fix: show a translated 404 to a signed-in user who mistypes a URL instead of the login page

app/(main)/[locale]/[...rest]/page.tsx

@@ -0,0 +1,8 @@
+import { notFound } from 'next/navigation';
+
+// Unknown paths below a locale (/de/typo) end here, so the 404 renders
+// inside the locale layout and is translated ([locale]/not-found.tsx).
+// Removed from the static Lite export, like (main)/[...rest].
+export default function LocaleCatchAll() {
+  notFound();
+}

app/(main)/[locale]/not-found.tsx

@@ -0,0 +1,10 @@
+"use client";
+
+import { useTranslations } from "next-intl";
+import { NotFoundView } from "@/components/error/not-found-view";
+
+export default function LocaleNotFound() {
+  const t = useTranslations("not_found");
+  const tErrors = useTranslations("errors");
+  return <NotFoundView title={t("title")} description={t("description")} homeLabel={tErrors("go_home")} />;
+}

app/(main)/not-found.tsx

@@ -1,14 +1,14 @@
 "use client";
 
 import { useEffect } from "react";
-import { useAuthStore } from "@/stores/auth-store";
 import { getPathPrefix } from "@/lib/browser-navigation";
+import { NotFoundView } from "@/components/error/not-found-view";
 import { IS_LITE } from "@/lib/lite";
 import { liteSurfaceRootFor, stashPendingLitePath } from "@/lib/lite-link-segments";
 
+// Outside the locale tree there are no translations: paths below a locale
+// get the translated page in [locale]/not-found.tsx.
 export default function NotFound() {
-  const isAuthenticated = useAuthStore((s) => s.isAuthenticated);
-
   useEffect(() => {
     // Static Lite build on a host without rewrite rules (GitHub Pages): a deep
     // link such as /en/mail/thread/abc lands here as 404.html. Park the link
@@ -21,42 +21,13 @@ export default function NotFound() {
         return;
       }
     }
-    if (!isAuthenticated) {
-      const prefix = getPathPrefix();
-      // Don't redirect admin routes to the webmail login page. Admin paths
-      // are mounted relative to the deployment prefix, so account for it.
-      const adminBase = `${prefix}/admin`;
-      const isAdminRoute = window.location.pathname === adminBase || window.location.pathname.startsWith(`${adminBase}/`);
-      if (!isAdminRoute) {
-        window.location.href = `${prefix}/login`;
-      }
-    }
-  }, [isAuthenticated]);
-
-  if (!isAuthenticated) {
-    let isAdmin = false;
-    if (typeof window !== 'undefined') {
-      const prefix = getPathPrefix();
-      const adminBase = `${prefix}/admin`;
-      isAdmin = window.location.pathname === adminBase || window.location.pathname.startsWith(`${adminBase}/`);
-    }
-    if (!isAdmin) return null;
-  }
-
-  const prefix = typeof window !== 'undefined' ? getPathPrefix() : '';
+  }, []);
 
   return (
-    <div className="min-h-screen flex items-center justify-center bg-background">
-      <div className="text-center max-w-md px-4">
-        <h1 className="text-4xl font-bold text-foreground mb-2">404</h1>
-        <p className="text-muted-foreground mb-6">This page could not be found.</p>
-        <a
-          href={`${prefix}/`}
-          className="inline-flex items-center px-4 py-2 bg-primary text-primary-foreground rounded-lg hover:opacity-90 transition-opacity"
-        >
-          Go home
-        </a>
-      </div>
-    </div>
+    <NotFoundView
+      title="Page not found"
+      description="This page doesn't exist or has moved. Check the address, or go back to your inbox."
+      homeLabel="Go to inbox"
+    />
   );
 }

