[BUG] using mcp prompt resource that has spaces, results with "Unknown slash command:"

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?

I have an MCP server that provides a prompt resource. In claude, I can successfully see my prompt when using the /mcp command but cannot directly use it.

<img width="414" height="93" alt="Image" src="https://github.com/user-attachments/assets/0a04de91-02be-47fd-9cb7-e50970ec0851" />

However, entering a raw URL causes an error:

<img width="442" height="56" alt="Image" src="https://github.com/user-attachments/assets/79ab1895-3830-4f34-b78d-3c7d6662438c" />

Workaround: The issue is resolved by enclosing the URL in quotes.

What Should Happen?

it should work without manually adding quotes

Error Messages/Logs

Unknown slash command:

Steps to Reproduce

1. connecting an mcp with a prompt
2. type /mcp
3. choose the new added prompt template
4. click enter

Claude Model

Opus

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.0.69

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_