Expo open-sources Exact to compile Contract UI specs to native OS views and a 20 KB web runtime

Expo open-sourced Exact on GitHub under the MIT licence on 9 November 2026, introducing an experimental cross-platform UI stack created by co-founder Charlie Cheever specifically for human-and-agent co-authoring. Instead of mixing imperative component trees with styling workarounds, Exact separates presentation into a constrained declarative language called Contract while keeping state and data logic in TypeScript or Rust.

Compiler pipeline and native painters

An ahead-of-time compiler lowers each Contract specification into a compact execution plan. On the web, that plan runs through a roughly 20 KB DOM runtime with zero virtual-DOM diffing overhead. On desktop and mobile targets, a shared Rust layout kernel computes geometry and hands draw commands directly to native platform painters across macOS AppKit, iOS UIKit and GPU-rendered Linux windows, with no embedded webview and no asynchronous JavaScript bridge. Because every UI node maps deterministically to its Contract source, Exact ships with a headless agent driver that lets coding agents build screens, inspect live layout bounds, trigger user actions and assert visual states programmatically. Windows and Android painters are listed on the repository roadmap rather than complete in the initial preview.