I work for a medium-sized proprietary/discretionary fund. AFAIK the principles trade all kinds of stuff, macro stuff. My current job is tuning up the execution on the cryptocurrency adjacent desk, but not like blockchain stuff, it's somewhere in between OG crypto trading stuff and like Wall St. HFT circa 2006-2010 depending on how you measure, it's in the "kernel bypass matters but FPGAs are still exotic" sort of regime, some of it is legacy REST APIs still but FIX 4.2 SBE and other real finance protocols (and real banks and stuff) are starting to be a part of the ecosystem.

I aspire to be a lot faster than this stuff (I've built faster stuff than this) but this is quite a good library (amazingly good by OSS standards, good stuff in this area is rarely OSS, props to the maintainers): https://github.com/crypto-chassis/ccapi, in particular this library does a really good job of being correct across a lot of surface area, it's serious people doing it, and there are forks of it that use DPDK floating around.

If by who's paying for it you mean the big Anthropic bill? My boss's boss is pretty enlightened about the fact that learning how to use AI well is expensive, so when I'm on a tight schedule I get a pretty forgiving budget for the model fees. It's a pretty serious perk in the sense that it's really expensive to master using these things :)