This is the classic 'plausible hallucination' problem. In my own testing with coding agents, we see this constantly—LLMs will invent a method that sounds correct but doesn't exist in the library.

The only fix is tight verification loops. You can't trust the generative step without a deterministic compilation/execution step immediately following it. The model needs to be punished/corrected by the environment, not just by the prompter.

Honestly, I feel humans are similar. It's the generator <-> executive loop that keeps things right

I've been using codex and never had a compile time error by the time it finishes. Maybe add to your agents to run TS compiler, lint and format before he finish and only stop when all passes.