[BUG] Chrome extension native messaging connection not initiated on Windows when Claude Desktop is closed

Environment

• OS: Windows 11 (Build 26220.7670)
• Claude Code version: 2.1.22
• Claude Desktop version: 1.1.1200 (installed but closed during testing)
• Chrome extension ID: fcoeoabgfenejglbffodgkkbkcdhcgfn
• Browsers tested: Google Chrome, Perplexity Comet (Chromium-based)
• Node.js: Installed at C:\Program Files\nodejs\node.exe

Summary

Claude Code's Chrome MCP tools (mcp__claude-in-chrome__*) fail with "Browser extension is not connected" even after:

1. Properly configuring the native messaging host manifest
2. Ensuring Claude Desktop is completely closed
3. Restarting the browser multiple times

The native messaging host (chrome-native-host.bat) is never spawned by Chrome because the extension never calls chrome.runtime.connectNative().

Root Cause Analysis

With Claude Desktop Running

• Desktop spawns its own chrome-native-host.exe directly (doesn't rely on Chrome/manifest)
• Extension connects successfully to Desktop
• Claude Code's MCP tools still fail (Desktop's host doesn't bridge to Code)

With Claude Desktop Closed

• No native host process spawns at all
• Manifest correctly points to Code's host (C:\Users\haymo\.claude\chrome\chrome-native-host.bat)
• Registry correctly points to manifest
• Extension ID is in allowed_origins
• But the extension never initiates the native messaging connection

Diagnostic Evidence

Registry Configuration (Correct)

HKCU\Software\Google\Chrome\NativeMessagingHosts\com.anthropic.claude_browser_extension
    (Default) = C:\Users\haymo\AppData\Roaming\Claude\ChromeNativeHost\com.anthropic.claude_browser_extension.json

Modified Manifest (Correct)

{
  "name": "com.anthropic.claude_browser_extension",
  "description": "Claude Browser Extension Native Host",
  "path": "C:\\Users\\haymo\\.claude\\chrome\\chrome-native-host.bat",
  "type": "stdio",
  "allowed_origins": [
    "chrome-extension://dihbgbndebgnbjfmelmegjepbnkhlgni/",
    "chrome-extension://fcoeoabgfenejglbffodgkkbkcdhcgfn/",
    "chrome-extension://dngcpimnedloihjnnfngkgjoidhnaolf/"
  ]
}

Native Host Script (Verified Working)

@echo off
REM Chrome native host wrapper script
REM Generated by Claude Code - do not edit manually
"C:\Program Files\nodejs\node.exe" "C:\Users\haymo\.npm-global\node_modules\@anthropic-ai\claude-code\cli.js" --chrome-native-host

• Bat file exists and runs manually (tested with timeout, waits on stdin as expected)
• CRLF line endings verified
• Node.js and CLI paths verified to exist

Process Observations

| Scenario | Native Host Process | MCP Tool Result |
|----------|---------------------|-----------------|
| Desktop running | chrome-native-host.exe from app-1.1.1200 | "Browser extension is not connected" |
| Desktop closed | No process spawned | "Browser extension is not connected" |

Extension Console

• No errors in extension's service worker console
• Extension loads, creates tab groups, but never initiates native messaging

Expected Behavior

When Claude Code's MCP tools are called (e.g., tabs_context_mcp), Claude Code should either:

1. Trigger the Chrome extension to call connectNative(), causing Chrome to spawn the native host
2. Or spawn the native host directly (like Claude Desktop does)

Actual Behavior

• MCP server responds to tool calls
• MCP server reports "Browser extension is not connected"
• No native host process is ever spawned
• Extension never attempts native messaging connection

Workaround Attempted (Failed)

Modified Desktop's manifest to point to Code's native host bat file. This correctly updates the manifest, but Chrome never spawns it because the extension never requests the connection.

Related Issues

• #20887 - Chrome MCP connects to Desktop instead of Code
• #20546 - Extension conflict: Desktop and Code compete
• #20341 - Desktop native host intercepts connection
• #20943 - Claude Desktop and Claude Code conflict over Chrome extension

Suggested Fix

Claude Code needs a mechanism to trigger the Chrome extension to initiate the native messaging connection — similar to whatever mechanism Claude Desktop uses. Without this trigger, the extension sits idle and never spawns the native host.

Possible approaches:

1. Claude Code could spawn the native host directly (like Desktop does)
2. Claude Code could signal the extension via another channel (WebSocket, etc.) to trigger connectNative()
3. The extension could poll for native messaging availability on a timer