diff --git a/app/Domains/Cart/Controllers/CartController.php b/app/Domains/Cart/Controllers/CartController.php
index ee914d1..610f67a 100644
--- a/app/Domains/Cart/Controllers/CartController.php
+++ b/app/Domains/Cart/Controllers/CartController.php
@@ -2,11 +2,11 @@
 
 namespace App\Domains\Cart\Controllers;
 
+use App\Domains\Cart\Models\CartItem;
 use App\Domains\Cart\Requests\AddCartItemRequest;
 use App\Domains\Cart\Requests\UpdateCartItemQuantityRequest;
 use App\Domains\Cart\Resources\CartResource;
 use App\Domains\Cart\Services\CartService;
-use App\Domains\Catalog\Models\ProductVariant;
 use App\Domains\Tenant\Models\Tenant;
 use App\Http\Controllers\Controller;
 use Illuminate\Http\JsonResponse;
@@ -16,8 +16,7 @@ class CartController extends Controller
 {
     public function __construct(
         protected CartService $cartService,
-    ) {
-    }
+    ) {}
 
     public function show(Request $request, Tenant $tenant): CartResource
     {
@@ -48,7 +47,7 @@ class CartController extends Controller
     public function updateItemQuantity(
         UpdateCartItemQuantityRequest $request,
         Tenant $tenant,
-        \App\Domains\Cart\Models\CartItem $cartItem,
+        CartItem $cartItem,
     ): CartResource {
         return CartResource::make(
             $this->cartService->updateItemQuantity(
@@ -60,7 +59,7 @@ class CartController extends Controller
         )->additional(['message' => 'Cantidad de producto actualizada.']);
     }
 
-    public function removeItem(Request $request, Tenant $tenant, \App\Domains\Cart\Models\CartItem $cartItem): CartResource
+    public function removeItem(Request $request, Tenant $tenant, CartItem $cartItem): CartResource
     {
         return CartResource::make(
             $this->cartService->removeItem($tenant, $request, $cartItem->getKey())
diff --git a/app/Domains/Cart/Requests/AddCartItemRequest.php b/app/Domains/Cart/Requests/AddCartItemRequest.php
index 1e3ec0b..2b44551 100644
--- a/app/Domains/Cart/Requests/AddCartItemRequest.php
+++ b/app/Domains/Cart/Requests/AddCartItemRequest.php
@@ -2,7 +2,10 @@
 
 namespace App\Domains\Cart\Requests;
 
+use App\Domains\Bundle\Models\Bundle;
+use App\Domains\Catalog\Models\ProductVariant;
 use Illuminate\Foundation\Http\FormRequest;
+use Illuminate\Validation\Rule;
 
 class AddCartItemRequest extends FormRequest
 {
@@ -17,7 +20,7 @@ class AddCartItemRequest extends FormRequest
     public function rules(): array
     {
         return [
-            'buyable_type' => ['required', 'string', \Illuminate\Validation\Rule::in(['variant', 'bundle'])],
+            'buyable_type' => ['required', 'string', Rule::in(['variant', 'bundle'])],
             'buyable_id' => ['required', 'integer'],
             'cantidad' => ['required', 'integer', 'min:1'],
         ];
@@ -26,8 +29,8 @@ class AddCartItemRequest extends FormRequest
     public function mappedBuyableType(): string
     {
         return match ($this->input('buyable_type')) {
-            'variant' => \App\Domains\Catalog\Models\ProductVariant::class,
-            'bundle' => \App\Domains\Bundle\Models\Bundle::class,
+            'variant' => ProductVariant::class,
+            'bundle' => Bundle::class,
             default => throw new \InvalidArgumentException('Invalid buyable type'),
         };
     }
diff --git a/app/Domains/Cart/Requests/UpdateCartItemQuantityRequest.php b/app/Domains/Cart/Requests/UpdateCartItemQuantityRequest.php
index 2a98754..c3db1ca 100644
--- a/app/Domains/Cart/Requests/UpdateCartItemQuantityRequest.php
+++ b/app/Domains/Cart/Requests/UpdateCartItemQuantityRequest.php
@@ -18,6 +18,8 @@ class UpdateCartItemQuantityRequest extends FormRequest
     {
         return [
             'cantidad' => ['required', 'integer', 'min:1'],
+            'buyable_type' => ['prohibited'],
+            'buyable_id' => ['prohibited'],
         ];
     }
 }
diff --git a/app/Domains/Cart/Resources/CartResource.php b/app/Domains/Cart/Resources/CartResource.php
index 36defee..ff02f81 100644
--- a/app/Domains/Cart/Resources/CartResource.php
+++ b/app/Domains/Cart/Resources/CartResource.php
@@ -2,11 +2,12 @@
 
 namespace App\Domains\Cart\Resources;
 
