Windows 15 App Development

Use this skill when building or modifying apps under apps/ in the Windows 15 desktop environment.

Quick Navigation

Task	Documentation
Create a new app	guides/creating-simple-app.md
Register an app / app config	core/app-architecture.md
Open/focus/minimize windows	core/window-lifecycle.md
Persist app state	guides/adding-persistence.md
Keyboard shortcuts	guides/hotkeys.md
Toast notifications	guides/notifications.md
UI components & styling	guides/styling-patterns.md, reference/ui-components.md
Full API lookup	reference/contexts.md, reference/hooks.md
Learn by example	examples/calculator-walkthrough.md, examples/notepad-walkthrough.md

Codebase Landmarks

App registration: apps/registry.ts (authoritative app registry)
Window lifecycle: context/WindowContext.tsx and components/Window.tsx
OS wrapper hook: context/OSContext.tsx (useOS())
Common hooks: hooks/index.ts
UI primitives: components/ui/

Essential Patterns

Creating a New App

Create component in apps/MyApp.tsx:

tsx

import { AppContainer } from '../components/ui/AppContainer';

export function MyApp() {
    return (
        <AppContainer padding>
            <h1>My App</h1>
        </AppContainer>
    );
}

{
  id: 'myapp',
  title: 'My App',
  icon: 'apps',
  color: 'bg-slate-400',
  component: React.lazy(() => import('./MyApp').then(m => ({ default: m.MyApp }))),
  defaultWidth: 520,
  defaultHeight: 420,
}

Persisting State

Use usePersistedState() (Dexie/IndexedDB-backed):

tsx

const { value, setValue, isLoading } = usePersistedState<Settings>('myapp.settings', defaultSettings);

Window Instance Control

Apps receive windowId as a prop to control their window:

tsx

const MyApp: React.FC<{ windowId: string }> = ({ windowId }) => {
    const { setTitle, setBadge } = useWindowInstance(windowId);
    // ...
};

Toast Notifications

tsx

const notify = useNotification();
notify.success('Saved!');
notify.error('Failed');

Keyboard Shortcuts

tsx

useStandardHotkeys({
    onSave: () => handleSave(),
    onFind: () => handleFind(),
});

Constraints

Prefer existing UI primitives in components/ui/
Prefer usePersistedState() over useLocalStorage() for persistence
Don't invent new global patterns when existing hooks/contexts solve it
Keep id in registry stable (used for session restore)

Documentation Index

Core Architecture

core/app-architecture.md - App registration and lazy loading
core/window-lifecycle.md - Window creation, focus, persistence
core/state-management.md - Where state lives
core/data-flow.md - Data flow diagrams

Guides

guides/creating-simple-app.md - Step-by-step new app
guides/adding-persistence.md - Persist app state
guides/state-persistence.md - Detailed persistence patterns
guides/hotkeys.md - Keyboard shortcuts
guides/notifications.md - Toast notifications
guides/styling-patterns.md - UI patterns
guides/building-apps.md - Full integration guide
guides/localization.md - Multi-language support
guides/db-migration.md - Migrate to IndexedDB

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