That's remarkably similar to something I've just started on - I want to create a self-compiling C compiler targeting (and to run on) an 8-bit micro via a custom VM. This a basically a retro-computing hobby project.

I've worked with Gemini Fast on the web to help design the VM ISA, then next steps will be to have some AI (maybe Gemini CLI - currently free) write an assembler, disassembler and interpreter for the ISA, and then the recursive descent compiler (written in C) too.

I already had Gemini 3.0 Fast write me a precedence climbing expression parser as a more efficient drop-in replacement for a recursive descent one, although I had it do that in C++ as a proof-of-concept since I don't know yet what C libraries I want to build and use (arena allocator, etc). This involved a lot of copy-paste between Gemini output and an online C++ dev environment (OnlineGDB), but that was not too bad, although Gemini CLI would have avoided that. Too bad that Gemini web only has "code interpreter" support for Python, not C and/or C++.

Using Gemini to help define the ISA was an interesting process. It had useful input in a "pair-design" process, working on various parts of the ISA, but then failed to bring all the ideas together into a single ISA document, repeatedly missing parts of what had been previously discussed until I gave up and did that manually. The default persona of Gemini seems not very well suited to this type of work flow where you want to direct what to do next, since it seems they've RL'd the heck out of it to want to suggest next step and ask questions rather than do what is asked and wait for further instruction. I eventually had to keep asking it to "please answer then stop", and interestingly quality of the "conversation" seemed to fall apart after that (perhaps because Gemini was now predicting/generating a more adversarial conversation than a collaborative one?).

I'm wondering/hoping that Gemini CLI might be better at working on documentation than Gemini web, since then the doc can be an actual file it is editing, and it can use it's edit tool for that, as opposed to hoping that Gemini web can assemble chunks of context (various parts of the ISA discussion) into a single document.

Just as a self follow-up here (I hate to do it!), after chatting to Gemini some more more about document creation alternatives, it does seem that Gemini CLI is by far the best way to go, since it's working in similar fashion to Claude Code and making targeted edits (string replacements) to files, rather than regenerating from scratch (unless it has misinterpreted something you said as a request to do that, which would be obvious when it showed you the suggested diff).

Another alternative (not recommended due to potential for "drift") is to use Gemini's Canvas capability where it is working on a document rather than a specification being spread out over Chat, but this document is fully regenerated for every update (unlike Claude's artifacts), so there is potential for it to summarize or drop sections of the document ("drift") rather than just making requested changes. Canvas also doesn't have Artifact's versioning to allow you to go back to undo unwanted drifts/changes.