diff --git a/public/admin.html b/public/admin.html
index 11815ba..982123e 100644
--- a/public/admin.html
+++ b/public/admin.html
@@ -74,10 +74,6 @@
           <label>Contraseña</label>
           <input v-model="login.password" type="password" placeholder="••••••" />
         </div>
-        <div class="field">
-          <label>Tenant</label>
-          <input v-model="login.tenantId" placeholder="default" />
-        </div>
         <button :disabled="loading" @click="loginUser">Iniciar sesión</button>
         <div :class="{ error: loginError, success: loginSuccess }">{{ loginMessage }}</div>
 
@@ -96,10 +92,6 @@
           <label>Contraseña</label>
           <input v-model="register.password" type="password" placeholder="••••••" />
         </div>
-        <div class="field">
-          <label>Tenant</label>
-          <input v-model="register.tenantId" placeholder="default" />
-        </div>
         <button :disabled="loading" @click="registerUser">Registrar</button>
         <div :class="{ error: registerError, success: registerSuccess }">{{ registerMessage }}</div>
       </div>
@@ -110,7 +102,7 @@
             <div style="display:flex; align-items:center; justify-content:space-between;">
               <div>
                 <div><strong>{{ user?.name || user?.email }}</strong></div>
-                <div style="font-size:0.85rem; color:#555;">Tenant: {{ tenantId }}</div>
+                <div style="font-size:0.85rem; color:#555;">Tenant: unificado</div>
               </div>
               <button @click="logout">Salir</button>
             </div>
@@ -174,15 +166,15 @@
 
           const token = ref(localStorage.getItem(tokenKey) || '');
           const user = ref(null);
-          const tenantId = ref('default');
+          const tenantId = ref('default'); // kept for compatibility (subdomain / future use)
           const status = ref('');
           const modules = ref([]);
           const selectedModule = ref('');
           const moduleHtml = ref('');
           const loading = ref(false);
 
-          const login = reactive({ email: '', password: '', tenantId: 'default' });
-          const register = reactive({ name: '', email: '', password: '', tenantId: 'default' });
+          const login = reactive({ email: '', password: '' });
+          const register = reactive({ name: '', email: '', password: '' });
 
           const loginMessage = ref('');
           const loginError = ref(false);
@@ -203,8 +195,7 @@
             setStatus('Consultando ' + path + '...');
             const headers = options.headers || {};
             if (token.value) headers.Authorization = `Bearer ${token.value}`;
-            headers['x-tenant-id'] = tenantId.value || 'default';
-            const res = await fetch(`${apiRoot}${path}?tenantId=${encodeURIComponent(tenantId.value)}`, {
+            const res = await fetch(`${apiRoot}${path}`, {
               ...options,
               headers,
             });
@@ -236,7 +227,6 @@
                 method: 'POST',
                 headers: { 'Content-Type': 'application/json' },
                 body: JSON.stringify({
-                  tenantId: login.tenantId || 'default',
                   email: login.email,
                   password: login.password,
                 }),
@@ -270,7 +260,6 @@
                 method: 'POST',
                 headers: { 'Content-Type': 'application/json' },
                 body: JSON.stringify({
-                  tenantId: register.tenantId || 'default',
                   name: register.name,
                   email: register.email,
                   password: register.password,
diff --git a/src/admin/admin.controller.ts b/src/admin/admin.controller.ts
index ef1cd89..24fa6d7 100644
--- a/src/admin/admin.controller.ts
+++ b/src/admin/admin.controller.ts
@@ -4,8 +4,6 @@ import { GuestService } from '../guest/services/guest.service';
 import { TodoService } from '../todo/services/todo.service';
 import { ModuleRegistryService } from '../core/services/module-registry.service';
 
-const DEFAULT_TENANT = process.env.DEFAULT_TENANT_ID ?? 'default';
-
 @Controller('admin')
 export class AdminController {
   constructor(
@@ -20,94 +18,64 @@ export class AdminController {
     return this.moduleRegistry.getModules();
   }
 
-  private getTenantId(tenantId?: string) {
-    return tenantId ?? DEFAULT_TENANT;
-  }
-
   // Guests
   @Get('guest')
-  listGuests(@Query('tenantId') tenantId?: string) {
-    return this.guestService.listGuests(this.getTenantId(tenantId));
+  listGuests() {
+    return this.guestService.listGuests();
   }
 
   @Post('guest')
-  createGuest(
-    @Query('tenantId') tenantId: string,
-    @Body() body: any,
-  ) {
-    return this.guestService.createGuest(this.getTenantId(tenantId), body as any);
+  createGuest(@Body() body: any) {
+    return this.guestService.createGuest(body as any);
   }
 
   @Patch('guest/:id/rsvp')
-  updateGuestRsvp(
-    @Query('tenantId') tenantId: string,
-    @Param('id') id: string,
-    @Body() body: any,
-  ) {
-    return this.guestService.updateRsvp(this.getTenantId(tenantId), id, body as any);
+  updateGuestRsvp(@Param('id') id: string, @Body() body: any) {
+    return this.guestService.updateRsvp(id, body as any);
   }
 
