From 517abca7993361acae324b69f312fca7ad356408 Mon Sep 17 00:00:00 2001
From: Alexander Ackermann <abackermann91@gmail.com>
Date: Thu, 27 Aug 2026 14:10:01 +0200
Subject: [PATCH] fix(runtime): preserve selected language on plain layout
 pages

---
 .../web-runtime/src/container/bootstrap.ts    |  6 +-
 packages/web-runtime/src/helpers/language.ts  | 59 ++++++++++++---
 .../tests/unit/helpers/language.spec.ts       | 71 +++++++++++++++++++
 3 files changed, 126 insertions(+), 10 deletions(-)
 create mode 100644 packages/web-runtime/tests/unit/helpers/language.spec.ts

diff --git a/packages/web-runtime/src/container/bootstrap.ts b/packages/web-runtime/src/container/bootstrap.ts
index 6eccce16955..1315e19ecf1 100644
--- a/packages/web-runtime/src/container/bootstrap.ts
+++ b/packages/web-runtime/src/container/bootstrap.ts
@@ -89,7 +89,7 @@ import {
   onSSESpaceDeletedEvent,
   onSSESpaceEnabledEvent
 } from './sse'
-import { loadAppTranslations } from '../helpers/language'
+import { loadAppTranslations, resolveInitialLanguage } from '../helpers/language'
 import { urlJoin } from '@opencloud-eu/web-client'
 import { sha256 } from '@noble/hashes/sha2.js'
 import { bytesToHex } from '@noble/hashes/utils.js'
@@ -440,7 +440,9 @@ export const announceGettext = ({
   app: App
 } & Partial<GetTextOptions>) => {
   const gettext = createGettext({
-    defaultLanguage: navigator.language.substring(0, 2),
+    defaultLanguage: resolveInitialLanguage({
+      browserLanguage: navigator.language
+    }),
     silent: true,
     ...options
   })
diff --git a/packages/web-runtime/src/helpers/language.ts b/packages/web-runtime/src/helpers/language.ts
index d39b7ca887f..d87c8dfc061 100644
--- a/packages/web-runtime/src/helpers/language.ts
+++ b/packages/web-runtime/src/helpers/language.ts
@@ -2,21 +2,64 @@ import { ApplicationInformation } from '@opencloud-eu/web-pkg'
 import { merge } from 'lodash-es'
 import { Language, Translations } from 'vue3-gettext'
 
+export const currentLanguageLocalStorageKey = 'oc_language'
+
+function normalizeLanguage(languageSetting: string): string {
+  const trimmed = languageSetting.trim()
+  if (!trimmed) {
+    return ''
+  }
+  return trimmed.includes('-') ? trimmed.split('-')[0] : trimmed
+}
+
+function getStoredLanguage(): string {
+  const storedLanguage = window.localStorage.getItem(currentLanguageLocalStorageKey) ?? ''
+  if (!storedLanguage) {
+    return ''
+  }
+  return normalizeLanguage(storedLanguage)
+}
+
+function storeLanguage(language: string): void {
+  window.localStorage.setItem(currentLanguageLocalStorageKey, language)
+}
+
+function setDocumentLanguage(languageSetting: string): void {
+  const currentLanguage = normalizeLanguage(languageSetting)
+  if (!currentLanguage) {
+    return
+  }
+
+  document.documentElement.lang = currentLanguage
+}
+
+export const resolveInitialLanguage = ({
+  browserLanguage
+}: {
+  browserLanguage: string
+}): string => {
+  const stored = getStoredLanguage()
+  const currentLanguage = stored || normalizeLanguage(browserLanguage) || 'en'
+
+  setDocumentLanguage(currentLanguage)
+  return currentLanguage
+}
+
 export const setCurrentLanguage = ({
   language,
   languageSetting = null
 }: {
   language: Language
-  languageSetting?: string
+  languageSetting?: string | null
 }): void => {
-  let currentLanguage = languageSetting
-  if (currentLanguage) {
-    if (currentLanguage.indexOf('-')) {
-      currentLanguage = currentLanguage.split('-')[0]
-    }
-    language.current = currentLanguage
-    document.documentElement.lang = currentLanguage
+  const currentLanguage = normalizeLanguage(languageSetting || language.current)
+  if (!currentLanguage) {
+    return
   }
+
+  language.current = currentLanguage
+  setDocumentLanguage(currentLanguage)
+  storeLanguage(currentLanguage)
 }
 
 /**
diff --git a/packages/web-runtime/tests/unit/helpers/language.spec.ts b/packages/web-runtime/tests/unit/helpers/language.spec.ts
new file mode 100644
index 00000000000..e60ce503db8
--- /dev/null
+++ b/packages/web-runtime/tests/unit/helpers/language.spec.ts
@@ -0,0 +1,71 @@
+import { mock } from 'vitest-mock-extended'
+import { nextTick } from 'vue'
+import type { Language } from 'vue3-gettext'
+import {
+  currentLanguageLocalStorageKey,
+  resolveInitialLanguage,
+  setCurrentLanguage
+} from '../../../src/helpers/language'
+
+describe('language helpers', () => {
+  beforeEach(() => {
+    window.localStorage.clear()
+    document.documentElement.lang = ''
+  })
+
+  it('prefers stored language over browser language', () => {
+    window.localStorage.setItem(currentLanguageLocalStorageKey, 'en')
+
+    const lang = resolveInitialLanguage({
+      browserLanguage: 'de-DE'
+    })
+
+    expect(lang).toBe('en')
+    expect(document.documentElement.lang).toBe('en')
+  })
+
+  it('falls back to browser language when no stored language exists', () => {
+    const lang = resolveInitialLanguage({
+      browserLanguage: 'de-DE'
+    })
+
+    expect(lang).toBe('de')
+    expect(document.documentElement.lang).toBe('de')
+  })
+
+  it('falls back to english when browser language is missing', () => {
+    const lang = resolveInitialLanguage({
+      browserLanguage: ''
+    })
+
+    expect(lang).toBe('en')
+    expect(document.documentElement.lang).toBe('en')
+  })
+
+  it('sets, normalizes and stores the selected language', async () => {
+    const language = mock<Language>({ current: 'de' })
+
+    setCurrentLanguage({
+      language,
+      languageSetting: 'en-US'
+    })
+    await nextTick()
+
+    expect(language.current).toBe('en')
+    expect(document.documentElement.lang).toBe('en')
+    expect(window.localStorage.getItem(currentLanguageLocalStorageKey)).toBe('en')
+  })
+
+  it('sets and stores current language when language setting is not provided', async () => {
+    const language = mock<Language>({ current: 'fr-FR' })
+
+    setCurrentLanguage({
+      language
+    })
+    await nextTick()
+
+    expect(language.current).toBe('fr')
+    expect(document.documentElement.lang).toBe('fr')
+    expect(window.localStorage.getItem(currentLanguageLocalStorageKey)).toBe('fr')
+  })
+})