diff --git a/backend/tests/integration/stream-lifecycle.test.ts b/backend/tests/integration/stream-lifecycle.test.ts
index ff1a5f1..9bde6ec 100644
--- a/backend/tests/integration/stream-lifecycle.test.ts
+++ b/backend/tests/integration/stream-lifecycle.test.ts
@@ -557,6 +557,72 @@ describe("Stream Lifecycle Integration Tests", () => {
     });
   });
 
+  describe("StreamEvent @@unique([transactionHash, eventType]) deduplication", () => {
+    it("rejects a duplicate (transactionHash, eventType) insert at the database level", async () => {
+      const streamId = 11;
+      const txHash = "unique-constraint-tx-hash";
+
+      await testPrisma.stream.create({
+        data: {
+          streamId,
+          sender: SENDER,
+          recipient: RECIPIENT,
+          tokenAddress: TOKEN,
+          ratePerSecond: "10",
+          depositedAmount: "86400",
+          withdrawnAmount: "0",
+          startTime: 1700000000,
+          endTime: 1700000000 + 8640,
+          lastUpdateTime: 1700000000,
+          isActive: true,
+          isPaused: false,
+        },
+      });
+
+      const eventData = {
+        streamId,
+        eventType: "CREATED",
+        transactionHash: txHash,
+        ledgerSequence: 12345,
+        timestamp: 1700000000,
+      };
+
+      await testPrisma.streamEvent.create({ data: eventData });
+
+      await expect(
+        testPrisma.streamEvent.create({
+          data: {
+            ...eventData,
+            ledgerSequence: 12346,
+            timestamp: 1700000001,
+          },
+        }),
+      ).rejects.toMatchObject({ code: "P2002" });
+
+      const count = await testPrisma.streamEvent.count({
+        where: { transactionHash: txHash, eventType: "CREATED" },
+      });
+      expect(count).toBe(1);
+    });
+
+    it("dedupes worker replay of the same event without creating a second row", async () => {
+      const streamId = 12;
+      const txHash = "worker-replay-dedup-tx-hash";
+      const event = { ...createStreamCreatedEvent(streamId), txHash };
+
+      await worker.processEvent(event);
+      await expect(worker.processEvent(event)).resolves.toBeUndefined();
+
+      const count = await testPrisma.streamEvent.count({
+        where: {
+          transactionHash: event.txHash,
+          eventType: "CREATED",
+        },
+      });
+      expect(count).toBe(1);
+    });
+  });
+
   describe("SSE client receives broadcast for each stream event", () => {
     let eventSource: EventSource;
 
diff --git a/backend/tests/stream.repository.test.ts b/backend/tests/stream.repository.test.ts
index a6297c0..8699661 100644
--- a/backend/tests/stream.repository.test.ts
+++ b/backend/tests/stream.repository.test.ts
@@ -23,6 +23,14 @@ describe('Stream Repository', () => {
     });
   });
 
+  it('should update isActive to false for COMPLETED', async () => {
+    await updateStatus(123, 'COMPLETED');
+    expect(prisma.stream.update).toHaveBeenCalledWith({
+      where: { streamId: 123 },
+      data: { isActive: false },
+    });
+  });
+
   it('should update isActive to true for ACTIVE', async () => {
     await updateStatus(123, 'ACTIVE');
     expect(prisma.stream.update).toHaveBeenCalledWith({