Explain a dead share link and a broken invite in the reader's terms

A practice opening an expired or revoked share link met the app's own
404, 'this page does not exist', with a button to a dashboard it has no
account for. The share segment now has its own not-found page: link
expired or invalid, ask the person who shared it for a new one, and no
link anywhere. It still answers 404 for every failure class alike.

A malformed invite link fell through to the plain registration form.
It now says the invitation is invalid and offers sign-in; the shape
check is public, so this reveals nothing about which tokens exist, and
a well-formed token still goes on to registration.

messages/de.json

@@ -540,6 +540,11 @@
       "errorRateLimit": "Zu viele Versuche. Warte ein paar Minuten und versuche es erneut.",
       "errorFailed": "Das hat nicht geklappt. Versuche es gleich noch einmal.",
       "errorOffline": "Das hat den Server nicht erreicht. Prüfe deine Verbindung und versuche es erneut."
+    },
+    "inviteInvalid": {
+      "title": "Einladung ungültig",
+      "description": "Dieser Einladungslink ist unvollständig oder falsch kopiert. Bitte die Person, die dich eingeladen hat, um einen neuen Link.",
+      "toLogin": "Zur Anmeldung"
     }
   },
   "dashboard": {
@@ -8713,7 +8718,11 @@
     },
     "course": "Phase {n}",
     "courseRange": "{start} bis {end}",
-    "courseSince": "seit {start}"
+    "courseSince": "seit {start}",
+    "unavailable": {
+      "title": "Link abgelaufen oder ungültig",
+      "description": "Dieser Freigabelink ist abgelaufen, wurde zurückgezogen oder ist unvollständig. Bitte die Person, die ihn geteilt hat, um einen neuen Link."
+    }
   },
   "cycle": {
     "symptomCategory": {

messages/en.json

@@ -540,6 +540,11 @@
       "errorRateLimit": "Too many attempts. Wait a few minutes and try again.",
       "errorFailed": "That did not work. Try again in a moment.",
       "errorOffline": "That did not reach the server. Check your connection and try again."
+    },
+    "inviteInvalid": {
+      "title": "Invitation invalid",
+      "description": "This invitation link is incomplete or was copied wrongly. Ask the person who invited you for a new link.",
+      "toLogin": "Go to sign in"
     }
   },
   "dashboard": {
@@ -8713,7 +8718,11 @@
     },
     "course": "Course {n}",
     "courseRange": "{start} to {end}",
-    "courseSince": "since {start}"
+    "courseSince": "since {start}",
+    "unavailable": {
+      "title": "Link expired or invalid",
+      "description": "This share link has expired, was revoked, or is incomplete. Ask the person who shared it for a new link."
+    }
   },
   "cycle": {
     "symptomCategory": {

messages/es.json

@@ -540,6 +540,11 @@
       "errorRateLimit": "Demasiados intentos. Espera unos minutos y vuelve a intentarlo.",
       "errorFailed": "No ha funcionado. Vuelve a intentarlo en un momento.",
       "errorOffline": "No se llegó al servidor. Comprueba tu conexión y vuelve a intentarlo."
+    },
+    "inviteInvalid": {
+      "title": "Invitación no válida",
+      "description": "Este enlace de invitación está incompleto o se copió mal. Pide un enlace nuevo a la persona que te invitó.",
+      "toLogin": "Ir a iniciar sesión"
     }
   },
   "dashboard": {
@@ -8713,7 +8718,11 @@
     },
     "course": "Tratamiento {n}",
     "courseRange": "del {start} al {end}",
-    "courseSince": "desde el {start}"
+    "courseSince": "desde el {start}",
+    "unavailable": {
+      "title": "Enlace caducado o no válido",
+      "description": "Este enlace para compartir ha caducado, se ha revocado o está incompleto. Pide un enlace nuevo a la persona que lo compartió."
+    }
   },
   "cycle": {
     "symptomCategory": {

messages/fr.json

@@ -540,6 +540,11 @@
       "errorRateLimit": "Trop de tentatives. Attendez quelques minutes puis réessayez.",
       "errorFailed": "Cela n'a pas fonctionné. Réessayez dans un instant.",
       "errorOffline": "Le serveur n'a pas été atteint. Vérifiez votre connexion et réessayez."
+    },
+    "inviteInvalid": {
+      "title": "Invitation invalide",
+      "description": "Ce lien d’invitation est incomplet ou a été mal copié. Demandez un nouveau lien à la personne qui vous a invité.",
+      "toLogin": "Aller à la connexion"
     }
   },
   "dashboard": {
@@ -8713,7 +8718,11 @@
     },
     "course": "Traitement {n}",
     "courseRange": "du {start} au {end}",
-    "courseSince": "depuis le {start}"
+    "courseSince": "depuis le {start}",
+    "unavailable": {
+      "title": "Lien expiré ou invalide",
+      "description": "Ce lien de partage a expiré, a été révoqué ou est incomplet. Demandez un nouveau lien à la personne qui l’a partagé."
+    }
   },
   "cycle": {
     "symptomCategory": {

