diff --git a/app/Domains/Catalog/Enums/InventorySubject.php b/app/Domains/Catalog/Enums/InventorySubject.php
new file mode 100644
index 0000000..e7d714f
--- /dev/null
+++ b/app/Domains/Catalog/Enums/InventorySubject.php
@@ -0,0 +1,16 @@
+<?php
+
+namespace App\Domains\Catalog\Enums;
+
+enum InventorySubject: string
+{
+    case Product = 'product';
+    case Seat = 'seat';
+    case Ticket = 'ticket';
+
+    /** @return array<int, string> */
+    public static function values(): array
+    {
+        return array_column(self::cases(), 'value');
+    }
+}
diff --git a/app/Domains/Catalog/Models/CatalogItem.php b/app/Domains/Catalog/Models/CatalogItem.php
index 5e9616e..32b9daa 100644
--- a/app/Domains/Catalog/Models/CatalogItem.php
+++ b/app/Domains/Catalog/Models/CatalogItem.php
@@ -5,6 +5,7 @@ namespace App\Domains\Catalog\Models;
 use App\Domains\Attachable\Models\Attachment;
 use App\Domains\Catalog\Enums\CatalogItemType;
 use App\Domains\Catalog\Enums\InventoryPolicy;
+use App\Domains\Catalog\Enums\InventorySubject;
 use App\Domains\Catalog\Services\CatalogInventoryService;
 use App\Domains\Tenant\Models\Tenant;
 use App\Domains\Ticket\Enums\TicketGenerationPolicy;
@@ -30,6 +31,7 @@ use Illuminate\Support\Collection;
     'descripcion',
     'precio',
     'inventory_policy',
+    'inventory_subject',
     'max_units_per_user',
     'has_tickets',
     'ticket_generation_policy',
@@ -46,6 +48,7 @@ class CatalogItem extends Model
     protected $attributes = [
         'type' => CatalogItemType::Standard->value,
         'inventory_policy' => InventoryPolicy::Tracked->value,
+        'inventory_subject' => InventorySubject::Product->value,
         'has_tickets' => false,
         'ticket_generation_policy' => TicketGenerationPolicy::PerEventDate->value,
     ];
@@ -59,6 +62,7 @@ class CatalogItem extends Model
             'type' => CatalogItemType::class,
             'precio' => 'decimal:2',
             'inventory_policy' => InventoryPolicy::class,
+            'inventory_subject' => InventorySubject::class,
             'max_units_per_user' => 'integer',
             'has_tickets' => 'boolean',
             'ticket_generation_policy' => TicketGenerationPolicy::class,
@@ -208,6 +212,11 @@ class CatalogItem extends Model
         return $this->nombre;
     }
 
+    public function getSelectionLabel(): string
+    {
+        return $this->getName();
+    }
+
     public function getDescription(): ?string
     {
         return $this->descripcion;
diff --git a/app/Domains/Catalog/Models/Variant.php b/app/Domains/Catalog/Models/Variant.php
index 7f6051f..762c987 100644
--- a/app/Domains/Catalog/Models/Variant.php
+++ b/app/Domains/Catalog/Models/Variant.php
@@ -12,6 +12,8 @@ use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Illuminate\Database\Eloquent\Relations\BelongsToMany;
 use Illuminate\Database\Eloquent\Relations\HasMany;
 use Illuminate\Support\Collection;
+use Illuminate\Support\Facades\Lang;
+use Illuminate\Support\Str;
 
 #[Fillable([
     'catalog_item_id',
@@ -113,6 +115,42 @@ class Variant extends Model
         return $this->catalogItem->nombre;
     }
 
+    public function getSelectionLabel(): string
+    {
+        $this->loadMissing([
+            'catalogItem.itemAttributes.attribute.options',
+            'definitions.itemAttribute.attribute.options',
+            'eventDates',
+            'eventDate',
+        ]);
+
+        $itemAttributes = $this->catalogItem->itemAttributes;
+
+        $label = $this->selectionOptions($itemAttributes)
+            ->map(function (array $option, string $attributeCode) use ($itemAttributes): ?string {
+                $itemAttribute = $itemAttributes->first(
+                    fn (ItemAttribute $candidate): bool => $candidate->attribute?->codigo === $attributeCode,
+                );
+                $translationKey = "api.catalog.attribute_labels.{$attributeCode}";
+                $attributeName = Lang::has($translationKey)
+                    ? __($translationKey)
+                    : ($itemAttribute?->attribute?->nombre ?? Str::headline($attributeCode));
+                $selectedOptions = array_is_list($option) ? $option : [$option];
+                $selectedLabels = collect($selectedOptions)
+                    ->pluck('label')
+                    ->filter()
