> There was no such instruction. I've never chatted with any AI about LaTeX. it leaked from the tokens of someone else's chat.

Nope. That's not how it works. Attention doesn't work across multiple independent prompts queued in the same batch. It's not physically possible for the tokens of another chat to leak.

What most likely happened is that the model glitched out to the instructions in its (hidden) system prompt, which most likely does include instructions about using LaTeX for mathematical and scientific notation.