diff --git a/src/controllers/syncController.js b/src/controllers/syncController.js
index 5ed8080..a16973c 100644
--- a/src/controllers/syncController.js
+++ b/src/controllers/syncController.js
@@ -1,5 +1,6 @@
 const jwt = require('jsonwebtoken');
 const syncService = require('../services/syncService');
+const sseManager = require('../services/sseManager');
 
 const JWT_SECRET = process.env.JWT_SECRET;
 
@@ -36,4 +37,35 @@ const sync = async (req, res) => {
   }
 };
 
-module.exports = { sync };
\ No newline at end of file
+const streamEvents = async (req, res) => {
+  try {
+    // Validar token (usa tu lógica existente o un middleware)
+    const token = req.headers.authorization.slice(7).trim();
+    const payload = jwt.verify(token, JWT_SECRET);
+    const userId = payload.id;
+
+    // Configurar cabeceras obligatorias para SSE
+    res.setHeader('Content-Type', 'text/event-stream');
+    res.setHeader('Cache-Control', 'no-cache');
+    res.setHeader('Connection', 'keep-alive');
+    res.flushHeaders(); // Enviar cabeceras inmediatamente
+
+    // Registrar este dispositivo en el manager
+    sseManager.addClient(userId, res);
+
+    // Latido (Heartbeat) para mantener la conexión viva a través de firewalls
+    const interval = setInterval(() => res.write(':keepalive\n\n'), 30000);
+
+    // Cuando el cliente (móvil/PC) cierre la app, limpiar la memoria
+    req.on('close', () => {
+      clearInterval(interval);
+      sseManager.removeClient(userId, res);
+      res.end();
+    });
+
+  } catch (error) {
+    res.status(401).json({ error: 'No autorizado' });
+  }
+};
+
+module.exports = { sync, streamEvents };
\ No newline at end of file
diff --git a/src/routes/syncRoutes.js b/src/routes/syncRoutes.js
index 2339226..555abe7 100644
--- a/src/routes/syncRoutes.js
+++ b/src/routes/syncRoutes.js
@@ -4,4 +4,6 @@ const syncController = require('../controllers/syncController');
 
 router.post('/sync', syncController.sync);
 
+router.get('/stream', syncController.streamEvents);
+
 module.exports = router;
\ No newline at end of file
diff --git a/src/services/sseManager.js b/src/services/sseManager.js
new file mode 100644
index 0000000..3419053
--- /dev/null
+++ b/src/services/sseManager.js
@@ -0,0 +1,39 @@
+class SseManager {
+  constructor() {
+    // Mapa para guardar los clientes conectados: { userId: [res1, res2, ...] }
+    this.clients = new Map();
+  }
+
+  addClient(userId, res) {
+    if (!this.clients.has(userId)) {
+      this.clients.set(userId, []);
+    }
+    this.clients.get(userId).push(res);
+  }
+
+  removeClient(userId, res) {
+    if (this.clients.has(userId)) {
+      const userClients = this.clients.get(userId);
+      const index = userClients.indexOf(res);
+      if (index !== -1) userClients.splice(index, 1);
+      
+      // Limpiar el mapa si el usuario ya no tiene dispositivos conectados
+      if (userClients.length === 0) {
+        this.clients.delete(userId);
+      }
+    }
+  }
+
+  // El "timbre": Avisar a todos los dispositivos de un usuario (excepto al que originó el cambio)
+  notifyUser(userId) {
+    if (this.clients.has(userId)) {
+      const userClients = this.clients.get(userId);
+      userClients.forEach(res => {
+        // Formato obligatorio de SSE: "data: {JSON}\n\n"
+        res.write(`data: ${JSON.stringify({ event: 'sync_needed' })}\n\n`);
+      });
+    }
+  }
+}
+
+module.exports = new SseManager();
\ No newline at end of file
diff --git a/src/services/syncService.js b/src/services/syncService.js
index a7e838d..50bab2a 100644
--- a/src/services/syncService.js
+++ b/src/services/syncService.js
@@ -2,7 +2,7 @@ const { Op } = require('sequelize');
 const sequelize = require('../config/database');
 const Note = require('../models/Note');
 const Category = require('../models/Category');
-const { randomUUID } = require('crypto');
+const sseManager = require('./sseManager');
 
 const toIso = (value) => (value ? new Date(value).toISOString() : null);
 
@@ -217,6 +217,12 @@ class SyncService {
       })
     ]);
 
+    if(incomingNotes && incomingNotes.length > 0 ||
+        incomingCategories && incomingCategories.length > 0
+    ) {
+      sseManager.notifyUser(userId);
+    }
+
     return {
       serverTimestamp: new Date().toISOString(),
       synced: true,