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fix(extension): await init in onMessage to fix lost click after SW sleeps (MV3 cold-start race) #24

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fix(extension): await init in onMessage to fix lost click after SW sleeps (MV3 cold-start race) #24

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110 changes: 68 additions & 42 deletions packages/chrome-extension/src/background.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -6,18 +6,29 @@ import ConfigStorageService from './services/config-storage-service';

let elementSender: ElementSenderService;
let currentConfig: ExtensionConfig;
let initPromise: Promise<void> | null = null;

// Initialize when service worker starts
async function initialize() {
currentConfig = await ConfigStorageService.load();
// Idempotent initialization. The MV3 service worker is terminated when idle and
// woken by the very message we need to handle, so the onMessage listener must
// AWAIT this before touching elementSender/currentConfig — otherwise the first
// click after the SW sleeps races the async config load and is silently lost
// (elementSender is still undefined -> TypeError).
function ensureInitialized(): Promise<void> {
if (!initPromise) {
initPromise = (async () => {
currentConfig = await ConfigStorageService.load();

// Create the service (no connection on startup)
elementSender = new ElementSenderService();
// Create the service (no connection on startup)
elementSender = new ElementSenderService();

logger.info('🚀 MCP Pointer background script loaded', {
enabled: currentConfig.enabled,
port: currentConfig.websocket.port,
});
logger.info('🚀 MCP Pointer background script loaded', {
enabled: currentConfig.enabled,
port: currentConfig.websocket.port,
});
})();
}

return initPromise;
}

// Listen for config changes
Expand All @@ -34,42 +45,57 @@ ConfigStorageService.onChange((newConfig: ExtensionConfig) => {
}
});

// Listen for messages from content script
// Listen for messages from content script.
// NOTE: the listener itself is registered synchronously at the top level and is
// NOT async; the async work runs in an inner IIFE and we return true to keep the
// channel open (per MV3 messaging guidance).
chrome.runtime.onMessage
.addListener((request: any, _sender: any, sendResponse: (response: any) => void) => {
if (request.type === 'DOM_ELEMENT_POINTED' && request.data) {
// Send element with current port and status callback
elementSender.sendElement(
request.data,
currentConfig.websocket.port,
(status, error) => {
// Status flow: CONNECTING -> CONNECTED -> SENDING -> SENT
switch (status) {
case ConnectionStatus.CONNECTING:
logger.info('🔄 Connecting to WebSocket...');
break;
case ConnectionStatus.CONNECTED:
logger.info('✅ Connected');
break;
case ConnectionStatus.SENDING:
logger.info('📤 Sending element...');
break;
case ConnectionStatus.SENT:
logger.info('✓ Element sent successfully');
break;
case ConnectionStatus.ERROR:
logger.error('❌ Failed:', error);
break;
default:
break;
}
},
);

sendResponse({ success: true });
(async () => {
try {
// Ensure config + sender are ready even on a cold SW start.
await ensureInitialized();

// Send element with current port and status callback
await elementSender.sendElement(
request.data,
currentConfig.websocket.port,
(status, error) => {
// Status flow: CONNECTING -> CONNECTED -> SENDING -> SENT
switch (status) {
case ConnectionStatus.CONNECTING:
logger.info('🔄 Connecting to WebSocket...');
break;
case ConnectionStatus.CONNECTED:
logger.info('✅ Connected');
break;
case ConnectionStatus.SENDING:
logger.info('📤 Sending element...');
break;
case ConnectionStatus.SENT:
logger.info('✓ Element sent successfully');
break;
case ConnectionStatus.ERROR:
logger.error('❌ Failed:', error);
break;
default:
break;
}
},
);

sendResponse({ success: true });
} catch (error) {
logger.error('❌ Failed to handle pointed element:', error);
sendResponse({ success: false, error: (error as Error).message });
}
})();

return true; // Keep message channel open for async response
}

return true; // Keep message channel open for async response
return true;
});

// Handle extension install/update
Expand All @@ -88,5 +114,5 @@ chrome.runtime.onInstalled.addListener((details) => {
}
});

// Start initialization
initialize();
// Best-effort warm start (messages also trigger ensureInitialized)
ensureInitialized();