diff --git a/public/js/piscina.js b/public/js/piscina.js
index 0c99783..c8309a3 100644
--- a/public/js/piscina.js
+++ b/public/js/piscina.js
@@ -29,14 +29,25 @@ document.addEventListener('DOMContentLoaded', async () => {
   tipoRutina.textContent = rutina.tipoCompetencia;
   modalidadRutina.textContent = modalidad;
 
-  const atletas = await fetch('/api/users/athletes').then(res => res.json());
-  atletas.forEach(a => {
-    const opt = document.createElement('option');
-    opt.value = a._id;
-    opt.textContent = a.name;
-    select.appendChild(opt);
-  });
+const atletas = await fetch('/api/users/athletes').then(res => res.json());
+atletas.forEach(a => {
+  const opt = document.createElement('option');
+  opt.value = JSON.stringify({ id: a._id, nombre: a.name, idPers: a.idPersonalizado });
+  opt.textContent = `${a.name} (${a.idPersonalizado || 'sin ID'})`;
+  select.appendChild(opt);
+});
 
+
+select.addEventListener('change', () => {
+  const datos = JSON.parse(select.value || '{}');
+  if (datos.idPers) {
+    document.getElementById('idPersonalizado').value = datos.idPers;
+    document.getElementById('idPersonalizado').disabled = true;
+  } else {
+    document.getElementById('idPersonalizado').value = '';
+    document.getElementById('idPersonalizado').disabled = false;
+  }
+});
   let figurasFINA = [];
   try {
     const res = await fetch('/catalog/figurasFINA.json');
diff --git a/public/piscina.html b/public/piscina.html
index 13404b4..8d7f051 100644
--- a/public/piscina.html
+++ b/public/piscina.html
@@ -57,7 +57,8 @@
 
           <div class="mb-3">
             <label for="idPersonalizado" class="form-label">ID personalizado</label>
-            <input type="text" id="idPersonalizado" class="form-control" placeholder="Ej: A, 1, V2">
+            <input type="text" id="idPersonalizado" class="form-control" placeholder="Ej: A, 1, V2" readonly>
+
           </div>
 
           <div class="mb-3">
diff --git a/routes/auth.js b/routes/auth.js
index 541efa9..0e8b9ad 100644
--- a/routes/auth.js
+++ b/routes/auth.js
@@ -4,27 +4,33 @@ const mongoose = require('mongoose');
 const bcrypt = require('bcrypt');
 require('dotenv').config();
 
-// === Conexión a MongoDB ===
 mongoose.connect(process.env.MONGODB_URI, {
   useNewUrlParser: true,
   useUnifiedTopology: true
 }).then(() => console.log('[auth.js] Conectado a MongoDB'))
   .catch(err => console.error(' [auth.js] Error de conexión:', err));
 
-// === Modelo de usuario ===
+// Schema corregido
 const userSchema = new mongoose.Schema({
   name: String,
   username: { type: String, unique: true, required: true },
   email: { type: String, unique: true, required: true },
   passwordHash: String,
   role: { type: String, enum: ['coach', 'athlete'], required: true },
-  language: { type: String, default: 'es' }, // <- CAMPO AÑADIDO
-  createdAt: { type: Date, default: Date.now }
+  language: { type: String, default: 'es' },
+  createdAt: { type: Date, default: Date.now },
+  idPersonalizado: { type: String, unique: true } // <- CAMBIO AQUÍ
 });
 
 const User = mongoose.model('User', userSchema);
 
-// === Ruta: Registro de usuario ===
+// Genera ID como JP, FM, etc.
+function generarIdPersonalizado(name) {
+  const [nombre, apellido = ''] = name.trim().toUpperCase().split(' ');
+  return (nombre[0] || '') + (apellido[0] || '');
+}
+
+// Registro de usuario
 router.post('/register', async (req, res) => {
   const { name, username, email, password, role, language } = req.body;
 
@@ -33,19 +39,34 @@ router.post('/register', async (req, res) => {
     if (existing) return res.status(400).send('Correo ya registrado');
 
     const passwordHash = await bcrypt.hash(password, 10);
-    const user = new User({ name, username, email, passwordHash, role, language });
+
+    let idPersonalizado = generarIdPersonalizado(name);
+
+    const repetido = await User.findOne({ idPersonalizado });
+    if (repetido) {
+      idPersonalizado += Math.floor(100 + Math.random() * 900);
+    }
+
+    const user = new User({
+      name,
+      username,
+      email,
+      passwordHash,
+      role,
+      language,
+      idPersonalizado // <- CAMBIO AQUÍ
+    });
+
     await user.save();
 
-    //res.redirect('/index.html');
     res.status(200).send('Usuario registrado correctamente');
-    
   } catch (error) {
     console.error('Error en registro:', error);
     res.status(500).send('Error interno del servidor');
   }
 });
 
-// === Ruta: Login de usuario ===
+// Login
 router.post('/login', async (req, res) => {
   const { email, password } = req.body;
 
@@ -60,7 +81,7 @@ router.post('/login', async (req, res) => {
       userId: user._id,
       name: user.name,
       role: user.role,
-      language: user.language // <- También puedes enviar este dato al frontend
+      language: user.language
     });
   } catch (error) {
     console.error('Error en login:', error);
diff --git a/routes/user.js b/routes/user.js
index 3a5c2bf..5eaa6e5 100644
--- a/routes/user.js
+++ b/routes/user.js
@@ -2,7 +2,8 @@ const mongoose = require('mongoose');
 
 const userSchema = new mongoose.Schema({
   name: String,
-  role: String
+  role: String,
+  idPersonalizado: { type: String, unique: true }
 });
 
 module.exports = mongoose.models.User || mongoose.model('User', userSchema);
diff --git a/routes/users.js b/routes/users.js
index b2fe061..f0d6717 100644
--- a/routes/users.js
+++ b/routes/users.js
@@ -13,7 +13,7 @@ router.get('/athletes', async (req, res) => {
     const db = client.db('swimartdb');
     const athletes = await db.collection('users')
       .find({ role: 'athlete' })
-      .project({ _id: 1, name: 1 }) 
+      .project({ _id: 1, name: 1, idPersonalizado: 1 }) 
       .toArray();
 
     res.json(athletes);