Actually, I'm curious what ChatGPT 5.5's ELO is- I wouldn't be too surprised if it's 2000+ just from its basic understanding of chess principles from all the content it has digested.
I've tried to pay chess with GPT-5.5, even played it again tonight, allowing it to use `python-chess` to keep track of the state of the position and to get a list of legal moves at each turn, so that it was fair. I also gave it blindfold odds, again to make it a fair fight, but it was not even close. GPT still isn't better than maybe 1000 Elo, maybe 1200 tops. Even with what amounts to being able to see the position and also being unable to make an illegal move, GPT-5.5 hangs material left and right, doesn't make a plan, and got smoked even when I gave it blindfold odds, to the point it's boring for me to play even under those conditions. I'm not sure it's better than whatever the GPT model was that was out about 8 months ago. I also thought it might be somewhat better than a beginner due to reading chess books, but no, it's complete garbage at playing chess, not even average-level skill.
LLMs truly are marvels with text but anything spatial seems to really mess it up, somehow.
Not at all? LLMs are a terrible match for the kind of analysis a chess engine does (scaled deep search, deeply trained position evaluations). It's just not that kind of tool.