The thing is that CLI utilities code is probably easier to write for an LLM than most other things. In my experience an LLM does best with backend and terminal things. Anything that resembles boilerplate is great. It does well refactoring unit tests, wrapping known code in a CLI, and does decent work with backend RESTful APIs. Where it fails utterly is things like HTML/CSS layout, JavaScript frontend code for SPAs, and particularly real world UI stuff that requires seeing and interacting with a web page/app where things like network latency and errors, browser UI, etc. can trip it up. Basically when the input and output are structured and known an LLM will do well. When they are “look and feel” they fail and fail until they make the code unmaintainable.

This experience for me is current but I do not normally use Opus so perhaps I should give it a try and figure out if it can reason around problems I myself do not foresee (for example a browser JS API quirk that I had never seen).

I've been having a surprising amount of success recently telling Claude Code to test the frontend it's building using Playwright, including interacting with the UI and having it take its own screenshots to feed into its vision ability to "see" what's going on.

In my experience with a combo of Claude Code and Gemini Pro (and having added Codex to the mix about a week ago as well), it matters less whether it’s CLI, backend, frontend, DB queries, etc. but more how cookiecutter the thing you’re building is. For building CRUD views or common web application flows, it crushes it, especially if you can point it to a folder and just tell it to do more of the same, adapted to a new use case.

But yes, the more specific you get and the more moving pieces you have, the more you need to break things down into baby steps. If you don’t just need it to make A work, but to make it work together with B and C. Especially given how eager Claude is to find cheap workarounds and escape hatches, botching things together in any way seemingly to please the prompter as fast as possible.

Since one of my holiday projects was completely rebuilding the Node-RED dashboard in Preact, I have to challenge that a bit. How were you using the model?

I couldn't disagree more. I've had Claude absolutely demolish large HTML/CSS/JS/React projects. One key is to give it some way to "see" and interact with the page. I usually use Playwright for this. Allowing it to see its own changes and iterate on them was the key unlock for me.