Fixed- configurable product not back in stock after updating qty for the variant product by API/import

InventoryConfigurableProduct/Plugin/CatalogInventory/Api/StockRegistry/UpdateLegacyStockStatusForConfigurableProduct.php

@@ -0,0 +1,86 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\InventoryConfigurableProduct\Plugin\CatalogInventory\Api\StockRegistry;
+
+use Magento\CatalogInventory\Api\Data\StockItemInterface;
+use Magento\CatalogInventory\Api\StockRegistryInterface;
+use Magento\Catalog\Model\ProductFactory;
+use Magento\ConfigurableProduct\Model\Inventory\ChangeParentStockStatus;
+
+/***
+ * Update stock status of configurable products when update children products stock status
+ */
+class UpdateLegacyStockStatusForConfigurableProduct
+{
+    /**
+     * @var ChangeParentStockStatus
+     */
+    private $changeParentStockStatus;
+
+    /**
+     * @var ProductFactory
+     */
+    private $productFactory;
+
+    /**
+     * @param ChangeParentStockStatus $changeParentStockStatus
+     * @param ProductFactory $productFactory
+     */
+    public function __construct(
+        ChangeParentStockStatus $changeParentStockStatus,
+        ProductFactory $productFactory
+    ) {
+        $this->changeParentStockStatus = $changeParentStockStatus;
+        $this->productFactory = $productFactory;
+    }
+
+    /**
+     * Update product stock item by product SKU
+     *
+     * @param StockRegistryInterface $subject
+     * @param int $result
+     * @param string $productSku
+     * @param StockItemInterface $stockItem
+     * @return int
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+     */
+    public function afterUpdateStockItemBySku(
+        StockRegistryInterface $subject,
+        $result,
+        string $productSku,
+        StockItemInterface $stockItem
+    ) {
+        $productIds = $this->resolveProductId($productSku);
+        if ($productIds) {
+            $this->changeParentStockStatus->execute([$productIds]);
+        }
+        return $result;
+    }
+
+    /**
+     * Resolve and retrieve the product ID based on the SKU
+     *
+     * @param string $productSku
+     * @return int
+     * @throws \Magento\Framework\Exception\NoSuchEntityException
+     */
+    private function resolveProductId($productSku)
+    {
+        $product = $this->productFactory->create();
+        $productId = $product->getIdBySku($productSku);
+        if (!$productId) {
+            throw new \Magento\Framework\Exception\NoSuchEntityException(
+                __(
+                    'The Product with the "%1" SKU doesn\'t exist.',
+                    $productSku
+                )
+            );
+        }
+        return $productId;
+    }
+}

InventoryConfigurableProduct/etc/di.xml

@@ -36,6 +36,8 @@
     <type name="Magento\CatalogInventory\Api\StockRegistryInterface">
         <plugin name="inventory_catalog_add_qty_to_legacy_stock_configurable"
                 type="Magento\InventoryConfigurableProduct\Plugin\CatalogInventory\Api\StockRegistry\SetQtyToLegacyStock" sortOrder="100"/>
+        <plugin name="inventory_stockupdate_legacy_stock_configurable"
+                type="Magento\InventoryConfigurableProduct\Plugin\CatalogInventory\Api\StockRegistry\UpdateLegacyStockStatusForConfigurableProduct"/>
     </type>
     <type name="Magento\CatalogInventory\Model\ResourceModel\Stock\Item">
         <plugin name="after_update_stock_item_for_new_configurable_product"