[BUG] "Jupyter notebook detected" Connect button injects mcp__jupyter tool reference, but tool is not available

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

When opening a Jupyter notebook in VS Code, the Claude Code extension shows a "Jupyter notebook detected" banner with a "Connect" button. Clicking the button injects a system message claiming mcp__jupyter tool is available, but the tool doesn't actually exist, causing get_cells to fail with "<tool_use_error>Error: No such tool available: mcp__jupyter__get_cells</tool_use_error>".

What Should Happen?

Either:

• The mcp__jupyter tool should be available and functional after clicking "Connect", OR
• The "Connect" button should not appear if the tool is not available

Error Messages/Logs

<tool_use_error>Error: No such tool available: mcp__jupyter__get_cells</tool_use_error>

Steps to Reproduce

1. Open a .ipynb file in VS Code with Claude Code extension installed
2. Ensure a kernel is selected and running
3. Observe "Jupyter notebook detected" banner appears above the input box with a "Connect" button
4. Click "Connect"
5. A message is automatically injected: "A Jupyter notebook is now connected. You have access to the mcp__jupyter tool to help me work with the notebook. Use get_cells to see the current notebook contents."
6. Claude attempts to call Jupyter [get_cells]
7. Error: <tool_use_error>Error: No such tool available: mcp__jupyter__get_cells</tool_use_error>

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.23

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

VS Code integrated terminal

Additional Information

Screenshots

<img width="1426" height="350" alt="Image" src="https://github.com/user-attachments/assets/2a4fa5b8-f6f5-4777-97dd-31253ee5ef01" />

<img width="1772" height="778" alt="Image" src="https://github.com/user-attachments/assets/a4edf531-ce45-4cc8-bb8e-01eb13d78148" />

Additional Context

• Kernel is running and confirmed working
• Restarted VS Code, issue persists

Environment

• Claude Code version: 2.1.23
• VS Code version: 1.108.2
• OS: macOS 26.2 (25C56)
• Jupyter extension version: 2025.9.1