+use App\Domains\Cart\Models\Cart;
 use Illuminate\Http\Request;
 use Illuminate\Http\Resources\Json\JsonResource;
 
 /**
- * @mixin \App\Domains\Cart\Models\Cart
+ * @mixin Cart
  */
 class CartResource extends JsonResource
 {
@@ -20,7 +21,7 @@ class CartResource extends JsonResource
             : collect();
 
         $subtotal = $items->reduce(
-            fn (float $carry, $item): float => $carry + ((float) ($item->variant?->product?->precio ?? 0) * $item->cantidad),
+            fn (float $carry, $item): float => $carry + ((float) ($item->buyable?->getPrice() ?? 0) * $item->cantidad),
             0.0,
         );
 
diff --git a/app/Domains/Cart/Services/CartService.php b/app/Domains/Cart/Services/CartService.php
index c790f6e..17d309b 100644
--- a/app/Domains/Cart/Services/CartService.php
+++ b/app/Domains/Cart/Services/CartService.php
@@ -2,10 +2,14 @@
 
 namespace App\Domains\Cart\Services;
 
-use App\Domains\Cart\Models\Cart;
 use App\Domains\Auth\Models\User;
+use App\Domains\Bundle\Models\Bundle;
+use App\Domains\Cart\Models\Cart;
+use App\Domains\Catalog\Models\ProductVariant;
 use App\Domains\Tenant\Models\Tenant;
+use Illuminate\Database\Eloquent\Relations\MorphTo;
 use Illuminate\Http\Request;
+use Illuminate\Support\Facades\Auth;
 use Illuminate\Support\Str;
 use Symfony\Component\HttpFoundation\Cookie;
 use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
@@ -93,9 +97,16 @@ class CartService
     protected function loadCart(Cart $cart): Cart
     {
         return $cart->fresh()->load([
-            'items.variant.product',
-            'items.variant.definitions.productAttribute.attribute',
-            'items.variant.attachments',
+            'items.buyable' => function (MorphTo $morphTo): void {
+                $morphTo->morphWith([
+                    ProductVariant::class => [
+                        'product',
+                        'definitions.productAttribute.attribute',
+                        'attachments',
+                    ],
+                    Bundle::class => ['items.variant'],
+                ]);
+            },
         ]);
     }
 
@@ -104,7 +115,7 @@ class CartService
      */
     protected function resolveIdentity(Request $request, bool $generateGuestToken = false): ?array
     {
-        $user = $request->user() ?? \Illuminate\Support\Facades\Auth::guard('sanctum')->user();
+        $user = $request->user() ?? Auth::guard('sanctum')->user();
 
         if ($user instanceof User) {
             return [
@@ -201,5 +212,4 @@ class CartService
 
         return Cart::query()->firstOrCreate($attributes, ['status' => 'active']);
     }
-
 }
diff --git a/app/Domains/Catalog/Models/ProductVariant.php b/app/Domains/Catalog/Models/ProductVariant.php
index d46d62c..79a9b14 100644
--- a/app/Domains/Catalog/Models/ProductVariant.php
+++ b/app/Domains/Catalog/Models/ProductVariant.php
@@ -99,7 +99,10 @@ class ProductVariant extends Model implements Buyable
 
         if ($this->relationLoaded('definitions') && $this->definitions->isNotEmpty()) {
             $definitions = $this->definitions->map(function ($def) {
-                return $def->value ?? $def->productAttribute?->attribute?->nombre;
+                $attributeName = $def->productAttribute?->attribute?->nombre;
+                $value = $def->value;
+
+                return $attributeName ? "{$attributeName}: {$value}" : $value;
             })->filter()->implode(', ');
 
             if ($definitions !== '') {
diff --git a/app/Domains/Purchase/Controllers/PurchaseController.php b/app/Domains/Purchase/Controllers/PurchaseController.php
index e976891..499536e 100644
--- a/app/Domains/Purchase/Controllers/PurchaseController.php
+++ b/app/Domains/Purchase/Controllers/PurchaseController.php
@@ -2,14 +2,20 @@
 
 namespace App\Domains\Purchase\Controllers;
 
