diff --git a/lib/core/src/lib/language-menu/service/language.service.spec.ts b/lib/core/src/lib/language-menu/service/language.service.spec.ts
new file mode 100644
index 0000000000..2e54d61b3f
--- /dev/null
+++ b/lib/core/src/lib/language-menu/service/language.service.spec.ts
@@ -0,0 +1,89 @@
+/*!
+ * @license
+ * Copyright © 2005-2025 Hyland Software, Inc. and its affiliates. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { TestBed } from '@angular/core/testing';
+import { LanguageService } from './language.service';
+import { AppConfigService } from '../../app-config/app-config.service';
+import { UserPreferencesService } from '../../common/services/user-preferences.service';
+import { DEFAULT_LANGUAGE_LIST } from '../../common/models/default-languages.model';
+import { LanguageItem } from '../../common/services/language-item.interface';
+
+describe('LanguageService', () => {
+    let service: LanguageService;
+    let appConfigService: jasmine.SpyObj<AppConfigService>;
+    let userPreferencesService: jasmine.SpyObj<UserPreferencesService>;
+
+    const customLanguages: LanguageItem[] = [
+        { key: 'en', label: 'English' },
+        { key: 'fr', label: 'French' },
+        { key: 'ar', label: 'Arabic', direction: 'rtl' }
+    ];
+
+    beforeEach(() => {
+        const appConfigSpy = jasmine.createSpyObj('AppConfigService', ['get']);
+        const userPrefsSpy = jasmine.createSpyObj('UserPreferencesService', ['set'], {
+            locale: 'en'
+        });
+
+        TestBed.configureTestingModule({
+            providers: [
+                LanguageService,
+                { provide: AppConfigService, useValue: appConfigSpy },
+                { provide: UserPreferencesService, useValue: userPrefsSpy }
+            ]
+        });
+
+        service = TestBed.inject(LanguageService);
+        appConfigService = TestBed.inject(AppConfigService) as jasmine.SpyObj<AppConfigService>;
+        userPreferencesService = TestBed.inject(UserPreferencesService) as jasmine.SpyObj<UserPreferencesService>;
+    });
+
+    it('should initialize with default languages when no custom languages are provided', (done) => {
+        appConfigService.get.and.returnValue(null);
+        service = new LanguageService(appConfigService, userPreferencesService);
+
+        service.languages$.subscribe((languages) => {
+            expect(languages).toEqual(DEFAULT_LANGUAGE_LIST);
+            done();
+        });
+    });
+
+    it('should initialize with custom languages when provided', (done) => {
+        appConfigService.get.and.returnValue(customLanguages);
+        service = new LanguageService(appConfigService, userPreferencesService);
+
+        service.languages$.subscribe((languages) => {
+            expect(languages).toEqual(customLanguages);
+            done();
+        });
+    });
+
+    it('should update HTML lang attribute when language is changed', () => {
+        const originalSetAttribute = document.documentElement.setAttribute;
+
+        const setAttributeSpy = jasmine.createSpy('setAttribute');
+        document.documentElement.setAttribute = setAttributeSpy;
+
+        try {
+            service.changeLanguage(customLanguages[1]);
+
+            expect(setAttributeSpy).toHaveBeenCalledWith('lang', 'fr');
+        } finally {
+            document.documentElement.setAttribute = originalSetAttribute;
+        }
+    });
+});
diff --git a/lib/core/src/lib/language-menu/service/language.service.ts b/lib/core/src/lib/language-menu/service/language.service.ts
index 2ce3e2bf28..a9c3fe8573 100644
--- a/lib/core/src/lib/language-menu/service/language.service.ts
+++ b/lib/core/src/lib/language-menu/service/language.service.ts
@@ -37,6 +37,7 @@ export class LanguageService implements LanguageServiceInterface {
     changeLanguage(language: LanguageItem) {
         this.userPreferencesService.locale = language.key;
         this.userPreferencesService.set('textOrientation', language.direction || 'ltr');
+        document.documentElement.setAttribute('lang', language.key);
     }
 
     setLanguages(items: LanguageItem[]) {