From b5b5131eeef9f4260a4902282053aed15420aa1f Mon Sep 17 00:00:00 2001
From: gnezim <gnezim@gmail.com>
Date: Wed, 22 Apr 2026 03:07:55 +0300
Subject: [PATCH] Emit document title on error pages (404/500) per TZ 4.1.21
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Previously the 404/500 React ErrorPage set the page content but not
document.title, so the browser tab showed the URL path instead of
a localized title. Added <title> element + imperative document.title
assignment (pattern from SeoHead.tsx) so both SSR and client set
the tab title to "<code> — <localized-title>", e.g. "404 — Страница
не найдена".
---
 src/ui/errors/ErrorPage.tsx | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/ui/errors/ErrorPage.tsx b/src/ui/errors/ErrorPage.tsx
index 555bbcaf..4f39e668 100644
--- a/src/ui/errors/ErrorPage.tsx
+++ b/src/ui/errors/ErrorPage.tsx
@@ -120,9 +120,19 @@ export function ErrorPage({ code }: ErrorPageProps): JSX.Element {
   const support = translations?.support ?? "Поддержка";
   const refresh = translations?.refresh ?? (config.refreshKey ? "Обновить страницу" : undefined);
   const displayCode = code ?? "?";
+  const documentTitle = `${displayCode} — ${title}`;
+
+  // React 18 doesn't hoist <title> inside body to document.head, so set
+  // document.title imperatively on the client once translations resolve.
+  useEffect(() => {
+    if (typeof document !== "undefined" && translations) {
+      document.title = documentTitle;
+    }
+  }, [documentTitle, translations]);
 
   return (
     <>
+      <title>{documentTitle}</title>
       {/* noindex: error pages must not be indexed (TZ §4.1.21) */}
       <meta name="robots" content="noindex,nofollow" />
       <div className="error-page" data-testid={`error-page-${code ?? "unknown"}`}>