As an addendum to this:

If I were to try to make something more useful out of this, I'd probably add the ability for LLMs to list buffers, probably give them an easier out for executing shell scripts in the way they prefer, give them an easier time to list docs and a few other things like that.

The tools and the interaction with Kakoune is really trivial to write; I already use this by having the agent write to the session FIFO (a very simple binary format) and I extract information via my own FIFO that Kakoune writes to (this is used for the buffer data only right now).

I think once you started using it more as a tool and not a pseudo-benchmark like I am you'd probably think of even more things to add but a lot of it comes down to just making Kakoune's state visible and making shell spam (which the LLMs love) easier.