feat(browser): 接入 CCS browser MCP 与最小交互闭环

新增 browser MCP 安装、Chrome 复用与运行时接线，
实现 navigate、click、type、take_screenshot 四个 phase-1 工具并补齐相关单测。

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/mcp/ccs-browser-server.cjs

@@ -0,0 +1,834 @@
+#!/usr/bin/env node
+
+const { WebSocket } = require('ws');
+
+const PROTOCOL_VERSION = '2024-11-05';
+const SERVER_NAME = 'ccs-browser';
+const SERVER_VERSION = '1.0.0';
+const TOOL_SESSION_INFO = 'browser_get_session_info';
+const TOOL_URL_TITLE = 'browser_get_url_and_title';
+const TOOL_VISIBLE_TEXT = 'browser_get_visible_text';
+const TOOL_DOM_SNAPSHOT = 'browser_get_dom_snapshot';
+const TOOL_NAVIGATE = 'browser_navigate';
+const TOOL_CLICK = 'browser_click';
+const TOOL_TYPE = 'browser_type';
+const TOOL_TAKE_SCREENSHOT = 'browser_take_screenshot';
+const TOOL_NAMES = [
+  TOOL_SESSION_INFO,
+  TOOL_URL_TITLE,
+  TOOL_VISIBLE_TEXT,
+  TOOL_DOM_SNAPSHOT,
+  TOOL_NAVIGATE,
+  TOOL_CLICK,
+  TOOL_TYPE,
+  TOOL_TAKE_SCREENSHOT,
+];
+const CDP_TIMEOUT_MS = 5000;
+const NAVIGATION_POLL_INTERVAL_MS = 100;
+
+let inputBuffer = Buffer.alloc(0);
+let requestCounter = 0;
+
+function shouldExposeTools() {
+  return Boolean(process.env.CCS_BROWSER_DEVTOOLS_HTTP_URL);
+}
+
+function writeMessage(message) {
+  process.stdout.write(`${JSON.stringify(message)}\n`);
+}
+
+function writeResponse(id, result) {
+  writeMessage({ jsonrpc: '2.0', id, result });
+}
+
+function writeError(id, code, message) {
+  writeMessage({ jsonrpc: '2.0', id, error: { code, message } });
+}
+
+function getTools() {
+  if (!shouldExposeTools()) {
+    return [];
+  }
+
+  return [
+    {
+      name: TOOL_SESSION_INFO,
+      description:
+        'List the current Chrome session pages available through the configured DevTools connection, including page ids, titles, URLs, and websocket endpoints.',
+      inputSchema: {
+        type: 'object',
+        properties: {},
+        additionalProperties: false,
+      },
+    },
+    {
+      name: TOOL_URL_TITLE,
+      description:
+        'Read the current page URL and title from the configured Chrome session. Optionally choose a page by index.',
+      inputSchema: {
+        type: 'object',
+        properties: {
+          pageIndex: {
+            type: 'integer',
+            minimum: 0,
+            description: 'Optional zero-based page index from browser_get_session_info. Defaults to the first page.',
+          },
+        },
+        additionalProperties: false,
+      },
+    },
+    {
+      name: TOOL_VISIBLE_TEXT,
+      description:
+        'Read visible text from the current page via DOM evaluation in the configured Chrome session. Optionally choose a page by index.',
+      inputSchema: {
+        type: 'object',
+        properties: {
+          pageIndex: {
+            type: 'integer',
+            minimum: 0,
+            description: 'Optional zero-based page index from browser_get_session_info. Defaults to the first page.',
+          },
+        },
+        additionalProperties: false,
+      },
+    },
+    {
+      name: TOOL_DOM_SNAPSHOT,
+      description:
+        'Read a DOM snapshot from the current page by returning the document outerHTML. Optionally choose a page by index.',
+      inputSchema: {
+        type: 'object',
+        properties: {
+          pageIndex: {
+            type: 'integer',
+            minimum: 0,
+            description: 'Optional zero-based page index from browser_get_session_info. Defaults to the first page.',
+          },
+        },
+        additionalProperties: false,
+      },
+    },
+    {
+      name: TOOL_NAVIGATE,
+      description:
