electron-dev

What this skill does

# Electron desktop development

Patterns and practices for building production-quality Electron applications with React and TypeScript.

## Security baseline (Electron 30+)

Electron's defaults have hardened over the past several releases. As of Electron 28+, `contextIsolation: true` and `sandbox: true` are the defaults for new BrowserWindow instances — most security advice from older guides assumed you had to opt in. You don't anymore; you have to opt OUT, and you should not.

Set explicitly anyway, so a config drift never weakens the security model:

```javascript
const win = new BrowserWindow({
  webPreferences: {
    contextIsolation: true,        // default since 12, mandatory for any prod app
    sandbox: true,                  // default since 28; renderer runs sandboxed
    nodeIntegration: false,         // never enable in renderer
    webSecurity: true,              // never disable
    preload: path.join(__dirname, 'preload.cjs')
  }
});
```

Validate every IPC message in main. Don't trust the renderer.

### Electron Fuses + ASAR integrity

Electron Fuses are package-time toggles baked into the binary. The two relevant for security distribution:

- `EnableEmbeddedAsarIntegrityValidation` — verifies the app.asar hash at runtime against a hash embedded in the binary. Defends against attackers swapping the asar contents post-install.
- `OnlyLoadAppFromAsar` — refuses to load app code from anywhere except the validated asar.

These are **opt-in**, not default. Enable both for production. Requires `@electron/asar` 3.1.0+ to generate the asar with embeddable integrity. electron-builder configures this via `electronFuses` in the build config; `@electron/fuses` does it programmatically.

CVE-2023-44402 (ASAR integrity bypass via filetype confusion) was the canonical motivation here — without integrity + only-load-from-asar, an attacker who can modify app files can swap behavior silently.

### Common renderer-side risks

- **Preload script confusion** — only expose narrow, typed surfaces via `contextBridge.exposeInMainWorld`. Never re-export `ipcRenderer` itself; expose specific methods that map to specific channels.
- **`file://` IPC and navigation** — restrict navigation with `webContents.on('will-navigate', e => e.preventDefault())` for windows that shouldn't change URL. Deny `setWindowOpenHandler` requests by default; allow-list specific origins.
- **`shell.openExternal` with user input** — validate the URL scheme before opening. An attacker-controlled `file://` or `javascript:` URL hands them code execution.

## Architecture patterns

### Project structure
```
app/
├── electron/
│   ├── main.cjs              # Main process (CommonJS required)
│   ├── preload.cjs           # Context bridge for secure IPC
│   └── server.cjs            # Optional: WebSocket/HTTP server
├── src/
│   ├── components/           # React components
│   ├── services/             # Business logic (API clients, Firebase)
│   ├── utils/                # Utilities (audio, formatting)
│   ├── types.ts              # TypeScript interfaces
│   ├── App.tsx               # Root component
│   └── index.tsx             # React entry
├── assets/                   # Icons, sounds, images
├── package.json
├── vite.config.ts
└── electron-builder.yml      # Build configuration
```

### IPC communication pattern

**Main process (main.cjs):**
```javascript
const { ipcMain } = require('electron');

// Handle async requests from renderer
ipcMain.handle('action-name', async (event, args) => {
  try {
    const result = await someAsyncOperation(args);
    return { success: true, data: result };
  } catch (error) {
    return { success: false, error: error.message };
  }
});

// Send data to renderer
mainWindow.webContents.send('event-name', data);
```

**Preload script (preload.cjs):**
```javascript
const { contextBridge, ipcRenderer } = require('electron');

contextBridge.exposeInMainWorld('electron', {
  actionName: (args) => ipcRenderer.invoke('action-name', args),
  onEventName: (callback) => {
    const handler = (event, data) => callback(data);
    ipcRenderer.on('event-name', handler);
    return () => ipcRenderer.removeListener('event-name', handler);
  }
});
```

**Renderer (React):**
```typescript
const result = await window.electron.actionName(args);

useEffect(() => {
  return window.electron.onEventName((data) => {
    setState(data);
  });
}, []);
```

