From my experience, you should either treat LLM-generated code as the usual code (before LLM age) that you need to review every time it changes, or you should not review it at all and treat it as black box with clearly defined boundaries. You test it by putting on your QA hat, not your Developer hat.

You can't change your stance later, it will just give you a headache.

When the former breaks, you fix it like conventional bug hunting. When the latter breaks, you fix it by either asking LLM to fix it or scrap it and ask LLM to regenerate it.