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Claude in Chrome MCP Troubleshooting

Name: Claude in Chrome MCP Troubleshooting
Author: trailofbits

Diagnose and fix Claude in Chrome MCP extension connectivity issues.

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Install this skill Read the source first Free Written by trailofbits · unverified publisher

Context cost: 2.6k tokensestimated from the bundle, loaded when it triggers
Bundle: 2 files · 10.4 kBtext throughout, nothing executable
Licence: Source-availablefree to use
Last change: —no release on file
Servers it uses: Noneruns standalone

What it does

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.

Installed, it changes the agent in these ways.

What this skill changes about the agent is not written down here yet. The listing was collected from its source, and the description is in its own SKILL.md.

Workflow

Runs a procedure end to end.

browserautomationmcp

Filed under

Web, Search & Scraping

The skill itself

This is the whole product. A skill is instructions the model reads, so there is nothing behind the listing you cannot see first — the front matter loads with every session, and the body below it loads when the skill triggers.

SKILL.md10.3 kB · 252 lines

--- 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. ---

6# Claude in Chrome MCP Troubleshooting

8Use this skill when Claude in Chrome MCP tools fail to connect or work unreliably.

10## When to Use

12- mcp__claude-in-chrome__* tools fail with "Browser extension is not connected"

13- Browser automation works erratically or times out

14- After updating Claude Code or Claude.app

15- When switching between Claude Code CLI and Claude.app (Cowork)

16- Native host process is running but MCP tools still fail

18## When NOT to Use

20- **Linux or Windows users** - This skill covers macOS-specific paths and tools (~/Library/Application Support/, osascript)

21- General Chrome automation issues unrelated to the Claude extension

22- Claude.app desktop issues (not browser-related)

23- Network connectivity problems

24- Chrome extension installation issues (use Chrome Web Store support)

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

28**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.

30### Two Native Hosts, Two Socket Formats

32| Component | Native Host Binary | Socket Location |

33|-----------|-------------------|-----------------|

34| **Claude.app (Cowork)** | /Applications/Claude.app/Contents/Helpers/chrome-native-host | /tmp/claude-mcp-browser-bridge-$USER/<PID>.sock |

35| **Claude Code CLI** | ~/.local/share/claude/versions/<version> --chrome-native-host | $TMPDIR/claude-mcp-browser-bridge-$USER (single file) |

37### Why They Conflict

391. Both register native messaging configs in Chrome:

40 - com.anthropic.claude_browser_extension.json → Claude.app helper

41 - com.anthropic.claude_code_browser_extension.json → Claude Code wrapper

432. Chrome extension requests a native host by name

443. If the wrong config is active, the wrong binary runs

454. The wrong binary creates sockets in a format/location the MCP client doesn't expect

465. Result: "Browser extension is not connected" even though everything appears to be running

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

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

52```bash

53# Disable the Claude.app native messaging config

54mv ~/Library/Application\ Support/Google/Chrome/NativeMessagingHosts/com.anthropic.claude_browser_extension.json \

55 ~/Library/Application\ Support/Google/Chrome/NativeMessagingHosts/com.anthropic.claude_browser_extension.json.disabled

57# Ensure the Claude Code config exists and points to the wrapper

58cat ~/Library/Application\ Support/Google/Chrome/NativeMessagingHosts/com.anthropic.claude_code_browser_extension.json

59```

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

63```bash

64# Disable the Claude Code native messaging config

65mv ~/Library/Application\ Support/Google/Chrome/NativeMessagingHosts/com.anthropic.claude_code_browser_extension.json \

66 ~/Library/Application\ Support/Google/Chrome/NativeMessagingHosts/com.anthropic.claude_code_browser_extension.json.disabled

67```

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

71### Toggle Script

73Add this to ~/.zshrc or run directly:

75```bash

76chrome-mcp-toggle() {

77 local CONFIG_DIR=~/Library/Application\ Support/Google/Chrome/NativeMessagingHosts

78 local CLAUDE_APP="$CONFIG_DIR/com.anthropic.claude_browser_extension.json"

79 local CLAUDE_CODE="$CONFIG_DIR/com.anthropic.claude_code_browser_extension.json"

