Overview

Yolk is a framework for writing app business logic in TypeScript and running it inside a native application. The native UI layer — currently SwiftUI on macOS — stays fully native. Yolk provides the bridge between the two.

The idea

Native apps split into two concerns: what the app does (business logic) and how it looks (UI). Yolk lets you write the first part in TypeScript — once, for all platforms — and leave the second part to each platform's best-in-class UI toolkit.

The TypeScript bundle runs on an embedded JavaScript engine (JavaScriptCore on Apple platforms). Your SwiftUI code calls into it; TypeScript calls back into Swift for platform capabilities like storage, networking, or notifications.

What Yolk is not

• Not a UI framework. There are no Yolk components. Your SwiftUI code is fully under your control.
• Not a web view. The TypeScript bundle runs in a JS engine, not a browser. There is no DOM.
• Not React Native. There is no virtual DOM, no bridge batching, no shadow thread.

How types flow

The boundary between TypeScript and Swift is typed end-to-end from a single source of truth:

counter.spec.ts
    │
    ├──▶ codegen ──▶ CounterModule.swift   (implement this with an actor)
    └──▶ codegen ──▶ Counter.ts            (use this in your TypeScript)

Type mismatches are caught at compile time, not at runtime.

Next steps

• Getting started — install Yolk and build your first module
• Concepts — understand how the spec → codegen → implementation pipeline works