Windsurf

Windsurf is Codeium's AI editor. Its MCP config lives in the GLOBAL file ~/.codeium/windsurf/mcp_config.json.

Connect (one-click)

Open cairn's web UI, go to the sidebar Connect, and click Connect next to Windsurf. cairn writes the config shown below, launching the cairn binary over stdio with the absolute binary path and --repo set to this project, under the identity agent:windsurf, then verifies the connection.

Manual setup

Paste this into ~/.codeium/windsurf/mcp_config.json:

{
  "mcpServers": {
    "cairn": {
      "command": "/absolute/path/to/bin/cairn",
      "args": ["serve", "--actor", "agent:windsurf", "--repo", "/absolute/path/to/project"]
    }
  }
}

command is the absolute path to your built cairn binary (the Connect page fills this in automatically; if writing by hand, use your bin/cairn absolute path), and --repo is this project's absolute path.

Identity

Windsurf connects as agent:windsurf by default. Edit the identity on the card to run multiple instances (e.g. agent:windsurf-2). See Sessions for how identity is enforced.

Gotchas

• Windsurf has NO project-level config. This file is global, shared across all your projects, so the --repo arg pins this entry to one project.
• Re-Connect from another project to repoint it, or add a second entry by hand.
• After writing, refresh MCP servers in Windsurf (Cascade → MCP) or restart.

Alternative: HTTP transport

While the cairn app is running it also exposes an MCP endpoint at http://127.0.0.1:7777/mcp?repo=<project>&actor=agent:windsurf (the port may differ; cairn prints CAIRN_WEB_URL= on startup). URL-based MCP clients can point at that instead of the stdio binary. The tradeoff: the app must be running for the endpoint to respond.