chore: forward disclaimers (#1082)

`chrome-devtools start` should forward underlying disclaimers. This is
achieved by piping stderr until the start indicator is seen.

Author: OrKoN

src/daemon/client.ts

@@ -9,6 +9,7 @@ import fs from 'node:fs';
 import net from 'node:net';
 
 import {logger} from '../logger.js';
+import {START_INDICATOR} from '../server.js';
 import type {CallToolResult} from '../third_party/index.js';
 import {PipeTransport} from '../third_party/index.js';
 
@@ -56,7 +57,7 @@ export async function startDaemon(mcpArgs: string[] = []) {
   logger('Starting daemon...');
   const child = spawn(process.execPath, [DAEMON_SCRIPT_PATH, ...mcpArgs], {
     detached: true,
-    stdio: 'ignore',
+    stdio: ['ignore', 'ignore', 'pipe'],
     cwd: process.cwd(),
   });
 
@@ -72,8 +73,19 @@ export async function startDaemon(mcpArgs: string[] = []) {
     waitForFile(getPidFilePath()).then(resolve).catch(reject);
   });
 
-  child.unref();
   logger(`Pid file found ${getPidFilePath()}`);
+
+  child.stderr.pipe(process.stderr);
+  await new Promise<void>(resolve => {
+    child.stderr.on('data', data => {
+      if (data.toString().includes(START_INDICATOR)) {
+        child.stderr.unpipe(process.stderr);
+        child.stderr.destroy();
+        child.unref();
+        resolve();
+      }
+    });
+  });
 }
 
 const SEND_COMMAND_TIMEOUT = 60_000; // ms

src/main.ts

@@ -10,7 +10,7 @@ import process from 'node:process';
 
 import {cliOptions, parseArguments} from './cli.js';
 import {logger, saveLogsToFile} from './logger.js';
-import {createMcpServer} from './server.js';
+import {createMcpServer, START_INDICATOR} from './server.js';
 import {computeFlagUsage} from './telemetry/flagUtils.js';
 import {StdioServerTransport} from './third_party/index.js';
 import {VERSION} from './version.js';
@@ -56,6 +56,8 @@ Google collects usage statistics to improve Chrome DevTools MCP. To opt-out, run
 For more details, visit: https://github.com/ChromeDevTools/chrome-devtools-mcp#usage-statistics`,
     );
   }
+
+  console.error(START_INDICATOR);
 };
 
 const {server, clearcutLogger} = await createMcpServer(args, {

src/server.ts

@@ -256,3 +256,5 @@ export async function createMcpServer(
 
   return {server, clearcutLogger};
 }
+
+export const START_INDICATOR = 'Server started.';