Claude, make Windows Phone OS for my iPhone. The OS:

Just kidding, it's a Windows XP sim.

I've been using Claude Code at work for a while. To no one's surprise, it performs extremely well, especially on codebases that follow standard patterns or ones that Claude implemented from scratch.

This weekend I gave it something different: rewrite the messiest codebase I've owned to Svelte 5 and make it deployable on Cloudflare Workers (as a web dev, I have an obsession with free hosting).

The domain is unusual, it's a Windows XP sim in the browser: window stacking, drag/resize, rubber-band selection, focus management, a virtual filesystem, all layered on top of each other. Not something you can Google when you run into an issue.

It was my hobby project written years ago when I barely knew webdev, with inconsistent patterns, ad-hoc components poking each other.

The tricky part with a UI like this is that everything interacts, wired in a weird way. Window state, dragging, selection, filesystem state, touch one thing and something else breaks.

Claude had to read bad code, infer what the code was trying to do, and make judgment calls.

When a lib broke on mobile, it dug through the lib source code in node_modules, reasoned through the event lifecycle, and replaced it with a custom implementation.

When inter component communication was ad-hoc and weird, it followed the existing patterns instead of fighting them.

It also somehow made the Windows XP UI usable on mobile, which XP was never designed for.

I didn't write or edit a single line of code in the rewrite (accept edits on all the way)

The repo.