Foldkit

been trying out foldkit.dev today, it's really interesting. initial thoughts: - agent really liked it. cursor w/ 5.5 one-shot a bunch of stuff that was super annoying before that i was trying to (keep a persistent music player playing across different pages, share state, load state back from local storage, etc). - it's all effect, which i like. dunno how well it integrates further down, gotta try some more httpapi integration stuff but should be fine w/ httpapi client - seems to handle a bunch of stuff that normally felt really finnicky with getting right with effect, schema stuff, state thing,s blah blah - the dev mode is insanely cool, can replay mesages and everything, super sweet idk probably more to think of later but been enjoying it a lot ty @devinjameson love the direction

I feel like it’s hard to appreciate the value of Foldkit until you’ve worked on a series of complex frontends with a library like React. It’s a major project to figure out what a large React app *does*, or even what it’s doing at any given moment. You need to trace imperative logic, add logs, inspect the Network tab, read through effects, parse five different styles of writing TypeScript in the span of a single feature, etc. Component tests are fatiguing to read, there are a million state management solutions, and the UI is cobbled together from several libraries. Through no single person’s fault, it is almost always a mess. Contrast this with Foldkit. If you want to know how state transitions, you read the update function. If you want to know what state the application holds, you read the Model. If you want to know what side effects result from any given Message, you look at what Commands are returned. If you want to know what your app is doing right now, you open DevTools. You’ll see every Message, every Model state, and every Command logged. Want to see what the UI looked like 10 Messages ago? You can rewind your UI and see it in the browser. You can trust the framework to be honest. Nothing is hidden. There is an idiomatic way to do everything. Foldkit isn’t about functional purity. It’s about making the frontend feel sane.

Foldkit programs are inspectable by construction. With DevTools, you can scrub through every session just like a video. Each Model state, dispatched Message, and issued Command is recorded. You get this for free. It falls straight out of the architecture because the view is a pure function of the Model, and every side effect is a Command the runtime records. Why is this more than a party trick? A. You can run DevTools and see what your program does in real time: every state change, every issued Command. Immensely valuable for understanding and debugging. B. All the data is exposed over MCP, so your agent can see what you see. Your agent can even issue Messages into the runtime to drive the program.