I was poking at this a bit here

https://github.com/maedoc/rwkv.js

using the Rwkv.cpp compiled with emscripten, but I didn’t quite figure out the tokenizers part (yet, only spent about an hour on it)

Nevertheless I am pretty sure the 1.6b rwkv6 would be totally usable offline browser only. It’s not capable enough for general chat but for rag etc it could be quite enough