[BUG] Bug in the official slack plugin's OAuth flow

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 am using Claude in the Terminal and it is not able to connect or authenticate to my slack MCP. When I try to connect and/or authenticate it keeps returning the error: _redirect_uri did not match any configured URIs. Passed URI: http://localhost:48125/oauth/callback_

Claude has advise me that this should be reported here given it is a bug in the official slack plugin's OAuth flow

What Should Happen?

Create a fix for me to connect my slack MCP

Error Messages/Logs

redirect_uri did not match any configured URIs. Passed URI: http://localhost:48125/oauth/callback

Steps to Reproduce

/mcp
navigate to slack (which shows as failed)
Hit reconnect
Opens up a browser with the shared error code

Claude Model

Not sure / Multiple models

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.77

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_