multi-tv-builder

name	multi-tv-builder
displayName	Multi-TV Builder
description	Complete knowledge base for building production-ready cross-platform TV applications with React Native - supporting Android TV, Apple TV, Fire TV (Fire OS & Vega OS), and Web TV platforms with a single codebase. Use when implementing TV apps, monorepo architecture, spatial navigation, video playback, platform-specific optimizations, or migrating from Vega to multi-platform.
keywords	["tv","react-native","android-tv","apple-tv","fire-tv","vega","tvos","web-tv","video","streaming","spatial-navigation","monorepo","expo","migration","typescript","cross-platform","remote-control","focus-management"]
author	Giovanni Laquidara

Multi-TV Builder - Complete Knowledge Base

Build production-ready cross-platform TV applications with React Native, supporting Android TV, Apple TV, Fire TV (Fire OS & Vega OS), and Web TV platforms with a single codebase.

Quick Reference

• Sample Repo: https://github.com/AmazonAppDev/react-native-multi-tv-app-sample
• Slash Commands: /multi-tv-help, /multi-tv-setup, /multi-tv-build, /multi-tv-platform
• Skills: multi-tv-builder, apple-tv-troubleshooter, tmdb-integration
• Author: Giovanni Laquidara

Core Capabilities

• Cross-platform TV support with single codebase for 5+ platforms
• Monorepo architecture with Yarn workspaces for apps and shared packages
• Spatial navigation optimized for TV remote controls and D-pad input
• Video playback with custom controls and remote integration
• Platform-specific optimizations using automatic file resolution
• Shared UI library with reusable TV-optimized components
• TypeScript-first with strict type safety across all packages

Supported Platforms

Platform	Technology	Output
Android TV	react-native-tvos	APK/AAB
Apple TV (tvOS)	react-native-tvos + Expo	IPA
Fire TV (Fire OS)	react-native-tvos	APK
Fire TV (Vega OS)	Amazon Vega SDK	Optimized VPKG
Web TV	React Native Web	HTML/JS Bundle

---

Product Overview

React Native Multi-TV App Sample

A production-ready TV application template for building cross-platform TV apps with a single React Native codebase.

Core Features

1. Video Playback

   • Integrated video player with react-native-video (universal) or W3C Media APIs (Vega)
   • Custom overlay controls with play/pause, seek bar, and time display
   • Remote control integration (play/pause, seek ±10s, exit)
   • Auto-hide controls after 5s of inactivity
   • Buffering indicators during loading

2. Spatial Navigation

   • React TV Space Navigation for focus management
   • D-pad/arrow key navigation optimized for TV remotes
   • Platform-specific remote control managers
   • Focus restoration when returning from player

3. Content Discovery

   • Dynamic content loading from external catalog API
   • Grid layouts optimized for TV screens
   • Detail screens with rich metadata (genre, rating, duration, year)
   • Dynamic hero banner based on focused content
   • Trending flags and content ratings

4. Navigation

   • Drawer navigation with left-side menu
   • Stack navigation for detail screens
   • Platform-specific navigation optimizations
   • Deep linking support (optional)

5. Responsive Design

   • Adaptive layouts for different TV screen sizes
   • Responsive scaling with useScale hook
   • Platform-specific layout adjustments
   • Safe zone handling for TV overscan

App Variants

1. expo-multi-tv - Universal app supporting Android TV, Apple TV, Fire TV (Fire OS), and Web
2. vega - Fire TV Vega OS optimized build using Amazon Vega SDK

Key Use Cases

• Streaming video applications
• Content discovery and browsing
• TV-optimized user interfaces
• Cross-platform TV development reference

---

Architecture & Structure

Monorepo Organization

project-root/
├── apps/                    # Application packages
│   ├── expo-multi-tv/      # Universal TV app
│   └── vega/               # Fire TV Vega optimized
├── packages/               # Shared packages
│   └── shared-ui/          # Shared components
├── package.json            # Workspace configuration
├── tsconfig.base.json      # Shared TypeScript config
├── babel.config.js         # Root babel configuration
└── yarn.lock               # Dependency lock file

Apps Directory

apps/expo-multi-tv/

Universal TV application built with Expo SDK.

Key Files:

• App.tsx - Main entry point
• app.json - Expo configuration
• package.json - App-specific dependencies
• tsconfig.json - TypeScript config extending base
• metro.config.js - Metro bundler configuration
• ios/ - iOS/tvOS native code
• android/ - Android TV native code

Platforms Supported:

• Android TV
• Apple TV (tvOS)
• Fire TV (Fire OS)
• Web (LG WebOS, Samsung Tizen)

apps/vega/

Fire TV Vega OS optimized application using Amazon Vega SDK.

Key Files:

• App.tsx - Main entry point
• package.json - Vega-specific dependencies
• tsconfig.json - TypeScript config
• metro.config.js - Metro bundler configuration
• android/ - Fire TV Vega native code

Platform Supported:

• Fire TV (Vega OS)

Shared UI Package Structure

packages/shared-ui/src/
├── app/                           # App-level configuration
│   └── remote-control/           # Platform-specific remote managers
│       ├── RemoteControlManager.android.ts
│       ├── RemoteControlManager.ios.ts
│       └── RemoteControlManager.kepler.ts
├── assets/                        # Static assets (fonts, images, icons)
├── components/                    # Reusable UI components
│   ├── player/                   # Video player components
│   ├── CustomDrawerContent.tsx   # Drawer menu
│   ├── FocusablePressable.tsx    # TV-optimized pressable
│   ├── LoadingIndicator.tsx      # Loading spinner
│   ├── MenuContext.tsx           # Menu state management
│   └── PlatformLinearGradient.tsx # Cross-platform gradient
├── data/                          # Data and API
│   └── moviesData.ts             # Movie catalog API
├── hooks/                         # Custom React hooks
│   └── useScale.ts               # Responsive scaling
├── navigation/                    # Navigation configuration
│   ├── AppNavigator.tsx          # Main app navigator
│   ├── DrawerNavigator.tsx       # Drawer navigation
│   ├── RootNavigator.tsx         # Root wrapper
│   └── types.ts                  # Navigation types
├── screens/                       # Screen components
│   ├── DetailsScreen.tsx         # Content detail
│   ├── ExploreScreen.tsx         # Content exploration
│   ├── HomeScreen.tsx            # Home/landing
│   ├── PlayerScreen.tsx          # Video player
│   ├── PlayerScreen.vega.tsx     # Vega-specific player
│   ├── SettingsScreen.tsx        # Settings
│   └── TVScreen.tsx              # TV content
├── theme/                         # Design system
│   ├── colors.ts                 # Color palette
│   ├── spacing.ts                # Spacing scale
│   ├── typography.ts             # Font styles
│   ├── safeZones.ts              # TV safe zones
│   └── index.ts                  # Theme exports
├── utils/                         # Utility functions
└── index.ts                       # Package exports

