diff --git a/next.config.ts b/next.config.ts
index 65c102b..a18b38e 100644
--- a/next.config.ts
+++ b/next.config.ts
@@ -2,6 +2,7 @@ import type { NextConfig } from "next";
 
 const nextConfig: NextConfig = {
   output: "export",
+  trailingSlash: true,
 };
 
 export default nextConfig;
diff --git a/public/error/404-messages.yml b/public/error/404-messages.yml
index 0253210..0540354 100644
--- a/public/error/404-messages.yml
+++ b/public/error/404-messages.yml
@@ -1,10 +1,10 @@
 # Random 404 messages grouped by locale.
-zh-CN:
+zh-Hans:
   - 人与人的悲欢不尽相同
   - 此处没有列车经过
   - 这条线路还没有开通
   - 你抵达了地图之外的地方
-zh-TW:
+zh-Hant:
   - 人與人的悲歡並不相同
   - 此處沒有列車經過
   - 這條路線尚未通車
@@ -14,7 +14,7 @@ en:
   - No train stops here
   - This line has not opened yet
   - You have reached the edge of the map
-ja:
+jp:
   - 人それぞれ、喜びも悲しみも違う
   - ここを通る列車はありません
   - この路線はまだ開通していません
diff --git a/src/app/403/page.tsx b/src/app/(legacy)/403/page.tsx
similarity index 100%
rename from src/app/403/page.tsx
rename to src/app/(legacy)/403/page.tsx
diff --git a/src/app/500/page.tsx b/src/app/(legacy)/500/page.tsx
similarity index 100%
rename from src/app/500/page.tsx
rename to src/app/(legacy)/500/page.tsx
diff --git a/src/app/502/page.tsx b/src/app/(legacy)/502/page.tsx
similarity index 100%
rename from src/app/502/page.tsx
rename to src/app/(legacy)/502/page.tsx
diff --git a/src/app/503/page.tsx b/src/app/(legacy)/503/page.tsx
similarity index 100%
rename from src/app/503/page.tsx
rename to src/app/(legacy)/503/page.tsx
diff --git a/src/app/504/page.tsx b/src/app/(legacy)/504/page.tsx
similarity index 100%
rename from src/app/504/page.tsx
rename to src/app/(legacy)/504/page.tsx
diff --git a/src/app/(legacy)/layout.tsx b/src/app/(legacy)/layout.tsx
new file mode 100644
index 0000000..7fbebd9
--- /dev/null
+++ b/src/app/(legacy)/layout.tsx
@@ -0,0 +1 @@
+export { default, metadata, viewport } from "@/components/layout/site-document";
diff --git a/src/app/news/[slug]/page.tsx b/src/app/(legacy)/news/[slug]/page.tsx
similarity index 75%
rename from src/app/news/[slug]/page.tsx
rename to src/app/(legacy)/news/[slug]/page.tsx
index 5242baf..117c8f9 100644
--- a/src/app/news/[slug]/page.tsx
+++ b/src/app/(legacy)/news/[slug]/page.tsx
@@ -1,6 +1,7 @@
 import type { Metadata } from "next";
 import { getNewsBySlug, getNewsCatalog, getNewsList } from "@/data/news";
 import { NewsDetailClient } from "@/components/news/news-detail-client";
+import { isLocale } from "@/lib/i18n";
 
 export async function generateStaticParams() {
   const news = await getNewsList();
@@ -11,10 +12,10 @@ export async function generateStaticParams() {
 export async function generateMetadata({
   params,
 }: {
-  params: Promise<{ slug: string }>;
+  params: Promise<{ slug: string; locale?: string }>;
 }): Promise<Metadata> {
-  const { slug } = await params;
-  const item = await getNewsBySlug(slug);
+  const { slug, locale } = await params;
+  const item = await getNewsBySlug(slug, isLocale(locale) ? locale : "zh-Hans");
 
   return {
     title: item?.title ?? "新闻",
diff --git a/src/app/news/page.tsx b/src/app/(legacy)/news/page.tsx
similarity index 52%
rename from src/app/news/page.tsx
rename to src/app/(legacy)/news/page.tsx
index 027f424..f46fcee 100644
--- a/src/app/news/page.tsx
+++ b/src/app/(legacy)/news/page.tsx
@@ -3,12 +3,16 @@ import { getNewsCatalog } from "@/data/news";
 import { PageBreadcrumb } from "@/components/layout/page-breadcrumb";
 import { NewsList } from "@/components/news/news-list";
 import { NewsPageHeading } from "@/components/news/news-page-heading";
+import { getLocaleMessages, isLocale } from "@/lib/i18n";
 
