GPT-4

GPT-4 was released on 14 March 2023, three and a half months after ChatGPT, and the gap between it and everything else was the largest the field had seen since AlexNet. It scored in the top ten percent on a simulated bar exam where GPT-3.5 had been in the bottom ten, passed most advanced-placement exams, and could describe a photograph or explain why a picture was funny. Microsoft, which had funded its training, confirmed that Bing had been running it for a month.

The technical report was 100 pages and disclosed neither the model's size nor its data nor its architecture, citing competition and safety. The company founded to be open had become, in its critics' phrase, ClosedAI, and the report's authors defended the choice. A section on the scaling laws showed that the model's final loss had been predicted, before training, from runs a ten-thousandth of its size.

GPT-4 held the top of every leaderboard for over a year, and its release, with Microsoft's Copilot products, Google's Bard and the pause letter within the same fortnight, is the moment the frontier became a race between companies rather than a research field. Later reporting put its training compute at more than 10²⁵ floating-point operations, the threshold the EU AI Act would adopt for systemic risk.