LLMs don’t even understand fucking TypeScript, which you would expect a computer program to be able to understand. I can’t get it to write valid Drizzle code to save my life, it will confidently hallucinate method imports that don’t even exist.
Claude Code refactored numerous projects for us into TS, often one-shotting it. Saying LLMs don't understand TS (which may be true, in that LLMs questionably understand anything) says more about your perception than model and agent abilities.
Hallucinations do occur, but they're becoming more rare (especially if you prompt to the strengths of the model and provide context) and tests catch them.