Earlier quoted context omitted.
It's about the complexity of the task. Front end apps tend do be much less complex and boilerplate-y than backends, hence AI tends to work better.
I disagree - having worked on backends most of the time, I find modern frontend much more complex (and difficult to test) than pure backend. When I say modern frontend - its mostly React, state management like Redux, Zustand, Router framework like React Router, a CSS framework like Tailwind and component framework like Shadcn. Not to mention different versions of React, different ways of managing state, animation/tra…
It's hard to generalize but modern frontend is very good at isolating you from dealing with complex state machine states and you're dealing with single user/limited concurrency. It's usually easy to find all references/usecases for something.
Most modern backend is building consistent distributed state machines, you need to cover all the edge cases, deal with concurrency, different clients/contracts etc. I would say getting BE right (beyond simple CRUD) is going to be hard for LLM simply because the context is usually wider and hard to compress/isolate.