How to Connect Multiple Slack Workspaces to Claude Cowork
Claude Cowork holds exactly one Slack workspace at a time, and authorizing a second overwrites the first. Connect every workspace to Carly, add Carly to Claude once, and a single Cowork task can search or post in whichever workspace you name. Carly holds your Gmail and Outlook mailboxes and every calendar on both sides in the same place.
One check first, because it takes five minutes and can end the problem. If you reach a client through a Slack Connect channel rather than as a member of their workspace, you are already covered on one connection.
What the finished setup gives you
With one Carly connector in Cowork, you can:
- search your own, a client’s, and a partner’s Slack in one task;
- get the source workspace named on every row that comes back;
- post in the workspace you name, not the last one authorized;
- pull a status brief from every workspace you belong to;
- keep a scheduled task pointed at the right company;
- match a Slack thread against the email and calendar accounts connected alongside it.
The workspaces stay separate underneath. Carly supplies the routing, and Claude remains where you run the task.
Why the native Slack connector does not solve this
Anthropic documents no way to add a second Slack workspace. The clearest account of the limit comes from users rather than from Anthropic: an open request on Anthropic’s public issue tracker, filed on 6 April 2026 and still active in August, states the built-in Slack connector supports only one workspace per Claude account, with no way to add a second through the UI or configuration. A separate, closed report describes the mechanism, which is that authenticating into one workspace overwrites the other’s token.
Those are user-filed reports with no staff reply, and they should be read that way. What is not in dispute is that no documented path to a second workspace exists. The loop people run today is disconnect, reconnect, re-authorize, every time the work moves.
The real cost is quieter than the reauthorizing. Cowork does not tell you it is looking in the wrong Slack. A search runs against whichever workspace is currently bound, finds nothing relevant, and returns a fluent, well-organized answer built from a different company’s channels. Nothing errors. You get a confident summary of the wrong week, and it gets worse when the work is handed to a scheduled task nobody is watching.
1. Sort your workspaces before you connect anything
| How you reach it | What it actually is | Native path in Cowork |
|---|---|---|
| Your own company Slack | Your workspace | Yes |
| A client channel shared via Slack Connect | A channel in your workspace | Yes, already covered |
| A client workspace you were added to as a member | A second workspace | No |
| A partner or community Slack you joined | A second workspace | No |
| Another workspace in your Enterprise Grid org | A separate installation | No |
Slack Connect is the row that surprises people. Slack documents that channels created in your workspace are hosted and owned by your organization, with up to 250 organizations in a single shared channel. Enterprise Grid does not solve it: Slack documents that workspaces in an Enterprise organization have their own application installations.
2. Connect the first workspace to Carly
- Sign in at carlyassistant.com.
- Open carlyassistant.com/integrations.
- Find Slack and click Connect.
- Authorize the first workspace, checking the name at the top of Slack’s consent screen.
- Confirm it appears in Carly’s connected list.
3. Add every other workspace
- Return to Carly’s integrations page.
- Select Slack → Connect again.
- Check the workspace name before approving, since Slack preselects whichever one you used last.
- Repeat for every remaining workspace, including client workspaces you joined as a guest.
Each workspace keeps its own authorization, and Carly reaches only the channels that account can already open. If a workspace restricts app installation, a Slack owner or admin approves Carly once.
4. Connect Carly to Claude Cowork
In Claude:
- Open Customize in the sidebar.
- Select Connectors.
- Click +, then Add custom connector.
- Paste
https://carlyassistant.com/mcp/. - Click Add and authorize your Carly account.
- In the Cowork task, open + → Connectors and enable Carly.
Anthropic documents this path in its remote MCP connector guide. Cowork is on paid plans only, and on Team or Enterprise an Owner enables connectors for the organization first.
5. Test each workspace read-only
One workspace per prompt until you trust the routing:
In the Databricks client workspace, list the five most recent messages in #project-updates with sender and timestamp. Do not post anything.
In my own workspace, find the newest thread mentioning the renewal date. Give me the channel and the link, and do not reply.
Then the question that was not possible on one connection:
Search my workspace, the Databricks workspace, and the Adobe workspace for “scope change” in the last 14 days. Show the source workspace and channel on every row.
6. Reuse this routing prompt
Treat my own Slack as Internal, the Databricks workspace as Client, and the founders community as Community. Name the source workspace on every result you return. Never post in a Client workspace without showing me the draft first.
Then name the target on each action:
Post the release note in Internal, channel #announcements. Reply in the Databricks thread only, and do not cross-post.
Cowork’s Slack connector versus Carly
| Need | Slack connector in Cowork | Carly connector |
|---|---|---|
| Search one workspace deeply | Yes | Yes |
| Send, draft, and preview messages | Yes, in-client | Yes |
| Create channels, canvases, and reactions | Yes | Not all of them |
| Hold several workspaces at once | No, one at a time | Yes |
| Name the source workspace on every answer | No | Yes |
| Start when a Slack message arrives | No | Yes |
Inside one workspace the native connector is deeper, because it is Slack’s own hosted MCP server: previewing a formatted message in the Slack client before it goes, creating and updating canvases, working through reactions and channel membership.
Across workspaces it has nothing to offer, and that is the case this page is about. Carly holds several at once and names the source workspace on every answer, so the wrong-company summary cannot happen quietly. It also fires on the event rather than waiting for the next scheduled sweep. Carly offers free Zapier-style workflows; AI agents start at $35/month.
Quick fixes when a workspace does not appear
| Problem | Fix |
|---|---|
| The second workspace replaced the first | Expected on the native connector. Keep every workspace in Carly instead |
| Cowork answers from the wrong Slack | Check which workspace is bound, and route by name through Carly |
| A client’s channels are missing | Confirm whether you are a member of their workspace or only in a Slack Connect channel |
| Slack authorized the wrong workspace | Slack preselects the last one used, so check the name on the consent screen |
| A scheduled task returns nothing | On the native connector it runs against whatever workspace is bound now |
Frequently asked questions
Can Cowork connect two Slack workspaces?
No documented path exists. A user-filed request on Anthropic’s public issue tracker, open since April 2026, reports one workspace per Claude account, and a related report describes authorizing one workspace as overwriting the other’s token. Connecting each workspace to Carly is what makes several reachable from one task.
Does Claude Cowork support Slack at all?
Yes, natively, through Slack’s own hosted MCP server. Cowork uses the same connector library as Claude chat, and the connector reads and writes, including searching channels and sending messages.
Is a Slack Connect client the same as a second workspace?
No, and this is the check worth doing first. Slack Connect channels created in your workspace are hosted and owned by your organization, so they are reachable on the single connection Cowork already has.
Does Cowork run when a Slack message arrives?
No. Scheduled tasks run at a cadence you set, and Anthropic’s own example is pull-shaped, summarizing Slack messages, email, or calendar events from the past 24 hours.
Related: What is Claude Cowork · Multiple Slack workspaces in Claude · Claude Cowork plugins · Best AI assistants for Slack
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