These documents define behavior that differs across Windows, Linux, macOS, Android, iOS, and Web. Shared visual standards are defined in ../DESIGN.md; shared architecture is defined in ../ARCHITECTURE.md.

Architecture invariants

go_router owns navigation state, route restoration, browser URLs, and platform back navigation.
Riverpod owns application state, dependencies, and asynchronous workflows.
Platform rule documents must not contain business logic or duplicate feature state.
Shared tokens and components remain the visual source of truth.
Platform adapters expose capabilities such as file access, clipboard, lifecycle, and window behavior.
Every platform-specific behavior must have a smoke-test scenario.

Platform comparison

Platform	Primary input	Navigation concerns	Capability concerns	Release concerns
Windows	Keyboard, mouse, context menus	Desktop shell and shortcuts	Windows, file dialogs, high-DPI	Installer/package and resize smoke tests
Linux	Keyboard and mouse	Desktop shell and shortcuts	Window managers, file selection	Distribution packaging and environment coverage
macOS	Keyboard, mouse, trackpad	Command-key conventions	Permissions, file access, window lifecycle	Signing, notarization, and release validation
Android	Touch, system back, keyboard	Back stack and route restoration	Insets, lifecycle, keyboard	APK/AAB builds and device/API coverage
iOS	Touch, gestures, keyboard	Route restoration and system gestures	Safe areas, lifecycle, permissions	Signing, archive, and device coverage
Web	Mouse, keyboard, touch	URLs, refresh, history	Downloads, clipboard, browser APIs	Hosted build, deep links, and browser coverage

Shared platform checklist

For every target:

Verify the correct shell is selected for the available constraints and platform capabilities.
Verify loading, success, empty, and recoverable error states.
Verify keyboard or touch access for every primary interaction.
Verify visible focus and accessibility labels.
Verify text scaling and content that wraps at narrow widths.
Verify unsaved work survives resize, route changes, and supported lifecycle transitions.
Verify file and clipboard behavior using the platform adapter.
Run the target's smoke tests before release.

Adding or changing a platform rule

Describe the platform behavior and why the shared implementation is insufficient.
Keep the change in the platform adapter or shell rather than in domain logic.
Add or update a smoke test scenario.
Check that the change does not duplicate go_router or Riverpod state.
Update the comparison table if capabilities or release requirements change.