+        'Navigate the selected page to an absolute http or https URL and wait until navigation is ready. Optionally choose a page by index.',
+      inputSchema: {
+        type: 'object',
+        properties: {
+          pageIndex: {
+            type: 'integer',
+            minimum: 0,
+            description: 'Optional zero-based page index from browser_get_session_info. Defaults to the first page.',
+          },
+          url: {
+            type: 'string',
+            description: 'Required absolute http or https URL to navigate to.',
+          },
+        },
+        required: ['url'],
+        additionalProperties: false,
+      },
+    },
+    {
+      name: TOOL_CLICK,
+      description:
+        'Click the first element matching a CSS selector in the selected page using synthetic element.click(). Optionally choose a page by index.',
+      inputSchema: {
+        type: 'object',
+        properties: {
+          pageIndex: {
+            type: 'integer',
+            minimum: 0,
+            description: 'Optional zero-based page index from browser_get_session_info. Defaults to the first page.',
+          },
+          selector: {
+            type: 'string',
+            description: 'Required CSS selector for the element to click.',
+          },
+        },
+        required: ['selector'],
+        additionalProperties: false,
+      },
+    },
+    {
+      name: TOOL_TYPE,
+      description:
+        'Type text into the first element matching a CSS selector when it is a supported text-editable target. Optionally choose a page by index.',
+      inputSchema: {
+        type: 'object',
+        properties: {
+          pageIndex: {
+            type: 'integer',
+            minimum: 0,
+            description: 'Optional zero-based page index from browser_get_session_info. Defaults to the first page.',
+          },
+          selector: {
+            type: 'string',
+            description: 'Required CSS selector for the target element.',
+          },
+          text: {
+            type: 'string',
+            description: 'Required text to assign. May be an empty string.',
+          },
+          clearFirst: {
+            type: 'boolean',
+            description: 'When true, clear the current value or content before assigning text.',
+          },
+        },
+        required: ['selector', 'text'],
+        additionalProperties: false,
+      },
+    },
+    {
+      name: TOOL_TAKE_SCREENSHOT,
+      description:
+        'Capture a PNG screenshot from the selected page. Optionally choose a page by index or request fullPage capture.',
+      inputSchema: {
+        type: 'object',
+        properties: {
+          pageIndex: {
+            type: 'integer',
+            minimum: 0,
+            description: 'Optional zero-based page index from browser_get_session_info. Defaults to the first page.',
+          },
+          fullPage: {
+            type: 'boolean',
+            description: 'Optional full-page capture flag.',
+          },
+        },
+        additionalProperties: false,
+      },
+    },
+  ];
+}
+
+async function fetchJson(url) {
+  const response = await fetch(url);
+  if (!response.ok) {
+    throw new Error(`HTTP ${response.status} for ${url}`);
+  }
+  return await response.json();
+}
+
+function getHttpUrl() {
+  const value = process.env.CCS_BROWSER_DEVTOOLS_HTTP_URL;
+  if (!value) {
+    throw new Error('Browser MCP is unavailable because CCS_BROWSER_DEVTOOLS_HTTP_URL is missing.');
+  }
+  return value.replace(/\/+$/, '');
+}
+
+async function listPageTargets() {
+  const targets = await fetchJson(`${getHttpUrl()}/json/list`);
+  if (!Array.isArray(targets)) {