Platform-Specific File Resolution

Metro bundler automatically resolves platform files:

• .kepler.ts/tsx - Fire TV Vega OS (highest priority for Vega builds)
• .android.ts/tsx - Android TV & Fire TV Fire OS
• .ios.ts/tsx - Apple TV (tvOS)
• .vega.tsx - Vega-specific screens
• .web.ts/tsx - Web platforms (LG WebOS, Samsung Tizen)
• .ts/tsx - Default/shared implementation (lowest priority)

Example:

RemoteControlManager.android.ts  → Android TV
RemoteControlManager.ios.ts      → Apple TV
RemoteControlManager.kepler.ts   → Fire TV Vega

Key Architectural Patterns

Shared UI Library Pattern

• All reusable components live in @project/shared-ui package
• Apps import from shared package, never local files
• Platform-specific implementations use file extensions
• Single source of truth for UI components and screens

TV-First Design

• 10-foot UI: Larger touch targets, high-contrast colors, readable typography
• Safe zones: Content positioned within TV safe areas (see theme/safeZones.ts)
• Focus management: Clear visual focus indicators for all interactive elements
• Remote control: D-pad navigation with platform-specific key mappings

---

Technology Stack

Build System

• Yarn Workspaces v4+: Monorepo management
• Metro Bundler: Module bundling with platform-specific resolution
• TypeScript v5.3+: Strict mode enabled across all packages

Core Technologies

• React Native: v0.74+ (react-native-tvos fork)
• Expo SDK: v51+ (for universal app)
• React: v18.2+
• TypeScript: v5.3+ with strict mode

Navigation & Focus

• React Navigation v6: Drawer and stack navigators
• React TV Space Navigation: Spatial navigation for TV remotes
• Platform Remote Managers: Android (react-native-keyevent), iOS (TVEventHandler), Vega (Kepler SDK)

Video Playback

• react-native-video v6+: Universal app video player
• W3C Media APIs: Native video for Vega OS
• Custom overlay controls with spatial navigation

Platform-Specific SDKs

• Amazon Vega SDK: Fire TV Vega OS builds
• @amazon-devices packages: Kepler SDK components
• react-native-tvos: TV platform support (Android TV, Apple TV, Fire TV FOS)

Development Tools

• ESLint: Code quality with TypeScript and React plugins
• Prettier: Code formatting (120 char width, single quotes)
• Husky: Git hooks for pre-commit checks
• Commitlint: Conventional commit enforcement
• Jest: Unit testing

---

Implementation Patterns

Workspace Configuration

Root package.json:

{
  "name": "tv-app-project",
  "private": true,
  "workspaces": ["apps/*", "packages/*"],
  "packageManager": "yarn@4.5.0",
  "scripts": {
    "dev": "yarn workspace @project/expo-multi-tv start",
    "dev:android": "yarn workspace @project/expo-multi-tv android",
    "dev:ios": "yarn workspace @project/expo-multi-tv ios",
    "dev:web": "yarn workspace @project/expo-multi-tv web",
    "dev:vega": "yarn workspace @project/vega start",
    "build:vega": "yarn workspace @project/vega run build",
    "test:all": "yarn workspaces foreach -pt run test",
    "lint:all": "yarn workspaces foreach -pt run lint",
    "clean:all": "yarn workspaces foreach run clean"
  }
}

Theme System

Centralized design tokens in packages/shared-ui/src/theme/:

colors.ts:

export const colors = {
  primary: '#E50914',      // Netflix-style red
  background: '#141414',   // Dark background
  card: '#2F2F2F',        // Card background
  text: '#FFFFFF',        // Primary text
  textSecondary: '#B3B3B3' // Secondary text
};

spacing.ts:

export const spacing = {
  xs: 4,
  sm: 8,
  md: 16,
  lg: 24,
  xl: 32,
  xxl: 48
};

safeZones.ts:

export const safeZones = {
  horizontal: 48,  // Left/right margins for TV overscan
  vertical: 27     // Top/bottom margins
};

Responsive Scaling

useScale hook:

import { Dimensions } from 'react-native';

const BASE_WIDTH = 1920;
const BASE_HEIGHT = 1080;

export const useScale = () => {
  const { width, height } = Dimensions.get('window');

  const scaleWidth = width / BASE_WIDTH;
  const scaleHeight = height / BASE_HEIGHT;
  const scale = Math.min(scaleWidth, scaleHeight);

  return {
    scale: (size: number) => size * scale,
    width,
    height
  };
};

Remote Control Manager Interface

All platform managers implement this interface:

export interface RemoteControlManagerInterface {
  initialize(): void;
  cleanup(): void;
}

Android/Fire TV FOS (RemoteControlManager.android.ts):

import ReactNativeKeyEvent from 'react-native-keyevent';

export class RemoteControlManager implements RemoteControlManagerInterface {
  initialize() {
    ReactNativeKeyEvent.onKeyDownListener((keyEvent) => {
      // Handle Android TV remote keys
    });
  }

  cleanup() {
    ReactNativeKeyEvent.removeKeyDownListener();
  }
}

Apple TV (RemoteControlManager.ios.ts):

import { TVEventHandler } from 'react-native';

export class RemoteControlManager implements RemoteControlManagerInterface {
  private tvEventHandler: TVEventHandler | null = null;

  initialize() {
    this.tvEventHandler = new TVEventHandler();
    this.tvEventHandler.enable(this, (component, evt) => {
      // Handle tvOS remote events
    });
  }

  cleanup() {
    this.tvEventHandler?.disable();
  }
}

Fire TV Vega (RemoteControlManager.kepler.ts):

import { TVEventHandler } from '@amazon-devices/react-native-kepler';

export class RemoteControlManager implements RemoteControlManagerInterface {
  private tvEventHandler: TVEventHandler | null = null;

  initialize() {
    this.tvEventHandler = new TVEventHandler();
    this.tvEventHandler.enable(this, (component, evt) => {
      // Handle Vega remote events
    });
  }

  cleanup() {
    this.tvEventHandler?.disable();
  }
}

Spatial Navigation Setup

Integration with React TV Space Navigation:

import { SpatialNavigation } from 'react-tv-space-navigation';

