SlackConnect multiple Slack workspaces to Claude
Claude's built-in Slack connector authorizes one workspace. If you work in more than one — your own, a client's, a community — the second workspace means re-authorizing, and the first one is gone until you do it again. The request to fix this is open on GitHub (anthropics/claude-code #44243).
This guide uses ProxyLoom to put several Slack workspaces behind a single MCP connection, so Claude can act in any of them and you say which one by name. It takes about five minutes and no Slack app or JSON config.
What you end up with
One connector in Claude called ProxyLoom. Behind it, each Slack workspace you connected, with a label you chose (for example acme, personal, client-b). Every Slack tool Claude sees carries an account argument, so "post this to #general in acme" and "list the channels in client-b" both work in the same conversation, without disconnecting anything.
1. Sign up for ProxyLoom
Create an account at https://app.proxyloom.dev/sign-up.
2. Connect each Slack workspace
Signing in puts you on the Connections screen. Click + Connect an account, pick Slack, and click Authenticate and connect →. Slack's own consent screen opens; choose the workspace at the top right and grant access. Repeat for each workspace you want. Each one becomes a separate connection with its own token.
Back on the Connections screen, give each connection a label: click Add a label in that connection's Label column. The label is what you and Claude will use to name the workspace, so pick something you would say out loud: the client's name,
personal,work. Without a label ProxyLoom falls back to the workspace name Slack reports.3. Add ProxyLoom to Claude
In Claude, open Settings → Connectors and click Add (top right). The Add custom connector dialog opens: give it a name — ProxyLoom — paste your ProxyLoom URL as the MCP server URL, and continue. The URL sits in the MCP Endpoint bar at the top of ProxyLoom's Connections screen, with a copy button next to it.
Continuing opens ProxyLoom's authorization in your browser: sign in once and approve, and the connector is authorized. That is the only connection Claude holds.
This works the same in the Claude desktop app, claude.ai and Claude Code. Any client that speaks Streamable HTTP MCP and OAuth 2.1 (Codex, Cursor, ChatGPT) is set up much the same way, with the same URL.
4. Use it
Ask Claude to list the connected accounts to confirm everything is there:
Which Slack workspaces do you have?
Claude asks ProxyLoom and answers with the labels. From then on, name the workspace in the request:
Read the last 20 messages in #support in acme and draft a reply.
Post the summary to #general in personal.
If a request is ambiguous, Claude asks which workspace you mean rather than guessing. Which account was used is recorded in ProxyLoom's audit log, so you can check afterwards.
Notes
- There is nothing to set up on the Slack side. Each connection has the scopes you granted on Slack's consent screen, and you can revoke that grant at any time: delete the connection on ProxyLoom's Connections screen, or revoke it on Slack.
- Adding a Slack workspace later does not mean repeating step 3, Add ProxyLoom to Claude — that one is done once and never again. Connect the workspace on ProxyLoom's Connections screen, and Claude sees it from then on.