+    throw new Error('Browser MCP received an invalid /json/list response.');
+  }
+
+  return targets
+    .filter((target) => target && typeof target === 'object' && target.type === 'page')
+    .map((target) => ({
+      id: typeof target.id === 'string' ? target.id : '',
+      title: typeof target.title === 'string' ? target.title : '',
+      url: typeof target.url === 'string' ? target.url : '',
+      type: typeof target.type === 'string' ? target.type : 'page',
+      webSocketDebuggerUrl:
+        typeof target.webSocketDebuggerUrl === 'string' ? target.webSocketDebuggerUrl : '',
+    }));
+}
+
+function parsePageIndex(toolArgs) {
+  if (!toolArgs || !Object.prototype.hasOwnProperty.call(toolArgs, 'pageIndex')) {
+    return 0;
+  }
+
+  if (!Number.isInteger(toolArgs.pageIndex) || toolArgs.pageIndex < 0) {
+    throw new Error('pageIndex must be a non-negative integer');
+  }
+
+  return toolArgs.pageIndex;
+}
+
+async function getSelectedPage(toolArgs) {
+  const pages = await listPageTargets();
+  if (pages.length === 0) {
+    throw new Error('Browser MCP did not find any page targets in the current Chrome session.');
+  }
+
+  const pageIndex = parsePageIndex(toolArgs);
+
+  const page = pages[pageIndex];
+  if (!page) {
+    throw new Error(`Browser MCP page index ${pageIndex} is out of range (found ${pages.length} pages).`);
+  }
+  if (!page.webSocketDebuggerUrl) {
+    throw new Error(`Browser MCP page ${pageIndex} does not expose a websocket debugger URL.`);
+  }
+
+  return { page, pageIndex, pages };
+}
+
+function formatSessionInfo(pages) {
+  return [
+    '[CCS Browser Session]',
+    '',
+    ...pages.map((page, index) => `${index}. ${page.title || '<untitled>'} | ${page.url || '<empty>'}`),
+  ].join('\n');
+}
+
+function createEvaluateExpression(kind) {
+  switch (kind) {
+    case 'url-title':
+      return `JSON.stringify({ title: document.title, url: location.href })`;
+    case 'visible-text':
+      return `document.body ? document.body.innerText : ''`;
+    case 'dom-snapshot':
+      return `document.documentElement ? document.documentElement.outerHTML : ''`;
+    default:
+      throw new Error(`Unknown browser evaluation kind: ${kind}`);
+  }
+}
+
+async function sendCdpCommand(page, method, params = {}) {
+  const ws = new WebSocket(page.webSocketDebuggerUrl);
+  const requestId = ++requestCounter;
+
+  return await new Promise((resolve, reject) => {
+    let settled = false;
+    const timer = setTimeout(() => {
+      if (!settled) {
+        settled = true;
+        ws.terminate();
+        reject(new Error('Browser MCP timed out waiting for a DevTools response.'));
+      }
+    }, CDP_TIMEOUT_MS);
+
+    function settleError(error) {
+      if (settled) {
+        return;
+      }
+      clearTimeout(timer);
+      settled = true;
+      reject(error);
+    }
+
+    ws.on('open', () => {
+      ws.send(
+        JSON.stringify({
+          id: requestId,
+          method,
+          params,
+        })
+      );
+    });
+
+    ws.on('message', (data) => {
+      if (settled) {
+        return;
+      }
+
+      let message;
+      try {
+        message = JSON.parse(data.toString());
+      } catch {
+        return;
+      }
+
+      if (message.id !== requestId) {
+        return;
+      }
+
+      clearTimeout(timer);
+      settled = true;
+      ws.close();
+
+      if (message.error) {
+        reject(new Error(message.error.message || 'DevTools request failed.'));
+        return;
+      }
+
+      resolve(message.result || null);
+    });
+
+    ws.on('error', (error) => {
+      settleError(error);
+    });
+
+    ws.on('close', () => {
+      if (settled) {
