[BUG] Slack browser OAuth → error

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?

from Claude code version 2.1.81 while loading slack
--
Then it's almost certainly a bug in the official plugin. The redirect URI http://localhost:3118/callback isn't registered in Anthropic's Slack OAuth app configuration —
nothing you can fix on your end.

Step 4 — File a bug report:
Go to https://github.com/anthropics/claude-code/issues and include:

• Version: 2.1.81
• Error: redirect_uri did not match any configured URIs. Passed URI: http://localhost:3118/callback
• Steps: claude plugin install --scope user slack → browser OAuth → error

That's the only path forward until Anthropic fixes it on their Slack app configuration.

What Should Happen?

Slack MCP should work. I am using officail Slack

Error Messages/Logs

Something went wrong when authorizing Claude.
Try going back to Claude and authorizing again. If problems persist, contact support for help.

Error details
redirect_uri did not match any configured URIs. Passed URI: http://localhost:3118/callback

Steps to Reproduce

1. Update Claude Code — you're on 2.1.81, there may be a fix:

claude update

1. Uninstall and reinstall the plugin:

claude plugin uninstall slack
claude plugin install --scope user slack

1. Check if port 3118 is blocked or in use:

! lsof -i :3118

1. Report the bug at https://github.com/anthropics/claude-code/issues — include the error and your version (2.1.81). The redirect_uri mismatch on an official plugin is almost

certainly a bug on Anthropic's side.

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.81

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_