+use App\Domains\Bundle\Models\Bundle;
+use App\Domains\Catalog\Models\ProductVariant;
+use App\Domains\Integration\Services\TelepagosIntegrationService;
 use App\Domains\Purchase\Models\Purchase;
+use App\Domains\Purchase\Requests\PaymentIntentRequest;
 use App\Domains\Purchase\Requests\StorePurchaseRequest;
 use App\Domains\Purchase\Resources\PurchaseResource;
 use App\Domains\Purchase\Services\CheckoutService;
 use App\Domains\Tenant\Models\Tenant;
 use App\Http\Controllers\Controller;
+use Illuminate\Database\Eloquent\Relations\MorphTo;
 use Illuminate\Http\JsonResponse;
 use Illuminate\Http\Request;
+use Illuminate\Support\Collection;
 use Illuminate\Support\Facades\Log;
 use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
 
@@ -46,12 +52,17 @@ class PurchaseController extends Controller
     {
         $compra = $this->resolveScopedPurchase($tenant, $request->user()->id, $compra);
 
-        return PurchaseResource::make(
-            $compra->loadMissing($this->purchaseDetailRelations())
-        );
+        $compra->loadMissing(['items', 'cart.items']);
+        $this->loadBuyables($compra->items);
+
+        if ($compra->cart !== null) {
+            $this->loadBuyables($compra->cart->items);
+        }
+
+        return PurchaseResource::make($compra);
     }
 
-    public function paymentIntent(\App\Domains\Purchase\Requests\PaymentIntentRequest $request, Tenant $tenant, Purchase $compra): JsonResponse
+    public function paymentIntent(PaymentIntentRequest $request, Tenant $tenant, Purchase $compra): JsonResponse
     {
         $compra = $this->resolveScopedPurchase($tenant, $request->user()->id, $compra);
         $method = $request->validated('method');
@@ -63,7 +74,7 @@ class PurchaseController extends Controller
         ]);
 
         if ($method === 'transfer') {
-            $telepagosService = new \App\Domains\Integration\Services\TelepagosIntegrationService();
+            $telepagosService = new TelepagosIntegrationService;
             $telepagosService->forTenant($tenant->codigo);
 
             try {
@@ -81,13 +92,13 @@ class PurchaseController extends Controller
                 ]);
             } catch (\Exception $e) {
                 return response()->json([
-                    'message' => 'Error getting account info: ' . $e->getMessage()
+                    'message' => 'Error getting account info: '.$e->getMessage(),
                 ], 500);
             }
         }
 
         if ($method === 'qr') {
-            $telepagosService = new \App\Domains\Integration\Services\TelepagosIntegrationService();
+            $telepagosService = new TelepagosIntegrationService;
             $telepagosService->forTenant($tenant->codigo);
 
             try {
@@ -100,11 +111,11 @@ class PurchaseController extends Controller
 
                 $telepagosQr = $compra->telepagosQr()->create([
                     'qr_order_id' => (string) ($qrResponse['qr_order_id'] ?? ''),
-                    'qr_code' =>  $qrResponse['qr_code'] ?? '',
+                    'qr_code' => $qrResponse['qr_code'] ?? '',
                 ]);
             } catch (\Exception $e) {
                 return response()->json([
-                    'message' => 'Error generating QR: ' . $e->getMessage()
+                    'message' => 'Error generating QR: '.$e->getMessage(),
                 ], 500);
             }
 
@@ -143,15 +154,19 @@ class PurchaseController extends Controller
     /**
      * @return list<string>
      */
-    protected function purchaseDetailRelations(): array
+    protected function loadBuyables(Collection $items): void
     {
-        return [
-            'items.variant.product',
-            'items.variant.definitions.productAttribute.attribute',
-            'items.variant.attachments',
-            'cart.items.variant.product',
-            'cart.items.variant.definitions.productAttribute.attribute',
-            'cart.items.variant.attachments',
-        ];
+        $items->load([
+            'buyable' => function (MorphTo $morphTo): void {
+                $morphTo->morphWith([
+                    ProductVariant::class => [
+                        'product',
+                        'definitions.productAttribute.attribute',
+                        'attachments',
+                    ],
+                    Bundle::class => ['items.variant'],
+                ]);
+            },
+        ]);
     }
 }
diff --git a/app/Domains/Purchase/Models/Purchase.php b/app/Domains/Purchase/Models/Purchase.php
index 7a18740..2d39e7a 100644
--- a/app/Domains/Purchase/Models/Purchase.php
+++ b/app/Domains/Purchase/Models/Purchase.php
@@ -10,6 +10,7 @@ use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Illuminate\Database\Eloquent\Relations\HasMany;
+use Illuminate\Database\Eloquent\Relations\HasOne;
 
 #[Fillable([
     'cart_id',
@@ -28,9 +29,13 @@ class Purchase extends Model
     use HasFactory;
 
     public const STATUS_CREATED = 'created';
+
     public const STATUS_PENDING_PAYMENT = 'pending_payment';
+
     public const STATUS_PAID = 'paid';
+
     public const STATUS_CANCELLED = 'cancelled';
+
     public const STATUS_REJECTED = 'rejected';
 
     protected $table = 'compras';
@@ -77,7 +82,7 @@ class Purchase extends Model
     }
 
