I use Claude Code daily to work on a large Python codebase and I'm yet to see the it hallucinating a variable or method (I always ask it to write and run unit tests, so that may be helping). Anyway, I don't think that's a problem at all, most problems I face with AI-generated code are not solved by a borrow-checker or a compiler: bad architecture, lack of forward-thinking, hallucinations in the contract of external API calls, etc.