-export const metadata: Metadata = {
-  title: "新闻",
-};
+export async function generateMetadata({ params }: { params: Promise<{ locale?: string }> }): Promise<Metadata> {
+  const { locale } = await params;
+  return { title: getLocaleMessages(isLocale(locale) ? locale : "zh-Hans").common.news };
+}
 
-export default async function NewsPage() {
+export default async function NewsPage({ params }: { params: Promise<{ locale?: string }> }) {
+  const { locale } = await params;
+  const messages = getLocaleMessages(isLocale(locale) ? locale : "zh-Hans");
   const catalog = await getNewsCatalog();
 
   return (
@@ -22,7 +26,7 @@ export default async function NewsPage() {
       </div>
       <div className="page-bottom-nav">
         <div className="page-bottom-nav-inner">
-          <PageBreadcrumb items={[{ label: "首页", href: "/" }, { label: "新闻" }]} />
+          <PageBreadcrumb items={[{ label: messages.common.home, href: "/" }, { label: messages.common.news }]} />
         </div>
       </div>
     </main>
diff --git a/src/app/not-found.tsx b/src/app/(legacy)/not-found.tsx
similarity index 100%
rename from src/app/not-found.tsx
rename to src/app/(legacy)/not-found.tsx
diff --git a/src/app/page.tsx b/src/app/(legacy)/page.tsx
similarity index 100%
rename from src/app/page.tsx
rename to src/app/(legacy)/page.tsx
diff --git a/src/app/policy/[slug]/page.tsx b/src/app/(legacy)/policy/[slug]/page.tsx
similarity index 73%
rename from src/app/policy/[slug]/page.tsx
rename to src/app/(legacy)/policy/[slug]/page.tsx
index b527d99..528b537 100644
--- a/src/app/policy/[slug]/page.tsx
+++ b/src/app/(legacy)/policy/[slug]/page.tsx
@@ -2,6 +2,7 @@ import type { Metadata } from "next";
 import { notFound } from "next/navigation";
 import { PolicyPageContent } from "@/components/policy/policy-page-content";
 import { getPolicyCatalog, getPolicySlugs } from "@/data/policy";
+import { isLocale } from "@/lib/i18n";
 
 export const dynamicParams = false;
 
@@ -9,16 +10,16 @@ export function generateStaticParams() {
   return getPolicySlugs();
 }
 
-export async function generateMetadata({ params }: { params: Promise<{ slug: string }> }): Promise<Metadata> {
-  const { slug } = await params;
+export async function generateMetadata({ params }: { params: Promise<{ slug: string; locale?: string }> }): Promise<Metadata> {
+  const { slug, locale } = await params;
   const catalog = await getPolicyCatalog(slug);
-  return { title: catalog["zh-CN"]?.title ?? "法律信息" };
+  return { title: catalog[isLocale(locale) ? locale : "zh-Hans"]?.title ?? "法律信息" };
 }
 
 export default async function PolicyPage({ params }: { params: Promise<{ slug: string }> }) {
   const { slug } = await params;
   const catalog = await getPolicyCatalog(slug);
-  if (!catalog["zh-CN"]) notFound();
+  if (!catalog["zh-Hans"]) notFound();
 