     /**
-     * @return \Illuminate\Database\Eloquent\Relations\HasOne<TelepagosQr, $this>
+     * @return HasOne<TelepagosQr, $this>
      */
     public function telepagosQr()
     {
@@ -113,7 +118,7 @@ class Purchase extends Model
 
         $cart = $this->relationLoaded('cart')
             ? $this->getRelation('cart')
-            : $this->cart()->with('items.variant.product')->first();
+            : $this->cart()->with('items.buyable')->first();
 
         if (! $cart) {
             return 0.0;
diff --git a/app/Domains/Purchase/Resources/PurchaseItemResource.php b/app/Domains/Purchase/Resources/PurchaseItemResource.php
index 875d770..e1524b5 100644
--- a/app/Domains/Purchase/Resources/PurchaseItemResource.php
+++ b/app/Domains/Purchase/Resources/PurchaseItemResource.php
@@ -2,13 +2,16 @@
 
 namespace App\Domains\Purchase\Resources;
 
+use App\Domains\Bundle\Models\Bundle;
 use App\Domains\Cart\Models\CartItem;
+use App\Domains\Catalog\Models\ProductVariant;
 use App\Domains\Purchase\Models\PurchaseItem;
+use App\Domains\Shared\Contracts\Buyable;
 use Illuminate\Http\Request;
 use Illuminate\Http\Resources\Json\JsonResource;
 
 /**
- * @mixin \App\Domains\Purchase\Models\PurchaseItem|\App\Domains\Cart\Models\CartItem
+ * @mixin PurchaseItem|CartItem
  */
 class PurchaseItemResource extends JsonResource
 {
@@ -17,15 +20,16 @@ class PurchaseItemResource extends JsonResource
      */
     public function toArray(Request $request): array
     {
-        /** @var \App\Domains\Shared\Contracts\Buyable|null $buyable */
+        /** @var Buyable|null $buyable */
         $buyable = $this->buyable;
         $quantity = (int) ($this->cantidad ?? 0);
         $unitPrice = $this->resolveUnitPrice();
         $lineTotal = $this->resolveLineTotal($unitPrice, $quantity);
+        $variant = $buyable instanceof ProductVariant ? $buyable : null;
 
         $imageUrl = null;
         $attributes = [];
-        if ($this->buyable_type === \App\Domains\Catalog\Models\ProductVariant::class && $buyable) {
+        if ($this->buyable_type === ProductVariant::class && $buyable) {
             $imageUrl = $this->resolveImageUrl($buyable);
             $attributes = $this->resolveAttributes($buyable);
         }
@@ -37,6 +41,16 @@ class PurchaseItemResource extends JsonResource
             'line_total' => $this->formatMoney($lineTotal),
             'buyable_type' => $this->mapBuyableTypeToAlias($this->buyable_type),
             'buyable_id' => $this->buyable_id,
+            'product' => $variant === null ? null : [
+                'id' => $variant->product?->id,
+                'nombre' => $variant->product?->nombre,
+                'slug' => $variant->product?->slug,
+                'imagen' => $imageUrl,
+            ],
+            'variant' => $variant === null ? null : [
+                'id' => $variant->id,
+                'attributes' => $attributes,
+            ],
             'item_details' => $buyable === null ? null : [
                 'nombre' => $buyable->getName(),
                 'imagen' => $imageUrl,
@@ -48,8 +62,8 @@ class PurchaseItemResource extends JsonResource
     protected function mapBuyableTypeToAlias(?string $type): string
     {
         return match ($type) {
-            \App\Domains\Catalog\Models\ProductVariant::class => 'variant',
-            \App\Domains\Bundle\Models\Bundle::class => 'bundle',
+            ProductVariant::class => 'variant',
+            Bundle::class => 'bundle',
             default => 'unknown',
         };
     }
diff --git a/app/Domains/Purchase/Resources/PurchaseResource.php b/app/Domains/Purchase/Resources/PurchaseResource.php
index d1a8537..b955849 100644
--- a/app/Domains/Purchase/Resources/PurchaseResource.php
+++ b/app/Domains/Purchase/Resources/PurchaseResource.php
@@ -3,13 +3,14 @@
 namespace App\Domains\Purchase\Resources;
 
 use App\Domains\Cart\Models\CartItem;
+use App\Domains\Purchase\Models\Purchase;
 use App\Domains\Purchase\Models\PurchaseItem;
 use Illuminate\Http\Request;
 use Illuminate\Http\Resources\Json\JsonResource;
 use Illuminate\Support\Collection;
 
