PlugWiki

Add Slack to Claude Code

Install Slack's official plugin in Claude Code and sign in, and Claude can search Slack, read threads and post as you from your terminal.

Use Slack's official plugin for Claude Code, then sign in to your workspace from /mcp. Claude Code can then search your Slack, read channels and threads, and send messages as you. Your Slack admin has to approve the connection before sign-in works. Do not add the Slack address by hand, because Slack rejects sign-in from entries that lack its app ID.

Good for

  • Developers who want Slack threads and decisions as context while they code
  • Engineers who post deploy or incident updates to a channel without leaving the terminal
  • Leads who want a standup or channel digest written from their Slack activity
  • Anyone stuck on a Slack sign-in error in Claude Code

Add Slack to Claude Code

Claude Code

  1. 1

    Copy this prompt.

    Add the Slack MCP server to Claude Code. Run this command:

/plugin install slack@claude-plugins-official

Then check that it loaded and tell me if I need to sign in or restart.
  2. 2

    Paste it into Claude Code. It shows the change and asks before running it.

Requires Slack workspace account, Slack admin approval.

Read-only mode: Slack has no read-only mode. In Claude Code, add deny rules for the Slack plugin's send and create tools (they start with mcp__plugin_slack_slack__), and never choose "don't ask again" on a send.

After the plugin installs, run /mcp, pick the Slack server and sign in to your workspace in the browser. Pick the plugin unless your company runs its own Slack app: a plain claude mcp add with only the URL fails with 'does not support dynamic client registration', because Slack only accepts known app IDs. If you added one by hand, run claude mcp remove slack first. The plugin also adds Slack slash commands such as /slack:summarize-channel. Sign-in uses port 3118, so finish it in one session at a time.

From the vendor's docs. Source.

Common errors and fixes

  • Incompatible auth server: does not support dynamic client registration

    Cause: Slack was added with claude mcp add and only the URL, so Claude Code has no Slack app ID to sign in with.

    Fix: Run claude mcp remove slack, then install the Slack plugin and sign in from /mcp.

    claude-code Source

  • redirect_uri did not match any configured URIs

    Cause: Claude Code 2.1.229 sent the sign-in callback to 127.0.0.1 instead of localhost, which Slack rejects.

    Fix: Update Claude Code to 2.1.231 or later and sign in again.

    claude-code Source

  • No Slack tools, and /mcp shows only claude.ai Slack as Needs Auth

    Cause: The Slack plugin and the claude.ai Slack connector point at the same address; one open report shows a dedup bug dropping both.

    Fix: Disconnect the Slack connector on claude.ai so only the plugin loads.

    claude-code Source

  • Sign-in fails in a second session or dev container (port 3118 already in use)

    Cause: The plugin always uses local port 3118 for the sign-in callback.

    Fix: Finish sign-in in one session at a time, and free port 3118 before signing in elsewhere.

    claude-code Source

  • Slack connection times out after 30 seconds in other open sessions

    Cause: One open report: only the session that signed in most recently connects.

    Fix: No fix has shipped; track the issue and work in the session that last signed in.

    claude-code Source

  • File upload tools are missing

    Cause: The plugin does not ask Slack for file write access, so Slack hides the upload tools.

    Fix: No plugin fix yet; a change that requests file access is proposed.

    claude-code Source

  • Sending fails with mcp_externally_shared_channel_restricted

    Cause: Slack's server blocks posting to Slack Connect channels shared with other companies.

    Fix: Post in that channel yourself; the restriction is on Slack's side.

    claude-code Source

  • OAuth flow does not complete or the connection shows inactive

    Cause: Your workspace admin has not approved the Slack MCP integration.

    Fix: Ask a Slack admin to approve it, then run /mcp and sign in again.

    claude-code Source

Permissions

Medium risk

Claude Code can send, schedule and react in Slack under your name in any conversation you can reach. Keep the approval prompt on for sending, or block the send tools with a deny rule if you only need search.

