[BUG] Slack MCP plugin fails with invalid_scope during OAuth

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 trying to authenticate the mcp server/plugin for slack. I am receiving the following Invalid permissions requested: invalid_scope error. The screen shot says Claude could not be installed. It is already installed and worked previously.

<img width="645" height="337" alt="Image" src="https://github.com/user-attachments/assets/7d9a2c4e-8518-4e32-8f37-8a38ca2aff5b" />

What Should Happen?

Claude code should authenticate as before. Or provide new steps to get past this error.

Error Messages/Logs

Claude could not be installed.
It looks like something has gone awry. Don’t worry it’s not your fault, but you won’t be able to install Claude at the moment.

Error details
Invalid permissions requested
invalid_scope

Steps to Reproduce

1. In the claude console /mcp
2. select plugin:slack:slack · △ needs authentication
3. Then select Authenticate - oauth kicks in

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.76

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_