 /**
- * @mixin \App\Domains\Purchase\Models\Purchase
+ * @mixin Purchase
  */
 class PurchaseResource extends JsonResource
 {
@@ -87,7 +88,7 @@ class PurchaseResource extends JsonResource
             return (float) $item->precio_unitario * $item->cantidad;
         }
 
-        return (float) ($item->variant?->product?->precio ?? 0) * $item->cantidad;
+        return (float) ($item->buyable?->getPrice() ?? 0) * $item->cantidad;
     }
 
     protected function resolveItemTotal(PurchaseItem|CartItem $item): float
diff --git a/database/migrations/2026_07_14_184802_make_cart_items_polymorphic.php b/database/migrations/2026_07_14_184802_make_cart_items_polymorphic.php
index fe1a0d1..b55c3b5 100644
--- a/database/migrations/2026_07_14_184802_make_cart_items_polymorphic.php
+++ b/database/migrations/2026_07_14_184802_make_cart_items_polymorphic.php
@@ -2,6 +2,7 @@
 
 use Illuminate\Database\Migrations\Migration;
 use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\DB;
 use Illuminate\Support\Facades\Schema;
 
 return new class extends Migration
@@ -14,17 +15,23 @@ return new class extends Migration
         Schema::table('carrito_items', function (Blueprint $table) {
             $table->string('buyable_type')->nullable();
             $table->unsignedBigInteger('buyable_id')->nullable();
+            $table->index('cart_id');
         });
 
         // Copy existing data
-        \Illuminate\Support\Facades\DB::table('carrito_items')->update([
+        DB::table('carrito_items')->update([
             'buyable_type' => 'App\Domains\Catalog\Models\ProductVariant',
-            'buyable_id' => \Illuminate\Support\Facades\DB::raw('producto_variante_id'),
+            'buyable_id' => DB::raw('producto_variante_id'),
         ]);
 
         Schema::table('carrito_items', function (Blueprint $table) {
             $table->dropForeign(['producto_variante_id']);
+        });
+
+        Schema::table('carrito_items', function (Blueprint $table) {
+            $table->dropUnique(['cart_id', 'producto_variante_id']);
             $table->dropColumn('producto_variante_id');
+            $table->unique(['cart_id', 'buyable_type', 'buyable_id']);
         });
     }
 
@@ -34,15 +41,18 @@ return new class extends Migration
     public function down(): void
     {
         Schema::table('carrito_items', function (Blueprint $table) {
+            $table->dropUnique(['cart_id', 'buyable_type', 'buyable_id']);
             $table->foreignId('producto_variante_id')->nullable()->constrained('productos_variantes')->onDelete('cascade');
         });
 
-        \Illuminate\Support\Facades\DB::table('carrito_items')->update([
-            'producto_variante_id' => \Illuminate\Support\Facades\DB::raw('buyable_id'),
+        DB::table('carrito_items')->update([
+            'producto_variante_id' => DB::raw('buyable_id'),
         ]);
 
         Schema::table('carrito_items', function (Blueprint $table) {
             $table->dropColumn(['buyable_type', 'buyable_id']);
+            $table->dropIndex(['cart_id']);
+            $table->unique(['cart_id', 'producto_variante_id']);
         });
     }
 };
diff --git a/tests/Feature/Cart/CartControllerTest.php b/tests/Feature/Cart/CartControllerTest.php
index 6f68ca7..313f25e 100644
--- a/tests/Feature/Cart/CartControllerTest.php
+++ b/tests/Feature/Cart/CartControllerTest.php
@@ -60,7 +60,8 @@ class CartControllerTest extends TestCase
         ]);
 
         $response = $this->postJson('/api/tenants/acme/cart/items', [
-            'product_variant_id' => $variant->id,
+            'buyable_type' => 'variant',
+            'buyable_id' => $variant->id,
             'cantidad' => 2,
         ]);
 
@@ -70,7 +71,8 @@ class CartControllerTest extends TestCase
             ->assertJsonPath('data.tenant_codigo', 'acme')
             ->assertJsonPath('data.items.0.cantidad', 2)
             ->assertJsonPath('data.items.0.precio_unitario', '49.90')
-            ->assertJsonPath('data.items.0.product_id', $variant->product->id)
+            ->assertJsonPath('data.items.0.buyable_type', 'variant')
+            ->assertJsonPath('data.items.0.buyable_id', $variant->id)
             ->assertJsonPath('data.items.0.product.nombre', 'Shirt acme (Color: Red)')
             ->assertJsonPath('data.items.0.product.imagen', null)
             ->assertJsonPath('data.subtotal', '99.80');
@@ -82,7 +84,8 @@ class CartControllerTest extends TestCase
         ]);
 
