diff --git a/assets/templates/auth.gohtml b/assets/templates/auth.gohtml
index 51b3cad56..8ac4ef709 100644
--- a/assets/templates/auth.gohtml
+++ b/assets/templates/auth.gohtml
@@ -30,6 +30,8 @@
       "session.provider",
       "session.scope",
       "session.error",
+      "session.messageId",
+      "session.messageParams",
     ];
     const storages = [localStorage, sessionStorage].filter(Boolean);
     const preferredStorage =
@@ -48,27 +50,23 @@
     const setItem = (key, value) => {
       preferredStorage.setItem(namespacedKey(key), value);
     };
-    const removeItem = (key) => {
-      storages.forEach((storage) => storage.removeItem(namespacedKey(key)));
-    };
 
+    {{/* clearSessionData() removes every session.* key (including session.error,
+         session.messageId, and session.messageParams), so each branch only sets
+         the keys it wants to persist. */}}
     {{ if eq .status "success" }}
     clearSessionData();
     setItem("session.id", {{ .session_id }});
     setItem("session.token", {{ .access_token }});
     setItem("session.provider", {{ .provider }});
     setItem("session.user", JSON.stringify({{ .user }}));
-    removeItem("session.error");
     {{ else if eq .status "failed" }}
     clearSessionData();
     setItem("session.error", {{ .error }});
+    {{ if .messageId }}setItem("session.messageId", {{ .messageId }});{{ end }}
+    {{ if .messageParams }}setItem("session.messageParams", JSON.stringify({{ .messageParams }}));{{ end }}
     {{ else }}
     clearSessionData();
-    removeItem("session.id");
-    removeItem("session.token");
-    removeItem("session.provider");
-    removeItem("session.user");
-    removeItem("session.error");
     {{ end }}
   })();
   window.location.href = {{ .config.LoginUri }};
diff --git a/frontend/src/common/notify.js b/frontend/src/common/notify.js
index 9f7ebe5bc..10692d7b5 100644
--- a/frontend/src/common/notify.js
+++ b/frontend/src/common/notify.js
@@ -30,26 +30,34 @@ let ajaxPending = 0;
 let ajaxCallbacks = [];
 
 const $notify = {
-  info: function (message) {
-    $event.publish("notify.info", { message });
+  // info publishes an info notification.
+  info: function (message, messageId, messageParams) {
+    $event.publish("notify.info", { message, messageId, messageParams });
   },
-  warn: function (message) {
-    $event.publish("notify.warning", { message });
+  // warn publishes a warning notification.
+  warn: function (message, messageId, messageParams) {
+    $event.publish("notify.warning", { message, messageId, messageParams });
   },
-  error: function (message) {
-    $event.publish("notify.error", { message });
+  // error publishes an error notification; the optional messageId/messageParams
+  // let notify.vue render it in the current UI locale via Tp.
+  error: function (message, messageId, messageParams) {
+    $event.publish("notify.error", { message, messageId, messageParams });
   },
-  success: function (message) {
-    $event.publish("notify.success", { message });
+  // success publishes a success notification.
+  success: function (message, messageId, messageParams) {
+    $event.publish("notify.success", { message, messageId, messageParams });
   },
-  logout: function (message) {
-    $event.publish("notify.error", { message });
-    $event.publish("session.logout", { message });
+  // logout publishes an error notification and triggers a session.logout event.
+  logout: function (message, messageId, messageParams) {
+    $event.publish("notify.error", { message, messageId, messageParams });
+    $event.publish("session.logout", { message, messageId, messageParams });
   },
+  // ajaxStart marks an AJAX request as started and emits ajax.start.
   ajaxStart: function () {
     ajaxPending++;
     $event.publish("ajax.start");
   },
+  // ajaxEnd marks an AJAX request as finished, emits ajax.end, and runs queued idle callbacks.
   ajaxEnd: function () {
     ajaxPending--;
     $event.publish("ajax.end");
@@ -60,6 +68,7 @@ const $notify = {
       callbacks.forEach((cb) => cb());
     }
   },
+  // ajaxBusy reports whether any AJAX requests are still pending.
   ajaxBusy: function () {
     if (ajaxPending < 0) {
       ajaxPending = 0;
@@ -67,6 +76,7 @@ const $notify = {
 
     return ajaxPending > 0;
   },
+  // ajaxWait resolves once no AJAX requests are pending or the timeout elapses.
   ajaxWait: function (idleDelay = 64, timeout = 8000) {
     return new Promise((resolve) => {
       const start = Date.now();
@@ -94,6 +104,7 @@ const $notify = {
       settle();
     });
   },
+  // blockUI shows the busy overlay, optionally setting its CSS class.
   blockUI: function (className) {
     const el = document.getElementById("busy-overlay");
 
@@ -104,6 +115,7 @@ const $notify = {
       }
     }
   },
+  // unblockUI hides the busy overlay.
   unblockUI: function () {
     const el = document.getElementById("busy-overlay");
 
