Anthropic Releases Fable 5.1 with Massive Gains
AGI Hunt · wechat · 2026-09-02
Anthropic released Fable 5.1 and Mythos 5.1.
Performance
- Science: 52.6% on Terminal-Bench-Science 0.1 (up from 24.7%).
- Coding: 56% on Terminal-Bench 4.0 (Mythos 5.1: 61%); 73.4% on CursorBench 3.2.0.
- Reasoning: 60.9% on Humanity's Last Exam (no tools).
- Computer Use: 41.7% strict score on OSWorld 2.0.
- Automation: 31.4% on AutomationBench.
PreservedThinking
- New anti-distillation protection validates thinking block context integrity. Requests fail or drop thinking blocks if context is tampered.
- Restriction applies only to new API accounts created after Aug 31, 2026.
Related event: Anthropic Releases Fable 5.1 and Mythos 5.1 with 75% Cheaper Caching(174 posts)→
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