         $this->assertDatabaseHas('carrito_items', [
-            'producto_variante_id' => $variant->id,
+            'buyable_type' => ProductVariant::class,
+            'buyable_id' => $variant->id,
             'cantidad' => 2,
         ]);
 
@@ -98,7 +101,8 @@ class CartControllerTest extends TestCase
         $variant = $this->createVariantForTenant('acme', 12, '25.00');
 
         $firstResponse = $this->postJson('/api/tenants/acme/cart/items', [
-            'product_variant_id' => $variant->id,
+            'buyable_type' => 'variant',
+            'buyable_id' => $variant->id,
             'cantidad' => 2,
         ]);
 
@@ -112,7 +116,8 @@ class CartControllerTest extends TestCase
             [],
             ['HTTP_Accept' => 'application/json', 'CONTENT_TYPE' => 'application/json'],
             json_encode([
-                'product_variant_id' => $variant->id,
+                'buyable_type' => 'variant',
+                'buyable_id' => $variant->id,
                 'cantidad' => 3,
             ])
         );
@@ -125,7 +130,8 @@ class CartControllerTest extends TestCase
         $this->assertDatabaseCount('carritos', 1);
         $this->assertDatabaseCount('carrito_items', 1);
         $this->assertDatabaseHas('carrito_items', [
-            'producto_variante_id' => $variant->id,
+            'buyable_type' => ProductVariant::class,
+            'buyable_id' => $variant->id,
             'cantidad' => 5,
         ]);
         $this->assertDatabaseHas('productos_variantes', [
@@ -140,15 +146,17 @@ class CartControllerTest extends TestCase
         $variant = $this->createVariantForTenant('acme', 10, '15.00');
 
         $createResponse = $this->postJson('/api/tenants/acme/cart/items', [
-            'product_variant_id' => $variant->id,
+            'buyable_type' => 'variant',
+            'buyable_id' => $variant->id,
             'cantidad' => 2,
         ]);
 
         $guestToken = $createResponse->getCookie('guest_token', false)?->getValue();
+        $cartItemId = $createResponse->json('data.items.0.id');
 
         $response = $this->call(
             'PATCH',
-            "/api/tenants/acme/cart/items/{$variant->id}",
+            "/api/tenants/acme/cart/items/{$cartItemId}",
             [],
             ['guest_token' => $guestToken],
             [],
@@ -164,7 +172,8 @@ class CartControllerTest extends TestCase
             ->assertJsonPath('data.subtotal', '75.00');
 
         $this->assertDatabaseHas('carrito_items', [
-            'producto_variante_id' => $variant->id,
+            'buyable_type' => ProductVariant::class,
+            'buyable_id' => $variant->id,
             'cantidad' => 5,
         ]);
         $this->assertDatabaseHas('productos_variantes', [
@@ -179,15 +188,17 @@ class CartControllerTest extends TestCase
         $variant = $this->createVariantForTenant('acme', 10, '15.00');
 
         $createResponse = $this->postJson('/api/tenants/acme/cart/items', [
-            'product_variant_id' => $variant->id,
+            'buyable_type' => 'variant',
+            'buyable_id' => $variant->id,
             'cantidad' => 4,
         ]);
 
         $guestToken = $createResponse->getCookie('guest_token', false)?->getValue();
+        $cartItemId = $createResponse->json('data.items.0.id');
 
         $response = $this->call(
             'DELETE',
-            "/api/tenants/acme/cart/items/{$variant->id}",
+            "/api/tenants/acme/cart/items/{$cartItemId}",
             [],
             ['guest_token' => $guestToken],
             [],
@@ -216,14 +227,16 @@ class CartControllerTest extends TestCase
 
         $this->actingAs($user)
             ->postJson('/api/tenants/acme/cart/items', [
-                'product_variant_id' => $acmeVariantA->id,
+                'buyable_type' => 'variant',
+                'buyable_id' => $acmeVariantA->id,
                 'cantidad' => 1,
             ])
             ->assertOk();
 
         $this->actingAs($user)
             ->postJson('/api/tenants/acme/cart/items', [
-                'product_variant_id' => $acmeVariantB->id,
+                'buyable_type' => 'variant',
+                'buyable_id' => $acmeVariantB->id,
                 'cantidad' => 2,
             ])
             ->assertOk()
@@ -231,7 +244,8 @@ class CartControllerTest extends TestCase
 
