Epoch AI capabilities index: Opus 5.5 edges out GPT-6 Astra for top spot

Choblin @choblin29Originally posted 2026.10.01

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Claude Opus 5.5 just took the #1 spot on Epoch AI’s Capabilities Index, narrowly beating GPT-6 Astra. Astra still leads on math, 170 vs 168, while Opus leads software engineering, 167 vs 165. The interesting bit: Opus and Sonnet 5.5 lose <1 ECI point from general to SWE. Astra drops ~2.

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