[BUG] Claude Desktop cannot connect to Claude in Chrome extension in any mode with "No tab available" on Windows

Preflight Checklist

• [x] I searched existing issues before filing this
• [x] This is one bug per report
• [x] I am on the latest version (v2.1.111)

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What's Wrong?

The Claude in Chrome extension has never successfully connected to the Claude Desktop application on Windows, in any mode (chat, Claude Code, or Cowork). Every tab operation returns No tab available immediately, with no additional detail.

The Chrome extension itself is fully functional — Claude operates correctly from the browser sidebar, can navigate pages, interact with elements, and fill forms. The broken link is specifically between the extension and Claude Desktop.

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What Should Happen?

Claude Desktop should be able to list, access, and interact with open Chrome tabs via the extension, across all modes.

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Error Messages / Logs

All tab operations return the same error with no further detail:

Error: No tab available

Exact calls attempted and responses:

| Tool call | Input | Response |
|-----------|-------|----------|
| browser_batch → tabs_list | {} | Error: No tab available |
| browser_batch → tabs_context_mcp | {"createIfEmpty": false} | Error: No tab available |
| browser_batch → tabs_context_mcp | {"createIfEmpty": true} | Error: No tab available |
| browser_batch → screenshot | {} | Error: No tab available |

Note: createIfEmpty: true should create a new tab group from scratch — its failure suggests the MCP server has no connection to the extension whatsoever, not merely a missing tab group.

Tools present (3): browser_batch, tabs_close_mcp, file_upload
Tools absent: navigate, read_page, click, find, javascript_tool, tabs_context_mcp, screenshot, and all other interaction tools

This degraded 3-tool state superficially resembles what was reported in #38783, although that issue affects computer use, an entirely different component.

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Steps to Reproduce

1. Install Claude Desktop on Windows and sign in
2. Install the Claude in Chrome extension (v1.0.68) in Chrome
3. Verify the extension works — open the sidebar in Chrome, confirm Claude can interact with page content
4. Open Claude Desktop in any mode (chat, Claude Code, or Cowork)
5. Open Chrome with at least one active tab
6. Attempt any tab operation (navigate, screenshot, tabs_context_mcp, etc.)
7. Observe: Error: No tab available regardless of mode or call

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System Information

• Claude Desktop version: 2.1.111 (claude --version)
• Claude in Chrome extension version: 1.0.68
• Chrome version: 147.0.7727.102 (Official Build) (64-bit)
• OS: Windows
• API platform: Anthropic (direct)
• Regression: No — has never worked on this machine since initial install

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Why This Is Different From Related Issues

• #21106 — Same No tab available symptom, but macOS only. Described as a regression where tabs_context_mcp lists tabs successfully before other calls fail. In our case, tabs_context_mcp itself fails immediately. Platform and failure mode differ.
• #38783 — Windows, similar degraded 3-tool state. But that issue pertains to the computer use MCP rather than to the Chrome extension
• #48806 — Chrome extension also broken, but on a different platform (macos) and with a different symptom and error message about failing to connect to the extension. In our case, Claude reports success in establishing the connection, but then fails with a different error when attempting to interact with it
• #50157 — Extension v1.0.68 blocking navigation to claude.ai (macOS). Unrelated symptom and platform.

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Additional Context

• The extension↔Desktop bridge appears entirely non-functional on Windows from first install, suggesting a possible issue with native messaging host registration on Windows during installation
• Environment confirms CLAUDE_CODE_HOST_PLATFORM=win32