         $this->actingAs($user)
             ->postJson('/api/tenants/globex/cart/items', [
-                'product_variant_id' => $globexVariant->id,
+                'buyable_type' => 'variant',
+                'buyable_id' => $globexVariant->id,
                 'cantidad' => 1,
             ])
             ->assertOk();
@@ -253,7 +267,8 @@ class CartControllerTest extends TestCase
         $otherVariant = $this->createVariantForTenant('globex', 10, '20.00');
 
         $this->postJson('/api/tenants/acme/cart/items', [
-            'product_variant_id' => $otherVariant->id,
+            'buyable_type' => 'variant',
+            'buyable_id' => $otherVariant->id,
             'cantidad' => 1,
         ])->assertNotFound();
     }
@@ -275,16 +290,19 @@ class CartControllerTest extends TestCase
         $variant = $this->createVariantForTenant('acme', 2, '10.00');
 
         $this->postJson('/api/tenants/acme/cart/items', [
-            'product_variant_id' => $variant->id,
+            'buyable_type' => 'variant',
+            'buyable_id' => $variant->id,
             'cantidad' => 0,
         ])->assertUnprocessable()->assertJsonValidationErrors(['cantidad']);
 
         $response = $this->postJson('/api/tenants/acme/cart/items', [
-            'product_variant_id' => $variant->id,
+            'buyable_type' => 'variant',
+            'buyable_id' => $variant->id,
             'cantidad' => 2,
         ]);
 
         $guestToken = $response->getCookie('guest_token', false)?->getValue();
+        $cartItemId = $response->json('data.items.0.id');
 
         $response1 = $this->call(
             'POST',
@@ -294,7 +312,8 @@ class CartControllerTest extends TestCase
             [],
             ['HTTP_Accept' => 'application/json', 'CONTENT_TYPE' => 'application/json'],
             json_encode([
-                'product_variant_id' => $variant->id,
+                'buyable_type' => 'variant',
+                'buyable_id' => $variant->id,
                 'cantidad' => 1,
             ])
         );
@@ -305,7 +324,7 @@ class CartControllerTest extends TestCase
 
         $response2 = $this->call(
             'PATCH',
-            "/api/tenants/acme/cart/items/{$variant->id}",
+            "/api/tenants/acme/cart/items/{$cartItemId}",
             [],
             ['guest_token' => $guestToken],
             [],
@@ -320,6 +339,32 @@ class CartControllerTest extends TestCase
             ->assertJsonValidationErrors(['cantidad' => 'El máximo que se puede agregar es 2.']);
     }
 
+    public function test_it_only_accepts_buyable_identity_when_adding_an_item(): void
+    {
+        $variant = $this->createVariantForTenant('acme', 10, '10.00');
+
+        $this->postJson('/api/tenants/acme/cart/items', [
+            'product_variant_id' => $variant->id,
+            'cantidad' => 1,
+        ])->assertUnprocessable()
+            ->assertJsonValidationErrors(['buyable_type', 'buyable_id']);
+
+        $createResponse = $this->postJson('/api/tenants/acme/cart/items', [
+            'buyable_type' => 'variant',
+            'buyable_id' => $variant->id,
+            'cantidad' => 1,
+        ])->assertOk();
+
+        $cartItemId = $createResponse->json('data.items.0.id');
+
+        $this->patchJson("/api/tenants/acme/cart/items/{$cartItemId}", [
+            'cantidad' => 2,
+            'buyable_type' => 'variant',
+            'buyable_id' => $variant->id,
+        ])->assertUnprocessable()
+            ->assertJsonValidationErrors(['buyable_type', 'buyable_id']);
+    }
+
     public function test_unlimited_inventory_can_be_reserved_updated_and_released_without_real_stock(): void
     {
         $variant = $this->createVariantForTenant(
@@ -331,11 +376,13 @@ class CartControllerTest extends TestCase
         );
 
         $response = $this->postJson('/api/tenants/acme/cart/items', [
-            'product_variant_id' => $variant->id,
+            'buyable_type' => 'variant',
+            'buyable_id' => $variant->id,
             'cantidad' => 100,
         ])->assertOk();
 
         $guestToken = $response->getCookie('guest_token', false)?->getValue();
+        $cartItemId = $response->json('data.items.0.id');
         $this->assertDatabaseHas('productos_variantes', [
             'id' => $variant->id,
             'stock_real' => 0,
@@ -344,7 +391,7 @@ class CartControllerTest extends TestCase
 
         $this->call(
             'PATCH',
-            "/api/tenants/acme/cart/items/{$variant->id}",
+            "/api/tenants/acme/cart/items/{$cartItemId}",
             [],
             ['guest_token' => $guestToken],
             [],
@@ -360,7 +407,7 @@ class CartControllerTest extends TestCase
 
