The AI Models Index keeps track of premium releases from 15 labs since 2023,...

https://holdenssplendiddigests.zenbloomer.com/posts/why-did-gpt-6.1-sol-improve-after-gpt-6-sol-regressed

The AI Models Index keeps track of premium releases from 15 labs since 2023, verified with blind-vote checks and accurate dates. Updated every two weeks, it shows how model development speeds up—GPT-5.2 launched just 4.5 days after GPT-5