diff --git a/extra/traefik-host-based-routing/.env.example b/extra/traefik-host-based-routing/.env.example
index 7badb17..bc7ea4d 100644
--- a/extra/traefik-host-based-routing/.env.example
+++ b/extra/traefik-host-based-routing/.env.example
@@ -1,6 +1,10 @@
-# Optional environment variables
+# Environment variables for JupyterHub deployment
 # Copy to .env and customize
 
+# Domain for Traefik routing (required)
+# Example: lab.example.com
+HOSTNAME=localhost
+
 # Enable CIFS mount for shared storage (0=disabled, 1=enabled)
 # Requires compose_cifs.yml to be configured with NAS credentials
 ENABLE_CIFS=0
diff --git a/extra/traefik-host-based-routing/README.md b/extra/traefik-host-based-routing/README.md
index d5ddad2..80fae05 100644
--- a/extra/traefik-host-based-routing/README.md
+++ b/extra/traefik-host-based-routing/README.md
@@ -15,7 +15,11 @@ Template for deploying stellars-jupyterhub-ds with local Traefik reverse proxy a
    ./generate-certs.sh yourdomain.example.com
    ```
 
-3. Edit `compose_override.yml` - replace `YOURDOMAIN` with your domain
+3. Create `.env` and set your hostname:
+   ```bash
+   cp .env.example .env
+   # Edit .env: HOSTNAME=yourdomain.example.com
+   ```
 
 4. Start:
    ```bash
@@ -44,8 +48,7 @@ Template for deploying stellars-jupyterhub-ds with local Traefik reverse proxy a
 
 ## Configuration
 
-Edit `compose_override.yml` to customize:
-- Domain name (replace `YOURDOMAIN` placeholder)
+Set `HOSTNAME` in `.env` for your domain. Edit `compose_override.yml` to customize:
 - Ports (default: 80/443)
 - Environment variables (idle culler, signup)
 - Network name
diff --git a/extra/traefik-host-based-routing/compose_override.yml b/extra/traefik-host-based-routing/compose_override.yml
index 6aa7a36..b247d02 100644
--- a/extra/traefik-host-based-routing/compose_override.yml
+++ b/extra/traefik-host-based-routing/compose_override.yml
@@ -3,11 +3,10 @@
 # =============================================================================
 #
 # PORTS:  80 (HTTP -> redirects to 443)  |  443 (HTTPS)
-# CERT:   Self-signed cert for *.YOURDOMAIN in ./certs/
-# ACCESS: https://jupyterhub.YOURDOMAIN/ or https://jupyterhub.localhost/
-# TRUST:  Import certs/_.YOURDOMAIN/cert.pem to browser
+# CERT:   Self-signed cert in ./certs/
+# ACCESS: https://jupyterhub.${HOSTNAME}/ or https://jupyterhub.localhost/
 #
-# Replace YOURDOMAIN with your actual domain (e.g., lab.example.com)
+# Set HOSTNAME in .env (e.g., HOSTNAME=lab.example.com)
 #
 # =============================================================================
 
@@ -57,8 +56,8 @@ services:
       - "traefik.http.middlewares.redirect-to-https.redirectscheme.scheme=https"
       - "traefik.http.middlewares.redirect-to-https.redirectscheme.permanent=true"
 
-      # Dashboard: traefik.YOURDOMAIN
-      - "traefik.http.routers.dashboard.rule=Host(`traefik.YOURDOMAIN`) || Host(`traefik.localhost`)"
+      # Dashboard: traefik.${HOSTNAME}
+      - "traefik.http.routers.dashboard.rule=Host(`traefik.${HOSTNAME}`) || Host(`traefik.localhost`)"
       - "traefik.http.routers.dashboard.entrypoints=websecure"
       - "traefik.http.routers.dashboard.tls=true"
       - "traefik.http.routers.dashboard.service=api@internal"
@@ -76,7 +75,7 @@ services:
       - "traefik.enable=true"
 
       # JupyterHub router (root path)
-      - "traefik.http.routers.jupyterhub-rtr.rule=Host(`jupyterhub.YOURDOMAIN`) || Host(`jupyterhub.localhost`)"
+      - "traefik.http.routers.jupyterhub-rtr.rule=Host(`jupyterhub.${HOSTNAME}`) || Host(`jupyterhub.localhost`)"
       - "traefik.http.routers.jupyterhub-rtr.entrypoints=websecure"
       - "traefik.http.routers.jupyterhub-rtr.tls=true"
       - "traefik.http.routers.jupyterhub-rtr.service=jupyterhub-svc"
diff --git a/extra/traefik-host-based-routing/start.sh b/extra/traefik-host-based-routing/start.sh
index 1845689..56ba0e0 100755
--- a/extra/traefik-host-based-routing/start.sh
+++ b/extra/traefik-host-based-routing/start.sh
@@ -58,4 +58,4 @@ docker compose ${COMPOSE_FILES} pull
 docker pull stellars/stellars-jupyterlab-ds:latest
 docker compose ${COMPOSE_FILES} up -d --no-build
 
-echo "Done. Access: https://jupyterhub.YOURDOMAIN/"
+echo "Done. Access: https://jupyterhub.${HOSTNAME:-localhost}/"