   // Todos
   @Get('todo')
-  listTodos(@Query('tenantId') tenantId?: string) {
-    return this.todoService.listTodos(this.getTenantId(tenantId));
+  listTodos() {
+    return this.todoService.listTodos();
   }
 
   @Post('todo')
-  createTodo(
-    @Query('tenantId') tenantId: string,
-    @Body() body: Record<string, any>,
-  ) {
-    return this.todoService.createTodo(this.getTenantId(tenantId), body);
+  createTodo(@Body() body: Record<string, any>) {
+    return this.todoService.createTodo(body);
   }
 
   @Patch('todo/:id/complete')
-  completeTodo(
-    @Query('tenantId') tenantId: string,
-    @Param('id') id: string,
-  ) {
-    return this.todoService.markComplete(this.getTenantId(tenantId), id);
+  completeTodo(@Param('id') id: string) {
+    return this.todoService.markComplete(id);
   }
 
   // Gifts
   @Get('gift')
-  listGifts(@Query('tenantId') tenantId?: string) {
-    return this.giftService.listGifts(this.getTenantId(tenantId));
+  listGifts() {
+    return this.giftService.listGifts();
   }
 
   @Post('gift')
-  createGift(
-    @Query('tenantId') tenantId: string,
-    @Body() body: any,
-  ) {
-    return this.giftService.createGift(this.getTenantId(tenantId), body as any);
+  createGift(@Body() body: any) {
+    return this.giftService.createGift(body as any);
   }
 
   @Get('gift/:id')
-  getGift(
-    @Query('tenantId') tenantId: string,
-    @Param('id') id: string,
-  ) {
-    return this.giftService.getGiftById(this.getTenantId(tenantId), id);
+  getGift(@Param('id') id: string) {
+    return this.giftService.getGiftById(id);
   }
 
   @Post('gift/:id/contribution')
-  createContribution(
-    @Query('tenantId') tenantId: string,
-    @Param('id') id: string,
-    @Body() body: any,
-  ) {
-    return this.giftService.createContribution(this.getTenantId(tenantId), {
+  createContribution(@Param('id') id: string, @Body() body: any) {
+    return this.giftService.createContribution({
       ...(body as any),
       giftId: id,
     });
   }
 
   @Get('gift/:id/contributions')
-  listContributions(
-    @Query('tenantId') tenantId: string,
-    @Param('id') id: string,
-  ) {
-    return this.giftService.listContributions(this.getTenantId(tenantId), id);
+  listContributions(@Param('id') id: string) {
+    return this.giftService.listContributions(id);
   }
 }
diff --git a/src/core/api/auth.controller.ts b/src/core/api/auth.controller.ts
index 721d7d8..a4ba9d3 100644
--- a/src/core/api/auth.controller.ts
+++ b/src/core/api/auth.controller.ts
@@ -13,22 +13,19 @@ export class AuthController {
   async register(
     @Body()
     body: {
-      tenantId?: string;
       name?: string;
       email: string;
       password: string;
     },
   ) {
-    const tenantId = body.tenantId || process.env.DEFAULT_TENANT_ID || 'default';
+    const tenantId = process.env.DEFAULT_TENANT_ID || 'default';
     const user = await this.userService.createUser(tenantId, body.email, body.password, body.name);
     return { id: user.id, email: user.email, name: user.name };
   }
 
   @Post('login')
-  async login(
-    @Body() body: { tenantId?: string; email: string; password: string },
-  ) {
-    const tenantId = body.tenantId || process.env.DEFAULT_TENANT_ID || 'default';
+  async login(@Body() body: { email: string; password: string }) {
+    const tenantId = process.env.DEFAULT_TENANT_ID || 'default';
     const user = await this.userService.validateUser(tenantId, body.email, body.password);
     if (!user) {
       return { message: 'Invalid credentials' };
diff --git a/src/gift/services/gift.service.ts b/src/gift/services/gift.service.ts
index 35b3b71..1c07f5f 100644
--- a/src/gift/services/gift.service.ts
+++ b/src/gift/services/gift.service.ts
@@ -16,9 +16,14 @@ export class GiftService {
     return this.orm.em.fork();
   }
 
-  async createGift(tenantId: string, dto: CreateGiftDto): Promise<Gift> {
+  private getTenantId(): string {
+    // Tenant is now fixed; multi-tenant handled by reverse proxy (subdomains)
+    return process.env.DEFAULT_TENANT_ID || 'default';
+  }
+
+  async createGift(dto: CreateGiftDto): Promise<Gift> {
     const gift = this.em.create(Gift, {
-      tenantId,
+      tenantId: this.getTenantId(),
       ...dto,
     } as any);
     this.em.persist(gift);
@@ -27,9 +32,9 @@ export class GiftService {
     return gift;
   }
 
