MCP in Rig

Rig runs a local MCP hub so Cursor, Claude, Codex, Copilot CLI, OpenCode, Pi, Windsurf, VS Code, or any other MCP client can read live logs, check status, and restart processes — without pasting stack traces or granting a raw shell.

Link an editor

Open Connections (or AI / MCP) in Rig.
Start the MCP hub if it is not already running.
One-click Link Cursor (or Claude / Codex / Copilot CLI / OpenCode / Pi / Windsurf / VS Code). Any other MCP client can paste the hub JSON.
Confirm the editor shows Rig tools available.
Ask the agent to list projects, start the right one, then open its URL — not a random localhost.

Works with

One-click Link in Connections for the first six. The rest paste Rig’s generic hub JSON.

Also one-click: Windsurf and VS Code.

Hub port vs project ports

Two different things people (and agents) mix up:

MCP hub — usually http://127.0.0.1:47823/mcp. That’s how the editor talks to Rig. It is not your app homepage.
Project ports — whatever each app binds (3000, 5173, 8787…). Rig tracks these per project as detectedPort / localUrl.

What the agent can do

Scoped tools (names may vary slightly by build):

list_projects / get_project / get_status / add_project
start_project / stop_project / restart_project
get_logs / diagnose_crash / get_health
who_owns_port / kill_port / set_port
open_url — always with project_id; prefer omitting url so Rig opens the bound project’s live URL
Env profiles, local Postgres/Redis, optional local HTTPS helpers

Watch the MCP activity feed in Rig so you know what the agent touched.

How to prompt the agent

“Use Rig MCP — start this project and open its URL.”
“What’s on port 5173? If it’s another Rig project, don’t open it for me.”
“Pull the last 100 log lines for project X and tell me why it crashed.”

Project-scoped vs hub-wide MCP

You can link the whole hub (all projects) or a single-project token. Project-scoped tokens can only act on that project — safer when the editor workspace maps 1:1 to a Rig project.

Stdio bridge

Some editors prefer stdio MCP. Rig ships a bridge that talks to the local HTTP hub — use the token Rig shows you. Confirm the hub URL in Connections if you changed the port.

Troubleshooting

Hub must be running; restart it from Connections.
Editor config must use the current token (regenerate invalidates old clients).
Agent opens the wrong localhost — update Rig (MCP open_url now refuses ports that don’t belong to the given project) and re-link so guidance refreshes.
Port conflicts on the hub itself — change the MCP port in Rig and re-link.
Firewall / VPN blocking localhost is rare but worth checking.

https://userig.app/docs/mcp