components/error/__tests__/not-found-view.test.tsx

@@ -0,0 +1,54 @@
+import { act, render, screen } from '@testing-library/react';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+
+// A mistyped URL with a still valid session: the 404 waits for the session
+// to be restored instead of sending the user to the login page.
+
+const { default: LocaleNotFound } = await import('@/app/(main)/[locale]/not-found');
+const { useAuthStore } = await import('@/stores/auth-store');
+
+const realLocation = window.location;
+let href = '';
+
+beforeEach(() => {
+  href = 'http://localhost/de/gibtsnicht';
+  Object.defineProperty(window, 'location', {
+    configurable: true,
+    value: {
+      ...realLocation,
+      pathname: '/de/gibtsnicht',
+      get href() { return href; },
+      set href(v: string) { href = v; },
+    },
+  });
+});
+afterEach(() => {
+  Object.defineProperty(window, 'location', { configurable: true, value: realLocation });
+});
+
+describe('404 page', () => {
+  it('restores the session before deciding, and shows the translated page to a signed-in user', async () => {
+    let finish: () => void = () => {};
+    const checkAuth = vi.fn(() => new Promise<void>((resolve) => {
+      finish = () => { useAuthStore.setState({ isAuthenticated: true } as never); resolve(); };
+    }));
+    useAuthStore.setState({ isAuthenticated: false, checkAuth } as never);
+
+    render(<LocaleNotFound />);
+    expect(checkAuth).toHaveBeenCalled();
+    expect(href).not.toContain('/login');
+
+    await act(async () => { finish(); });
+    expect(href).not.toContain('/login');
+    expect(screen.getByRole('heading', { name: 'title' })).toBeInTheDocument();
+    expect(screen.getByRole('link', { name: 'go_home' })).toBeInTheDocument();
+  });
+
+  it('sends a visitor without a session to the login page once that is known', async () => {
+    const checkAuth = vi.fn(() => Promise.resolve());
+    useAuthStore.setState({ isAuthenticated: false, checkAuth } as never);
+    render(<LocaleNotFound />);
+    await act(async () => {});
+    expect(href).toBe('/login');
+  });
+});

components/error/not-found-view.tsx

@@ -0,0 +1,71 @@
+"use client";
+
+import { useEffect, useState } from "react";
+import { SearchX } from "@/components/icons";
+import { useAuthStore } from "@/stores/auth-store";
+import { getPathPrefix } from "@/lib/browser-navigation";
+
+/** Whether the current URL is an admin page, which has its own sign-in. */
+function isAdminPath(): boolean {
+  if (typeof window === "undefined") return false;
+  const adminBase = `${getPathPrefix()}/admin`;
+  const path = window.location.pathname;
+  return path === adminBase || path.startsWith(`${adminBase}/`);
+}
+
+/**
+ * Who is looking at a missing page: "checking" until the stored session has
+ * been restored, then signed in or not. Deciding before that sent a signed-in
+ * user with a mistyped URL to the login page.
+ */
+export function useNotFoundAuth(): "checking" | "signed-in" | "signed-out" {
+  const isAuthenticated = useAuthStore((s) => s.isAuthenticated);
+  const [checked, setChecked] = useState(() => useAuthStore.getState().isAuthenticated);
+
+  useEffect(() => {
+    if (useAuthStore.getState().isAuthenticated) {
+      setChecked(true);
+      return;
+    }
+    let cancelled = false;
+    void useAuthStore.getState().checkAuth().finally(() => { if (!cancelled) setChecked(true); });
+    return () => { cancelled = true; };
+  }, []);
+
+  useEffect(() => {
+    if (!checked || isAuthenticated || isAdminPath()) return;
+    window.location.href = `${getPathPrefix()}/login`;
+  }, [checked, isAuthenticated]);
+
+  if (isAuthenticated) return "signed-in";
+  return checked ? "signed-out" : "checking";
+}
+
+export interface NotFoundViewProps {
+  title: string;
+  description: string;
+  homeLabel: string;
+}
+
+/** The 404 page: what happened and the way back. Signed out, it shows only on admin paths. */
+export function NotFoundView({ title, description, homeLabel }: NotFoundViewProps) {
+  const auth = useNotFoundAuth();
+  if (auth !== "signed-in" && !isAdminPath()) return null;
+
+  const prefix = typeof window !== "undefined" ? getPathPrefix() : "";
+  return (
+    <div className="min-h-screen flex items-center justify-center bg-background">
+      <div className="text-center max-w-md px-4">
+        <SearchX className="w-12 h-12 mx-auto mb-4 text-muted-foreground" aria-hidden="true" />
+        <h1 className="text-xl font-semibold text-foreground mb-2">{title}</h1>
+        <p className="text-muted-foreground mb-6">{description}</p>
+        <a
+          href={`${prefix}/`}
+          className="inline-flex items-center justify-center h-9 px-3 text-sm font-medium rounded-md bg-primary text-primary-foreground hover:bg-primary/90 transition-colors"
+        >
+          {homeLabel}
+        </a>
+      </div>
+    </div>
+  );
+}