   return (
     <main className="policy-page">
@@ -27,4 +28,4 @@ export default async function PolicyPage({ params }: { params: Promise<{ slug: s
       </div>
     </main>
   );
-}
\ No newline at end of file
+}
diff --git a/src/app/[locale]/403/page.tsx b/src/app/[locale]/403/page.tsx
new file mode 100644
index 0000000..bb689c6
--- /dev/null
+++ b/src/app/[locale]/403/page.tsx
@@ -0,0 +1 @@
+export { default } from "@/app/(legacy)/403/page";
diff --git a/src/app/[locale]/500/page.tsx b/src/app/[locale]/500/page.tsx
new file mode 100644
index 0000000..f8856cb
--- /dev/null
+++ b/src/app/[locale]/500/page.tsx
@@ -0,0 +1 @@
+export { default } from "@/app/(legacy)/500/page";
diff --git a/src/app/[locale]/502/page.tsx b/src/app/[locale]/502/page.tsx
new file mode 100644
index 0000000..351a22a
--- /dev/null
+++ b/src/app/[locale]/502/page.tsx
@@ -0,0 +1 @@
+export { default } from "@/app/(legacy)/502/page";
diff --git a/src/app/[locale]/503/page.tsx b/src/app/[locale]/503/page.tsx
new file mode 100644
index 0000000..3c6fa7b
--- /dev/null
+++ b/src/app/[locale]/503/page.tsx
@@ -0,0 +1 @@
+export { default } from "@/app/(legacy)/503/page";
diff --git a/src/app/[locale]/504/page.tsx b/src/app/[locale]/504/page.tsx
new file mode 100644
index 0000000..336c8ef
--- /dev/null
+++ b/src/app/[locale]/504/page.tsx
@@ -0,0 +1 @@
+export { default } from "@/app/(legacy)/504/page";
diff --git a/src/app/[locale]/layout.tsx b/src/app/[locale]/layout.tsx
new file mode 100644
index 0000000..490d8c0
--- /dev/null
+++ b/src/app/[locale]/layout.tsx
@@ -0,0 +1,43 @@
+import { notFound } from "next/navigation";
+import SiteDocument from "@/components/layout/site-document";
+import { getLocaleMessages, locales, matchLocale } from "@/lib/i18n";
+
+export { viewport } from "@/components/layout/site-document";
+export const dynamicParams = false;
+
+export function generateStaticParams() {
+  return [
+    ...locales,
+    "zh-hans",
+    "zh-hant",
+    "zh-CN",
+    "zh-cn",
+    "zh-SG",
+    "zh-sg",
+    "zh-TW",
+    "zh-tw",
+    "zh-HK",
+    "zh-hk",
+    "zh-MO",
+    "zh-mo",
+    "ja",
+  ].map((locale) => ({ locale }));
+}
+
+export async function generateMetadata({ params }: { params: Promise<{ locale: string }> }) {
+  const { locale } = await params;
+  const canonicalLocale = matchLocale(locale);
+  if (!canonicalLocale) notFound();
+  const title = getLocaleMessages(canonicalLocale).common.siteTitle;
+  return { title: { default: title, template: `%s | ${title}` }, icons: { icon: "/icon/icon.svg" } };
+}
+
+export default async function LocaleLayout({ children, params }: {
+  children: React.ReactNode;
+  params: Promise<{ locale: string }>;
+}) {
+  const { locale } = await params;
+  const canonicalLocale = matchLocale(locale);
+  if (!canonicalLocale) notFound();
+  return <SiteDocument locale={canonicalLocale}>{children}</SiteDocument>;
+}
diff --git a/src/app/[locale]/news/[slug]/page.tsx b/src/app/[locale]/news/[slug]/page.tsx
new file mode 100644
index 0000000..2e7c43e
--- /dev/null
+++ b/src/app/[locale]/news/[slug]/page.tsx
@@ -0,0 +1 @@
+export { default, generateMetadata, generateStaticParams } from "@/app/(legacy)/news/[slug]/page";
diff --git a/src/app/[locale]/news/page.tsx b/src/app/[locale]/news/page.tsx
new file mode 100644
index 0000000..9fd541a
--- /dev/null
+++ b/src/app/[locale]/news/page.tsx
@@ -0,0 +1 @@
+export { default, generateMetadata } from "@/app/(legacy)/news/page";
diff --git a/src/app/[locale]/not-found.tsx b/src/app/[locale]/not-found.tsx
new file mode 100644
index 0000000..643f134
--- /dev/null
+++ b/src/app/[locale]/not-found.tsx
@@ -0,0 +1 @@
+export { default } from "@/app/(legacy)/not-found";
diff --git a/src/app/[locale]/page.tsx b/src/app/[locale]/page.tsx
new file mode 100644
index 0000000..a1d4b8a
--- /dev/null
+++ b/src/app/[locale]/page.tsx
@@ -0,0 +1 @@
+export { default } from "@/app/(legacy)/page";
diff --git a/src/app/[locale]/policy/[slug]/page.tsx b/src/app/[locale]/policy/[slug]/page.tsx
new file mode 100644
index 0000000..0ebb270
--- /dev/null
+++ b/src/app/[locale]/policy/[slug]/page.tsx
@@ -0,0 +1 @@
+export { default, generateMetadata, generateStaticParams } from "@/app/(legacy)/policy/[slug]/page";
diff --git a/src/app/layout.tsx b/src/app/layout.tsx
deleted file mode 100644
index c9b22bb..0000000
--- a/src/app/layout.tsx
+++ /dev/null
@@ -1,50 +0,0 @@
-import type { Metadata, Viewport } from "next";
-import "./globals.css";
-import { SiteFooter } from "@/components/layout/site-footer";
-import { SiteHeader } from "@/components/layout/site-header";
-
-export const metadata: Metadata = {
-  title: {
-    default: "基沃托斯铁道公团 KivotosRailway",
-    template: "%s | 基沃托斯铁道公团 KivotosRailway",
-  },
-  description: "Kivotos Railway website",
-  icons: {
-    icon: "/icon/icon.svg",
-  },
-};
-
-export const viewport: Viewport = {
-  width: "device-width",
-  initialScale: 1,
-};
-
-export default function RootLayout({
-  children,
-}: Readonly<{ children: React.ReactNode }>) {
-  return (
-    <html lang="zh-CN" suppressHydrationWarning>
-      <head>
-        {/* Run during HTML parsing, before the body can paint. */}
-        <script
-          id="theme-preference"
-          dangerouslySetInnerHTML={{ __html: `(() => {
-            const isTheme = (value) => value === 'light' || value === 'system' || value === 'dark';
-            let preference = 'system';
-            try {
-              const cookieTheme = document.cookie.split(';').map((entry) => entry.trim()).find((entry) => entry.startsWith('kr-theme='))?.slice('kr-theme='.length);
-              const savedTheme = isTheme(cookieTheme) ? cookieTheme : localStorage.getItem('kr-theme');
-              if (isTheme(savedTheme)) preference = savedTheme;
-            } catch {}
-            const theme = preference === 'system' ? (matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light') : preference;
-            document.documentElement.dataset.theme = theme;
-            document.documentElement.style.colorScheme = theme;
-          })();` }}
-        />
-      </head>
-      <body>
-        <SiteHeader />{children}<SiteFooter />
-      </body>
-    </html>
-  );
-}
diff --git a/src/components/home/home-page-content.tsx b/src/components/home/home-page-content.tsx
index 78ffde8..86e58b7 100644
--- a/src/components/home/home-page-content.tsx
+++ b/src/components/home/home-page-content.tsx
@@ -1,12 +1,14 @@
 "use client";
 
