The Information’s report from earlier this month claimed that GPT-5 was only developed in the last 1-2 months, after some sort of breakthrough in training methodology.
> As recently as June, the technical problems meant none of OpenAI’s models under development seemed good enough to be labeled GPT-5, according to a person who has worked on it.
But it could be that this refers to post-training and the base model was developed earlier.
https://www.theinformation.com/articles/inside-openais-rocky...