As someone that's been working on a game with Claude Code in a more human-in-the-loop, iterative fashion, I have to say that OP's claim that "LLMs barely know GDScript" does not match my current experience at all even though it seems to have matched yours. Maybe it was true a while ago in both cases; how long ago was your "vibecode" attempt? I've gotten completely fine GDScript and even decent perfectly functional if placeholder-quality TSCN files from Opus 4.5, 4.6, and Sonnet 4.6 with very little issue and no special tricks; just a CLAUDE.md file, the project itself, and going through plan mode before each change. I did start from a playable project with a fair amount of hand-written scaffolding already in place, and I have no idea if that would make a difference. Every once in a while there will be some confusion that I get something appropriate for Godot 3 instead of Godot 4, but never Python despite the similarities of the language.

Ah thanks, I see. This was 8-9 months ago.

I was starting from scratch and mainly relying on Opus/Sonnet 4.

I also kept running into the Godot 3 vs 4 issue before adding specific guidance about this into CLAUDE.md

I agree, Claude does a great job of synthesizing Godot docs, and even of writing unit and integration tests with GUT. I have not tried any e2e testing but I’m not convinced that you couldn’t get a good result there, too, depending on the kind of game.