locales/ar/common.json

@@ -2625,6 +2625,10 @@
     "retry": "إعادة المحاولة",
     "go_home": "الانتقال إلى البريد الوارد"
   },
+  "not_found": {
+    "title": "الصفحة غير موجودة",
+    "description": "هذه الصفحة غير موجودة أو نُقلت. تحقّق من العنوان أو عُد إلى صندوق الوارد."
+  },
   "context_menu": {
     "reply": "رد",
     "reply_all": "الرد على الجميع",

locales/ca/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Reintenta",
     "go_home": "Vés a la safata d'entrada"
   },
+  "not_found": {
+    "title": "No s'ha trobat la pàgina",
+    "description": "Aquesta pàgina no existeix o s'ha mogut. Comproveu l'adreça o torneu a la safata d'entrada."
+  },
   "context_menu": {
     "reply": "Respon",
     "reply_all": "Respon a tots",

locales/cs/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Opakovat",
     "go_home": "Přejít do doručené pošty"
   },
+  "not_found": {
+    "title": "Stránka nenalezena",
+    "description": "Tato stránka neexistuje nebo byla přesunuta. Zkontrolujte adresu nebo se vraťte do doručené pošty."
+  },
   "context_menu": {
     "reply": "Odpovědět",
     "reply_all": "Odpovědět všem",

locales/da/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Prøv igen",
     "go_home": "Gå til indbakke"
   },
+  "not_found": {
+    "title": "Siden blev ikke fundet",
+    "description": "Siden findes ikke eller er flyttet. Tjek adressen, eller gå tilbage til din indbakke."
+  },
   "context_menu": {
     "reply": "Svar",
     "reply_all": "Svar alle",

locales/de/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Wiederholen",
     "go_home": "Zum Posteingang"
   },
+  "not_found": {
+    "title": "Seite nicht gefunden",
+    "description": "Diese Seite gibt es nicht oder sie wurde verschoben. Prüfen Sie die Adresse oder kehren Sie zu Ihrem Posteingang zurück."
+  },
   "context_menu": {
     "reply": "Antworten",
     "reply_all": "Allen antworten",

locales/en/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Retry",
     "go_home": "Go to inbox"
   },
+  "not_found": {
+    "title": "Page not found",
+    "description": "This page doesn't exist or has moved. Check the address, or go back to your inbox."
+  },
   "context_menu": {
     "reply": "Reply",
     "reply_all": "Reply All",

locales/es/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Reintentar",
     "go_home": "Ir a bandeja de entrada"
   },
+  "not_found": {
+    "title": "No se ha encontrado la página",
+    "description": "Esta página no existe o se ha movido. Comprueba la dirección o vuelve a tu bandeja de entrada."
+  },
   "context_menu": {
     "reply": "Responder",
     "reply_all": "Responder a Todos",

locales/et/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Proovi uuesti",
     "go_home": "Mine postkasti"
   },
+  "not_found": {
+    "title": "Lehte ei leitud",
+    "description": "Seda lehte pole olemas või see on teisaldatud. Kontrollige aadressi või minge tagasi postkasti."
+  },
   "context_menu": {
     "reply": "Vasta",
     "reply_all": "Vasta kõigile",

locales/fa/common.json

@@ -2625,6 +2625,10 @@
     "retry": "تلاش مجدد",
     "go_home": "رفتن به صندوق ورودی"
   },
+  "not_found": {
+    "title": "صفحه پیدا نشد",
+    "description": "این صفحه وجود ندارد یا جابه‌جا شده است. نشانی را بررسی کنید یا به صندوق ورودی برگردید."
+  },
   "context_menu": {
     "reply": "پاسخ",
     "reply_all": "پاسخ به همه",

locales/fr/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Réessayer",
     "go_home": "Aller à la boîte de réception"
   },
+  "not_found": {
+    "title": "Page introuvable",
+    "description": "Cette page n'existe pas ou a été déplacée. Vérifiez l'adresse ou revenez à votre boîte de réception."
+  },
   "context_menu": {
     "reply": "Répondre",
     "reply_all": "Répondre à tous",