// Initialize in App.tsx
SpatialNavigation.init({
  debug: __DEV__,
  visualDebug: __DEV__
});

// Use in components
import { useFocusable } from 'react-tv-space-navigation';

const MyComponent = () => {
  const { ref, focused } = useFocusable();

  return (
    <View ref={ref} style={focused ? styles.focused : styles.default}>
      {/* Content */}
    </View>
  );
};

Video Player Implementation

Universal App (expo-multi-tv):

import Video from 'react-native-video';

<Video
  source={{ uri: videoUrl }}
  style={styles.video}
  controls={Platform.OS === 'ios'} // Native controls on iOS
  resizeMode="contain"
  onLoad={handleLoad}
  onProgress={handleProgress}
  ref={videoRef}
/>

Vega App:

// Use W3C Media APIs through Kepler SDK
import { VideoView } from '@amazon-devices/react-native-kepler';

<VideoView
  source={{ uri: videoUrl }}
  style={styles.video}
  onLoad={handleLoad}
  ref={videoRef}
/>

Dynamic Content Loading

Catalog API Integration:

// packages/shared-ui/src/data/moviesData.ts
export interface Movie {
  id: string;
  title: string;
  genre: string;
  rating: number;
  contentRating: string;
  year: number;
  duration: number;
  videoUrl: string;
  imageUrl: string;
  trending: boolean;
}

export const fetchMovies = async (): Promise<Movie[]> => {
  const response = await fetch('https://api.example.com/catalog.json');
  const data = await response.json();
  return transformCatalogData(data);
};

---

Common Commands

Development

# Install all dependencies
yarn install

# Start Metro bundler for expo-multi-tv
yarn dev

# Run on specific platforms
yarn dev:android    # Android TV & Fire TV FOS
yarn dev:ios        # Apple TV
yarn dev:web        # Web TV platforms

# Start Metro bundler for vega
yarn dev:vega

Building

Expo Multi-TV App:

# Build for all platforms
cd apps/expo-multi-tv

# Android TV / Fire TV (Fire OS)
npx expo build:android
# or: npx expo run:android

# Apple TV (tvOS)
npx expo build:ios
# or: npx expo run:ios

# Web TV platforms
npx expo export --platform web

Fire TV Vega App:

# From project root
yarn build:vega         # Build release VPKG
yarn build:vega:debug   # Build debug VPKG

# From apps/vega directory
cd apps/vega

# Build with npm (default from Vega CLI)
npm run build:app       # Builds for all architectures

# Build with Vega CLI (more control)
vega build --arch armv7 --buildType release    # Fire TV Stick
vega build --arch aarch64 --buildType release  # M-series Mac virtual devices
vega build --arch x86_64 --buildType release   # Intel virtual devices

# Clean build
rm -rf build && npm run build:app

Testing & Linting

# Run tests across all workspaces
yarn test:all

# Lint all workspaces
yarn lint:all

# Type check
yarn typecheck

# Format code
yarn format

Vega CLI Commands

Project Management:

# List available project templates
vega project list-templates

# Generate new Vega project (files are created in current directory)
# First create and cd into target directory, then generate:
mkdir -p myapp && cd myapp
vega project generate -n myapp --template helloWorld

# Verify Vega SDK installation
vega --version

Building:

# Build for specific architecture and build type
vega build --arch <armv7|aarch64|x86_64> --buildType <debug|release>

# Examples:
vega build --arch armv7 --buildType release     # Production Fire TV Stick build
vega build --arch aarch64 --buildType debug     # Debug build for M-series Mac
vega build --arch x86_64 --buildType debug      # Debug build for Intel virtual device

Device Management:

# List connected devices
vega device list

# Install VPKG on device
vega install --vpkg <path-to-vpkg-file>

# Run app on device
vega run --packageId com.company.myapp

---

Getting Started

Quick Start (Recommended)

The fastest way to get started is to clone the official React Native Multi-TV App Sample repository.

Clone the Repository:

# Clone the official sample repository
git clone https://github.com/AmazonAppDev/react-native-multi-tv-app-sample.git
cd react-native-multi-tv-app-sample

# Install dependencies
yarn install

# Bootstrap the monorepo
yarn bootstrap

What's Included:

• ✅ Pre-configured monorepo with Yarn workspaces
• ✅ expo-multi-tv app - Universal app for Android TV, Apple TV, Fire TV (Fire OS), and Web
• ✅ vega app - Fire TV Vega OS optimized app
• ✅ shared-ui package - Complete component library
• ✅ All configuration files

Next Steps After Cloning:

1. Review the codebase
2. Set up for Expo TV - Follow Expo TV documentation
3. Set up for Vega (optional) - Install Vega SDK
4. Run on platforms
5. Customize for your needs

Alternative: Build from Scratch

1. Initialize Project Structure

# Create project directory
mkdir my-tv-app && cd my-tv-app

# Initialize package.json
yarn init -y

# Create directory structure
mkdir -p apps packages/shared-ui

2. Configure Shared TypeScript

Create tsconfig.base.json:

{
  "compilerOptions": {
    "target": "ESNext",
    "module": "CommonJS",
    "lib": ["ES2021"],
    "jsx": "react-native",
    "strict": true,
    "moduleResolution": "node",
    "allowSyntheticDefaultImports": true,
    "esModuleInterop": true,
    "skipLibCheck": true
  }
}

3. Set Up Shared UI Package

cd packages/shared-ui
yarn init -y

# Install dependencies
yarn add react react-native
yarn add -D typescript @types/react @types/react-native

# Create src directory structure
mkdir -p src/{components,screens,navigation,hooks,theme,app/remote-control,data,utils,assets}

4. Create Universal App (expo-multi-tv)

IMPORTANT: Follow the official Expo TV setup guide.

