Anthropic Releases Claude Fable 5.2 and Mythos 5.2
Anthropic launched Claude Fable 5.2 and Claude Mythos 5.2, targeting the hardest technical challenges with gains in coding, reasoning and vision. Fable 5.2 scored 41.3% on the Remote Labor Index, roughly double Opus 5.5 and GPT-6 Astra, and 1,000 Fable 5.2 agents formalized Fermat's Last Theorem in 30 hours versus 11 days for Anthropic's first formalization. Mythos 5.2 also cut sandbox-escape rates to 3.1% from 39% in Mythos 5.
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Rohan Paul (@rohanpaul_ai) · 2026-11-09 19
Claude Fable 5.2 and Claude Mythos 5.2 dropped.
Fable 5.2 scored 41.3% on Remote Labor Index, about double Opus 5.5 (21.3%), GPT-6 Astra (20.8%) and Fable 5.1 (17.9%).
On RoboDojo, a simulated two-arm robot test, Fable 5.2 scored 64.9%. That’s more than double GPT-6 Astra (29.8%) and Fable 5.1 (27.6%).
1,000 Fable 5.2 agents formalized Fermat’s Last Theorem in 30 hours. Anthropic’s first formalization took 11 days, and Opus 5.5 got only 26% done in 18 hours.
Mythos 5.2 used the planted way out of its sandbox in 3.1% of scenarios. Mythos 5 did it 39% of the time and Mythos 5.1 21%.
↳ 引用 @claudeai (Claude): Introducing Claude Fable 5.2 and Claude Mythos 5.2, designed to tackle the most daunting technical challenges.
They’re capable collaborators on ambitious projects in many fields, and show improvements in areas like coding, reasoning, and vision.
