Anthropic's internal AECI index suggests minimal gains for next model
ChrisGPT · x · 2026-08-21
Anthropic inadvertently revealed the performance of its upcoming model on its internal Anthropic ECI (AECI) index. AECI is Anthropic's version of Epoch's Capabilities Index, compressing various benchmark results into a single score using internal data. Mythos 5 lands around 161 AECI, while Model 2 is only 1.5 points higher (162.5 - 163), with large error bars. However, a larger gap on CoBench suggests Anthropic is currently focusing on scaling internal researcher capabilities rather than broader AECI metrics.
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