messages/it.json

@@ -540,6 +540,11 @@
       "errorRateLimit": "Troppi tentativi. Attendi qualche minuto e riprova.",
       "errorFailed": "Non ha funzionato. Riprova tra un momento.",
       "errorOffline": "Il server non è stato raggiunto. Controlla la connessione e riprova."
+    },
+    "inviteInvalid": {
+      "title": "Invito non valido",
+      "description": "Questo link di invito è incompleto o è stato copiato male. Chiedi un nuovo link alla persona che ti ha invitato.",
+      "toLogin": "Vai all’accesso"
     }
   },
   "dashboard": {
@@ -8713,7 +8718,11 @@
     },
     "course": "Ciclo {n}",
     "courseRange": "dal {start} al {end}",
-    "courseSince": "dal {start}"
+    "courseSince": "dal {start}",
+    "unavailable": {
+      "title": "Link scaduto o non valido",
+      "description": "Questo link di condivisione è scaduto, è stato revocato o è incompleto. Chiedi un nuovo link alla persona che lo ha condiviso."
+    }
   },
   "cycle": {
     "symptomCategory": {

messages/ko.json

@@ -540,6 +540,11 @@
       "errorRateLimit": "시도 횟수가 너무 많습니다. 몇 분 후 다시 시도하세요.",
       "errorFailed": "처리하지 못했습니다. 잠시 후 다시 시도하세요.",
       "errorOffline": "서버에 연결하지 못했습니다. 연결을 확인하고 다시 시도하세요."
+    },
+    "inviteInvalid": {
+      "title": "유효하지 않은 초대예요",
+      "description": "이 초대 링크가 불완전하거나 잘못 복사되었어요. 초대한 분께 새 링크를 요청해 주세요.",
+      "toLogin": "로그인으로 이동"
     }
   },
   "dashboard": {
@@ -8713,7 +8718,11 @@
     },
     "course": "복용 기간 {n}",
     "courseRange": "{start}부터 {end}까지",
-    "courseSince": "{start}부터"
+    "courseSince": "{start}부터",
+    "unavailable": {
+      "title": "링크가 만료되었거나 유효하지 않아요",
+      "description": "이 공유 링크는 만료되었거나 취소되었거나 불완전해요. 공유한 분께 새 링크를 요청해 주세요."
+    }
   },
   "cycle": {
     "symptomCategory": {

messages/pl.json

@@ -540,6 +540,11 @@
       "errorRateLimit": "Zbyt wiele prób. Odczekaj kilka minut i spróbuj ponownie.",
       "errorFailed": "Nie udało się. Spróbuj ponownie za chwilę.",
       "errorOffline": "Nie udało się połączyć z serwerem. Sprawdź połączenie i spróbuj ponownie."
+    },
+    "inviteInvalid": {
+      "title": "Nieprawidłowe zaproszenie",
+      "description": "Ten link z zaproszeniem jest niekompletny lub został źle skopiowany. Poproś osobę, która cię zaprosiła, o nowy link.",
+      "toLogin": "Przejdź do logowania"
     }
   },
   "dashboard": {
@@ -8713,7 +8718,11 @@
     },
     "course": "Kuracja {n}",
     "courseRange": "od {start} do {end}",
-    "courseSince": "od {start}"
+    "courseSince": "od {start}",
+    "unavailable": {
+      "title": "Link wygasł lub jest nieprawidłowy",
+      "description": "Ten link udostępniania wygasł, został cofnięty lub jest niekompletny. Poproś osobę, która go udostępniła, o nowy link."
+    }
   },
   "cycle": {
     "symptomCategory": {

src/app/c/[token]/not-found.tsx

@@ -0,0 +1,40 @@
+import { LinkIcon } from "lucide-react";
+
+import { resolveShareViewLocale } from "@/lib/clinician-share/request-locale";
+import { getServerTranslator } from "@/lib/i18n/server-translator";
+
+/**
+ * What a practice sees when a shared link no longer opens: expired, revoked,
+ * mistyped. The page still answers 404 for every failure class alike (the
+ * share page's `notFound()`), so a probe learns nothing from it; what changes
+ * is the copy. The app's own 404 said "this page does not exist" and offered
+ * a dashboard the reader has no account for. This one says what happened in
+ * the reader's terms and what to do, and links nowhere.
+ */
+export default async function ClinicianShareNotFound() {
+  const locale = await resolveShareViewLocale();
+  const { t } = getServerTranslator(locale);
+
+  return (
+    <main
+      id="main-content"
+      data-slot="clinician-share-unavailable"
+      className="bg-background text-foreground flex min-h-dvh flex-col items-center justify-center gap-6 px-4 py-12 pt-[calc(env(safe-area-inset-top)+3rem)]"
+    >
+      <div
+        aria-hidden="true"
+        className="bg-muted text-muted-foreground flex size-14 items-center justify-center rounded-xl"
+      >
+        <LinkIcon className="size-6" />
+      </div>
+      <div className="max-w-md space-y-2 text-center">
+        <h1 className="text-2xl font-bold tracking-tight">
+          {t("clinicianView.unavailable.title")}
+        </h1>
+        <p className="text-foreground text-sm">
+          {t("clinicianView.unavailable.description")}
+        </p>
+      </div>
+    </main>
+  );
+}

