01 · WHAT YOU ASSUME
Two measurements, one answer
What most people think
Open models are hobby projects. The paid ones are a generation ahead, and closing that gap will take years.
What the data shows
Epoch AI, a research group that scores models on hard tests, measures the best open model four months behind the best closed one.
A second measure asks which model people prefer. The closed lead there grew from 0.5% to 3.3%.
Four months behind, and the gap has stopped shrinking.
Source · Epoch AI, open-closed capability gap · May 2026
02 · THREE WORDS FIRST
What the labels actually mean
Four months, then. Three words decide what those four months are worth, and one of them is doing work you did not agree to.
Open weights. You get the finished model file to download and run. That is the cake, not the recipe.
Open source. Weights plus the code and the data that made them. Almost no large model ships all three.
ECI. Epoch AI's capability index. One score from many hard tests, so two models rank on the same scale.
03 · FIVE DATES
Three months behind, then four
Two readings of the same gap, seven months apart. In between, the day an open model caught April's best closed one.
- 2025-10-30
Epoch AI reads the gap. Three months behind, averaged across nearly three years.
- 2026-04-23
GPT-5.5 · ECI 158.22. The closed frontier sets a mark.
- 2026-05-29
Epoch AI reads it again. Four months now. The gap widened, it did not close.
- 2026-07-16
Kimi K3 · ECI 158. Announced 16 July. Weights released 27 July. April's frontier, reached 84 days later.
- 2026-09-03
GPT-6 Astra · ECI 166. Eight points ahead again.
Three months behind in October 2025. Four months behind in May 2026.
Source · Epoch AI data insights and model pages · September 2026
04 · INSIDE THE AVERAGE
Eight points, spread very unevenly
Eight points ahead on the index, four months ahead in time. Those are two readings of the same gap: the points say how far behind, the months say how long the catch-up took. Only these four tests score both models on the same terms.
Near parity on graduate science. Chess puzzles and world knowledge sit in between. On a puzzle game the open model scores 26% against 84%. Epoch AI warns this reading may understate the gap, because open models are tuned hard on public tests.
Source · Epoch AI model pages · September 2026
05 · WHO IS ACTUALLY THERE
Not the labs you have heard of
Those gaps run from three points to fifty-eight. So who releases these open models? Three Chinese labs: DeepSeek, Moonshot, which makes Kimi, and Zhipu, which makes GLM. Each has one column below, and a line joins every model to the one built from it.
Moonshot's column climbs to the open model that caught April's closed frontier. OpenAI's closed models stand alone in the last column. Eight of these ten releases are open weights, and the newest landed in July.
Source · Epoch AI Benchmarking Hub model pages · September 2026
06 · THE WHOLE STACK
Free is only the top layer
Eight of those ten releases are free to download. Nothing under them is, so the rest of the stack stays somebody else's bill, and that kharcha does not come with the file.
Training data is almost never released. The compute to serve a model is not downloadable at any licence.
Source · Stanford HAI, Hugging Face open-model census, AI Now Institute · September 2026
07 · WHAT IT COSTS
Three prices for the same million tokens
The one layer you can rent has a price. Here it is, per million tokens, which means the small chunks of text a model reads and writes.
A million output tokens costs $50 from the closed frontier. The best open model charges $15 for the same million. Ask in an Indian language and you pay about five times the English price.
Source · Epoch AI model pages · September 2026
08 · WHO TOOK IT
The offer nobody took
Renting the open model costs less than a third of renting the closed one, and downloading it costs nothing at all. One count of state-backed AI projects found 139, across 56 countries. About 40% picked Llama, Meta's open-weight model. Not one picked a model from the labs actually at the open frontier. Think of a free textbook nobody opens because the shelf sits in another building.
That means the four months is not what keeps people away. The bottom slab of that stack does, the compute to run the model, and no licence makes that part free. Of all downloads, 83% go to models under a billion parameters, the smallest on offer. India's pull is different. Sarvam AI adapts open-weight models to Indian languages, work you can only do when you hold the weights instead of renting them by the token.
Source · Rest of World, Hugging Face open-model census · September 2026
The four months is free. Almost nobody takes it.