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Exact is a new, pre-1.0 cross-platform application runtime that describes interfaces in Contract and targets web, macOS, iOS and Linux from one app. Its documentation says native platforms use AppKit, UIKit or a GPU renderer rather than a webview, and provides an agent driver for testing apps across hosts. The project warns that its API changes daily and is not backward-compatible.
Exact, a new cross-platform application runtime, is being presented as a way to build one interface for web, macOS, iOS and Linux. The project’s GitHub documentation says developers describe screens in its Contract language and write application logic in TypeScript or Rust; it also emphasizes tools that let an AI coding agent run and test the same app on multiple platforms.
Exact’s documentation describes a compiler that turns Contract interface declarations into a compact plan. In the browser, a small JavaScript runtime uses that plan to drive the native DOM. On Apple platforms, a Rust runner executes the same plan and renders through UIKit on iOS or AppKit on macOS; Linux is also listed as a target, with a GPU-based painter. The project says its native UI path has no webview or JavaScript bridge and does not run app JavaScript before the first pixel.
The repository also provides scripts/agent.mjs, a driver with ten operations, including taking screenshots, tapping controls, entering text, inspecting state and reading logs. According to the project, a single app.test.contract test script can run unchanged across supported hosts. Its suggested demonstration asks a coding agent to create a to-do app, test it on web, macOS and the iOS Simulator, then open the app on each platform.
The project reports that an agent completed an earlier version of that task in about 57 minutes on October 4, 2026, with tests passing on all three platforms. It says roughly 25 minutes went to initial macOS and iOS builds, about 13 minutes apiece, while later builds took one or two minutes. Those figures are the project’s account of a specific run, not an independent benchmark. The repository says setup now downloads and verifies pinned host and iOS bundles once, after which ordinary builds can work offline.
One Interface, Multiple Renderers
Exact’s approach matters because cross-platform tools often trade access to platform-specific behavior for shared code, or rely on web technology inside an app. Exact says it instead shares the interface description while letting each host render with its own controls and drawing system. If that works as described, teams could maintain one screen definition while still producing interfaces that use platform-native rendering on Apple devices and a browser DOM on the web.
The agent-oriented testing tools are another part of the pitch. A common test file and a driver that can inspect, operate and capture an app could make automated verification across platforms easier, including for software written by coding agents. But the repository’s reported build times and performance figures are project-reported results; the supplied material does not establish independent testing or adoption by outside developers.
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How Exact Defines an App
Exact separates an interface from its data logic: Contract declares the view, while TypeScript or Rust handles application behavior. The project says its layout kernel applies CSS rules on native hosts, and its platform renderers provide controls and other host-specific behavior. For the web, it describes a separate runtime of about 20 KB; it also cites a 26 KB code size in a RealWorld “Conduit” comparison with a React server-rendered build listed at 81 KB. These are figures published by the project, and the source material does not provide independent verification.
The repository is called exact2 and is a rebuild of an earlier project, exact1. Its authors explicitly label the software pre-1.0: it changes frequently, has no API stability or backward compatibility, and comes without a migration guide. A separate example, Softwear, is described as a generated demonstration store that is not affiliated with Alternative Apparel and does not accept real orders or payments.
“Write an app once. It runs natively on the web, macOS, iOS, and Linux”
— Exact project documentation
Stability and Independent Results
Exact’s production readiness remains uncertain. Its maintainers say the API is unstable and backward compatibility is not promised, but the supplied material gives no release schedule or criteria for a stable version. It also does not identify independent users, production deployments or external evaluations of the framework’s rendering and performance claims.
The documentation describes Linux as a target, but the highlighted agent demonstration covers only web, macOS and the iOS Simulator. The source material does not explain the current state of Linux testing, the range of supported controls and accessibility features, or how closely native behavior matches each platform’s conventions. The reported build times also depend on machine setup and cached components, according to the project.
What Developers Can Test
The immediate next step for interested developers is to follow the repository’s quick-start instructions and try the framework with a coding agent or build a small app directly. The project’s demonstration calls for Xcode, Rust, Bun and Chrome on a Mac, plus a one-time setup command; its documentation recommends running the same contract test on each host. Since the software is changing daily, developers should check the repository for current setup instructions and breaking changes before relying on it.
No release date for a stable API or independent roadmap is provided in the source material. Further evidence will come from the project’s ongoing development and from whether developers can reproduce its cross-platform behavior and performance claims on their own machines.
Key Questions
What is Exact?
Exact is a cross-platform application runtime. Its documentation says developers define interfaces in Contract and write app logic in TypeScript or Rust, targeting web, macOS, iOS and Linux.
Does Exact use a webview for native apps?
The project says it does not. It describes native rendering through UIKit on iOS, AppKit on macOS and a GPU painter on Linux, without a webview or JavaScript bridge in the UI.
Can one test file run across platforms?
According to the repository, an app.test.contract script can run unchanged through its agent driver on different hosts. The documentation’s example covers web, macOS and the iOS Simulator.
Is Exact ready for production use?
The project does not present Exact as a stable release. It says the framework is pre-1.0, changes daily, and offers no API stability or backward compatibility.
Are Exact’s performance figures independently verified?
The supplied figures, including runtime size, build timing and the agent’s reported completion time, come from Exact’s own documentation. The source material does not provide independent verification.
Source: github.com