Option 1: Start with the basic TV template:

cd apps
npx create-expo-app@latest expo-multi-tv -e with-tv

Option 2: Start with the TV Router template (recommended):

cd apps
npx create-expo-app@latest expo-multi-tv -e with-router-tv

After creating the app:

1. Link shared-ui package by editing apps/expo-multi-tv/package.json
2. Install additional TV dependencies
3. Configure Metro bundler for monorepo

5. Create Vega App (Optional - Fire TV Vega OS Only)

Prerequisites: Install Vega SDK

Required Dependencies (macOS):

# For Apple Silicon Macs (includes Rosetta 2)
[[ $(arch) == "arm64" ]] && softwareupdate --install-rosetta --agree-to-license; brew update && brew install binutils coreutils gawk findutils grep jq lz4 gnu-sed watchman

# For Intel Macs
brew update && brew install binutils coreutils gawk findutils grep jq lz4 gnu-sed watchman

Install Vega SDK:

1. Close VS Code before installing
2. Download and run installer
3. Add export commands to shell config
4. Verify: kepler --version

Create Vega Project:

# Files are generated in current directory, so create and cd into target first
mkdir -p apps/vega
cd apps/vega

vega project generate -n vega --template helloWorld

6. Configure Metro Bundler

metro.config.js (in each app):

const { getDefaultConfig } = require('expo/metro-config');
const path = require('path');

const config = getDefaultConfig(__dirname);

// Add monorepo support
const projectRoot = __dirname;
const workspaceRoot = path.resolve(projectRoot, '../..');

config.watchFolders = [workspaceRoot];
config.resolver.nodeModulesPaths = [
  path.resolve(projectRoot, 'node_modules'),
  path.resolve(workspaceRoot, 'node_modules'),
];

module.exports = config;

---

Vega to Multi-TV Migration Guide

Prerequisites

• Node.js 18+
• Yarn 4.x (Berry)
• Java 17 (for Android builds)
• Android SDK with TV emulator
• Xcode (for Apple TV builds)

Phase 1: Monorepo Setup

1.1 Initialize Yarn Workspaces

Create root package.json:

{
  "name": "@mycompany/multi-tv",
  "version": "1.0.0",
  "private": true,
  "packageManager": "yarn@4.5.0",
  "workspaces": [
    "apps/*",
    "packages/*"
  ],
  "resolutions": {
    "metro-source-map": "0.80.12"
  }
}

CRITICAL: The metro-source-map resolution is required to fix a babel plugin error. Without it, you'll get:

.plugins[0] must be a string, object, function

1.2 Create Root Babel Config

CRITICAL: Create babel.config.js at monorepo root. Metro looks for babel config starting from the project root.

const path = require('path');

module.exports = function (api) {
  api.cache(true);

  // Try to resolve reanimated plugin from the universal TV app
  let reanimatedPlugin;
  try {
    reanimatedPlugin = require.resolve('react-native-reanimated/plugin', {
      paths: [path.join(__dirname, 'apps/universal-tv/node_modules')]
    });
  } catch (e) {
    try {
      reanimatedPlugin = require.resolve('react-native-reanimated/plugin');
    } catch (e2) {
      reanimatedPlugin = null;
    }
  }

  const plugins = reanimatedPlugin ? [reanimatedPlugin] : [];

  return {
    presets: ['babel-preset-expo'],
    plugins,
  };
};

Phase 2: Shared UI Package Setup

Platform-Specific File Resolution

Extension	Platform	Description
.ts / .tsx	All	Base/shared implementation
.native.ts	React Native	Android TV, Apple TV, Fire TV FOS
.android.ts	Android	Android TV, Fire TV FOS
.ios.ts	iOS/tvOS	Apple TV
.kepler.ts	Vega	Fire TV Vega OS specific
.web.ts	Web	Web TV specific

CRITICAL - Avoiding Circular Dependencies:

When you have a base class that platform-specific files extend, Metro's platform resolution can create a circular dependency.

# BAD - Creates circular dependency
RemoteControlManager.ts        # Base class
RemoteControlManager.android.ts # Imports from RemoteControlManager.ts

FIX: Rename base files to use .base.ts extension:

# GOOD - No circular dependency
RemoteControlManager.base.ts    # Base class
RemoteControlManager.android.ts # Imports from RemoteControlManager.base.ts
RemoteControlManager.ios.ts     # Imports from RemoteControlManager.base.ts

Phase 3: Universal TV App Setup (Expo)

Fix HMRClient Error (CRITICAL)

CRITICAL: The react-native-tvos fork has an HMR (Hot Module Replacement) incompatibility.

Fix: Add HMRClient polyfill to apps/universal-tv/index.js:

import { registerRootComponent } from 'expo';
import { AppRegistry } from 'react-native';
import App from './App';

// Polyfill for HMRClient to prevent "Module has not been registered as callable" error
if (!AppRegistry.getRunnable('HMRClient')) {
  AppRegistry.registerCallableModule('HMRClient', {
    setup: () => {},
    enable: () => {},
    disable: () => {},
  });
}

registerRootComponent(App);

Configure app.json

{
  "expo": {
    "name": "MyTVApp",
    "slug": "my-tv-app",
    "version": "1.0.0",
    "orientation": "landscape",
    "userInterfaceStyle": "dark",
    "plugins": [
      "@react-native-tvos/config-tv"
    ]
  }
}

Phase 4: Platform Abstraction Layer

Remote Control Manager Pattern

Create base class in packages/shared-ui/src/app/remote-control/RemoteControlManager.base.ts:

export type RemoteKey =
  | 'up' | 'down' | 'left' | 'right'
  | 'select' | 'back'
  | 'play' | 'pause' | 'playPause'
  | 'fastForward' | 'rewind'
  | 'menu';

export interface RemoteKeyEvent {
  key: RemoteKey;
  action: 'keyDown' | 'keyUp';
  timestamp: number;
}

export type RemoteKeyHandler = (event: RemoteKeyEvent) => void;

export interface RemoteControlManagerInterface {
  initialize(): void;
  cleanup(): void;
  addKeyListener(handler: RemoteKeyHandler): () => void;
  removeKeyListener(handler: RemoteKeyHandler): void;
}

export class BaseRemoteControlManager implements RemoteControlManagerInterface {
  protected listeners: Set<RemoteKeyHandler> = new Set();

  initialize(): void {
    // Override in platform-specific implementation
  }

  cleanup(): void {
    this.listeners.clear();
  }

  addKeyListener(handler: RemoteKeyHandler): () => void {
    this.listeners.add(handler);
    return () => this.removeKeyListener(handler);
  }

  removeKeyListener(handler: RemoteKeyHandler): void {
    this.listeners.delete(handler);
  }

  protected notifyListeners(event: RemoteKeyEvent): void {
    this.listeners.forEach((handler) => handler(event));
  }
}

Video Player Service Pattern

Create interface in packages/shared-ui/src/services/videoPlayer/VideoPlayerService.ts:

export interface VideoSource {
  uri: string;
  type?: 'hls' | 'dash' | 'mp4';
  headers?: Record<string, string>;
  drm?: DRMConfig;
}

export interface DRMConfig {
  type: 'widevine' | 'fairplay' | 'playready';
  licenseServer: string;
  headers?: Record<string, string>;
}

export interface PlaybackState {
  isPlaying: boolean;
  isPaused: boolean;
  isBuffering: boolean;
  currentTime: number;
  duration: number;
}

export interface VideoPlayerService {
  initialize(): Promise<void>;
  load(source: VideoSource): Promise<void>;
  play(): Promise<void>;
  pause(): Promise<void>;
  seek(timeInSeconds: number): Promise<void>;
  destroy(): Promise<void>;
  getPlaybackState(): PlaybackState;
}

export const DEFAULT_SEEK_SECONDS = 10;

Create native implementation in VideoPlayerService.native.ts (uses react-native-video). Create Vega implementation in VideoPlayerService.kepler.ts (uses Shaka/W3C Media).

