The AI Models Index tracks premium releases from 15 leading labs since 2023,...

https://technivorz.com/how-long-does-google-take-between-announcing-and-shipping-a-model/

The AI Models Index tracks premium releases from 15 leading labs since 2023, with verified launch dates and blind-vote accuracy checks. Updated every two weeks, it shows a 56% improvement rate between GPT-5.1 and GPT-5.2