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MCPX_DOCKER_DAEMON_DOWN

Severity: error Domain: Docker

What happened​

A server is configured with isolation.enabled: true (or auto-detected as needing isolation), but mcpproxy could not connect to the Docker daemon. The upstream server cannot start without Docker.

Common causes​

  • Docker Desktop is installed but not running (macOS / Windows).
  • The Docker service hasn't been started (Linux: dockerd, containerd).
  • DOCKER_HOST points to a stale socket (e.g. left over from a previous Colima session).
  • Permissions issue — see MCPX_DOCKER_NO_PERMISSION for that variant.

How to fix​

docker info               # works → daemon is up
docker context ls         # which context (rootful, rootless, colima, …) is active
echo "$DOCKER_HOST"       # should be empty or point at a real socket

macOS / Windows — start Docker Desktop or Colima​

open -a Docker            # macOS Docker Desktop
colima start              # macOS / Linux Colima

Linux — start the daemon​

sudo systemctl start docker
sudo systemctl enable docker     # auto-start on boot

Disable isolation for one server​

If you don't need isolation for a particular server, turn it off:

{ "isolation": { "enabled": false } }

Note this means the upstream runs directly on the host with the host's PATH / network — only do it for servers you trust.