Migration Troubleshooting

Error: .plugins[0] must be a string, object, function

Cause: metro-source-map version mismatch in monorepo Fix: Add resolution in root package.json:

"resolutions": {
  "metro-source-map": "0.80.12"
}

Error: Super expression must either be null or a function

Cause: Circular dependency in class inheritance due to Metro's platform resolution Fix: Rename base class files from ClassName.ts to ClassName.base.ts

Error: HMRClient.setup() Module has not been registered

Cause: react-native-tvos HMR incompatibility with Expo Fix: Add HMRClient polyfill in index.js

Error: Cannot find module '@mycompany/shared-ui'

Cause: Metro not configured for monorepo workspace resolution Fix:

1. Add watchFolders in metro.config.js
2. Add extraNodeModules mapping
3. Run yarn install from root

Warning: Require cycle: X.ts -> X.ts

Cause: Platform-specific file importing itself due to Metro resolution Fix: Rename base file to use .base.ts extension

Version Compatibility Matrix

Package	Version	Notes
expo	~51.0.0	Required for TV support
react	18.2.0	Must match expo requirement
react-native-tvos	~0.74.3-0	Use instead of react-native
metro-source-map	0.80.12	Force via resolution
react-native-reanimated	~3.10.1	For animations
@react-native-tvos/config-tv	^0.0.12	Expo plugin for TV
react-tv-space-navigation	^3.6.1	Spatial navigation
Java	17	Required for Android Gradle
Node.js	18+	Required for Expo
Yarn	4.x	Berry with workspaces

---

Best Practices

TV-Specific Design

• Always test on actual TV hardware, not just emulators
• Maintain 10-foot UI standards (large text, high contrast)
• Position critical UI within safe zones (48px horizontal, 27px vertical)
• Provide clear focus indicators (borders, scale, highlights)
• Design for remote control first, touch second

Focus Management

• Set default focus on screen mount
• Restore focus when returning from navigation
• Prevent focus traps (ensure all UI is reachable)
• Test navigation flow with D-pad only
• Handle edge cases (first/last item in grid)

Performance

• Optimize image sizes for TV resolution (1920x1080)
• Use FlatList for long scrolling lists
• Implement image caching strategy
• Lazy load video content
• Monitor memory usage on low-end devices

Platform-Specific Code

• Use file extensions for platform variants
• Keep shared logic in base files
• Document platform differences
• Test each platform independently
• Abstract platform APIs behind common interfaces

Video Player

• Always show buffering state
• Handle network failures gracefully
• Implement playback controls with remote support
• Test with various video formats and codecs
• Support multiple video qualities/bitrates

Content Loading

• Implement retry logic for failed requests
• Show loading states during fetch
• Cache catalog data locally
• Handle empty states gracefully
• Validate API response structure

---

Testing

Unit Tests

• Test business logic in shared-ui package
• Mock platform-specific modules
• Test remote control event handlers
• Validate navigation flows
• Test data transformations

Integration Tests

• Test cross-platform file resolution
• Validate navigation between screens
• Test video player controls
• Verify focus management
• Test catalog API integration

Platform Testing

• Test on Android TV emulator and device
• Test on Apple TV simulator and device
• Test on Fire TV device
• Test on web browser with keyboard navigation
• Verify remote control functionality per platform

---

Troubleshooting

Metro Bundler Issues

• Clear cache: yarn start --reset-cache
• Check for port conflicts (default 8081)
• Verify workspace resolution in metro.config.js

Platform-Specific Build Failures

• iOS/tvOS: Check Node binary path in .xcode.env.local
• Android TV: Verify Android SDK and emulator setup
• Vega: See Vega-specific troubleshooting below

Vega SDK Issues

Installation Problems

'Electron quit unexpectedly' during installation

• This is expected if VS Code is running during installation
• Restart VS Code after installation completes

Vega SDK not found / kepler command not available

• Verify: kepler --version
• Check environment variables:

  echo $KEPLER_SDK_PATH
  echo $PATH | grep kepler
  

• Add exports to shell config if missing

Development utilities missing (macOS)

brew update && brew install binutils coreutils gawk findutils grep jq lz4 gnu-sed watchman

Build Failures

npm run build:app fails

• Ensure dependencies installed: npm install
• Check Node.js version: node --version (requires 16.x or later)
• Verify package ID format (reverse DNS, no com.amazon)
• Check Metro not already running on port 8081

VPKG file not generated

• Check build output: build/<architecture>-<buildType>/
• Try clean build: rm -rf build && npm run build:app

Runtime Issues

App crashes on Vega device

• Check device logs for errors
• Verify VPKG architecture matches device
• Test with debug build first
• Ensure native dependencies compatible with Vega SDK

Metro bundler connection issues

• Verify Metro is running: yarn start
• Check firewall settings
• Ensure device and dev machine on same network

Navigation Issues

• Verify React Navigation installation
• Check focus restoration logic
• Test with D-pad/arrow keys only
• Enable spatial navigation debug mode

Video Playback Issues

• Verify video URL accessibility
• Check video format compatibility (MP4 recommended)
• Test with different video codecs
• Monitor network bandwidth

---

Additional Resources

Sample Repositories

React Native Multi-TV App Sample

• Repository: https://github.com/AmazonAppDev/react-native-multi-tv-app-sample
• Complete monorepo setup
• Working implementations for all platforms
• Reference for best practices

Official Documentation

Expo TV Documentation

• System requirements and prerequisites
• Quick start with TV templates
• EAS Build profiles for TV
• Platform-specific build instructions

