chrome-mcp-troubleshooting

What the source does

• FilesystemNone observedNo reads or writes in the source
• NetworkNone observedNo outbound calls in the source
• ShellNone observedNo commands run in the source
• DependenciesPinnedNothing floats
• SecretsNone foundNo keys in source

Five audit layers

Gates applied: no behavioural pass.

# Fix: Add to ~/.zshrc

plugins/modern-python/hooks/shims/pip3

plugins/modern-python/hooks/shims/python3

Audit 0.4.1 · source sha dea80e4aaaef · 31 Oct 2026Report an issue or request a re-scan

• Publishertrailofbits GitHub organizationOwner of the repository this skill is read from
• Source foldertrailofbits/skills/plugins/chrome-mcp-troubleshooting/skills/chrome-mcp-troubleshootingThe exact folder we audited
• LicenceCC-BY-SA-4.0As the repository states it
• Commit pinned for this verdictdea80e4aaaefA new audit runs when the source changes
• Repository statusNot archivedLast push 2 days ago
• Sandboxed runNot runSkills are read, not executed; layer L4 is skipped

Its description: Diagnose and fix Claude in Chrome MCP extension connectivity issues. Use when mcp__claude-in-chrome__* tools fail, return "Browser extension is not connected", or behave erratically.

---
name: chrome-mcp-troubleshooting
description: Diagnose and fix Claude in Chrome MCP extension connectivity issues. Use when mcp__claude-in-chrome__* tools fail, return "Browser extension is not connected", or behave erratically.
---

# Claude in Chrome MCP Troubleshooting

Use this skill when Claude in Chrome MCP tools fail to connect or work unreliably.

## When to Use

- `mcp__claude-in-chrome__*` tools fail with "Browser extension is not connected"
- Browser automation works erratically or times out
- After updating Claude Code or Claude.app
- When switching between Claude Code CLI and Claude.app (Cowork)
- Native host process is running but MCP tools still fail

## When NOT to Use

- **Linux or Windows users** - This skill covers macOS-specific paths and tools (`~/Library/Application Support/`, `osascript`)
- General Chrome automation issues unrelated to the Claude extension
- Claude.app desktop issues (not browser-related)
- Network connectivity problems
- Chrome extension installation issues (use Chrome Web Store support)

## The Claude.app vs Claude Code Conflict (Primary Issue)

**Background:** When Claude.app added Cowork support (browser automation from the desktop app), it introduced a competing native messaging host that conflicts with Claude Code CLI.

### Two Native Hosts, Two Socket Formats

| Component | Native Host Binary | Socket Location |
|-----------|-------------------|-----------------|
| **Claude.app (Cowork)** | `/Applications/Claude.app/Contents/Helpers/chrome-native-host` | `/tmp/claude-mcp-browser-bridge-$USER/<PID>.sock` |
| **Claude Code CLI** | `~/.local/share/claude/versions/<version> --chrome-native-host` | `$TMPDIR/claude-mcp-browser-bridge-$USER` (single file) |

### Why They Conflict

1. Both register native messaging configs in Chrome:
   - `com.anthropic.claude_browser_extension.json` → Claude.app helper
   - `com.anthropic.claude_code_browser_extension.json` → Claude Code wrapper

2. Chrome extension requests a native host by name
3. If the wrong config is active, the wrong binary runs
4. The wrong binary creates sockets in a format/location the MCP client doesn't expect
5. Result: "Browser extension is not connected" even though everything appears to be running

### The Fix: Disable Claude.app's Native Host

**If you use Claude Code CLI for browser automation (not Cowork):**

```bash
# Disable the Claude.app native messaging config
mv ~/Library/Application\ Support/Google/Chrome/NativeMessagingHosts/com.anthropic.claude_browser_extension.json \
   ~/Library/Application\ Support/Google/Chrome/NativeMessagingHosts/com.anthropic.claude_browser_extension.json.disabled

# Ensure the Claude Code config exists and points to the wrapper
cat ~/Library/Application\ Support/Google/Chrome/NativeMessagingHosts/com.anthropic.claude_code_browser_extension.json
```