## System tray integration

```javascript
const { Tray, Menu, nativeImage } = require('electron');

let tray = null;

function createTray() {
  const icon = nativeImage.createFromPath(path.join(__dirname, '../assets/tray-icon.png'));
  tray = new Tray(icon.resize({ width: 16, height: 16 }));

  tray.setToolTip('App Name');
  tray.setContextMenu(Menu.buildFromTemplate([
    { label: 'Show', click: () => mainWindow.show() },
    { label: 'Quit', click: () => app.quit() }
  ]));

  tray.on('click', () => {
    mainWindow.isVisible() ? mainWindow.hide() : mainWindow.show();
  });
}

// Hide to tray instead of closing
mainWindow.on('close', (event) => {
  if (!app.isQuitting) {
    event.preventDefault();
    mainWindow.hide();
  }
});
```

## Global shortcuts

```javascript
const { globalShortcut } = require('electron');

app.whenReady().then(() => {
  // Register with conflict detection
  const registered = globalShortcut.register('Alt+S', () => {
    mainWindow.webContents.send('shortcut-triggered', 'toggle-recording');
  });

  if (!registered) {
    console.error('Shortcut registration failed - conflict detected');
  }
});

app.on('will-quit', () => {
  globalShortcut.unregisterAll();
});
```

## PTY terminal integration (node-pty)

```javascript
const pty = require('node-pty');

const shell = process.platform === 'win32' ? 'powershell.exe' : process.env.SHELL || '/bin/bash';

const ptyProcess = pty.spawn(shell, [], {
  name: 'xterm-256color',
  cols: 80,
  rows: 24,
  cwd: process.env.HOME,
  env: process.env
});

ptyProcess.onData((data) => {
  mainWindow.webContents.send('terminal-data', { tabId, data });
});

ipcMain.on('terminal-write', (event, { tabId, data }) => {
  ptyProcess.write(data);
});

ipcMain.on('terminal-resize', (event, { tabId, cols, rows }) => {
  ptyProcess.resize(cols, rows);
});
```

## Audio recording workflow

```typescript
// Request microphone access
const stream = await navigator.mediaDevices.getUserMedia({
  audio: {
    echoCancellation: true,
    noiseSuppression: true,
    autoGainControl: true
  }
});

// Record audio
const mediaRecorder = new MediaRecorder(stream, { mimeType: 'audio/webm' });
const chunks: Blob[] = [];

mediaRecorder.ondataavailable = (e) => chunks.push(e.data);
mediaRecorder.onstop = async () => {
  const blob = new Blob(chunks, { type: 'audio/webm' });
  const base64 = await blobToBase64(blob);
  // Send to transcription API
};

mediaRecorder.start();
// Later: mediaRecorder.stop();
```

## WebRTC patterns (PeerJS)

```typescript
import Peer from 'peerjs';

const peer = new Peer(userId, {
  host: 'peerjs-server.com',
  port: 443,
  secure: true
});

// Answer incoming calls
peer.on('call', (call) => {
  call.answer(localStream);
  call.on('stream', (remoteStream) => {
    audioElement.srcObject = remoteStream;
  });
});

// Make outgoing calls
const call = peer.call(remoteUserId, localStream);
call.on('stream', (remoteStream) => {
  audioElement.srcObject = remoteStream;
});

// Screen sharing via replaceTrack (no renegotiation)
const screenStream = await navigator.mediaDevices.getDisplayMedia({ video: true });
const videoTrack = screenStream.getVideoTracks()[0];
const sender = peerConnection.getSenders().find(s => s.track?.kind === 'video');
await sender.replaceTrack(videoTrack);
```

## Build configuration (electron-builder.yml)

```yaml
appId: com.yourname.appname
productName: AppName
directories:
  output: release

win:
  target:
    - target: nsis
      arch: [x64]
  icon: assets/icon.ico

nsis:
  oneClick: false
  allowToChangeInstallationDirectory: true
  installerIc