-  async createContribution(tenantId: string, dto: CreateContributionDto): Promise<GiftContribution> {
+  async createContribution(dto: CreateContributionDto): Promise<GiftContribution> {
     const contribution = this.em.create(GiftContribution, {
-      tenantId,
+      tenantId: this.getTenantId(),
       ...dto,
     } as any);
     this.em.persist(contribution);
@@ -38,16 +43,15 @@ export class GiftService {
     return contribution;
   }
 
-  async listGifts(tenantId: string): Promise<Gift[]> {
-    return this.em.find(Gift, { tenantId });
+  async listGifts(): Promise<Gift[]> {
+    return this.em.find(Gift, { tenantId: this.getTenantId() });
   }
 
   async getGiftById(
-    tenantId: string,
     id: string,
     requesterId?: string,
   ): Promise<Gift | null> {
-    const gift = await this.em.findOne(Gift, { tenantId, id });
+    const gift = await this.em.findOne(Gift, { tenantId: this.getTenantId(), id });
     if (!gift) return null;
     if (requesterId && gift.ownerId && gift.ownerId !== requesterId) {
       return null;
@@ -56,12 +60,11 @@ export class GiftService {
   }
 
   async listContributions(
-    tenantId: string,
     giftId: string,
     requesterId?: string,
   ): Promise<GiftContribution[]> {
-    const gift = await this.getGiftById(tenantId, giftId, requesterId);
+    const gift = await this.getGiftById(giftId, requesterId);
     if (!gift) return [];
-    return this.em.find(GiftContribution, { tenantId, giftId });
+    return this.em.find(GiftContribution, { tenantId: this.getTenantId(), giftId });
   }
 }
diff --git a/src/guest/services/guest.service.ts b/src/guest/services/guest.service.ts
index bfc9b4d..0ae2e68 100644
--- a/src/guest/services/guest.service.ts
+++ b/src/guest/services/guest.service.ts
@@ -16,9 +16,14 @@ export class GuestService {
     return this.orm.em.fork();
   }
 
-  async createGuest(tenantId: string, dto: CreateGuestDto): Promise<Guest> {
+  private getTenantId(): string {
+    // Tenant is now fixed; multi-tenant will be handled by routing (subdomains) later.
+    return process.env.DEFAULT_TENANT_ID || 'default';
+  }
+
+  async createGuest(dto: CreateGuestDto): Promise<Guest> {
     const guest = this.em.create(Guest, {
-      tenantId,
+      tenantId: this.getTenantId(),
       ...dto,
     } as any);
     this.em.persist(guest);
@@ -27,8 +32,8 @@ export class GuestService {
     return guest;
   }
 
-  async updateRsvp(tenantId: string, guestId: string, dto: UpdateRsvpDto): Promise<Guest | null> {
-    const guest = await this.em.findOne(Guest, { tenantId, id: guestId });
+  async updateRsvp(guestId: string, dto: UpdateRsvpDto): Promise<Guest | null> {
+    const guest = await this.em.findOne(Guest, { tenantId: this.getTenantId(), id: guestId });
     if (!guest) return null;
     guest.rsvp = dto.rsvp;
     if (dto.tableId) {
@@ -40,7 +45,7 @@ export class GuestService {
     return guest;
   }
 
-  async listGuests(tenantId: string): Promise<Guest[]> {
-    return this.em.find(Guest, { tenantId });
+  async listGuests(): Promise<Guest[]> {
+    return this.em.find(Guest, { tenantId: this.getTenantId() });
   }
 }
diff --git a/src/todo/services/todo.service.ts b/src/todo/services/todo.service.ts
index 0255b24..0aefc64 100644
--- a/src/todo/services/todo.service.ts
+++ b/src/todo/services/todo.service.ts
@@ -14,9 +14,14 @@ export class TodoService {
     return this.orm.em.fork();
   }
 
-  async createTodo(tenantId: string, dto: Partial<TodoItem>): Promise<TodoItem> {
+  private getTenantId(): string {
+    // Tenant is now fixed; multi-tenant handled by reverse proxy (subdomains)
+    return process.env.DEFAULT_TENANT_ID || 'default';
+  }
+
+  async createTodo(dto: Partial<TodoItem>): Promise<TodoItem> {
     const todo = this.em.create(TodoItem, {
-      tenantId,
+      tenantId: this.getTenantId(),
       ...dto,
     } as any);
     this.em.persist(todo);
@@ -25,12 +30,12 @@ export class TodoService {
     return todo;
   }
 
-  async listTodos(tenantId: string): Promise<TodoItem[]> {
-    return this.em.find(TodoItem, { tenantId });
+  async listTodos(): Promise<TodoItem[]> {
+    return this.em.find(TodoItem, { tenantId: this.getTenantId() });
   }
 
-  async markComplete(tenantId: string, id: string): Promise<TodoItem | null> {
-    const todo = await this.em.findOne(TodoItem, { tenantId, id });
+  async markComplete(id: string): Promise<TodoItem | null> {
+    const todo = await this.em.findOne(TodoItem, { tenantId: this.getTenantId(), id });
     if (!todo) return null;
     todo.completed = true;
     this.em.persist(todo);