chore: add browser logs to the log file

src/browser.ts

@@ -61,6 +61,7 @@ type McpLaunchOptions = {
   userDataDir?: string;
   headless: boolean;
   isolated: boolean;
+  logFile?: fs.WriteStream;
 };
 
 export async function launch(options: McpLaunchOptions): Promise<Browser> {
@@ -100,7 +101,7 @@ export async function launch(options: McpLaunchOptions): Promise<Browser> {
   }
 
   try {
-    return await puppeteer.launch({
+    const browser = await puppeteer.launch({
       ...connectOptions,
       channel: puppeterChannel,
       executablePath,
@@ -110,6 +111,13 @@ export async function launch(options: McpLaunchOptions): Promise<Browser> {
       headless,
       args,
     });
+    if (options.logFile) {
+      // FIXME: we are probably subscribing too late to catch startup logs. We
+      // should expose the process earlier or expose the getRecentLogs() getter.
+      browser.process()?.stderr?.pipe(options.logFile);
+      browser.process()?.stdout?.pipe(options.logFile);
+    }
+    return browser;
   } catch (error) {
     // TODO: check browser logs for `Failed to create a ProcessSingleton for
     // your profile directory` instead.
@@ -145,6 +153,7 @@ export async function resolveBrowser(options: {
   channel?: Channel;
   headless: boolean;
   isolated: boolean;
+  logFile?: fs.WriteStream;
 }) {
   const browser = options.browserUrl
     ? await ensureBrowserConnected(options.browserUrl)

src/index.ts

@@ -113,9 +113,7 @@ export const args = yargsInstance
   .help()
   .parseSync();
 
-if (args.logFile) {
-  saveLogsToFile(args.logFile);
-}
+const logFile = args.logFile ? saveLogsToFile(args.logFile) : undefined;
 
 function readPackageJson(): {version?: string} {
   const currentDir = import.meta.dirname;
@@ -155,6 +153,7 @@ async function getContext(): Promise<McpContext> {
     customDevTools: args.customDevtools,
     channel: args.channel as Channel,
     isolated: args.isolated,
+    logFile,
   });
   if (context?.browser !== browser) {
     context = await McpContext.from(browser, logger);

src/logger.ts

@@ -14,7 +14,7 @@ const namespacesToEnable = [
   ...(process.env['DEBUG'] ? [process.env['DEBUG']] : []),
 ];
 
-export function saveLogsToFile(fileName: string) {
+export function saveLogsToFile(fileName: string): fs.WriteStream {
   // Enable overrides everything so we need to add them
   debug.enable(namespacesToEnable.join(','));
 
@@ -27,6 +27,7 @@ export function saveLogsToFile(fileName: string) {
     logFile.end();
     process.exit(1);
   });
+  return logFile;
 }
 
 export const logger = debug(mcpDebugNamespace);