diff --git a/backend/migrations/2026_02_09_100000_fix_products_unique_index_nulls_not_distinct.php b/backend/migrations/2026_02_09_100000_fix_products_unique_index_nulls_not_distinct.php
new file mode 100644
index 0000000..099122c
--- /dev/null
+++ b/backend/migrations/2026_02_09_100000_fix_products_unique_index_nulls_not_distinct.php
@@ -0,0 +1,28 @@
+<?php
+
+use Hyperf\Database\Schema\Schema;
+use Hyperf\Database\Migrations\Migration;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * 修复 products 表唯一索引：添加 NULLS NOT DISTINCT
+     * 解决 platform_model_id 为 NULL 时唯一约束不生效的问题（PostgreSQL 15+）
+     */
+    public function up(): void
+    {
+        Schema::getConnection()->statement('ALTER TABLE products DROP CONSTRAINT products_store_item_model_unique');
+        Schema::getConnection()->statement('CREATE UNIQUE INDEX products_store_item_model_unique ON products (store_id, platform_item_id, platform_model_id) NULLS NOT DISTINCT');
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::getConnection()->statement('DROP INDEX IF EXISTS products_store_item_model_unique');
+        Schema::getConnection()->statement('ALTER TABLE products ADD CONSTRAINT products_store_item_model_unique UNIQUE (store_id, platform_item_id, platform_model_id)');
+    }
+};