+                    ->implode(', ');
+
+                return $selectedLabels === ''
+                    ? null
+                    : "{$attributeName} {$selectedLabels}";
+            })
+            ->filter()
+            ->implode(' · ');
+
+        return $label !== '' ? $label : $this->getName();
+    }
+
     /** @return Collection<string, string|array<int, string>> */
     public function selectionValues(): Collection
     {
diff --git a/app/Domains/Catalog/Requests/StoreCatalogItemRequest.php b/app/Domains/Catalog/Requests/StoreCatalogItemRequest.php
index 09c8762..6f07e98 100644
--- a/app/Domains/Catalog/Requests/StoreCatalogItemRequest.php
+++ b/app/Domains/Catalog/Requests/StoreCatalogItemRequest.php
@@ -4,6 +4,7 @@ namespace App\Domains\Catalog\Requests;
 
 use App\Domains\Catalog\Enums\CatalogItemType;
 use App\Domains\Catalog\Enums\InventoryPolicy;
+use App\Domains\Catalog\Enums\InventorySubject;
 use App\Domains\Shared\Rules\ImageOrBase64Rule;
 use App\Domains\Ticket\Enums\TicketGenerationPolicy;
 use Illuminate\Foundation\Http\FormRequest;
@@ -54,6 +55,7 @@ class StoreCatalogItemRequest extends FormRequest
             'descripcion' => ['sometimes', 'nullable', 'string'],
             'precio' => ['required', 'numeric', 'min:0'],
             'inventory_policy' => [Rule::prohibitedIf($isBundle), 'sometimes', Rule::enum(InventoryPolicy::class)],
+            'inventory_subject' => ['sometimes', Rule::enum(InventorySubject::class)],
             'max_units_per_user' => ['sometimes', 'nullable', 'integer', 'min:1'],
             'has_tickets' => [Rule::prohibitedIf($isBundle), 'sometimes', 'boolean'],
             'ticket_generation_policy' => [Rule::prohibitedIf($isBundle), 'sometimes', Rule::enum(TicketGenerationPolicy::class)],
diff --git a/app/Domains/Catalog/Resources/CatalogItemDetailResource.php b/app/Domains/Catalog/Resources/CatalogItemDetailResource.php
index 6fc11c1..016624f 100644
--- a/app/Domains/Catalog/Resources/CatalogItemDetailResource.php
+++ b/app/Domains/Catalog/Resources/CatalogItemDetailResource.php
@@ -33,6 +33,7 @@ class CatalogItemDetailResource extends JsonResource
             'category' => $this->category?->nombre,
             'brand' => $this->brand?->nombre,
             'inventory_policy' => $this->inventory_policy?->value,
+            'inventory_subject' => $this->inventory_subject->value,
             'max_units_per_user' => $this->max_units_per_user,
             'has_tickets' => $this->has_tickets,
             'ticket_generation_policy' => $this->ticket_generation_policy->value,
diff --git a/app/Domains/Catalog/Resources/CatalogItemResource.php b/app/Domains/Catalog/Resources/CatalogItemResource.php
index e25495a..d2b0635 100644
--- a/app/Domains/Catalog/Resources/CatalogItemResource.php
+++ b/app/Domains/Catalog/Resources/CatalogItemResource.php
@@ -23,6 +23,7 @@ class CatalogItemResource extends JsonResource
             'descripcion' => $this->descripcion,
             'precio' => $this->precio,
             'inventory_policy' => $this->inventory_policy?->value,
+            'inventory_subject' => $this->inventory_subject->value,
             'max_units_per_user' => $this->max_units_per_user,
             'has_tickets' => $this->has_tickets,
             'ticket_generation_policy' => $this->ticket_generation_policy->value,
diff --git a/app/Domains/Purchase/Services/Checkout/InsufficientStockMessageBuilder.php b/app/Domains/Purchase/Services/Checkout/InsufficientStockMessageBuilder.php
new file mode 100644
index 0000000..e3c5ea2
--- /dev/null
+++ b/app/Domains/Purchase/Services/Checkout/InsufficientStockMessageBuilder.php
@@ -0,0 +1,43 @@
+<?php
+
+namespace App\Domains\Purchase\Services\Checkout;
+
+use App\Domains\Catalog\Enums\InventorySubject;
+use App\Domains\Catalog\Models\CatalogItem;
+use App\Domains\Catalog\Models\Variant;
+
+class InsufficientStockMessageBuilder
+{
+    public function build(
+        CatalogItem $catalogItem,
+        CatalogItem|Variant $selection,
+        int $availableQuantity,
+    ): string {
+        return match ($catalogItem->inventory_subject) {
+            InventorySubject::Seat => __('api.purchase.stock.seat_unavailable', [
+                'selection' => $selection->getSelectionLabel(),
+            ]),
+            InventorySubject::Ticket => __('api.purchase.stock.ticket_unavailable', [
