[BUG] Smithery MCP OAuth fails with "Unregistered redirect_uri" on Windows

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?

OS: Windows 10
Command: npx -y @smithery/cli@latest mcp add googlesheets --client claude-code
Error: {"error":"invalid_request","error_description":"Unregistered redirect_uri"}
The browser opens but OAuth fails immediately.
A colleague on Windows succeeded with the same command.

What Should Happen?

Browser should open Google OAuth login page and allow authentication to complete successfully.

Error Messages/Logs

{"error":"invalid_request","error_description":"Unregistered redirect_uri"}

Steps to Reproduce

1. Install Claude Code on Windows: npm install -g @anthropic-ai/claude-code
2. Run: npx -y @smithery/cli@latest mcp add googlesheets --client claude-code
3. Browser opens with Smithery OAuth URL
4. Immediately get error: {"error":"invalid_request","error_description":"Unregistered redirect_uri"}
5. Google login page never appears

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Claude Code version 2.1.81.

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_