It's not totally a mystery
replyhttps://arxiv.org/html/2604.24827v1
The short of it is by using hard facts knowledge that is difficult to compress, and then quizzing models on these facts and calibrating against a bunch of open models, you can kind of feel out the size of closed models.
I really like that one, but it kinda highlights what I could have far better explained. Their 90% PI is three times in both directions. Between 3T and 24T for GPT-5.5.
replyThat’s a massively wide, inaccurate and at best barely informative range, demonstrating that even the most well thought out method will yield little usable information.
Additionally, I got some private evaluation taking a similar approach towards gauging models in topics I’ve found either over or underfitted by labs. If we just used that to rank models (not get a potential size range but just a rough order) Thinking Machines Inkling would need to be lager than Fable 5.