81 if [[ -f "$CLAUDE_APP" && ! -f "$CLAUDE_APP.disabled" ]]; then

82 # Currently using Claude.app, switch to Claude Code

83 mv "$CLAUDE_APP" "$CLAUDE_APP.disabled"

84 [[ -f "$CLAUDE_CODE.disabled" ]] && mv "$CLAUDE_CODE.disabled" "$CLAUDE_CODE"

85 echo "Switched to Claude Code CLI"

86 echo "Restart Chrome and Claude Code to apply"

87 elif [[ -f "$CLAUDE_CODE" && ! -f "$CLAUDE_CODE.disabled" ]]; then

88 # Currently using Claude Code, switch to Claude.app

89 mv "$CLAUDE_CODE" "$CLAUDE_CODE.disabled"

90 [[ -f "$CLAUDE_APP.disabled" ]] && mv "$CLAUDE_APP.disabled" "$CLAUDE_APP"

91 echo "Switched to Claude.app (Cowork)"

92 echo "Restart Chrome to apply"

93 else

94 echo "Current state unclear. Check configs:"

95 ls -la "$CONFIG_DIR"/com.anthropic*.json* 2>/dev/null

96 fi

97}

98```

100Usage: chrome-mcp-toggle then restart Chrome (and Claude Code if switching to CLI).

101

102## Quick Diagnosis

103

104```bash

105# 1. Which native host binary is running?

106ps aux | grep chrome-native-host | grep -v grep

107# Claude.app: /Applications/Claude.app/Contents/Helpers/chrome-native-host

108# Claude Code: ~/.local/share/claude/versions/X.X.X --chrome-native-host

109

110# 2. Where is the socket?

111# For Claude Code (single file in TMPDIR):

112ls -la "$(getconf DARWIN_USER_TEMP_DIR)/claude-mcp-browser-bridge-$USER" 2>&1

113

114# For Claude.app (directory with PID files):

115ls -la /tmp/claude-mcp-browser-bridge-$USER/ 2>&1

116

117# 3. What's the native host connected to?

118lsof -U 2>&1 | grep claude-mcp-browser-bridge

119

120# 4. Which configs are active?

121ls ~/Library/Application\ Support/Google/Chrome/NativeMessagingHosts/com.anthropic*.json

122```

123

124## Critical Insight

125

126**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.

127

128## Full Reset Procedure (Claude Code CLI)

129

130```bash

131# 1. Ensure correct config is active

132mv ~/Library/Application\ Support/Google/Chrome/NativeMessagingHosts/com.anthropic.claude_browser_extension.json \

133 ~/Library/Application\ Support/Google/Chrome/NativeMessagingHosts/com.anthropic.claude_browser_extension.json.disabled 2>/dev/null

134

135# 2. Update the wrapper to use latest Claude Code version

136cat > ~/.claude/chrome/chrome-native-host << 'EOF'

137#!/bin/bash

138LATEST=$(ls -t ~/.local/share/claude/versions/ 2>/dev/null | head -1)

139exec "$HOME/.local/share/claude/versions/$LATEST" --chrome-native-host

140EOF

141chmod +x ~/.claude/chrome/chrome-native-host

142

143# 3. Kill existing native host and clean sockets

144pkill -f chrome-native-host

145rm -rf /tmp/claude-mcp-browser-bridge-$USER/

146rm -f "$(getconf DARWIN_USER_TEMP_DIR)/claude-mcp-browser-bridge-$USER"

147

148# 4. Restart Chrome

149osascript -e 'quit app "Google Chrome"' && sleep 2 && open -a "Google Chrome"

150

151# 5. Wait for Chrome, click Claude extension icon

152

153# 6. Verify correct native host is running

154ps aux | grep chrome-native-host | grep -v grep

155# Should show: ~/.local/share/claude/versions/X.X.X --chrome-native-host

156

157# 7. Verify socket exists

158ls -la "$(getconf DARWIN_USER_TEMP_DIR)/claude-mcp-browser-bridge-$USER"

159

160# 8. Restart Claude Code

161```

162

163## Other Common Causes

164

165### Multiple Chrome Profiles

166

167If you have the Claude extension installed in multiple Chrome profiles, each spawns its own native host and socket. This can cause confusion.