+        return;
+      }
+      settleError(new Error('Browser MCP lost the DevTools websocket connection.'));
+    });
+  });
+}
+
+async function evaluateInPage(page, kind) {
+  const response = await sendCdpCommand(page, 'Runtime.evaluate', {
+    expression: createEvaluateExpression(kind),
+    returnByValue: true,
+  });
+
+  const result = response && response.result ? response.result : null;
+  if (!result) {
+    throw new Error('Browser MCP received an invalid DevTools evaluation response.');
+  }
+
+  if (result.subtype === 'error') {
+    throw new Error(result.description || 'DevTools evaluation returned an error.');
+  }
+
+  return typeof result.value === 'string' ? result.value : result.value ?? '';
+}
+
+async function evaluateExpression(page, expression) {
+  const response = await sendCdpCommand(page, 'Runtime.evaluate', {
+    expression,
+    returnByValue: true,
+  });
+
+  const result = response && response.result ? response.result : null;
+  if (!result) {
+    throw new Error('Browser MCP received an invalid DevTools evaluation response.');
+  }
+
+  if (result.subtype === 'error') {
+    throw new Error(result.description || 'DevTools evaluation returned an error.');
+  }
+
+  return typeof result.value === 'string' ? result.value : result.value ?? '';
+}
+
+function requireNonEmptyString(value, label) {
+  if (typeof value !== 'string' || value.trim() === '') {
+    throw new Error(`${label} is required`);
+  }
+  return value.trim();
+}
+
+function requireString(value, label) {
+  if (typeof value !== 'string') {
+    throw new Error(`${label} is required`);
+  }
+  return value;
+}
+
+function requireValidHttpUrl(value) {
+  const raw = requireNonEmptyString(value, 'url');
+  let parsed;
+  try {
+    parsed = new URL(raw);
+  } catch {
+    throw new Error('url must be an absolute http or https URL');
+  }
+
+  if (parsed.protocol !== 'http:' && parsed.protocol !== 'https:') {
+    throw new Error('url must be an absolute http or https URL');
+  }
+
+  return parsed.toString();
+}
+
+function sleep(ms) {
+  return new Promise((resolve) => setTimeout(resolve, ms));
+}
+
+async function getNavigationState(page) {
+  const raw = await evaluateExpression(page, `JSON.stringify({ href: location.href, readyState: document.readyState })`);
+  const parsed = JSON.parse(raw);
+  return {
+    href: typeof parsed.href === 'string' ? parsed.href : '',
+    readyState: typeof parsed.readyState === 'string' ? parsed.readyState : '',
+  };
+}
+
+function isSameDocumentHashNavigation(beforeHref, requestedUrl) {
+  try {
+    const before = new URL(beforeHref);
+    const requested = new URL(requestedUrl);
+    return (
+      before.origin === requested.origin &&
+      before.pathname === requested.pathname &&
+      before.search === requested.search &&
+      before.hash !== requested.hash
+    );
+  } catch {
+    return false;
+  }
+}
+
+function isNavigationReady(state, beforeHref, requestedUrl) {
+  if (state.readyState !== 'interactive' && state.readyState !== 'complete') {
+    return false;
+  }
+
+  if (state.href === requestedUrl) {
+    return true;
+  }
+
+  if (state.href && state.href !== beforeHref) {
+    return true;
+  }
+
+  if (isSameDocumentHashNavigation(beforeHref, requestedUrl) && state.href === requestedUrl) {
+    return true;
+  }
+
+  return false;
+}
+
+async function waitForNavigationReady(page, beforeHref, requestedUrl) {
+  const deadline = Date.now() + CDP_TIMEOUT_MS;
+
+  while (Date.now() <= deadline) {
+    const state = await getNavigationState(page);
+    if (isNavigationReady(state, beforeHref, requestedUrl)) {
+      return state.href;
