Claude Fable 5.2 sets ECI record at 174, third-biggest frontier jump since reasoning era began
ChrisGPT · x · 2026-11-10
Epoch AI reports Claude Fable 5.2 set a new record on its Epoch Capabilities Index (ECI) at 174.24, surpassing GPT-6 Astra's 169.16 and beating what the pre-Astra reasoning-model trend would have predicted.
Per ChrisGPT's tally, the +5.08-point gain is the third-biggest frontier jump of the reasoning scaling era, behind only o1 (+5.78) and o1-mini (+5.38), ahead of GPT-5.2 Pro (+4.32) and o3 (+3.10). Epoch notes this is relevant to recent discussion of AI contributions to AI R&D and plans more work in the area. Scores are based on Epoch's own pre-launch benchmarks and may change.
Related event: Claude Fable 5.2 Sets ECI Record of 174, Topping GPT-6 Astra(4 posts)→
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