locales/he/common.json

@@ -2591,6 +2591,10 @@
     "retry": "נסה שוב",
     "go_home": "עבור לתיבת הדואר הנכנס"
   },
+  "not_found": {
+    "title": "הדף לא נמצא",
+    "description": "הדף הזה לא קיים או שהועבר. בדקו את הכתובת או חזרו לתיבת הדואר הנכנס."
+  },
   "context_menu": {
     "reply": "השב",
     "reply_all": "השב לכולם",

locales/hu/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Újra",
     "go_home": "Ugrás a beérkezőhöz"
   },
+  "not_found": {
+    "title": "Az oldal nem található",
+    "description": "Ez az oldal nem létezik, vagy áthelyezték. Ellenőrizze a címet, vagy térjen vissza a beérkezett üzenetekhez."
+  },
   "context_menu": {
     "reply": "Válasz",
     "reply_all": "Válasz mindenkinek",

locales/it/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Riprova",
     "go_home": "Vai alla posta in arrivo"
   },
+  "not_found": {
+    "title": "Pagina non trovata",
+    "description": "Questa pagina non esiste o è stata spostata. Controlla l'indirizzo o torna alla posta in arrivo."
+  },
   "context_menu": {
     "reply": "Rispondi",
     "reply_all": "Rispondi a tutti",

locales/ja/common.json

@@ -2625,6 +2625,10 @@
     "retry": "リトライ",
     "go_home": "受信トレイに移動"
   },
+  "not_found": {
+    "title": "ページが見つかりません",
+    "description": "このページは存在しないか、移動されました。アドレスを確認するか、受信トレイに戻ってください。"
+  },
   "context_menu": {
     "reply": "返信",
     "reply_all": "全員に返信",

locales/ko/common.json

@@ -2625,6 +2625,10 @@
     "retry": "재시도",
     "go_home": "받은편지함으로 이동"
   },
+  "not_found": {
+    "title": "페이지를 찾을 수 없습니다",
+    "description": "이 페이지가 없거나 이동되었습니다. 주소를 확인하거나 받은편지함으로 돌아가세요."
+  },
   "context_menu": {
     "reply": "답장",
     "reply_all": "전체 답장",

locales/lv/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Mēģināt vēlreiz",
     "go_home": "Uz iesūtni"
   },
+  "not_found": {
+    "title": "Lapa nav atrasta",
+    "description": "Šī lapa nepastāv vai ir pārvietota. Pārbaudiet adresi vai atgriezieties iesūtnē."
+  },
   "context_menu": {
     "reply": "Atbildēt",
     "reply_all": "Atbildēt visiem",

locales/mn/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Дахин оролдох",
     "go_home": "Ирсэн имэйл рүү очих"
   },
+  "not_found": {
+    "title": "Хуудас олдсонгүй",
+    "description": "Энэ хуудас байхгүй эсвэл зөөгдсөн байна. Хаягаа шалгах эсвэл ирсэн захидал руу буцна уу."
+  },
   "context_menu": {
     "reply": "Хариулах",
     "reply_all": "Бүгдэд нь хариулах",

locales/nb/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Prøv på nytt",
     "go_home": "Gå til innboksen"
   },
+  "not_found": {
+    "title": "Fant ikke siden",
+    "description": "Denne siden finnes ikke eller er flyttet. Sjekk adressen, eller gå tilbake til innboksen."
+  },
   "context_menu": {
     "reply": "Svar",
     "reply_all": "Svar alle",

locales/nl/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Opnieuw proberen",
     "go_home": "Ga naar postvak IN"
   },
+  "not_found": {
+    "title": "Pagina niet gevonden",
+    "description": "Deze pagina bestaat niet of is verplaatst. Controleer het adres of ga terug naar je inbox."
+  },
   "context_menu": {
     "reply": "Beantwoorden",
     "reply_all": "Allen beantwoorden",

locales/pl/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Ponów",
     "go_home": "Przejdź do skrzynki odbiorczej"
   },
+  "not_found": {
+    "title": "Nie znaleziono strony",
+    "description": "Ta strona nie istnieje lub została przeniesiona. Sprawdź adres albo wróć do skrzynki odbiorczej."
+  },
   "context_menu": {
     "reply": "Odpowiedz",
     "reply_all": "Odpowiedz wszystkim",

