Epoch AI's Capabilities Index scores language models on one aggregate scale, and nothing since has held first place as long as GPT-4 did after its March 2023 release — roughly a year. The second-longest lead, by OpenAI's o1, lasted
Epoch AI's Capabilities Index (ECI) is an aggregate measure of language model capability, computed from over 50 benchmarks. GPT-4 held the top position on the ECI for 352 days, from its release on March 14, 2023, until Claude 3 Opus surpassed it on February 29, 2024. This was the longest lead recorded in the data, with OpenAI's o1 having the second-longest lead at 98 days.
Verified 2026-08-12
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Leads at the top of AI now last much shorter, so no lab stays ahead for long.
More on Models
- AI models can now win gold at the International Mathematical Olympiad, yet Stanford's 2026 AI Index found they still fumble a task most children master early. Across ClockBench's 180 clock designs and 720 questions, the top model, GPT-5.4 High, read analog clocks correctly only 50.6% of the time, versus 90.1% for humans
- After briefly nearly closing in 2024, the performance gap between the best closed-weight and open-weight AI models widened again on the Arena leaderboard. As of March 2026, Stanford's 2026 AI Index finds the top closed model leads the top open model by 3.3%, up from a 0.5% lead in August 2024
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