[BUG] Claude Code Can't (Safely, Securely) Access Slack ... Seriously?!?

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?

Here's a summary Claude wrote for me:

--- Claude Code cannot connect to the official Slack MCP server due to a mismatch in OAuth support: - Slack's MCP server does not support OAuth 2.0 Dynamic Client Registration (DCR) - Claude Code currently requires DCR when authenticating with HTTP-based MCP servers - This is despite the MCP spec (2025-11-25) treating DCR as optional ("MAY"), not mandatory Other services work fine (Confluence, Jira, Gmail) because they either support DCR or use different auth mechanisms. Slack's additional constraint: Even if Claude Code fixed the DCR requirement, Slack only allows MCP access from apps that are either published to the Slack App Directory or registered as internal workspace apps. Unlike Claude.ai (web), which ships with Anthropic's pre-registered Slack app, Claude Code has no bundled credentials. The only current workaround is to have a workspace admin create an internal Slack app and manually pass --client-id / --client-secret to claude mcp add.

I'll just add that it's pretty awkward that Claude Code works great with all other major tools I've tried to integrate with. Gmail works. Confluence and Jira both work. And (according to Claude) on the terrible/lowest priced web interface, Slack works.

But in Clade Code, on my super expensive business plan ... Claude can't even lookup a simple Slack message? Really?

What Should Happen?

I don't care how, but there should be a safe/secure way for Claude Code to access Slack. It could be an MCP server, a plugin, or anything else ... but third party MCP servers are not enough (I can't trust anything my company says on Slack being exposed to a third party).

Error Messages/Logs

Steps to Reproduce

Ask Claude to connect to Slack, which it can do with other major tools. It can't.

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.61

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_