywhere today as Anthropic’s most advanced coding and knowledge-work model
  • ✓It sets a new bar on Terminal-Bench 4.0 (55.8%) and more than doubles science-terminal scores
  • ✓Mythos 5.1 ships via trusted access; Enterprise Frontier Safeguards roll out in phases this fall
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Key Decision Metrics at a Glance

TL;DR Verdict
🏆 Benchmark RankRank
It sets a new bar on Terminal-Bench 4.0 (55.8%) and more than doubles science-terminal scores
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💰 Cost & PlansCompare
Claude Fable 5.1 · in: $10 / out: $50
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🛠️ Ecosystem & IDERules
AI · LLM · Coding
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