diff --git a/tests/unit/server.test.ts b/tests/unit/server.test.ts
index 6d91cbc..a0ac4ca 100644
--- a/tests/unit/server.test.ts
+++ b/tests/unit/server.test.ts
@@ -446,4 +446,40 @@ describe('WebhookServer', () => {
       })
     );
   });
+
+  test('should normalize sender ID before processing', async () => {
+    const payload = {
+      event: 'messages.upsert',
+      instance: 'test-instance',
+      data: {
+        key: {
+          remoteJid: 'group-id@g.us',
+          participant: '1234567890:12@s.whatsapp.net' // ID with participant
+        },
+        message: { conversation: '/tarea nueva Test' }
+      }
+    };
+    const request = createTestRequest(payload);
+    const response = await WebhookServer.handleRequest(request);
+    expect(response.status).toBe(200);
+    expect(mockAdd).toHaveBeenCalled();
+  });
+
+  test('should ignore messages with invalid sender ID', async () => {
+    const payload = {
+      event: 'messages.upsert',
+      instance: 'test-instance',
+      data: {
+        key: {
+          remoteJid: 'group-id@g.us',
+          participant: 'invalid-id!' // Invalid ID
+        },
+        message: { conversation: '/tarea nueva Test' }
+      }
+    };
+    const request = createTestRequest(payload);
+    const response = await WebhookServer.handleRequest(request);
+    expect(response.status).toBe(200);
+    expect(mockAdd).not.toHaveBeenCalled();
+  });
 });