MVVM Architecture

The new standard for desktop and mobile apps

• New code for ledger-live-desktop and ledger-live-mobile must go into src/mvvm/
• Eventually no feature code within these apps will live outside of src/mvvm
• New features, screens, components, hooks, and utilities belong in src/mvvm/
• Code changes with src/mvvm must conform to these mvvm patterns
• Code reviews enforce strict adherence

Folder Structure

src/mvvm/
├── features/
│   └── FeatureName/
│       ├── __integrations__/    ← mandatory integration tests
│       ├── components/          ← reusable UI across screens
│       ├── screens/             ← individual screen folders
│       ├── hooks/               ← feature-specific hooks
│       └── utils/               ← feature-scoped utilities
├── components/                  ← global shared UI
├── hooks/
└── utils/

Feature Folder Responsibilities

• components/ gathers reusable UI elements across multiple screens.
• screens/ contains individual screen folders and their private building blocks.
• hooks/ contains feature-specific reusable hooks.
• utils/ contains feature-scoped utilities.

Nesting Guidelines

• Place elements inside the closest folder matching their reuse scope.
• Screen-specific building blocks stay inside the screen folder.
• Feature-level components belong to FeatureName/components/.
• Global shared UI belongs to src/mvvm/components/.

Component & File Patterns

• Each component in its own folder with index.tsx as entry.
• ViewModel hooks always named use<ComponentName>ViewModel.ts.
• Support files alongside: types.ts, styles.ts.
• Use List / Detail naming for multi-view workflows.
• Utilities stay in utils/, separate from component folders.

ViewModel Pattern

Components needing external logic use Container → ViewModel → View:

• The ViewModel produces data and handlers.
• The View receives everything via props — no direct hook calls to external systems.

Violation checklist — flag if any index.tsx View under screens/ or components/ within src/mvvm/:

• Imports useSelector or useDispatch from react-redux
• Imports useNavigation or useRoute from @react-navigation/*
• Calls any RTK Query hook (useGet*Query, use*Mutation)
• Has no corresponding use<Name>ViewModel.ts in the same directory

❌ screens/UserProfileScreen/
     index.tsx   ← imports useSelector, useNavigation directly

✅ screens/UserProfileScreen/
     index.tsx                         ← props only
     useUserProfileScreenViewModel.ts  ← useSelector, useNavigation, RTK Query

Import Rules

• Keep relative imports shallow (within one directory level).
• Use TypeScript path aliases for broader access.
• Never import index.tsx explicitly — use folder alias exports.

Data Fetching

Use RTK Query (dada-client and cal-client are reference implementations). See rtk-query-api skill.

Design System

New UI in src/mvvm/ must use Lumen:

• Desktop: ldls-web skill
• Mobile: ldls-native skill

Testing

Every new feature under src/mvvm/ must have an integration test in __integrations__/ — create a minimal test when the folder is first added. See testing skill.