diff --git a/mcp-stack.compose.yml b/mcp-stack.compose.yml
index b73f6cc..6726bf2 100644
--- a/mcp-stack.compose.yml
+++ b/mcp-stack.compose.yml
@@ -230,7 +230,11 @@ services:
       # /config only. /data is a volume instead, because Caddy keeps the certificate and its ACME
       # account key there: on tmpfs both would be thrown away at every restart, and asking the CA
       # for a fresh certificate each time runs into its duplicate-issuance limit within a week.
-      - /config:rw,noexec,nosuid,size=16m
+      #
+      # With the uid and gid of the user it runs as: a tmpfs starts out owned by root, and Caddy
+      # could not even create /config/caddy. Compose's long tmpfs syntax has no uid/gid field, so
+      # this is the raw mount-options string, as for the proxy's /var/log/squid below.
+      - /config:rw,noexec,nosuid,size=16m,uid=${MCP_UID:-10001},gid=${MCP_GID:-10001}
     volumes:
       - type: bind
         source: ${MCP_GATEWAY_CADDYFILE:-./mcp-stack.Caddyfile}
@@ -262,10 +266,39 @@ services:
       - "127.0.0.1:${BROWSER_MCP_PORT:-3103}:3103"
       - "127.0.0.1:${MINIO_MCP_PORT:-3104}:3104"
     networks: [gateway, coding-control, dev-server-control, workspace-browser, minio-control]
-    depends_on: [coding-agent-mcp, dev-server-mcp, browser-mcp, minio-mcp]
+    depends_on:
+      caddy-data-init:
+        condition: service_completed_successfully
+      coding-agent-mcp:
+        condition: service_started
+      dev-server-mcp:
+        condition: service_started
+      browser-mcp:
+        condition: service_started
+      minio-mcp:
+        condition: service_started
     restart: unless-stopped
     logging: *default-logging
 
+  # Gives Caddy's /data volume to the user the gateway runs as, every time the stack starts. A
+  # named volume belongs to whoever created it - root, or the user of an earlier run - and the
+  # gateway, running as MCP_UID, then cannot write the certificate or the ACME account key: it
+  # answers on port 80 but never gets a certificate, and port 443 fails the TLS handshake. Runs as
+  # root with nothing but CAP_CHOWN, no network, and exits.
+  caddy-data-init:
+    image: caddy:2
+    user: "0:0"
+    command: ["chown", "-R", "${MCP_UID:-10001}:${MCP_GID:-10001}", "/data"]
+    read_only: true
+    cap_drop: [ALL]
+    cap_add: [CHOWN]
+    security_opt: [no-new-privileges:true]
+    network_mode: none
+    volumes:
+      - caddy-data:/data
+    restart: "no"
+    logging: *default-logging
+
 networks:
   gateway:
   coding-control: