How to support multiple Slack workspaces on MCP for Claude Code

Claude Code talks to Slack over MCP, but out of the box you only get 1 workspace. Here’s how to run 2 or more at once. The trick: every workspace beyond the first runs as its own token-based stdio MCP server. stdio servers don’t collide (more on why later), so they all load in every session. Grab your Slack tokens For each extra workspace, you need 2 values from a logged-in Slack web tab: xoxc: from localStorage, key localConfig_v2. xoxd: the d cookie. It’s httpOnly, so read it from a request’s Cookie header in devtools, not document.cookie. Sanity-check them before wiring anything: curl -s "https://<workspace>.slack.com/api/auth.test" \ -H "Cookie: d=<xoxd>" \ --data-urlencode "token=<xoxc>" {"ok":true} means you’re good. Wire up the stdio server I use korotovsky’s slack-mcp-server. It auths with those browser tokens, no Slack app or admin approval needed. Drop the tokens in a gitignored .env, and have the MCP command source it so secrets stay out of ~/.claude.json: claude mcp add…