Vega SDK Documentation

• Installation guide
• Vega CLI guide
• Device setup
• Deployment to Amazon Appstore

External Resources

• React Native TV (react-native-tvos)
• React TV Space Navigation
• Expo Examples - TV
• Expo Examples - TV Router
• React Navigation
• React Native Directory

---

Adding New Features

New Shared Component

1. Create in packages/shared-ui/src/components/ComponentName.tsx
2. Export from packages/shared-ui/src/index.ts
3. Import in apps: import { ComponentName } from '@project/shared-ui'

Platform-Specific Implementation

1. Create base file: Feature.base.ts
2. Create platform files: Feature.android.ts, Feature.ios.ts, Feature.kepler.ts
3. Metro automatically resolves correct file at build time

New Screen

1. Create in packages/shared-ui/src/screens/ScreenName.tsx
2. Add to navigation in navigation/AppNavigator.tsx
3. Export from packages/shared-ui/src/index.ts
4. Use in app's navigation configuration

---

Vega App in Monorepo

Critical Configuration

1. Prevent Dependency Hoisting

Add to apps/vega/package.json:

{
  "installConfig": {
    "hoistingLimits": "dependencies"
  }
}

2. Fix Metro Source Map

Create apps/vega/fix-metro.js:

const fs = require('fs');
const path = require('path');

const metroSourceMapPath = path.join(__dirname, 'node_modules/metro-source-map');
const packageJsonPath = path.join(metroSourceMapPath, 'package.json');

if (!fs.existsSync(packageJsonPath)) {
  console.log('⚠ metro-source-map not found');
  process.exit(0);
}

const pkg = JSON.parse(fs.readFileSync(packageJsonPath, 'utf8'));
pkg.exports = {
  ".": "./src/source-map.js",
  "./package.json": "./package.json",
  "./private/*": "./src/*.js",
  "./src/*": "./src/*.js"
};

fs.writeFileSync(packageJsonPath, JSON.stringify(pkg, null, 2));
console.log('✓ Patched metro-source-map exports for Vega');

3. Add Postinstall Script

In apps/vega/package.json:

{
  "scripts": {
    "postinstall": "node fix-metro.js",
    "build:debug": "react-native build-kepler --build-type Debug",
    "build:release": "react-native build-kepler --build-type Release"
  }
}

Note: Use build-kepler command, not build-vega.

4. Manifest Configuration (CRITICAL)

The manifest.toml MUST include a [processes] section or the app will crash immediately on launch with no error message.

apps/vega/manifest.toml:

schema-version = 1

[package]
title = "My Vega App"
version = "0.1.0"
id = "com.mycompany.myapp"

[components]
[[components.interactive]]
id = "com.mycompany.myapp.main"
runtime-module = "/com.amazon.kepler.keplerscript.runtime.loader_2@IKeplerScript_2_0"
launch-type = "singleton"
categories = ["com.amazon.category.main"]

# CRITICAL: This section is REQUIRED or the app will crash on launch
[processes]
[[processes.group]]
component-ids = ["com.mycompany.myapp.main"]

Common Symptom: App installs successfully, shows "Successfully launched the app", but immediately crashes (black screen) with no visible error. The fix is adding the [processes] section.

5. Metro Configuration

apps/vega/metro.config.js:

const {getDefaultConfig, mergeConfig} = require('@react-native/metro-config');
const path = require('path');

const config = {
  watchFolders: [
    path.resolve(__dirname, '../../packages/shared-ui'),
  ],
  resolver: {
    unstable_enableSymlinks: true,
    sourceExts: ['kepler.tsx', 'kepler.ts', 'kepler.js', 'tsx', 'ts', 'jsx', 'js', 'json'],
    nodeModulesPaths: [
      path.resolve(__dirname, 'node_modules'),
      path.resolve(__dirname, '../../node_modules'),
    ],
  },
};

module.exports = mergeConfig(getDefaultConfig(__dirname), config);

5. Required Dependencies

In apps/vega/package.json:

{
  "dependencies": {
    "@amazon-devices/react-native-kepler": "^2.0.0",
    "@babel/runtime": "^7.28.6",
    "react": "18.2.0",
    "react-native": "0.72.0",
    "react-tv-space-navigation": "^6.0.0-beta1"
  },
  "devDependencies": {
    "@amazon-devices/kepler-cli-platform": "^0",
    "@amazon-devices/kepler-module-manifest-builder": "^0.1.0",
    "@react-native/metro-config": "^0.72.6",
    "jest-worker": "^28.0.0"
  }
}

6. Spatial Navigation with Vega (react-tv-space-navigation)

react-tv-space-navigation is compatible with Vega but requires a remote control configuration to map Vega's TVEventHandler to spatial navigation directions.

Create packages/shared-ui/src/app/remote-control/SupportedKeys.ts:

export enum SupportedKeys {
  Up = 'up',
  Down = 'down',
  Left = 'left',
  Right = 'right',
  Enter = 'enter',
  Back = 'back',
  PlayPause = 'playPause',
  Rewind = 'rewind',
  FastForward = 'fastForward',
}

Create packages/shared-ui/src/app/remote-control/RemoteControlManager.kepler.ts:

import { SupportedKeys } from './SupportedKeys';

type Listener = (event: SupportedKeys) => void;

const EVENT_TYPE_MAPPING: Record<string, SupportedKeys> = {
  left: SupportedKeys.Left,
  right: SupportedKeys.Right,
  down: SupportedKeys.Down,
  up: SupportedKeys.Up,
  select: SupportedKeys.Enter,
  back: SupportedKeys.Back,
  playpause: SupportedKeys.PlayPause,
  skip_backward: SupportedKeys.Rewind,
  skip_forward: SupportedKeys.FastForward,
};

class RemoteControlManager {
  private listeners: Set<Listener> = new Set();
  private tvEventHandler: any;

  constructor() {
    const { TVEventHandler } = require('react-native');
    this.tvEventHandler = new TVEventHandler();
    this.tvEventHandler.enable(this, this.handleHWEvent);
  }

  private handleHWEvent = (_component: any, event: any): void => {
    if (event.eventKeyAction === 0 || event.eventKeyAction === undefined) {
      const mappedKey = EVENT_TYPE_MAPPING[event.eventType];
      if (mappedKey) {
        this.listeners.forEach(listener => listener(mappedKey));
      }
    }
  };

  addKeydownListener = (listener: Listener) => {
    this.listeners.add(listener);
    return listener;
  };

  removeKeydownListener = (listener: Listener) => {
    this.listeners.delete(listener);
  };
}

export default new RemoteControlManager();

