diff --git a/core/components/minishop3/lexicon/en/cart.inc.php b/core/components/minishop3/lexicon/en/cart.inc.php
index 8f632936d..7fbcdc67d 100644
--- a/core/components/minishop3/lexicon/en/cart.inc.php
+++ b/core/components/minishop3/lexicon/en/cart.inc.php
@@ -29,6 +29,7 @@
 $_lang['ms3_cart_change_error'] = 'Error changing product count in cart';
 $_lang['ms3_cart_change_options_success'] = 'Product options in cart successfully changed';
 $_lang['ms3_cart_change_options_error'] = 'Error changing product options in cart';
+$_lang['ms3_err_cart_options'] = 'options must be an object or a JSON string';
 
 $_lang['ms3_cart_clean_success'] = 'Cart successfully cleared';
 $_lang['ms3_cart_is_empty'] = 'Your cart is empty';
diff --git a/core/components/minishop3/lexicon/en/default.inc.php b/core/components/minishop3/lexicon/en/default.inc.php
index 163378ff0..12be2e6e0 100644
--- a/core/components/minishop3/lexicon/en/default.inc.php
+++ b/core/components/minishop3/lexicon/en/default.inc.php
@@ -168,6 +168,7 @@
 $_lang['ms3_err_unknown'] = 'Unknown error';
 $_lang['ms3_err_ns'] = 'This field is required';
 $_lang['ms3_err_product_key_required'] = 'Product key is required';
+$_lang['ms3_err_cart_options'] = 'options must be an object or a JSON string';
 $_lang['ms3_err_field_key_required'] = 'Field key is required';
 $_lang['ms3_err_fields_required'] = 'Fields array is required';
 $_lang['ms3_err_field_nf'] = 'Field not found';
diff --git a/core/components/minishop3/lexicon/ru/cart.inc.php b/core/components/minishop3/lexicon/ru/cart.inc.php
index eb251fe9c..1bf9ec336 100644
--- a/core/components/minishop3/lexicon/ru/cart.inc.php
+++ b/core/components/minishop3/lexicon/ru/cart.inc.php
@@ -29,6 +29,7 @@
 $_lang['ms3_cart_change_error'] = 'Ошибка при изменении количества товара в корзине';
 $_lang['ms3_cart_change_options_success'] = 'Опции товара в корзине успешно изменены';
 $_lang['ms3_cart_change_options_error'] = 'Ошибка при изменении опций товара в корзине';
+$_lang['ms3_err_cart_options'] = 'options должен быть объектом или JSON-строкой';
 
 $_lang['ms3_cart_clean_success'] = 'Корзина успешно очищена';
 $_lang['ms3_cart_is_empty'] = 'Ваша корзина пуста';
diff --git a/core/components/minishop3/lexicon/ru/default.inc.php b/core/components/minishop3/lexicon/ru/default.inc.php
index 266ae656c..05e97d061 100644
--- a/core/components/minishop3/lexicon/ru/default.inc.php
+++ b/core/components/minishop3/lexicon/ru/default.inc.php
@@ -168,6 +168,7 @@
 $_lang['ms3_err_unknown'] = 'Неизвестная ошибка';
 $_lang['ms3_err_ns'] = 'Это поле обязательно';
 $_lang['ms3_err_product_key_required'] = 'Не указан ключ товара';
+$_lang['ms3_err_cart_options'] = 'options должен быть объектом или JSON-строкой';
 $_lang['ms3_err_field_key_required'] = 'Не указан ключ поля';
 $_lang['ms3_err_fields_required'] = 'Требуется массив полей';
 $_lang['ms3_err_field_nf'] = 'Поле не найдено';
diff --git a/core/components/minishop3/src/Controllers/Api/Web/CartController.php b/core/components/minishop3/src/Controllers/Api/Web/CartController.php
index ebffe0f41..0c150012f 100644
--- a/core/components/minishop3/src/Controllers/Api/Web/CartController.php
+++ b/core/components/minishop3/src/Controllers/Api/Web/CartController.php
@@ -7,6 +7,7 @@
 use MiniShop3\Router\HttpStatus;
 use MiniShop3\Router\Response;
 use MiniShop3\Services\Api\WebApiContextResolver;
+use MiniShop3\Services\Cart\CartItemManager;
 use MODX\Revolution\modX;
 
 /**
@@ -24,7 +25,7 @@ class CartController
     public function __construct(modX $modx)
     {
         $this->modx = $modx;
-        $this->modx->lexicon->load('minishop3:customer', 'minishop3:default');
+        $this->modx->lexicon->load('minishop3:customer', 'minishop3:default', 'minishop3:cart');
     }
 
     /**
@@ -117,14 +118,23 @@ public function changeOption(array $params = []): Response
             );
         }
 
-        if (!is_array($options) || $options === []) {
+        if (!is_array($options) && !is_string($options)) {
             return Response::error(
-                $this->modx->lexicon('ms3_cart_change_options_error'),
+                $this->modx->lexicon('ms3_err_cart_options'),
                 HttpStatus::BAD_REQUEST
             );
         }
 
