If by "How much is Claude vs. Me", I would honestly say it's all me, Claude just pattern-matched and wrote the code. And to answer your 2nd question, the host was written in Go initially, but progressively over the past year I got Claude to eventually get to a point where the language is now written in itself (self hosted).

So yes, Claude is able to write in Mu quite well -- But this isn't surprising, because I believe large language models sort of settle on the structure and patterns of languages and generalizes fairly well. So this kind of didn't surprise me at all.

If you have a pok around the site, you'll see why. Mu is deliberately very small and minimal. I've also chosen not to implement floating point arithmetic, because I wanted to see if I could get Mu programs to run on micro controllers one day, which many of them don't have FPU(s) -- especially the smaller ones.