Core Native SDK guide for AI agents. Read this before explaining the Native SDK or changing a Native SDK app. Covers the mental model (native-rendered apps by default, WebView shells as a coexisting architecture), project structure, app.zon, App and Runtime patterns, frontend integration, web engines, JavaScript bridge commands, permissions, windows, WebViews, dialogs, packaging, debugging, testing, and when to load deeper references. For authoring native-rendered UI (Native markup .native views, Model/Msg/update, UiApp), load the native-ui skill. Use when the user asks what the Native SDK is, how to build or modify an app, how to package or debug it, or how to add native capabilities.