diff --git a/application/Espo/Core/Utils/Client/DevModeExtensionInitJsFileListProvider.php b/application/Espo/Core/Utils/Client/DevModeExtensionInitJsFileListProvider.php
new file mode 100644
index 0000000000..a3a0ab625e
--- /dev/null
+++ b/application/Espo/Core/Utils/Client/DevModeExtensionInitJsFileListProvider.php
@@ -0,0 +1,91 @@
+<?php
+/************************************************************************
+ * This file is part of EspoCRM.
+ *
+ * EspoCRM – Open Source CRM application.
+ * Copyright (C) 2014-2025 Yurii Kuznietsov, Taras Machyshyn, Oleksii Avramenko
+ * Website: https://www.espocrm.com
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ *
+ * The interactive user interfaces in modified source and object code versions
+ * of this program must display Appropriate Legal Notices, as required under
+ * Section 5 of the GNU Affero General Public License version 3.
+ *
+ * In accordance with Section 7(b) of the GNU Affero General Public License version 3,
+ * these Appropriate Legal Notices must retain the display of the "EspoCRM" word.
+ ************************************************************************/
+
+namespace Espo\Core\Utils\Client;
+
+use Espo\Core\Utils\Config;
+use Espo\Core\Utils\File\Manager as FileManager;
+use Espo\Core\Utils\Module;
+use Espo\Core\Utils\Util;
+
+/**
+ * Allows bundled extensions to work when the system is in the developer mode.
+ */
+class DevModeExtensionInitJsFileListProvider
+{
+    public function __construct(
+        private Module $module,
+        private FileManager $fileManager,
+        private Config $config,
+    ) {}
+
+    /**
+     * @return string[]
+     */
+    public function get(): array
+    {
+        $developedModule = $this->config->get('developedModule');
+
+        if (!$developedModule) {
+            return [];
+        }
+
+        $output = [];
+
+        foreach ($this->getBundledModuleList() as $module) {
+            if ($module === $developedModule) {
+                continue;
+            }
+
+            $file = "client/custom/modules/$module/lib/init.js";
+
+            if ($this->fileManager->exists($file)) {
+                $output[] = $file;
+            }
+        }
+
+        return $output;
+    }
+
+    /**
+     * @return string[]
+     */
+    private function getBundledModuleList(): array
+    {
+        $modules = array_values(array_filter(
+            $this->module->getList(),
+            fn ($item) => $this->module->get([$item, 'bundled'])
+        ));
+
+        return array_map(
+            fn ($item) => Util::fromCamelCase($item, '-'),
+            $modules
+        );
+    }
+}
diff --git a/application/Espo/Core/Utils/ClientManager.php b/application/Espo/Core/Utils/ClientManager.php
index 7e92b2cd24..ae7bedca64 100644
--- a/application/Espo/Core/Utils/ClientManager.php
+++ b/application/Espo/Core/Utils/ClientManager.php
@@ -31,6 +31,7 @@ namespace Espo\Core\Utils;
 
 use Espo\Core\Api\Response;
 use Espo\Core\Api\ResponseWrapper;
+use Espo\Core\Utils\Client\DevModeExtensionInitJsFileListProvider;
 use Espo\Core\Utils\Client\DevModeJsFileListProvider;
 use Espo\Core\Utils\Client\LoaderParamsProvider;
 use Espo\Core\Utils\Client\RenderParams;
@@ -67,6 +68,7 @@ class ClientManager
         private Metadata $metadata,
         private FileManager $fileManager,
         private DevModeJsFileListProvider $devModeJsFileListProvider,
+        private DevModeExtensionInitJsFileListProvider $devModeExtensionInitJsFileListProvider,
         private Module $module,
         private LoaderParamsProvider $loaderParamsProvider,
         private SystemConfig $systemConfig,
@@ -304,6 +306,7 @@ class ClientManager
             return array_merge(
                 $this->metadata->get(['app', 'client', 'developerModeScriptList']) ?? [],
                 $this->getDeveloperModeBundleLibFileList(),
+                $this->devModeExtensionInitJsFileListProvider->get(),
             );
         }