It's in Cursor as well, I've been using it today and I can't say I'm that impressed with it. Definitely not Sonnet 4 or GPT5-high level. It's fast for sure, but it seems to pay no heed at all to instructions. I tell it "no fallbacks" and it makes a file full of fallbacks, and it looked at an error and said that it had fixed it about 10 times before I gave up and gave it to Claude which fixed it first try.
(seems to be an xAI model according to some rumors on X)
and due to simply asking it...:)
Ironically the first time I asked it said it's Claude Sonnet 3.5, probably they trained on that corpus as well