         $this->call(
             'DELETE',
-            "/api/tenants/acme/cart/items/{$variant->id}",
+            "/api/tenants/acme/cart/items/{$cartItemId}",
             [],
             ['guest_token' => $guestToken],
             [],
diff --git a/tests/Feature/Integration/TelepagosWebhookTest.php b/tests/Feature/Integration/TelepagosWebhookTest.php
index af75602..db8ec16 100644
--- a/tests/Feature/Integration/TelepagosWebhookTest.php
+++ b/tests/Feature/Integration/TelepagosWebhookTest.php
@@ -113,7 +113,8 @@ class TelepagosWebhookTest extends TestCase
 
         $this->assertDatabaseHas('compra_items', [
             'compra_id' => $matchingPurchase->id,
-            'producto_variante_id' => $variant->id,
+            'buyable_type' => ProductVariant::class,
+            'buyable_id' => $variant->id,
             'cantidad' => 1,
             'total' => 50,
         ]);
@@ -201,7 +202,7 @@ class TelepagosWebhookTest extends TestCase
             'status' => 'active',
         ]);
 
-        $cart->addItem($variantId, $quantity);
+        $cart->addItem(ProductVariant::class, $variantId, $quantity);
 
         /** @var CheckoutService $checkoutService */
         $checkoutService = app(CheckoutService::class);
diff --git a/tests/Feature/Purchase/StorePurchaseTest.php b/tests/Feature/Purchase/StorePurchaseTest.php
index bd9549a..b822797 100644
--- a/tests/Feature/Purchase/StorePurchaseTest.php
+++ b/tests/Feature/Purchase/StorePurchaseTest.php
@@ -51,7 +51,8 @@ class StorePurchaseTest extends TestCase
 
         $cartResponse = $this->actingAs($user, 'sanctum')
             ->postJson('/api/tenants/sonder/cart/items', [
-                'product_variant_id' => $variant->id,
+                'buyable_type' => 'variant',
+                'buyable_id' => $variant->id,
                 'cantidad' => 2,
             ])
             ->assertOk();
@@ -111,7 +112,8 @@ class StorePurchaseTest extends TestCase
         ]);
         $this->assertDatabaseHas('carrito_items', [
             'cart_id' => $cartId,
-            'producto_variante_id' => $variant->id,
+            'buyable_type' => ProductVariant::class,
+            'buyable_id' => $variant->id,
             'cantidad' => 2,
         ]);
         $this->assertDatabaseHas('productos_variantes', [
@@ -131,7 +133,8 @@ class StorePurchaseTest extends TestCase
 
         $cartId = $this->actingAs($user, 'sanctum')
             ->postJson('/api/tenants/sonder/cart/items', [
-                'product_variant_id' => $variant->id,
+                'buyable_type' => 'variant',
+                'buyable_id' => $variant->id,
                 'cantidad' => 2,
             ])
             ->assertOk()
@@ -280,7 +283,8 @@ class StorePurchaseTest extends TestCase
         $purchase = $this->createCheckoutPurchase($user, 'sonder', $variant, 2);
 
         $purchase->items()->create([
-            'producto_variante_id' => $variant->id,
+            'buyable_type' => ProductVariant::class,
+            'buyable_id' => $variant->id,
             'cantidad' => 1,
             'precio_unitario' => '50.00',
             'discount_total' => null,
@@ -326,7 +330,8 @@ class StorePurchaseTest extends TestCase
 
         $cartId = $this->actingAs($owner, 'sanctum')
             ->postJson('/api/tenants/sonder/cart/items', [
-                'product_variant_id' => $variant->id,
+                'buyable_type' => 'variant',
+                'buyable_id' => $variant->id,
                 'cantidad' => 1,
             ])
             ->assertOk()
@@ -352,7 +357,8 @@ class StorePurchaseTest extends TestCase
 
         $cartId = $this->actingAs($user, 'sanctum')
             ->postJson('/api/tenants/globex/cart/items', [
-                'product_variant_id' => $variant->id,
+                'buyable_type' => 'variant',
+                'buyable_id' => $variant->id,
                 'cantidad' => 1,
             ])
             ->assertOk()
@@ -492,7 +498,7 @@ class StorePurchaseTest extends TestCase
             'status' => 'active',
         ]);
 
-        $cart->addItem($variant->id, $quantity);
+        $cart->addItem(ProductVariant::class, $variant->id, $quantity);
 
         return app(CheckoutService::class)->startCheckout($tenant, $user->id, [
             'cart_id' => $cart->id,