Claude in Chrome: "Browser extension is not connected" from claude.ai web interface (MCP tools)

Claude in Chrome: "Browser extension is not connected" from claude.ai web interface (MCP tools)

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report
• [x] I am using the latest version of Claude Code

Environment

• OS: macOS (please confirm version, e.g. macOS 15.x)
• Chrome version: (check chrome://settings/help and fill in)
• Extension version: (check chrome://extensions/ and fill in)
• Extension ID: fcoeoabgfenejglbffodgkkbkcdhcgfn
• Interface: claude.ai web chat (NOT Claude Code CLI or Claude Desktop)
• Plan: Pro/Max (please confirm)
• Account: kuladej@kongkafurniture.com

Description

The Claude in Chrome MCP tools (tabs_context_mcp, switch_browser, etc.) consistently return "Browser extension is not connected" when called from a claude.ai web chat conversation. The extension is installed, enabled, logged in with the correct account, and the settings page is fully accessible.

Important distinction: This is happening from the claude.ai web interface, not from Claude Code CLI or Claude Desktop. The MCP tools are available and loadable via tool_search, but every call fails with the connection error.

Notably, Control Chrome MCP tools DO work from the same conversation. Control Chrome:list_tabs successfully returns all open tabs, confirming some level of browser connectivity exists. Only the Claude in Chrome toolset fails to connect.

Steps to Reproduce

1. Open Chrome with Claude in Chrome extension installed and signed in
2. Go to claude.ai and start a new conversation
3. Ask Claude to use Chrome browser tools
4. Claude loads Claude in Chrome tools via tool_search
5. Call Claude in Chrome:tabs_context_mcp with createIfEmpty: true
6. Receive error: "Browser extension is not connected"
7. Call Claude in Chrome:switch_browser — same error
8. Call Control Chrome:list_tabs — this succeeds and returns all tabs

Expected Behavior

Claude in Chrome:tabs_context_mcp should connect to the browser extension and return tab context, enabling full browser automation (screenshots, clicking, typing, form filling).

Actual Behavior

All Claude in Chrome MCP tool calls return:

"Browser extension is not connected. The Chrome extension isn't reachable right now."

Meanwhile, Control Chrome tools work fine from the same conversation.

Troubleshooting Already Attempted

• Fully quit and restarted Chrome
• Toggled extension off/on in chrome://extensions/
• Cleared browser cache and cookies for claude.ai
• Signed out and back into Claude account
• Disabled other extensions
• Verified Chrome is up to date
• Confirmed extension is logged in with correct account (verified in extension settings page)
• Microphone access granted, permissions page shows correct configuration
• Multiple retry attempts of MCP tool calls across the conversation

Additional Context

This appears to be the same family of issues as #21371, #20298, #24593, #31971, #37541, #40174 — but those are all filed for Claude Code CLI. This report is specifically about the claude.ai web interface where Claude in Chrome MCP tools are exposed but fail to connect, while Control Chrome tools succeed.