+                'selection' => $selection->getSelectionLabel(),
+            ]),
+            InventorySubject::Product => __('api.purchase.stock.product_unavailable', [
+                'selection' => $this->productSelectionLabel($catalogItem, $selection),
+                'max' => $availableQuantity,
+            ]),
+        };
+    }
+
+    private function productSelectionLabel(
+        CatalogItem $catalogItem,
+        CatalogItem|Variant $selection,
+    ): string {
+        if ($selection instanceof CatalogItem) {
+            return $selection->getSelectionLabel();
+        }
+
+        return __('api.purchase.stock.product_selection', [
+            'product' => $catalogItem->getName(),
+            'selection' => $selection->getSelectionLabel(),
+        ]);
+    }
+}
diff --git a/app/Domains/Purchase/Services/Checkout/StartCheckoutService.php b/app/Domains/Purchase/Services/Checkout/StartCheckoutService.php
index 153812e..152dadf 100644
--- a/app/Domains/Purchase/Services/Checkout/StartCheckoutService.php
+++ b/app/Domains/Purchase/Services/Checkout/StartCheckoutService.php
@@ -22,6 +22,7 @@ class StartCheckoutService
         private readonly UserPurchaseLimitService $purchaseLimits,
         private readonly CatalogSelectionResolver $selections,
         private readonly PurchaseItemSnapshotFactory $snapshots,
+        private readonly InsufficientStockMessageBuilder $stockMessages,
     ) {}
 
     /** @param array<string, mixed> $purchaseData */
@@ -128,17 +129,25 @@ class StartCheckoutService
 
             if ($availableQuantity !== null && $availableQuantity < $line['quantity']) {
                 throw ValidationException::withMessages([
-                    "{$line['field']}.cantidad" => __('api.purchase.direct_items_max_stock', [
-                        'max' => $availableQuantity,
-                    ]),
+                    "{$line['field']}.cantidad" => $this->stockMessages->build(
+                        $line['catalog_item'],
+                        $line['selection'],
+                        $availableQuantity,
+                    ),
                 ]);
             }
 
             try {
                 $this->inventory->reserve($line['selection'], $line['quantity']);
             } catch (\InvalidArgumentException) {
+                $availableQuantity = $this->inventory->availableQuantity($line['selection']) ?? 0;
+
                 throw ValidationException::withMessages([
-                    "{$line['field']}.cantidad" => __('api.purchase.insufficient_stock'),
+                    "{$line['field']}.cantidad" => $this->stockMessages->build(
+                        $line['catalog_item'],
+                        $line['selection'],
+                        $availableQuantity,
+                    ),
                 ]);
             }
         }
diff --git a/database/migrations/2026_08_12_070000_add_inventory_subject_to_catalog_items.php b/database/migrations/2026_08_12_070000_add_inventory_subject_to_catalog_items.php
new file mode 100644
index 0000000..39c706a
--- /dev/null
+++ b/database/migrations/2026_08_12_070000_add_inventory_subject_to_catalog_items.php
@@ -0,0 +1,31 @@
+<?php
+
+use App\Domains\Catalog\Enums\InventorySubject;
+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
+{
+    public function up(): void
+    {
+        Schema::table('catalog_items', function (Blueprint $table): void {
+            $table->enum('inventory_subject', InventorySubject::values())
+                ->default(InventorySubject::Product->value)
+                ->after('inventory_policy');
+        });
+
+        DB::table('catalog_items')
+            ->where('tenant_code', 'desfile_pura_tendencia')
+            ->where('slug', 'entrada')
+            ->update(['inventory_subject' => InventorySubject::Seat->value]);
+    }
+
+    public function down(): void
+    {
+        Schema::table('catalog_items', function (Blueprint $table): void {
+            $table->dropColumn('inventory_subject');
+        });
+    }
+};
diff --git a/lang/en/api.php b/lang/en/api.php
index c6a4a74..e4ad48d 100644
--- a/lang/en/api.php
+++ b/lang/en/api.php
@@ -42,7 +42,12 @@ return [
         'cannot_confirm' => 'A cancelled, rejected, or expired purchase cannot be confirmed.',