+    }
+    if (Date.now() + NAVIGATION_POLL_INTERVAL_MS > deadline) {
+      break;
+    }
+    await sleep(NAVIGATION_POLL_INTERVAL_MS);
+  }
+
+  throw new Error(`navigation did not complete for URL: ${requestedUrl}`);
+}
+
+async function handleNavigate(toolArgs) {
+  const { page, pageIndex } = await getSelectedPage(toolArgs);
+  const url = requireValidHttpUrl(toolArgs.url);
+  const before = await getNavigationState(page);
+  const navigateResult = await sendCdpCommand(page, 'Page.navigate', { url });
+  if (navigateResult && typeof navigateResult.errorText === 'string' && navigateResult.errorText) {
+    throw new Error(`navigation failed for URL: ${url}: ${navigateResult.errorText}`);
+  }
+  const finalUrl = await waitForNavigationReady(page, before.href, url);
+  return `pageIndex: ${pageIndex}\nurl: ${finalUrl}\nstatus: navigated`;
+}
+
+async function handleClick(toolArgs) {
+  const { page, pageIndex } = await getSelectedPage(toolArgs);
+  const selector = requireNonEmptyString(toolArgs.selector, 'selector');
+
+  const expression = `(() => {
+    const selector = JSON.parse(${JSON.stringify(JSON.stringify(selector))});
+    const element = document.querySelector(selector);
+    if (!element) {
+      throw new Error('element not found for selector: ' + selector);
+    }
+    if ('disabled' in element && element.disabled) {
+      throw new Error('element is disabled for selector: ' + selector);
+    }
+    element.scrollIntoView({ block: 'center', inline: 'center' });
+    element.click();
+    return 'ok';
+  })()`;
+
+  await evaluateExpression(page, expression);
+  return `pageIndex: ${pageIndex}\nselector: ${selector}\nstatus: clicked`;
+}
+
+async function handleType(toolArgs) {
+  const { page, pageIndex } = await getSelectedPage(toolArgs);
+  const selector = requireNonEmptyString(toolArgs.selector, 'selector');
+  const text = requireString(toolArgs.text, 'text');
+  const clearFirst = toolArgs.clearFirst === true;
+
+  const expression = `(() => {
+    const selector = JSON.parse(${JSON.stringify(JSON.stringify(selector))});
+    const text = JSON.parse(${JSON.stringify(JSON.stringify(text))});
+    const clearFirst = ${clearFirst ? 'true' : 'false'};
+    const element = document.querySelector(selector);
+    if (!element) {
+      throw new Error('element not found for selector: ' + selector);
+    }
+
+    const dispatchEvents = (target) => {
+      target.dispatchEvent(new Event('input', { bubbles: true }));
+      target.dispatchEvent(new Event('change', { bubbles: true }));
+    };
+
+    const focusTarget = (target) => {
+      if (typeof target.focus === 'function') {
+        target.focus();
+      }
+    };
+
+    let readback = '';
+    let expectedValue = '';
+
+    if (element instanceof HTMLTextAreaElement) {
+      focusTarget(element);
+      const setter = Object.getOwnPropertyDescriptor(HTMLTextAreaElement.prototype, 'value')?.set;
+      expectedValue = (clearFirst ? '' : element.value) + text;
+      if (setter) {
+        setter.call(element, expectedValue);
+      } else {
+        element.value = expectedValue;
+      }
+      dispatchEvents(element);
+      readback = element.value;
+    } else if (element instanceof HTMLInputElement) {
+      const supportedTypes = new Set(['', 'text', 'search', 'email', 'url', 'tel', 'password']);
+      const normalizedType = (element.getAttribute('type') || '').toLowerCase();
+      if (!supportedTypes.has(normalizedType)) {
+        throw new Error('element is not text-editable for selector: ' + selector);
+      }
+      focusTarget(element);
+      const setter = Object.getOwnPropertyDescriptor(HTMLInputElement.prototype, 'value')?.set;
