Debug Chrome Extension

Debug Chrome Extension Connection

Overview

The Claude in Chrome extension uses a three-component architecture:

Chrome Extension ──► Native Host ──► MCP Server ◄── Claude Code CLI
                    (named pipe)

Components:

1. Chrome Extension - Browser extension that controls Chrome
2. Native Host (--chrome-native-host) - Spawned by extension, creates named pipe
3. MCP Server (--claude-in-chrome-mcp) - Provides tools to Claude Code
4. CLI Session (--chrome) - Connects to MCP server for browser tools

Connection failures occur when any component is missing, stale, or miscommunicated.

Quick Diagnosis

Run these commands to check component status:

1. Check Running Processes

# Windows (PowerShell)
Get-CimInstance Win32_Process -Filter 'name="claude.exe"' | Select-Object ProcessId, CommandLine | Format-List

# Look for these three processes:
# - claude.exe --chrome (or --permission-mode ... --chrome) - CLI session
# - claude.exe --chrome-native-host - Native messaging host
# - claude.exe --claude-in-chrome-mcp - MCP server providing tools

2. Check Named Pipe Exists

# Windows (PowerShell)
Get-ChildItem //./pipe/ | Where-Object Name -like '*claude*'

# Should see: claude-mcp-browser-bridge-{username}

3. Check Debug Log for Errors

# Find current session log
tail -100 ~/.claude/debug/latest | grep -i "chrome\|mcp\|error"

# Look for:
# - "Connection timeout" - MCP server not responding
# - "Connection failed" - Pipe or process issue
# - "Tool not found" - MCP server not connected

4. Check Extension Installation

# Windows - verify extension is installed
ls "$env:LOCALAPPDATA/Google/Chrome/User Data/Default/Extensions/fcoeoabgfenejglbffodgkkbkcdhcgfn/"

Common Failure Modes

1. MCP Connection Timeout

Symptoms:

• /chrome shows "Status: Disabled"
• Debug log shows: Connection to MCP server "claude-in-chrome" timed out
• Chrome tools return "Tool not found"

Cause: CLI session failed to connect to MCP server at startup.

Fix:

# Restart Claude Code session
exit
claude --chrome

2. Stale Native Host Process

Symptoms:

• Native host process exists but was started hours ago
• MCP server process is missing
• New connection attempts fail

Cause: Old native host from previous Chrome session blocking new connections.

Fix:

# Kill stale processes (Windows)
Get-Process claude | Where-Object {$_.StartTime -lt (Get-Date).AddHours(-1)} | Stop-Process -Force

# Click Chrome extension icon to spawn fresh native host
# Then restart Claude Code with: claude --chrome

3. Missing MCP Server Process

Symptoms:

• Native host running (--chrome-native-host)
• CLI running (--chrome)
• No --claude-in-chrome-mcp process

Cause: CLI startup failed before spawning MCP server.

Fix:

# Full restart required
# 1. Kill all Claude processes except your terminal
# 2. Close Chrome completely
# 3. Reopen Chrome
# 4. Click Claude extension icon
# 5. Run: claude --chrome

4. Named Pipe Missing

Symptoms:

• No claude-mcp-browser-bridge-* pipe in pipe directory
• Native host not running

Cause: Chrome extension not activated or native host crashed.

Fix:

1. Open Chrome
2. Click the Claude extension icon (puzzle piece menu if pinned)
3. Wait for native host to spawn
4. Verify pipe exists, then start claude --chrome

5. Extension Not Installed

Symptoms:

• Debug log shows "Extension not found in Default"
• No extension directory in Chrome extensions folder

Fix: Install from Chrome Web Store: Search "Claude" by Anthropic

6. Registry/Manifest Mismatch

Symptoms:

• Extension installed but native host never spawns
• No Claude processes appear when clicking extension

Diagnosis:

# Check registry points to correct manifest
reg query "HKCU\Software\Google\Chrome\NativeMessagingHosts\com.anthropic.claude_code_browser_extension"

# Check manifest exists at that path
cat "$env:APPDATA/Claude Code/ChromeNativeHost/com.anthropic.claude_code_browser_extension.json"

# Verify manifest points to valid batch file
cat ~/.claude/chrome/chrome-native-host.bat

Fix: Reinstall Claude Code to reset native messaging configuration.

Full Reset Procedure

When individual fixes don't work:

# 1. Kill all Claude processes
Get-Process claude -ErrorAction SilentlyContinue | Stop-Process -Force

# 2. Close Chrome completely
Get-Process chrome -ErrorAction SilentlyContinue | Stop-Process -Force

# 3. Wait a moment
Start-Sleep -Seconds 2

# 4. Start Chrome
Start-Process chrome

# 5. Click Claude extension icon in Chrome

# 6. Verify native host spawned
Get-Process claude

# 7. Start Claude Code
claude --chrome

Verifying Success

After fixes, verify all components:

# 1. Run /chrome command - should show "Status: Enabled"

# 2. Check processes (should see 3 claude.exe)
tasklist | grep claude

# 3. Test a tool
# The MCP tools like tabs_context_mcp should work

Debug Log Locations

• Windows: ~/.claude/debug/*.txt
• Current session: ~/.claude/debug/latest (symlink)

Search patterns:

grep "claude-in-chrome" ~/.claude/debug/latest
grep "Connection" ~/.claude/debug/latest
grep "MCP server" ~/.claude/debug/latest