         'inconsistent_reservation' => 'The purchase has an inconsistent stock reservation.',
         'paid_cannot_cancel' => 'A paid purchase cannot be cancelled.',
-        'direct_items_max_stock' => 'There is not enough stock. Maximum available: :max.',
+        'stock' => [
+            'seat_unavailable' => 'Seat :selection is no longer available.',
+            'ticket_unavailable' => 'Ticket :selection is no longer available.',
+            'product_unavailable' => 'There is not enough stock for :selection. Maximum available: :max.',
+            'product_selection' => ':product (:selection)',
+        ],
         'empty_cart' => 'The selected cart does not contain items.',
         'catalog_item_missing' => 'One or more catalog items could not be loaded.',
         'catalog_item_wrong_tenant' => 'One or more catalog items do not belong to the tenant.',
@@ -80,6 +85,13 @@ return [
         'test_sent' => 'Test email sent successfully.',
     ],
     'catalog' => [
+        'attribute_labels' => [
+            'tipo' => 'Type',
+            'sector' => 'Sector',
+            'fila' => 'Row',
+            'asiento' => 'Seat',
+            'event_date' => 'Date',
+        ],
         'standard_with_components' => 'A standard item cannot have components.',
         'duplicate_component' => 'The component is duplicated.',
         'component_wrong_tenant' => 'The item does not belong to the bundle tenant.',
diff --git a/lang/es/api.php b/lang/es/api.php
index e5c7e76..5727f87 100644
--- a/lang/es/api.php
+++ b/lang/es/api.php
@@ -42,7 +42,12 @@ return [
         'cannot_confirm' => 'Una compra cancelada, rechazada o vencida no se puede confirmar.',
         'inconsistent_reservation' => 'La compra tiene una reserva de stock inconsistente.',
         'paid_cannot_cancel' => 'Una compra pagada no se puede cancelar.',
-        'direct_items_max_stock' => 'Stock insuficiente. Máximo disponible: :max.',
+        'stock' => [
+            'seat_unavailable' => 'El asiento :selection ya no está disponible.',
+            'ticket_unavailable' => 'La entrada :selection ya no está disponible.',
+            'product_unavailable' => 'No hay stock suficiente de :selection. Máximo disponible: :max.',
+            'product_selection' => ':product (:selection)',
+        ],
         'empty_cart' => 'El carrito seleccionado no contiene productos.',
         'catalog_item_missing' => 'No se pudieron cargar uno o más productos del catálogo.',
         'catalog_item_wrong_tenant' => 'Uno o más productos no pertenecen al tenant.',
@@ -80,6 +85,13 @@ return [
         'test_sent' => 'Correo de prueba enviado correctamente.',
     ],
     'catalog' => [
+        'attribute_labels' => [
+            'tipo' => 'Tipo',
+            'sector' => 'Sector',
+            'fila' => 'Fila',
+            'asiento' => 'Asiento',
+            'event_date' => 'Fecha',
+        ],
         'standard_with_components' => 'Un ítem standard no puede tener componentes.',
         'duplicate_component' => 'El componente está duplicado.',
         'component_wrong_tenant' => 'El ítem no pertenece al tenant del bundle.',
diff --git a/tests/Unit/Catalog/CatalogModelsTest.php b/tests/Unit/Catalog/CatalogModelsTest.php
index cb69cfb..d200347 100644
--- a/tests/Unit/Catalog/CatalogModelsTest.php
+++ b/tests/Unit/Catalog/CatalogModelsTest.php
@@ -7,6 +7,7 @@ use App\Domains\Catalog\Enums\CatalogItemType;
 use App\Domains\Catalog\Enums\FeaturedGroupSource;
 use App\Domains\Catalog\Enums\GroupLayout;
 use App\Domains\Catalog\Enums\InventoryPolicy;
+use App\Domains\Catalog\Enums\InventorySubject;
 use App\Domains\Catalog\Enums\ProductLayout;
 use App\Domains\Catalog\Models\Attribute;
 use App\Domains\Catalog\Models\AttributeOption;
@@ -89,6 +90,7 @@ class CatalogModelsTest extends TestCase
             'type' => CatalogItemType::Standard->value,
             'precio' => '12.50',
             'inventory_policy' => InventoryPolicy::Tracked->value,
+            'inventory_subject' => InventorySubject::Seat->value,
             'has_tickets' => 1,
         ]);
 
@@ -100,6 +102,7 @@ class CatalogModelsTest extends TestCase
         $this->assertSame(CatalogItemType::Standard, $item->type);
         $this->assertSame('12.50', $item->precio);
         $this->assertSame(InventoryPolicy::Tracked, $item->inventory_policy);
