diff --git a/.env.example b/.env.example
index ef9f640..e1745bd 100644
--- a/.env.example
+++ b/.env.example
@@ -4,7 +4,10 @@
 NODE_ENV=development
 
 # Datenbank (Postgres)
-DATABASE_URL=postgres://floriannetz:floriannetz@localhost:5432/floriannetz
+# Datenbank (Postgres). Format: postgresql://USER:PASSWORT@HOST:PORT/DB
+# Lokal (Host -> Docker-Postgres via docker-compose.dev.yml): HOST=localhost.
+# Im Container setzt docker-compose.yml HOST automatisch auf den Service "postgres".
+DATABASE_URL=postgresql://floriannetz:floriannetz@localhost:5432/floriannetz
 
 # Auth.js / NextAuth
 # AUTH_SECRET muss >= 32 Zeichen sein (z. B. `openssl rand -base64 32`)
diff --git a/docker-compose.yml b/docker-compose.yml
index 1b4c36c..898e98f 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -28,7 +28,7 @@ services:
         condition: service_healthy
     environment:
       NODE_ENV: production
-      DATABASE_URL: postgres://${POSTGRES_USER:-floriannetz}:${POSTGRES_PASSWORD:-floriannetz}@postgres:5432/${POSTGRES_DB:-floriannetz}
+      DATABASE_URL: postgresql://${POSTGRES_USER:-floriannetz}:${POSTGRES_PASSWORD:-floriannetz}@postgres:5432/${POSTGRES_DB:-floriannetz}
       # Forwarded-Header + sichere Cookies hinter Traefik.
       AUTH_TRUST_HOST: "true"
       AUTH_URL: https://${APP_HOST}
diff --git a/src/lib/__tests__/env.test.ts b/src/lib/__tests__/env.test.ts
index 85f819e..7625d78 100644
--- a/src/lib/__tests__/env.test.ts
+++ b/src/lib/__tests__/env.test.ts
@@ -8,7 +8,7 @@ import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 
 const VALID_ENV = {
   NODE_ENV: "test",
-  DATABASE_URL: "postgres://user:pass@localhost:5432/floriannetz",
+  DATABASE_URL: "postgresql://user:pass@localhost:5432/floriannetz",
   AUTH_SECRET: "x".repeat(32),
   AUTH_URL: "http://localhost:3000",
   AUTHENTIK_ISSUER: "http://localhost:9000/application/o/floriannetz/",
diff --git a/vitest.setup.ts b/vitest.setup.ts
index 17f5ee5..74ee4f2 100644
--- a/vitest.setup.ts
+++ b/vitest.setup.ts
@@ -3,7 +3,7 @@
 // Es wird KEINE echte DB-Verbindung geöffnet (Pool ist lazy bis zur Query).
 const TEST_ENV: Record<string, string> = {
   NODE_ENV: "test",
-  DATABASE_URL: "postgres://test:test@localhost:5432/test",
+  DATABASE_URL: "postgresql://test:test@localhost:5432/test",
   AUTH_SECRET: "test-secret-mindestens-32-zeichen-lang-xxxx",
   AUTH_URL: "http://localhost:3000",
   AUTH_TRUST_HOST: "true",