+      expectedValue = (clearFirst ? '' : element.value) + text;
+      if (setter) {
+        setter.call(element, expectedValue);
+      } else {
+        element.value = expectedValue;
+      }
+      dispatchEvents(element);
+      readback = element.value;
+    } else if (element.isContentEditable === true) {
+      focusTarget(element);
+      expectedValue = (clearFirst ? '' : (element.textContent || '')) + text;
+      element.textContent = expectedValue;
+      dispatchEvents(element);
+      readback = element.textContent || '';
+    } else {
+      throw new Error('element is not text-editable for selector: ' + selector);
+    }
+
+    if (readback !== expectedValue) {
+      throw new Error('typed text verification failed for selector: ' + selector);
+    }
+
+    return JSON.stringify({ value: readback, typedLength: readback.length });
+  })()`;
+
+  const raw = await evaluateExpression(page, expression);
+  const parsed = JSON.parse(raw);
+  const typedLength = typeof parsed.typedLength === 'number' ? parsed.typedLength : String(parsed.value || '').length;
+  return `pageIndex: ${pageIndex}\nselector: ${selector}\ntypedLength: ${typedLength}\nstatus: typed`;
+}
+
+async function handleScreenshot(toolArgs) {
+  const { page, pageIndex } = await getSelectedPage(toolArgs);
+  const fullPage = toolArgs.fullPage === true;
+  const response = await sendCdpCommand(page, 'Page.captureScreenshot', {
+    format: 'png',
+    captureBeyondViewport: fullPage,
+  });
+
+  const data = response && typeof response.data === 'string' ? response.data : '';
+  if (!data) {
+    throw new Error('screenshot capture failed');
+  }
+
+  return `pageIndex: ${pageIndex}\nformat: png\nfullPage: ${fullPage ? 'true' : 'false'}\ndata: ${data}`;
+}
+
+async function handleToolCall(message) {
+  const id = message.id;
+  const params = message.params || {};
+  const toolName = params.name || '<missing>';
+  const toolArgs = params.arguments || {};
+
+  if (!TOOL_NAMES.includes(toolName)) {
+    writeError(id, -32602, `Unknown tool: ${toolName}`);
+    return;
+  }
+
+  if (!shouldExposeTools()) {
+    writeResponse(id, {
+      content: [
+        {
+          type: 'text',
+          text: 'Browser MCP is unavailable because browser reuse is not configured for this Claude session.',
+        },
+      ],
+      isError: true,
+    });
+    return;
+  }
+
+  try {
+    if (toolName === TOOL_SESSION_INFO) {
+      const pages = await listPageTargets();
+      writeResponse(id, {
+        content: [{ type: 'text', text: formatSessionInfo(pages) }],
+      });
+      return;
+    }
+
+    if (toolName === TOOL_NAVIGATE) {
+      const text = await handleNavigate(toolArgs);
+      writeResponse(id, {
+        content: [{ type: 'text', text }],
+      });
+      return;
+    }
+
+    if (toolName === TOOL_CLICK) {
+      const text = await handleClick(toolArgs);
+      writeResponse(id, {
+        content: [{ type: 'text', text }],
+      });
+      return;
+    }
+
+    if (toolName === TOOL_TYPE) {
+      const text = await handleType(toolArgs);
+      writeResponse(id, {
+        content: [{ type: 'text', text }],
+      });
+      return;
+    }
+
+    if (toolName === TOOL_TAKE_SCREENSHOT) {
+      const text = await handleScreenshot(toolArgs);
+      writeResponse(id, {
+        content: [{ type: 'text', text }],
+      });
+      return;
+    }
+
+    const { page, pageIndex } = await getSelectedPage(toolArgs);
+
+    if (toolName === TOOL_URL_TITLE) {
+      const raw = await evaluateInPage(page, 'url-title');
+      const parsed = JSON.parse(raw);
+      writeResponse(id, {