Create packages/shared-ui/src/app/configureRemoteControl.ts:

import { Directions, SpatialNavigation } from 'react-tv-space-navigation';
import { SupportedKeys } from './remote-control/SupportedKeys';
import RemoteControlManager from './remote-control/RemoteControlManager';

SpatialNavigation.configureRemoteControl({
  remoteControlSubscriber: (callback) => {
    const mapping: { [key in SupportedKeys]: Directions | null } = {
      [SupportedKeys.Right]: Directions.RIGHT,
      [SupportedKeys.Left]: Directions.LEFT,
      [SupportedKeys.Up]: Directions.UP,
      [SupportedKeys.Down]: Directions.DOWN,
      [SupportedKeys.Enter]: Directions.ENTER,
      [SupportedKeys.Back]: null,
      [SupportedKeys.PlayPause]: null,
      [SupportedKeys.Rewind]: null,
      [SupportedKeys.FastForward]: null,
    };

    const remoteControlListener = (keyEvent: SupportedKeys) => {
      callback(mapping[keyEvent]);
    };

    return RemoteControlManager.addKeydownListener(remoteControlListener);
  },
  remoteControlUnsubscriber: (remoteControlListener) => {
    RemoteControlManager.removeKeydownListener(remoteControlListener);
  },
});

Import in Vega App.tsx:

import '../../../packages/shared-ui/src/app/configureRemoteControl';

Build Commands

# Install dependencies
yarn install

# Build JS bundle and VPKG (from root)
yarn workspace @your-app/vega run build:debug

# Or from vega directory
cd apps/vega
npm run build:debug

# Build VPKG separately
vega build -t armv7 -b Debug

Why This Works

• installConfig.hoistingLimits - Forces Yarn to install dependencies locally instead of hoisting to monorepo root
• Metro fix - Patches package.json exports for Node.js 23+ compatibility with strict package exports
• nodeModulesPaths - Tells Metro to check local node_modules first, then fall back to root
• Local dependencies - @babel/runtime and jest-worker installed locally prevent monorepo version conflicts
• kepler-module-manifest-builder - Required Vega SDK tool for building VPKG

Common Issues

App crashes immediately on launch (black screen, no error)

• Cause: Missing [processes] section in manifest.toml
• Fix: Add the following to your manifest.toml:

  [processes]
  [[processes.group]]
  component-ids = ["com.yourcompany.yourapp.main"]
  

• Note: The component-id must match the one defined in [[components.interactive]]

Error: "Package subpath './src/DeltaBundler/Worker' not exported"

• Cause: jest-worker loading metro from wrong location
• Fix: Install jest-worker locally + run postinstall script

Error: "Unable to resolve @babel/runtime"

• Cause: Yarn hoisted @babel/runtime to root
• Fix: Add installConfig.hoistingLimits + install @babel/runtime locally

Error: "Could not find binary kepler-module-manifest-builder"

• Cause: Missing Vega SDK tool
• Fix: Install @amazon-devices/kepler-module-manifest-builder

---

Next Steps

Recommended Path (Quick Start)

1. Clone the repository - git clone https://github.com/AmazonAppDev/react-native-multi-tv-app-sample.git
2. Install dependencies - yarn install && yarn bootstrap
3. Review the codebase
4. Review documentation
5. Review steering files
6. Configure for Expo TV
7. Install Vega SDK (optional)
8. Test on platforms
9. Customize for your project
10. Deploy

Alternative Path (Build from Scratch)

Follow the step-by-step "Build from Scratch" guide above to understand:

• Monorepo setup with Yarn workspaces
• Expo TV configuration
• Vega SDK integration
• Shared component library architecture
• Platform-specific file resolution
• Theme system implementation
• Spatial navigation setup
• Remote control integration

---

For detailed implementation guides, see:

• multi-tv-builder/POWER.md - Complete implementation guide
• multi-tv-builder/steering/product.md - Product overview
• multi-tv-builder/steering/structure.md - Project structure details
• multi-tv-builder/steering/tech.md - Technology stack reference
• multi-tv-builder/steering/VEGA_TO_MONOREPO_MIGRATION_GUIDE.md - Migration guide

---

Android TV / Fire TV Troubleshooting

Common Runtime Errors

TypeError: Cannot read property 'displayName' of undefined

Symptoms:

• App builds successfully but crashes immediately on launch
• Metro shows: ERROR TypeError: Cannot read property 'displayName' of undefined, js engine: hermes
• App returns to launcher after brief flash

Common Causes & Fixes:

1. Wrong import in index.js (Most Common)

   // ❌ WRONG - Named import when App uses default export
   import { App } from './App';
   
   // ✅ CORRECT - Default import
   import App from './App';
   

2. Metro cache corruption

   # Clear all caches
   pkill -f "expo" 2>/dev/null || true
   pkill -f "metro" 2>/dev/null || true
   rm -rf node_modules/.cache
   rm -rf /tmp/metro-*
   rm -rf /tmp/haste-map-*
   npx expo start --clear
   

3. react-tv-space-navigation v6 missing configuration

   • v6 requires explicit remote control configuration
   • Create src/configureRemoteControl.ts:

   import { SpatialNavigation } from 'react-tv-space-navigation';
   
   SpatialNavigation.configureRemoteControl({
     remoteControlSubscriber: (callback) => () => {},
     remoteControlUnsubscriber: () => {},
   });
   

   • Import at top of App.tsx: import './src/configureRemoteControl';

App Launches But Shows Black Screen / Returns to Launcher

Diagnostic Steps:

1. Check if app process is running:

   adb shell "ps -A | grep <package_name>"
   

2. Check Metro bundler connection:

   # Verify Metro is running
   curl -s http://localhost:8081/status
   
   # Set up ADB reverse port forwarding
   adb reverse tcp:8081 tcp:8081
   

3. Check device logs for JS errors:

   adb logcat -d | grep -iE "(ReactNativeJS|ERROR|TypeError)" | tail -30
   

4. Verify bundle is loading:

   adb logcat -d | grep -i "bundled" | tail -5
   

Metro Bundler Connection Issues

Symptoms:

• Couldn't connect to "ws://localhost:8081/message..."
• App shows loading screen indefinitely
• ReactInstanceManager: Instance detached from instance manager

Fixes:

