LLMs are terrible at that in my experience. In what world is refactoring "very local in reasoning"?
Switching libraries/frameworks or switching piecemeal to a new language for a codebase that's already well structured seems like it would be noticeably less costly though.
In a situation where the transformations are explicit and can almost be mechanical with little to no involved reasoning. With those requirements, the LLM just has to recognize the patterns and "translate" them to the new pattern. Which is almost exactly what they were designed to do.
