[WarmWash]

Opus is estimated to be around 4T parameters, and 5.5 around 9T. [1] And while 3.5 at least qualifies to be in the same neighborhood, which is stunning if these numbers are all true, it may be that closing that last ~10% difference needs 50x more parameters.

[1]https://arxiv.org/pdf/2604.24827

[SavioMak]

Note that this paper is vibe-coded and overestimating due to incorrect analysis, though "the core idea behind the paper is largely sound".

https://x.com/justanotherlaw/status/2050399317782155726 https://www.lesswrong.com/posts/veFMEzDDyWaer2Sms/sanity-che...

[easygenes]

Their methods are only calibrated on open models (of course) and they admit very broad confidence bounds. You can also just see from comparing their estimates of the same models at different reasoning levels that there are major confounders to this. I would err on the absolute lowest side of their estimates for frontier models (e.g. 3T for GPT-5.5, 1.5-2T for Opus 4.5+).