1. Set up ADB reverse port forwarding:

   adb reverse tcp:8081 tcp:8081
   

2. Verify emulator is connected:

   adb devices -l
   

3. Restart ADB if stale:

   adb kill-server && adb start-server
   

4. Use correct Metro start command:

   # For development builds (not Expo Go)
   npx expo start --dev-client --clear
   
   # Or run directly
   npx expo run:android
   

Android TV Emulator Setup

Starting the Emulator

# List available emulators
emulator -list-avds

# Start Android TV emulator (cold boot recommended for stability)
emulator -avd Android_TV_720p -no-snapshot-load -gpu swiftshader_indirect &

# Wait for boot and verify
adb wait-for-device
adb devices -l

Emulator Not Responding

# Kill stale processes
pkill -9 qemu-system 2>/dev/null || true
pkill -9 emulator 2>/dev/null || true
adb kill-server
sleep 1
adb start-server

# Start fresh
emulator -avd Android_TV_720p -no-snapshot-load &

Fire TV Emulator Specific Issues

The Fire TV emulator (Android_TV_720p with Fire OS) may show system errors in logs like:

• NEO_DIAL_SVC: DIAL_register_app error allocating memory
• libc++abi: terminating with uncaught exception

These are system service errors unrelated to your app - ignore them and focus on ReactNativeJS or your package name in logs.

Build & Launch Commands

Quick Launch Sequence

# 1. Ensure emulator is running
adb devices

# 2. Set up port forwarding
adb reverse tcp:8081 tcp:8081

# 3. Build and run (from app directory)
cd apps/expo-multi-tv
yarn android
# or: npx expo run:android

# 4. If app crashes, force restart
adb shell am force-stop <package_name>
adb shell am start -n <package_name>/.MainActivity

Debugging Workflow

# Clear logs before launch
adb logcat -c

# Launch app
adb shell am start -n com.example.app/.MainActivity

# Wait and capture logs
sleep 5
adb logcat -d | grep -iE "(ReactNativeJS|error|exception)" | tail -50

Expo Go vs Development Builds

Important: TV apps should use development builds, not Expo Go.

• Expo Go has SDK version mismatches on TV emulators
• Use npx expo run:android or npx expo start --dev-client
• If prompted about Expo Go version, choose development build instead

# ❌ May cause issues on TV
npx expo start

# ✅ Correct for TV development
npx expo run:android
# or
npx expo start --dev-client

Vega Virtual Device Notes

is-app-running Command May Report False Negatives

The command vega device is-app-running --appName <package> may incorrectly report that an app is not running even when it's visible and functioning on the virtual device.

Workaround: Visually verify the app is running in the virtual device window rather than relying on the CLI command.

# This may report "not running" even when app is visible
vega device is-app-running --appName com.example.app

# Instead, just launch and visually verify
vega run-app <vpkg-path> <package-id>
# Check the virtual device window

---

Monorepo React Version Conflict Resolution

Problem: Expo + Vega in Same Monorepo

When running Expo (React 19) and Vega (React 18) apps in the same Yarn workspace, Metro bundles the wrong React version causing runtime crashes:

TypeError: Cannot read property 'ReactCurrentOwner' of undefined
TypeError: Cannot read property 'render' of undefined

Root Cause

Yarn hoists dependencies to the workspace root. When Metro bundles the Vega app, it finds React 19 in the root node_modules/ before finding React 18 in apps/vega/node_modules/.

Solution: Move Root React Packages

Before running the Vega app, move the root React packages out of the way:

cd <workspace-root>
mv node_modules/react node_modules/react.bak
mv node_modules/react-native node_modules/react-native.bak

This forces Metro to use Vega's local React 18.2.0.

Note: After running yarn install, you'll need to move these packages again.

Alternative Solutions

1. Separate repositories - Keep Expo and Vega apps in different repos
2. Publish shared-ui - Publish as npm package instead of workspace dependency
3. Use consistent React versions - Not always possible due to SDK requirements

---

Node.js 23 Compatibility Issues

Problem: Metro Package Exports

Node.js 23 enforces strict package exports. Metro packages don't export internal paths, causing errors:

Package subpath './src/Consumer/search' is not defined by "exports"
Package subpath './src/DeltaBundler/Worker' is not defined by "exports"

Solution: Remove Exports Field

Create a script to remove the exports field from metro packages:

// fix-metro-exports.js
const fs = require('fs');
const path = require('path');

const packages = [
  'node_modules/metro',
  'node_modules/metro-source-map',
  'node_modules/metro-transform-worker',
  'node_modules/metro-runtime',
];

packages.forEach(pkgPath => {
  const packageJsonPath = path.join(pkgPath, 'package.json');
  if (!fs.existsSync(packageJsonPath)) return;
  
  const pkg = JSON.parse(fs.readFileSync(packageJsonPath, 'utf8'));
  delete pkg.exports;
  fs.writeFileSync(packageJsonPath, JSON.stringify(pkg, null, 2));
  console.log(`✓ Removed exports from ${path.basename(pkgPath)}`);
});

Run after yarn install:

node fix-metro-exports.js

Best Practice

Add to package.json scripts:

{
  "scripts": {
    "postinstall": "node fix-metro-exports.js"
  }
}

---

Vega Development Workflow (Complete)

Prerequisites

1. Vega SDK installed
2. Vega virtual device running: vega virtual-device start
3. Metro packages patched for Node 23 (if using Node 23)
4. Root React moved (if in Expo+Vega monorepo)

Step-by-Step

1. Patch Metro (Node 23 only)

node fix-metro-exports.js

2. Move Root React (Monorepo only)

mv node_modules/react node_modules/react.bak
mv node_modules/react-native node_modules/react-native.bak

3. Start Metro

cd apps/vega
npm start

4. Set Up Port Forwarding

vega device start-port-forwarding --port 8081 --forward false

5. Launch App

vega device launch-app --appName <package-id>

6. Verify

vega device running-apps | grep <app-name>

Troubleshooting Checklist

Issue	Check	Fix
Black screen	Metro running?	npm start in apps/vega
Black screen	Port forwarding?	vega device start-port-forwarding --port 8081 --forward false
ReactCurrentOwner error	Root React moved?	mv node_modules/react node_modules/react.bak
Package exports error	Metro patched?	Run fix-metro-exports.js
App not in running-apps	May be false negative	Visually verify in virtual device

---

Required Dependencies for Vega in Monorepo

When using Vega in a Yarn workspace, ensure these dependencies are installed locally in the Vega app:

cd apps/vega
npm install @babel/runtime --save

The @babel/runtime package is required for Babel transforms but may not be hoisted correctly in monorepos.