@@ -112,9 +124,11 @@ const $notify = {
       el.className = "";
     }
   },
+  // wait shows a "Please wait" info notification.
   wait: function () {
     this.info($gettext("Please wait…"));
   },
+  // busy shows a "Busy, please wait" warning notification.
   busy: function () {
     this.warn($gettext("Busy, please wait…"));
   },
diff --git a/frontend/src/common/session.js b/frontend/src/common/session.js
index f4a881f66..7eb06a4b5 100644
--- a/frontend/src/common/session.js
+++ b/frontend/src/common/session.js
@@ -351,6 +351,8 @@ export default class Session {
     this.clearLegacyKey("session.scope");
     this.clearLegacyKey("authError");
     this.clearLegacyKey("session.error");
+    this.clearLegacyKey("session.messageId");
+    this.clearLegacyKey("session.messageParams");
 
     delete $api.defaults.headers.common[RequestHeader];
   }
diff --git a/frontend/src/common/storage.js b/frontend/src/common/storage.js
index 1334779a0..d29909bdc 100644
--- a/frontend/src/common/storage.js
+++ b/frontend/src/common/storage.js
@@ -38,6 +38,8 @@ const defaultLegacyClearKeys = new Set([
   "session.provider",
   "session.scope",
   "session.error",
+  "session.messageId",
+  "session.messageParams",
   "clipboard",
   "clipboard.photos",
   "clipboard.albums",
diff --git a/frontend/src/page/auth/login.vue b/frontend/src/page/auth/login.vue
index bd4466cc9..c2481e865 100644
--- a/frontend/src/page/auth/login.vue
+++ b/frontend/src/page/auth/login.vue
@@ -274,10 +274,24 @@ export default {
     // stashed by the auth bridge before its full-page redirect. In mounted() so
     // the notification component has already subscribed (its created() runs
     // before any mounted()).
+    const messageId = getAppStorage().getItem("session.messageId");
     const authError = getAppStorage().getItem("session.error");
-    if (authError) {
+    if (messageId || authError) {
+      let messageParams = [];
+      const rawParams = getAppStorage().getItem("session.messageParams");
+      if (rawParams) {
+        try {
+          messageParams = JSON.parse(rawParams);
+        } catch (e) {
+          messageParams = [];
+        }
+      }
       getAppStorage().removeItem("session.error");
-      this.$notify.error(authError);
+      getAppStorage().removeItem("session.messageId");
+      getAppStorage().removeItem("session.messageParams");
+      // Render in the current UI locale via the message key (notify.vue applies
+      // Tp); the server-rendered string stays as the fallback.
+      this.$notify.error(authError, messageId, messageParams);
     }
   },
   unmounted() {
diff --git a/frontend/tests/vitest/common/notify.test.js b/frontend/tests/vitest/common/notify.test.js
index a80079dc9..056a7ff2a 100644
--- a/frontend/tests/vitest/common/notify.test.js
+++ b/frontend/tests/vitest/common/notify.test.js
@@ -1,6 +1,7 @@
-import { describe, it } from "vitest";
+import { describe, it, expect, vi } from "vitest";
 import "../fixtures";
 import $notify from "common/notify";
+import $event from "common/event";
 
 describe("common/alert", () => {
   it("should call alert.info", () => {
@@ -19,6 +20,20 @@ describe("common/alert", () => {
     $notify.success("message");
   });
 
+  it("error forwards an optional message id and params for UI-locale rendering", async () => {
+    const handler = vi.fn();
+    const token = $event.subscribe("notify.error", handler);
+    $notify.error("fallback", "Registration disabled", ["x"]);
+    // pubsub.js delivers asynchronously, so wait a tick before asserting.
+    await new Promise((resolve) => setTimeout(resolve, 0));
+    $event.unsubscribe(token);
+    expect(handler).toHaveBeenCalledWith("notify.error", {
+      message: "fallback",
+      messageId: "Registration disabled",
+      messageParams: ["x"],
+    });
+  });
+
   it("should call wait", () => {
     $notify.wait();
   });
diff --git a/frontend/tests/vitest/page/auth/login.test.js b/frontend/tests/vitest/page/auth/login.test.js
index 70a6637df..ebd8b5d5a 100644
--- a/frontend/tests/vitest/page/auth/login.test.js
+++ b/frontend/tests/vitest/page/auth/login.test.js
@@ -173,9 +173,25 @@ describe("page/auth/login", () => {
 
     const { wrapper } = mountLogin({ oidcEnabled: true });
 
-    // Consumed on mount so it does not reappear on the next reload.
+    // Consumed on mount so it does not reappear on the next reload. With no
+    // messageId, the server-rendered fallback string is surfaced as-is.
     expect(window.localStorage.getItem(`${storagePrefix}session.error`)).toBeNull();
-    expect(wrapper.vm.$notify.error).toHaveBeenCalledWith("You do not have access to this instance.");
+    expect(wrapper.vm.$notify.error).toHaveBeenCalledWith("You do not have access to this instance.", null, []);
+  });
+
+  it("forwards a stored OIDC error by message key so it renders in the current UI locale", () => {
+    window.localStorage.setItem(`${storagePrefix}session.error`, "Registration disabled");
+    window.localStorage.setItem(`${storagePrefix}session.messageId`, "Registration disabled");
+    window.localStorage.setItem(`${storagePrefix}session.messageParams`, JSON.stringify([]));
+
+    const { wrapper } = mountLogin({ oidcEnabled: true });
+
+    // All three keys are consumed on mount so the toast does not reappear.
+    expect(window.localStorage.getItem(`${storagePrefix}session.error`)).toBeNull();
+    expect(window.localStorage.getItem(`${storagePrefix}session.messageId`)).toBeNull();
+    expect(window.localStorage.getItem(`${storagePrefix}session.messageParams`)).toBeNull();
+    // The message key is forwarded so notify.vue translates it via Tp.
+    expect(wrapper.vm.$notify.error).toHaveBeenCalledWith("Registration disabled", "Registration disabled", []);
   });
 
   // Auto-OIDC redirect for unauthenticated visitors now lives in the