diff --git a/docker-compose.yml b/docker-compose.yml
index 01bb144..9cc6ea6 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -21,10 +21,17 @@ services:
       context: .
       dockerfile: docker/php/Dockerfile
     container_name: dmtools-php
+    # Real container env vars always beat Symfony's own .env.$APP_ENV cascade
+    # (that's the point of Dotenv - it never overrides a var the platform
+    # already set) - so .env.prod has to be loaded here too, or its values
+    # (e.g. PUZZLE_RELAY_PUBLIC_URL) never reach the app; the plain .env
+    # default silently wins instead. Order matters: later files win.
     env_file:
       - path: .env
       - path: .env.local
         required: false
+      - path: .env.prod
+        required: false
     volumes:
       - .:/var/www/html:cached
       - php_var:/var/www/html/var
@@ -43,6 +50,8 @@ services:
       - path: .env
       - path: .env.local
         required: false
+      - path: .env.prod
+        required: false
     volumes:
       - .:/var/www/html:cached
       - php_var:/var/www/html/var