[BUG]

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?

After updating to Claude Desktop 1.0.734 (November 14, 2025), my Python-based MCP server fails to start with error: "Cannot read properties of undefined (reading 'cmd')"

Node.js MCP servers in the same config work fine. Python server works perfectly when tested manually via stdio.

This appears to be a regression in Claude Desktop's Python MCP server initialization code.

What Should Happen?

Python MCP server should start successfully like it did before the November 14 update, and like Node.js servers currently do.

Error Messages/Logs

2025-11-16T04:39:52.417Z [info]  Initializing server...
2025-11-16T04:39:52.421Z [error] Cannot read properties of undefined (reading 'cmd')

Steps to Reproduce

1. Configure a Python MCP server in claude_desktop_config.json
2. Restart Claude Desktop 1.0.734
3. Server fails to initialize with "Cannot read properties of undefined (reading 'cmd')" error
4. Note: Node.js MCP servers in same config start successfully

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Unknown - worked before November 14, 2025. This is Claude Desktop, not Claude Code.

Claude Code Version

N/A - This is Claude Desktop 1.0.734 (b8f837), not Claude Code

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

• OS: Windows 11
• Claude Desktop Version: 1.0.734 (b8f837) 2025-11-14T18:56:13.000Z
• Python: 3.13.9
• MCP Package: 1.14.0