The problem is that it will have been trained on multiple open source spectrum emulators. Even "don't access the internet" isn't going to help much if it can parrot someone else's emulator verbatim just from training.

Maybe a more sensible challenge would be to describe a system that hasn't previously been emulated before (or had an emulator source released publicly as far as you can tell from the internet) and then try it.

For fun, try using obscure CPUs giving it the same level of specification as you needed for this, or even try an imagined Z80-like but swapping the order of the bits in the encodings and different orderings for the ALU instructions and see how it manages it.

I think you are into something here.

I tried creating an emulator for CPU that is very well known but lacks working open source emulators.

Claude, Codex and Gemini were very good at starting something that looked great but all failed to reach a working product. They all ended up in a loop where fixing one issues caused something else to break and could never get out of it.