Exact: Cross-Platform UI Framework Built for AI-Driven Development

Exact enables developers to write a single UI codebase that executes natively across web, macOS, iOS, and Linux. The framework uses Contract, a declarative language for interface definitions, paired with TypeScript or Rust for data logic. A compiler produces an intermediate representation that each platform interprets through its own rendering layer—the web gets a compact ES module runtime, while macOS, iOS, and Linux run compiled Rust with platform-specific graphics. This design eliminates webviews and JavaScript bridges entirely from the UI layer.

The framework is explicitly designed around AI agent workflows. It exposes a deliberately limited ten-operation API that lets agents build, test, and validate applications across all platforms autonomously. The system includes a programmable clock for deterministic testing that eliminates timing flakes, and test specifications written in Contract run unchanged across every supported platform. The project’s example demonstrates an agent successfully completing end-to-end builds and testing in roughly an hour.

Exact remains pre-release with intentionally unstable APIs. The web runtime weighs approximately 20 kilobytes against React’s 81 kilobytes, with performance budgets tracked on every commit. Fresh edits compile and reload in around 100 milliseconds. The framework optimizes boot time by baking the initial frame into the compiled plan, with subsequent builds staying offline. Platform-specific details like system colors, standard controls, and accessibility features inherit sensible defaults unless explicitly overridden.