Their model card [0] has some information. It is quite a standard architecture though; it's always been that their alpha is in their internal training stack.
This is super helpful and I had not seen it, thanks so much for sharing! And I hear you on training being an alpha, at the size of the model I wonder how much of this is distillation and using o3/o4 data.
[0] https://cdn.openai.com/pdf/419b6906-9da6-406c-a19d-1bb078ac7...