168

169**Fix:** Only enable the Claude extension in ONE Chrome profile.

170

171### Multiple Claude Code Sessions

172

173Running multiple Claude Code instances can cause socket conflicts.

174

175**Fix:** Only run one Claude Code session at a time, or use /mcp to reconnect after closing other sessions.

176

177### Hardcoded Version in Wrapper

178

179The wrapper at ~/.claude/chrome/chrome-native-host may have a hardcoded version that becomes stale after updates.

180

181**Diagnosis:**

182```bash

183cat ~/.claude/chrome/chrome-native-host

184# Bad: exec "/Users/.../.local/share/claude/versions/2.0.76" --chrome-native-host

185# Good: Uses $(ls -t ...) to find latest

186```

187

188**Fix:** Use the dynamic version wrapper shown in the Full Reset Procedure above.

189

190### TMPDIR Not Set

191

192Claude Code expects TMPDIR to be set to find the socket.

193

194```bash

195# Check

196echo $TMPDIR

197# Should show: /var/folders/XX/.../T/

198

199# Fix: Add to ~/.zshrc

200export TMPDIR="${TMPDIR:-$(getconf DARWIN_USER_TEMP_DIR)}"

201```

202

203## Diagnostic Deep Dive

204

205```bash

206echo "=== Native Host Binary ==="

207ps aux | grep chrome-native-host | grep -v grep

208

209echo -e "\n=== Socket (Claude Code location) ==="

210ls -la "$(getconf DARWIN_USER_TEMP_DIR)/claude-mcp-browser-bridge-$USER" 2>&1

211

212echo -e "\n=== Socket (Claude.app location) ==="

213ls -la /tmp/claude-mcp-browser-bridge-$USER/ 2>&1

214

215echo -e "\n=== Native Host Open Files ==="

216pgrep -f chrome-native-host | xargs -I {} lsof -p {} 2>/dev/null | grep -E "(sock|claude-mcp)"

217

218echo -e "\n=== Active Native Messaging Configs ==="

219ls ~/Library/Application\ Support/Google/Chrome/NativeMessagingHosts/com.anthropic*.json 2>/dev/null

220

221echo -e "\n=== Custom Wrapper Contents ==="

222cat ~/.claude/chrome/chrome-native-host 2>/dev/null || echo "No custom wrapper"

223

224echo -e "\n=== TMPDIR ==="

225echo "TMPDIR=$TMPDIR"

226echo "Expected: $(getconf DARWIN_USER_TEMP_DIR)"

227```

228

229## File Reference

230

231| File | Purpose |

232|------|---------|

233| ~/.claude/chrome/chrome-native-host | Custom wrapper script for Claude Code |

234| /Applications/Claude.app/Contents/Helpers/chrome-native-host | Claude.app (Cowork) native host |

235| ~/.local/share/claude/versions/<version> | Claude Code binary (run with --chrome-native-host) |

236| ~/Library/Application Support/Google/Chrome/NativeMessagingHosts/com.anthropic.claude_browser_extension.json | Config for Claude.app native host |

237| ~/Library/Application Support/Google/Chrome/NativeMessagingHosts/com.anthropic.claude_code_browser_extension.json | Config for Claude Code native host |

238| $TMPDIR/claude-mcp-browser-bridge-$USER | Socket file (Claude Code) |

239| /tmp/claude-mcp-browser-bridge-$USER/<PID>.sock | Socket files (Claude.app) |

240

241## Summary

242

2431. **Primary issue:** Claude.app (Cowork) and Claude Code use different native hosts with incompatible socket formats

2442. **Fix:** Disable the native messaging config for whichever one you're NOT using

2453. **After any fix:** Must restart Chrome AND Claude Code (MCP connects at startup)

2464. **One profile:** Only have Claude extension in one Chrome profile

2475. **One session:** Only run one Claude Code instance

248

249---

250

251*Original skill by [@jeffzwang](https://github.com/jeffzwang) from [@ExaAILabs](https://github.com/ExaAILabs). Enhanced and updated for current versions of Claude Desktop and Claude Code.*

252

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# Claude in Chrome MCP Troubleshooting · 2.6k tokens when loaded
npx mcprush@latest skill add trailofbits/claude-in-chrome-mcp-troubleshooting

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