**If you use Cowork (Claude.app) for browser automation:**

```bash
# Disable the Claude Code native messaging config
mv ~/Library/Application\ Support/Google/Chrome/NativeMessagingHosts/com.anthropic.claude_code_browser_extension.json \
   ~/Library/Application\ Support/Google/Chrome/NativeMessagingHosts/com.anthropic.claude_code_browser_extension.json.disabled
```

**You cannot use both simultaneously.** Pick one and disable the other.

### Toggle Script

Add this to `~/.zshrc` or run directly:

```bash
chrome-mcp-toggle() {
    local CONFIG_DIR=~/Library/Application\ Support/Google/Chrome/NativeMessagingHosts
    local CLAUDE_APP="$CONFIG_DIR/com.anthropic.claude_browser_extension.json"
    local CLAUDE_CODE="$CONFIG_DIR/com.anthropic.claude_code_browser_extension.json"

    if [[ -f "$CLAUDE_APP" && ! -f "$CLAUDE_APP.disabled" ]]; then
        # Currently using Claude.app, switch to Claude Code
        mv "$CLAUDE_APP" "$CLAUDE_APP.disabled"
        [[ -f "$CLAUDE_CODE.disabled" ]] && mv "$CLAUDE_CODE.disabled" "$CLAUDE_CODE"
        echo "Switched to Claude Code CLI"
        echo "Restart Chrome and Claude Code to apply"
    elif [[ -f "$CLAUDE_CODE" && ! -f "$CLAUDE_CODE.disabled" ]]; then
        # Currently using Claude Code, switch to Claude.app
        mv "$CLAUDE_CODE" "$CLAUDE_CODE.disabled"
        [[ -f "$CLAUDE_APP.disabled" ]] && mv "$CLAUDE_APP.disabled" "$CLAUDE_APP"
        echo "Switched to Claude.app (Cowork)"
        echo "Restart Chrome to apply"
    else
        echo "Current state unclear. Check configs:"
        ls -la "$CONFIG_DIR"/com.anthropic*.json* 2>/dev/null
    fi
}
```

Usage: `chrome-mcp-toggle` then restart Chrome (and Claude Code if switching to CLI).

## Quick Diagnosis

```bash
# 1. Which native host binary is running?
ps aux | grep chrome-native-host | grep -v grep
# Claude.app: /Applications/Claude.app/Contents/Helpers/chrome-native-host
# Claude Code: ~/.local/share/claude/versions/X.X.X --chrome-native-host

# 2. Where is the socket?
# For Claude Code (single file in TMPDIR):
ls -la "$(getconf DARWIN_USER_TEMP_DIR)/claude-mcp-browser-bridge-$USER" 2>&1

# For Claude.app (directory with PID files):
ls -la /tmp/claude-mcp-browser-bridge-$USER/ 2>&1

# 3. What's the native host connected to?
lsof -U 2>&1 | grep claude-mcp-browser-bridge

# 4. Which configs are active?
ls ~/Library/Application\ Support/Google/Chrome/NativeMessagingHosts/com.anthropic*.json
```

## Critical Insight

**MCP connects at startup.** If the browser bridge wasn't ready when Claude Code started, the connection will fail for the entire session. The fix is usually: ensure Chrome + extension are running with correct config, THEN restart Claude Code.

## Full Reset Procedure (Claude Code CLI)

```bash
# 1. Ensure correct config is active
mv ~/Library/Application\ Support/Google/Chrome/NativeMessagingHosts/com.anthropic.claude_browser_extension.json \
   ~/Library/Application\ Support/Google/Chrome/NativeMessagingHosts/com.anthropic.claude_browser_extension.json.disabled 2>/dev/null

# 2. Update the wrapper to use latest Claude Code version
cat > ~/.claude/chrome/chrome-native-host << 'EOF

Excerpt, first 6,000 characters of SKILL.md, verbatim from the audited commit. It is text from someone else’s repository, quoted so you can judge it before your agent reads it.

1. 2026-10-31
   ✕BLOCK D 69 / 100

   first audit · source dea80e4aaaef

Questions about chrome-mcp-troubleshooting

• github.com/trailofbits/skills/tree/main/plugins/chrome-mcp-troub — the audited source at commit dea80e4aaaef and every finding aboveObserved · 31 Oct 2026

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