I don't know which LLM did this because I asked it on Arena, but...

Prompt:

Find me an evidence trail for how the x character got changed in OpenType fonts to display differently when used in 2x3 versus axe. Trace the first implementation of this in fonts and write a report how this evolved, with evidence and links.

that was among the evidence, including a massive report. It ran for 1.5h.

Actually kinda awesome.