src/app/invite/[token]/__tests__/page.test.tsx

@@ -24,6 +24,11 @@ vi.mock("next/navigation", () => ({
   redirect: (href: string) => redirectMock(href),
 }));
 
+vi.mock("@/lib/i18n/server-locale", () => ({
+  resolveServerLocale: async () => "en",
+}));
+
+import { renderToStaticMarkup } from "react-dom/server";
 import InviteLandingPage from "../page";
 
 beforeEach(() => {
@@ -56,9 +61,10 @@ describe("<InviteLandingPage> universal-link landing", () => {
     expect(url.searchParams.get("invite")).toBe(VALID_TOKEN);
   });
 
-  it("drops a malformed token to plain register (no enumeration oracle)", async () => {
-    // Wrong prefix, wrong length, and outright garbage all land on the
-    // identical target — the page never reveals whether a token exists.
+  it("names a malformed link as invalid instead of opening registration", async () => {
+    // Wrong prefix, wrong length, and outright garbage all render the same
+    // invalid-invite state. The shape is public, so this reveals nothing
+    // about which well-formed tokens exist; those still go on to register.
     for (const bad of [
       "not-a-token",
       `hlk_${"a".repeat(64)}`,
@@ -66,8 +72,14 @@ describe("<InviteLandingPage> universal-link landing", () => {
       `hlv_${"G".repeat(64)}`,
     ]) {
       redirectMock.mockClear();
-      const href = await runRedirect(bad);
-      expect(href).toBe("/auth/register");
+      const node = await InviteLandingPage({
+        params: Promise.resolve({ token: bad }),
+      });
+      expect(redirectMock).not.toHaveBeenCalled();
+      const html = renderToStaticMarkup(node);
+      expect(html).toContain('data-slot="invite-invalid"');
+      expect(html).toContain("Invitation invalid");
+      expect(html).not.toContain("/auth/register");
     }
   });
 });

src/app/invite/[token]/page.tsx

@@ -1,6 +1,10 @@
+import Link from "next/link";
 import { redirect } from "next/navigation";
+import { MailX } from "lucide-react";
 
 import { looksLikeInviteToken } from "@/lib/auth/invite-token";
+import { resolveServerLocale } from "@/lib/i18n/server-locale";
+import { getServerTranslator } from "@/lib/i18n/server-translator";
 
 /**
  * v1.17.0 — invite universal-link landing (iOS #16).
@@ -41,7 +45,40 @@ export default async function InviteLandingPage({
     redirect(`/auth/register?invite=${encodeURIComponent(token)}`);
   }
 
-  // Malformed token: behave exactly like a visitor with no invite. No DB
-  // hit, no leak of whether any token exists.
-  redirect("/auth/register");
+  // Malformed token: say so. This used to fall through to the plain
+  // registration form, which on an open instance invited a stranger to sign
+  // up and on a closed one refused them without saying why. The shape check
+  // is public knowledge and needs no database, so naming a malformed link as
+  // invalid leaks nothing about which tokens exist: a well-formed unknown
+  // token still goes on to register, where the signup decides.
+  const locale = await resolveServerLocale();
+  const { t } = getServerTranslator(locale);
+  return (
+    <main
+      id="main-content"
+      data-slot="invite-invalid"
+      className="bg-background text-foreground flex min-h-dvh flex-col items-center justify-center gap-6 px-4 py-12 pt-[calc(env(safe-area-inset-top)+3rem)]"
+    >
+      <div
+        aria-hidden="true"
+        className="bg-muted text-muted-foreground flex size-14 items-center justify-center rounded-xl"
+      >
+        <MailX className="size-6" />
+      </div>
+      <div className="max-w-md space-y-2 text-center">
+        <h1 className="text-2xl font-bold tracking-tight">
+          {t("auth.inviteInvalid.title")}
+        </h1>
+        <p className="text-foreground text-sm">
+          {t("auth.inviteInvalid.description")}
+        </p>
+      </div>
+      <Link
+        href="/auth/login"
+        className="border-border hover:bg-accent inline-flex min-h-11 items-center justify-center rounded-md border px-4 text-sm font-medium transition-colors"
+      >
+        {t("auth.inviteInvalid.toLogin")}
+      </Link>
+    </main>
+  );
 }