diff --git a/backend/prisma/seed.ts b/backend/prisma/seed.ts
index 95805e2..7bb4ae1 100644
--- a/backend/prisma/seed.ts
+++ b/backend/prisma/seed.ts
@@ -15,12 +15,13 @@ const TENANT_DEMO_PASSWORD = 'Mieter2026!';
  * - je 1 offene Mietzahlung für den aktuellen Monat (für den Banking-Test)
  */
 async function main() {
-  console.log('Seed: lösche vorhandene Testdaten...');
-  await prisma.invitation.deleteMany();
-  await prisma.payment.deleteMany();
-  await prisma.contract.deleteMany();
-  await prisma.room.deleteMany();
-  await prisma.user.deleteMany();
+  const existingUsers = await prisma.user.count();
+  if (existingUsers > 0) {
+    console.log('Seed: Datenbank enthält bereits Daten, überspringe Seed.');
+    return;
+  }
+
+  console.log('Seed: lege Testdaten an...');
 
   const landlord = await prisma.user.create({
     data: {