locales/pt/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Tentar novamente",
     "go_home": "Ir para caixa de entrada"
   },
+  "not_found": {
+    "title": "Página não encontrada",
+    "description": "Esta página não existe ou foi movida. Verifique o endereço ou volte à caixa de entrada."
+  },
   "context_menu": {
     "reply": "Responder",
     "reply_all": "Responder a Todos",

locales/ro/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Reîncearcă",
     "go_home": "Accesați căsuța de intrare"
   },
+  "not_found": {
+    "title": "Pagina nu a fost găsită",
+    "description": "Această pagină nu există sau a fost mutată. Verificați adresa sau reveniți la Inbox."
+  },
   "context_menu": {
     "reply": "Răspunde",
     "reply_all": "Răspunde tuturor",

locales/ru/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Повторить",
     "go_home": "В папку «Входящие»"
   },
+  "not_found": {
+    "title": "Страница не найдена",
+    "description": "Этой страницы нет или она перемещена. Проверьте адрес или вернитесь во «Входящие»."
+  },
   "context_menu": {
     "reply": "Ответить",
     "reply_all": "Ответить всем",

locales/sk/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Opakovať",
     "go_home": "Prejsť do doručenej pošty"
   },
+  "not_found": {
+    "title": "Stránka sa nenašla",
+    "description": "Táto stránka neexistuje alebo bola presunutá. Skontrolujte adresu alebo sa vráťte do doručenej pošty."
+  },
   "context_menu": {
     "reply": "Odpovedať",
     "reply_all": "Odpovedať všetkým",

locales/th/common.json

@@ -101,6 +101,10 @@
     "retry": "ลองใหม่",
     "go_home": "ไปยังกล่องข้อความ"
   },
+  "not_found": {
+    "title": "ไม่พบหน้านี้",
+    "description": "ไม่มีหน้านี้หรือหน้านี้ถูกย้ายแล้ว ตรวจสอบที่อยู่ หรือกลับไปที่กล่องจดหมายเข้า"
+  },
   "login": {
     "title": "เข้าสู่ระบบจดหมายอิเล็กทรอนิกส์",
     "username_label": "อีเมล",

locales/tr/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Yeniden dene",
     "go_home": "Gelen kutusuna git"
   },
+  "not_found": {
+    "title": "Sayfa bulunamadı",
+    "description": "Bu sayfa yok veya taşınmış. Adresi kontrol edin ya da gelen kutunuza dönün."
+  },
   "context_menu": {
     "reply": "Yanıtla",
     "reply_all": "Tümünü Yanıtla",

locales/uk/common.json

@@ -2625,6 +2625,10 @@
     "retry": "Повторіть спробу",
     "go_home": "Перейти до папки \"Вхідні\"."
   },
+  "not_found": {
+    "title": "Сторінку не знайдено",
+    "description": "Цієї сторінки немає або її переміщено. Перевірте адресу або поверніться до вхідних."
+  },
   "context_menu": {
     "reply": "Відповісти",
     "reply_all": "Відповісти всім",

locales/zh-TW/common.json

@@ -2625,6 +2625,10 @@
     "retry": "重試",
     "go_home": "前往收件匣"
   },
+  "not_found": {
+    "title": "找不到頁面",
+    "description": "此頁面不存在或已移動。請檢查網址，或返回收件匣。"
+  },
   "context_menu": {
     "reply": "回覆",
     "reply_all": "全部回覆",

locales/zh/common.json

@@ -2625,6 +2625,10 @@
     "retry": "重试",
     "go_home": "前往收件箱"
   },
+  "not_found": {
+    "title": "找不到页面",
+    "description": "此页面不存在或已移动。请检查地址，或返回收件箱。"
+  },
   "context_menu": {
     "reply": "回复",
     "reply_all": "全部回复",

scripts/lite/lib.mjs

@@ -39,6 +39,7 @@ export const LITE_REMOVED_PATHS = [
   "instrumentation.ts",
   "instrumentation.node.ts",
   "app/(main)/[...rest]",
+  "app/(main)/[locale]/[...rest]",
   "app/(main)/protocol",
   "e2e",
   "integration",