What it can do

  • Read your data
  • Create and change things
  • Delete things
  • Read-only mode

Watch out for

  • Claude Code can post to Slack as you

    Messages, drafts, reactions and canvases appear under your name. Read each send prompt, and do not pick "don't ask again" for send tools. code.claude.com

  • You can block the write tools

    Add deny rules for the Slack plugin's send and create tools in your Claude Code settings. Claude then keeps to search and reading. code.claude.com

  • Your admin approves and can audit it

    A Slack workspace admin must approve the integration before you can sign in. Slack logs MCP activity for admins. docs.slack.dev

Security advisories

No published security advisories as of Nov 2, 2026.

Technical details
Turning on read-onlySlack has no read-only mode. In Claude Code you can deny the Slack plugin's write tools with permission rules of the form mcp__plugin_slack_slack__<tool>, or pin a smaller scope set with oauth.scopes on a manual .mcp.json entry.
Talks tomcp.slack.com
Sign-in and keysClaude Code stores the Slack OAuth token after you sign in from /mcp; the plugin pins Slack's client ID and callback port 3118.

Works in

Slack documents the plugin setup for Claude Code. Several sign-in and tool problems are still open, mostly when you run many sessions or also use the claude.ai Slack connector.

Tap an app to see how to set it up and any known problems.

Questions

How do I add Slack to Claude Code?

Install Slack's official plugin with the command in the install box, then run /mcp and sign in to Slack in your browser. Your Slack admin must have approved the integration.

Why does Claude Code say Slack does not support dynamic client registration?

Slack only accepts sign-in from apps it knows, and a server added with just the URL has no Slack app ID. Run claude mcp remove slack, then install the Slack plugin, which carries Slack's app ID.

Why does Slack not show up in Claude Code after I installed the plugin?

Run /mcp and check the Slack entry. If it says it needs sign-in, sign in there. If the claude.ai Slack connector is also on for your account, one open report shows both being dropped, so disconnect the connector on claude.ai.

Why does Slack say redirect_uri did not match?

Claude Code 2.1.229 sent the sign-in callback to a different local address than Slack expects. Version 2.1.231 fixed it, so update Claude Code and sign in again.

Why can't I sign in to Slack in a second session or dev container?

The plugin always uses local port 3118 for sign-in, so only one session can listen there at a time. Finish sign-in in one session, or close the other one first.

Why does Slack time out in my other Claude Code sessions?

One open report says only the session that signed in most recently connects, and the others time out after 30 seconds. No fix has shipped yet.

Can Claude Code upload files to Slack?

Not through the plugin today. It does not ask Slack for file write access, so the upload tools stay hidden. A fix is proposed but not merged.

Can I keep Claude Code from posting to Slack?

Yes. Slack has no read-only mode, but Claude Code deny rules can block the Slack plugin's send and create tools. Claude Code also asks before each tool call unless you allowed it.

Do I need the plugin, or can I use the claude.ai Slack connector?

Either works, but turn on only one. The claude.ai Slack connector loads in Claude Code when you sign in with a claude.ai Team or Enterprise account, and one open report shows both being dropped when it is on next to the plugin.

Can Claude Code post in Slack Connect channels?

No. Slack's server blocks sending to channels shared with other companies, so those messages fail.

Information

updated Nov 1, 2026

DocsClaude connectors directoryConnect to ClaudeChangelogSlack Help Center guide

More on this

Sources

Docs, issue trackers and discussions this page is built from.

Show all 14
  1. docs.slack.dev · docs.slack.dev
  2. docs.slack.dev · docs.slack.dev
  3. github.com · github.com
  4. github.com · github.com
  5. github.com · github.com
  6. code.claude.com · code.claude.com
  7. code.claude.com · code.claude.com
  8. github.com · github.com
  9. github.com · github.com
  10. github.com · github.com
  11. github.com · github.com
  12. docs.slack.dev · docs.slack.dev
  13. github.com · github.com
  14. claude.com · claude.com

Updated Nov 1, 2026.