Data Insight
May 29, 2026

Open models lag state-of-the-art closed models by 4 months

Default avatarLuke Emberson's avatar
By Jack Edwards and Luke Emberson

Since January 2026, the most capable open-weight models have lagged frontier closed models by an average of four months in the Epoch Capabilities Index (ECI), our aggregate measure of model capability. The average ECI gap was 8 points, similar to the gap between GPT-5 and GPT-5.5.

This gap between open and closed models is slightly larger than the one we identified in our October 2025 Data Insight, which found that open models lagged by an average of three months between January 2023 and October 2025.

Epoch's work is free to use, distribute, and reproduce provided the source and authors are credited under the Creative Commons BY license.

Learn more about this graph

We calculate the average amount of time it takes for the best open-weight models to catch up with state-of-the-art performance according to our internal capability metric, the Epoch Capability Index (ECI). ECI is a composite measure that captures performance across many benchmarks.

Analysis

Limitations

Download this data

ECI scores of open- and closed-weight models
CSV, Updated May 29, 2026

Explore this data

AI Capabilities
AI Capabilities

Benchmark results featuring the performance of leading AI models on challenging tasks.

Open-weight models lag state-of-the-art by around 3 months on average
Data Insight
Oct. 30, 2025
Open-weight models lag state-of-the-art by around 3 months on average

Related topics

CapabilitiesOpen models