#3838th of 78 in SaaS and app starters
exact
Cross-platform app runtime with a declarative UI language and agent test driver
- Stars
- 2.7k
- License
- MIT
- Last commit
- Nov 2026
- Language
- Rust
Checked on GitHub.
Overview
Exact compiles UI written in Contract, a small declarative language, into a plan that runs as DOM on the web and as AppKit, UIKit or GPU-painted views on macOS, iOS and Linux, with no webview. Data logic is TypeScript on Hermes or Rust. A ten-operation driver, scripts/agent.mjs, lets a coding agent build, screenshot, tap and test an app on every host. Pre-1.0 with no API stability.
Who it is for: Developers building native cross-platform apps with coding agents
Strengths
- One app.contract renders natively on web, macOS, iOS and Linux without a webview
- Same ten driver operations and app.test.contract files run unchanged on every host
- Agent-controlled clock and machine-readable diagnostics make tests deterministic
- Reports 99 ms dev rebuilds and a ~20 KB web runtime, measured by the authors
Weaknesses
- Pre-1.0 and changes daily; no API stability or migration guide by design
- Native hosts need macOS with Xcode 27.1+; first native build takes 10-15 minutes
- UI must be written in Contract, a new language with little outside tooling
- TypeScript on native hosts requires installing a pinned Hermes bundle separately
What it needs
- Rust
- Needs Rust (rustup), Bun 1.4.2, Google Chrome, Xcode 27.1+, Hermes bundle
Quick answers
Is exact open source?
Yes. Its code is on GitHub under the MIT license.
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