The AI Models Index keeps tabs on premium releases from 15 top labs since 2023,...

https://stateofseo.com/understanding-the-difference-between-point-releases-and-new-generations-in-large-language-models/

The AI Models Index keeps tabs on premium releases from 15 top labs since 2023, with verified dates and blind-vote accuracy checks. Updated every two weeks, it shows a 56% improvement rate between GPT-5.1 and GPT-5