I'm a little confused by your distinction between vendor and lab. AI2 (Allen Institute for AI) is a western lab and they did release a fully open source model, with open weights, data, and training code (Olmo3).

Their technical report on the release is excellent: https://allenai.org/blog/olmo3

They're a public research institute as opposed to one of the proprietary frontier labs, but they've been very open about the science.

Yeah, I mentioned them in my comment. They're my favorite lab/vendor. Everything is open and reproducible.

It's just that their models were never frontier-level. By major, I meant frontier or popular.