+        content: [
+          {
+            type: 'text',
+            text: `pageIndex: ${pageIndex}\ntitle: ${parsed.title || ''}\nurl: ${parsed.url || ''}`,
+          },
+        ],
+      });
+      return;
+    }
+
+    if (toolName === TOOL_VISIBLE_TEXT) {
+      const text = await evaluateInPage(page, 'visible-text');
+      writeResponse(id, {
+        content: [{ type: 'text', text: text || '' }],
+      });
+      return;
+    }
+
+    const html = await evaluateInPage(page, 'dom-snapshot');
+    writeResponse(id, {
+      content: [{ type: 'text', text: html || '' }],
+    });
+  } catch (error) {
+    writeResponse(id, {
+      content: [
+        {
+          type: 'text',
+          text: `Browser MCP failed: ${(error && error.message) || String(error)}`,
+        },
+      ],
+      isError: true,
+    });
+  }
+}
+
+async function handleMessage(message) {
+  if (!message || message.jsonrpc !== '2.0' || typeof message.method !== 'string') {
+    return;
+  }
+
+  switch (message.method) {
+    case 'initialize':
+      writeResponse(message.id, {
+        protocolVersion: PROTOCOL_VERSION,
+        capabilities: { tools: {} },
+        serverInfo: { name: SERVER_NAME, version: SERVER_VERSION },
+      });
+      return;
+    case 'notifications/initialized':
+      return;
+    case 'ping':
+      writeResponse(message.id, {});
+      return;
+    case 'tools/list':
+      writeResponse(message.id, { tools: getTools() });
+      return;
+    case 'tools/call':
+      await handleToolCall(message);
+      return;
+    default:
+      if (message.id !== undefined) {
+        writeError(message.id, -32601, `Method not found: ${message.method}`);
+      }
+  }
+}
+
+function parseMessages() {
+  while (true) {
+    let body;
+    const startsWithLegacyHeaders = inputBuffer
+      .subarray(0, Math.min(inputBuffer.length, 32))
+      .toString('utf8')
+      .toLowerCase()
+      .startsWith('content-length:');
+
+    if (startsWithLegacyHeaders) {
+      const headerEnd = inputBuffer.indexOf('\r\n\r\n');
+      if (headerEnd === -1) {
+        return;
+      }
+
+      const headerText = inputBuffer.subarray(0, headerEnd).toString('utf8');
+      const match = headerText.match(/content-length:\s*(\d+)/i);
+      if (!match) {
+        inputBuffer = Buffer.alloc(0);
+        return;
+      }
+
+      const contentLength = Number.parseInt(match[1], 10);
+      const messageEnd = headerEnd + 4 + contentLength;
+      if (inputBuffer.length < messageEnd) {
+        return;
+      }
+
+      body = inputBuffer.subarray(headerEnd + 4, messageEnd).toString('utf8');
+      inputBuffer = inputBuffer.subarray(messageEnd);
+    } else {
+      const newlineIndex = inputBuffer.indexOf('\n');
+      if (newlineIndex === -1) {
+        return;
+      }
+
+      body = inputBuffer.subarray(0, newlineIndex).toString('utf8').replace(/\r$/, '').trim();
+      inputBuffer = inputBuffer.subarray(newlineIndex + 1);
+      if (!body) {
+        continue;
+      }
+    }
+
+    let message;
+    try {
+      message = JSON.parse(body);
+    } catch {
+      continue;
+    }
+
+    Promise.resolve(handleMessage(message)).catch((error) => {
+      if (message && message.id !== undefined) {
+        writeError(message.id, -32603, (error && error.message) || 'Internal error');
+      }
+    });
+  }
+}
+
+process.stdin.on('data', (chunk) => {
+  inputBuffer = Buffer.concat([inputBuffer, chunk]);
+  parseMessages();
+});
+
+process.stdin.on('error', () => {
+  process.exit(0);
+});
+
+['SIGINT', 'SIGTERM', 'SIGHUP'].forEach((signal) => {
+  process.on(signal, () => process.exit(0));
+});
+
+process.stdin.resume();