+        $this->assertSame(InventorySubject::Seat, $item->inventory_subject);
         $this->assertTrue($item->has_tickets);
         $this->assertInstanceOf(Tenant::class, $item->tenant()->getRelated());
         $this->assertInstanceOf(Category::class, $item->category()->getRelated());
diff --git a/tests/Unit/Purchase/InsufficientStockMessageBuilderTest.php b/tests/Unit/Purchase/InsufficientStockMessageBuilderTest.php
new file mode 100644
index 0000000..c84016a
--- /dev/null
+++ b/tests/Unit/Purchase/InsufficientStockMessageBuilderTest.php
@@ -0,0 +1,97 @@
+<?php
+
+namespace Tests\Unit\Purchase;
+
+use App\Domains\Catalog\Enums\InventorySubject;
+use App\Domains\Catalog\Models\Attribute;
+use App\Domains\Catalog\Models\AttributeOption;
+use App\Domains\Catalog\Models\CatalogItem;
+use App\Domains\Catalog\Models\ItemAttribute;
+use App\Domains\Catalog\Models\Variant;
+use App\Domains\Catalog\Models\VariantDefinition;
+use App\Domains\Purchase\Services\Checkout\InsufficientStockMessageBuilder;
+use Illuminate\Database\Eloquent\Collection as EloquentCollection;
+use Illuminate\Support\Facades\App;
+use Tests\TestCase;
+
+class InsufficientStockMessageBuilderTest extends TestCase
+{
+    public function test_it_builds_a_localized_seat_message_from_the_variant_selection(): void
+    {
+        [$catalogItem, $variant] = $this->seatSelection();
+        $builder = app(InsufficientStockMessageBuilder::class);
+
+        App::setLocale('es');
+        $this->assertSame(
+            'Sector A · Fila 2 · Asiento 3',
+            $variant->getSelectionLabel(),
+        );
+        $this->assertSame(
+            'El asiento Sector A · Fila 2 · Asiento 3 ya no está disponible.',
+            $builder->build($catalogItem, $variant, 0),
+        );
+
+        App::setLocale('en');
+        $this->assertSame(
+            'Sector A · Row 2 · Seat 3',
+            $variant->getSelectionLabel(),
+        );
+        $this->assertSame(
+            'Seat Sector A · Row 2 · Seat 3 is no longer available.',
+            $builder->build($catalogItem, $variant, 0),
+        );
+    }
+
+    /** @return array{CatalogItem, Variant} */
+    private function seatSelection(): array
+    {
+        $catalogItem = new CatalogItem([
+            'nombre' => 'Entrada',
+            'inventory_subject' => InventorySubject::Seat->value,
+        ]);
+        $itemAttributes = collect([
+            ['id' => 1, 'code' => 'sector', 'name' => 'Sector', 'value' => 'A'],
+            ['id' => 2, 'code' => 'fila', 'name' => 'Fila', 'value' => '2'],
+            ['id' => 3, 'code' => 'asiento', 'name' => 'Asiento', 'value' => '3'],
+        ])->map(function (array $data): ItemAttribute {
+            $attribute = new Attribute([
+                'codigo' => $data['code'],
+                'nombre' => $data['name'],
+            ]);
+            $attribute->setRelation('options', new EloquentCollection([
+                new AttributeOption([
+                    'value' => $data['value'],
+                    'label' => $data['value'],
+                ]),
+            ]));
+
+            $itemAttribute = new ItemAttribute([
+                'sort_order' => $data['id'],
+                'allow_multi_select' => false,
+            ]);
+            $itemAttribute->id = $data['id'];
+            $itemAttribute->setRelation('attribute', $attribute);
+
+            return $itemAttribute;
+        })->values();
+
+        $catalogItem->setRelation('itemAttributes', new EloquentCollection($itemAttributes));
+
+        $definitions = $itemAttributes->map(function (ItemAttribute $itemAttribute): VariantDefinition {
+            $value = $itemAttribute->attribute->options->first()->value;
+            $definition = new VariantDefinition(['value' => $value]);
+            $definition->item_attribute_id = $itemAttribute->id;
+            $definition->setRelation('itemAttribute', $itemAttribute);
+
+            return $definition;
+        });
+
+        $variant = new Variant;
+        $variant->setRelation('catalogItem', $catalogItem);
+        $variant->setRelation('definitions', new EloquentCollection($definitions));
+        $variant->setRelation('eventDates', new EloquentCollection);
+        $variant->setRelation('eventDate', null);
+
+        return [$catalogItem, $variant];
+    }
+}