[BUG] Custom Plugin MCP Connector fails to connect and authorize in Desktop App but works after adding via claude.ai

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 I try to connect to a remote MCP server added to the desktop app via a custom plugin the connection fails and I get this message:

{"type":"error","error":{"type":"not_found_error","message":"Server not found","details":{"error_visibility":"user_facing"}},"request_id":"req_011Ca3LCdwJMh2Pdw6LBNzap"}

If I then go to claude.ai and add the MCP by adding the URL and a name it then connects. If I then go back to the desktop app and go to the custom plugin the connector which previously didn't connect now connects. Although the connector is in the custom plugin's settings the connector itself now has the name set from adding in claude.ai.

This is in the windows desktop app.

What Should Happen?

Add a custom Plugin in the desktop app that includes an HTTP MCP Server. Click Connect. Connector Authorizes.

Error Messages/Logs

This appears in teh browser when you try to connect:

{"type":"error","error":{"type":"not_found_error","message":"Server not found","details":{"error_visibility":"user_facing"}},"request_id":"req_011Ca3LCdwJMh2Pdw6LBNzap"}

Steps to Reproduce

1. Create a custom Plugin with a remote MCP
2. Add plugin to Claude Desktop APP
3. Navigate to the plugin in Customize>Organisation Plugins.
4. Click Connectors
5. Click Connect
6. Browser page opens and navigates to claude.ai and error message appears
7. Now go claude.ai. Click Customize>connectors
8. Click plus symbol to add > Add Custom Connector
9. Enter Name "MCP-added-via-Claude-ai"
10. Add the same MCP URL as specified in the Custom Plugin (leave advanced blank)
11. Click connect and the Connector successfully connects with the remote
12. Now go back to claude desktop
13. Click the connect button that previously failed and now it works.
14. Although it is inside the Custom Plugin the connector now has the name set from adding in Claude.AI "MCP-added-via-Claude-ai"

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Windwos Desktop App Claude 1.1617.0

Platform

Other

Operating System

Windows

Terminal/Shell

Other

Additional Information

_No response_