[BUG] MCP command parser incorrectly converts /c flag to C:/ on Windows when using cmd /c wrapper

Environment

• Platform (select one):
• Google Vertex AI
• Claude CLI version: 1.0.57
• Operating System: Windows 11
• Terminal: Command Prompt / Powershell

Bug Description

The claude mcp add command incorrectly parses the /c flag when using the cmd /c wrapper for Windows MCP servers. The /c flag is being converted to C:/ in the saved
configuration, causing MCP server connection failures.

Steps to Reproduce

1. Run: claude mcp add -s user context7 -- cmd /c npx -y @upstash/context7-mcp
2. Check the configuration with: claude mcp list
3. Observe the saved command in the output

Expected Behavior

The MCP server should be saved with the command: cmd /c npx -y @upstash/context7-mcp

Actual Behavior

The MCP server is saved with the command: cmd C:/ npx -y @upstash/context7-mcp (note /c became C:/)

Additional Context

• The official documentation at https://docs.anthropic.com/en/docs/claude-code/mcp#configure-mcp-servers which states: "On native Windows

(not WSL), local MCP servers that use npx require the cmd /c wrapper"

• The issue persists even when wrapping arguments in quotes: claude mcp add -s user context7 -- "cmd" "/c" "npx" "-y" "@upstash/context7-mcp"
• This affects any MCP server installation on Windows that requires the cmd /c wrapper
• The bug makes it impossible to properly configure local MCP servers on Windows following the official documentation.