         $ms3 = $this->modx->services->get('ms3');
+        $options = CartItemManager::normalizeOptions($options);
+
+        if ($options === []) {
+            return Response::error(
+                $this->modx->lexicon('ms3_cart_change_options_error'),
+                HttpStatus::BAD_REQUEST
+            );
+        }
+
         $cart = $ms3->cart;
         $cart->initialize($this->pageContextKey(), $token);
 
diff --git a/core/components/minishop3/src/Services/Cart/CartItemManager.php b/core/components/minishop3/src/Services/Cart/CartItemManager.php
index 64db2bfd5..e94ff0b01 100644
--- a/core/components/minishop3/src/Services/Cart/CartItemManager.php
+++ b/core/components/minishop3/src/Services/Cart/CartItemManager.php
@@ -328,14 +328,15 @@ public function generateProductKey(array $product, array $options = []): string
      * @param mixed $options Options (array or JSON string)
      * @return array Normalized options
      */
-    public function normalizeOptions(mixed $options): array
+    public static function normalizeOptions(mixed $options): array
     {
-        if (is_string($options)) {
-            $decoded = json_decode($options, true);
-            return is_array($decoded) ? $decoded : [];
+        if (!is_string($options)) {
+            return is_array($options) ? $options : [];
         }
 
-        return is_array($options) ? $options : [];
+        $decoded = json_decode($options, true);
+
+        return is_array($decoded) ? $decoded : [];
     }
 
     /**
diff --git a/core/components/minishop3/tests/Integration/WebApi/HeadlessStorefrontErrorsTest.php b/core/components/minishop3/tests/Integration/WebApi/HeadlessStorefrontErrorsTest.php
index 546a3410f..763de2ecc 100644
--- a/core/components/minishop3/tests/Integration/WebApi/HeadlessStorefrontErrorsTest.php
+++ b/core/components/minishop3/tests/Integration/WebApi/HeadlessStorefrontErrorsTest.php
@@ -66,6 +66,52 @@ public function testChangeOptionEmptyOptionsReturns400(): void
         $this->assertApiError($res, HttpStatus::BAD_REQUEST, 'ms3_cart_change_options_error');
     }
 
+    public function testChangeOptionJsonStringOptionsReturns200(): void
+    {
+        $add = $this->dispatch('POST', '/api/v1/cart/add', [], [
+            'id' => JourneyProductCatalog::FIXTURE_PRODUCT_ID,
+            'count' => 1,
+            'options' => ['size' => 'M'],
+        ]);
+        $token = $this->lastMs3Token();
+        $key = (string) ($add['data']['last_key'] ?? '');
+
+        $res = $this->dispatch(
+            'POST',
+            '/api/v1/cart/change-option',
+            [],
+            ['product_key' => $key, 'options' => '{"size":"L"}'],
+            [],
+            $token
+        );
+
+        self::assertSame(HttpStatus::OK, $res['status']);
+        self::assertTrue($res['success']);
+        $newKey = (string) ($res['data']['last_key'] ?? $key);
+        self::assertSame('L', $res['data']['cart'][$newKey]['options']['size'] ?? null);
+    }
+
+    public function testChangeOptionInvalidOptionsTypeReturns400(): void
+    {
+        $add = $this->dispatch('POST', '/api/v1/cart/add', [], [
+            'id' => JourneyProductCatalog::FIXTURE_PRODUCT_ID,
+            'count' => 1,
+            'options' => ['size' => 'M'],
+        ]);
+        $token = $this->lastMs3Token();
+        $key = (string) ($add['data']['last_key'] ?? '');
+
+        $res = $this->dispatch(
+            'POST',
+            '/api/v1/cart/change-option',
+            [],
+            ['product_key' => $key, 'options' => 42],
+            [],
+            $token
+        );
+        $this->assertApiError($res, HttpStatus::BAD_REQUEST, 'ms3_err_cart_options');
+    }
+
     public function testSubmitEmptyCartReturnsBusinessError(): void
     {
         $token = $this->modx->journeyTokens->generateCustomerToken()['token'];
diff --git a/core/components/minishop3/tests/Unit/Services/Cart/CartItemManagerPureTest.php b/core/components/minishop3/tests/Unit/Services/Cart/CartItemManagerPureTest.php
index f3e7ad709..6e9f6459b 100644
--- a/core/components/minishop3/tests/Unit/Services/Cart/CartItemManagerPureTest.php
+++ b/core/components/minishop3/tests/Unit/Services/Cart/CartItemManagerPureTest.php
@@ -58,10 +58,10 @@ public static function countCases(): iterable
 
     public function testNormalizeOptions(): void
     {
-        self::assertSame(['color' => 'red'], $this->manager->normalizeOptions('{"color":"red"}'));
-        self::assertSame(['a' => 1], $this->manager->normalizeOptions(['a' => 1]));
-        self::assertSame([], $this->manager->normalizeOptions('{bad'));
-        self::assertSame([], $this->manager->normalizeOptions(null));
+        self::assertSame(['color' => 'red'], CartItemManager::normalizeOptions('{"color":"red"}'));
+        self::assertSame(['a' => 1], CartItemManager::normalizeOptions(['a' => 1]));
+        self::assertSame([], CartItemManager::normalizeOptions('{bad'));
+        self::assertSame([], CartItemManager::normalizeOptions(null));
     }
 
     public function testGenerateProductKeyDiffersByOptions(): void