diff --git a/Dockerfile b/Dockerfile
index cfa6b133..20a678c6 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -61,6 +61,14 @@ COPY . .
 COPY --from=vendor /app/vendor ./vendor
 COPY --from=assets /app/public/build ./public/build
 
+# Symfony's Dotenv::bootEnv() hard-requires a .env file to exist, even in prod.
+# The repo's .env is gitignored (it holds dev secrets), so Coolify's clone has
+# none and the app fatals with "Unable to read /app/.env". Write a minimal prod
+# .env if one wasn't copied in — every real value still comes from the compose
+# environment (clear_env=no lets it through), and Dotenv never overwrites an
+# already-set env var, so this only satisfies the file-existence requirement.
+RUN [ -f .env ] || printf 'APP_ENV=prod\nAPP_DEBUG=0\n' > .env
+
 # Container configuration.
 COPY docker/php/php.ini /usr/local/etc/php/conf.d/zz-app.ini
 COPY docker/php/zz-pool.conf /usr/local/etc/php-fpm.d/zz-pool.conf