Claude Fable 5.1 Launches: Doubles Science Benchmarks, Solves Data Retention
dotey · x · 2026-09-02
Anthropic released Claude Fable 5.1 and Mythos 5.1. They share the same model but have different safety guardrails. Fable 5.1 is public, while Mythos 5.1 is restricted to approved researchers.
Key Upgrades:
- Research: Scored 52.6% on Terminal-Bench-Science 0.1 (vs 24.7%), more than doubling performance.
- Coding: Scored 55.8% on Terminal-Bench 4.0 (60.9% for Mythos), surpassing Opus 5.
- Automation: AutomationBench score rose from 17.1% to 31.4%.
- Enterprise: Addresses the data retention controversy with zero-data retention options.
- Cost: Price reductions (detailed in review).
Real-world Case: Investment firm Millennium used Fable 5.1 to identify the root cause of a rare system crash that had stumped engineers for years.
Related event: Anthropic Releases Fable 5.1 and Mythos 5.1 with 75% Cheaper Caching(174 posts)→
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