+import { useRouteLocale } from "@/components/layout/locale-context";
+
 import Link from "next/link";
 import { useEffect, useState } from "react";
 import type { NewsItem } from "@/data/news";
-import { applyLocale, getInitialLocale, getLocaleMessages, type Locale } from "@/lib/i18n";
+import { applyLocale, getInitialLocale, withLocale, getLocaleMessages, type Locale } from "@/lib/i18n";
 
 export function HomePageContent({ newsByLocale }: { newsByLocale: Record<Locale, NewsItem[]> }) {
-  const [locale, setLocale] = useState<Locale>("zh-CN");
+  const [locale, setLocale] = useState<Locale>(useRouteLocale());
 
   useEffect(() => {
     const syncLocale = (nextLocale: Locale) => setLocale(nextLocale);
@@ -38,7 +40,7 @@ export function HomePageContent({ newsByLocale }: { newsByLocale: Record<Locale,
   }, []);
 
   const t = getLocaleMessages(locale);
-  const visibleNews = newsByLocale[locale] ?? newsByLocale["zh-CN"] ?? [];
+  const visibleNews = newsByLocale[locale] ?? newsByLocale["zh-Hans"] ?? [];
 
   return (
     <main className="home-page">
@@ -56,7 +58,7 @@ export function HomePageContent({ newsByLocale }: { newsByLocale: Record<Locale,
       <section className="home-news" id="about" aria-labelledby="latest-news-title">
         <div className="news-header">
           <h2 id="latest-news-title">{t.home.latest}</h2>
-          <Link href="/news" className="news-more-link">
+          <Link href={withLocale("/news", locale)} className="news-more-link">
             {t.home.more} <span aria-hidden="true">→</span>
           </Link>
         </div>
@@ -64,7 +66,7 @@ export function HomePageContent({ newsByLocale }: { newsByLocale: Record<Locale,
         <div className="news-grid" aria-label={t.home.latest}>
           {visibleNews.slice(0, 3).map((post) => (
             <article key={post.id} className="news-card">
-              <Link href={post.href} className="news-card-link" aria-label={post.title}>
+              <Link href={withLocale(post.href, locale)} className="news-card-link" aria-label={post.title}>
                 <div className="news-visual" style={{ backgroundImage: `url(${post.cover})` }} />
                 <h3>{post.title}</h3>
                 <time dateTime={post.date}>{post.date}</time>
diff --git a/src/components/layout/locale-context.tsx b/src/components/layout/locale-context.tsx
new file mode 100644
index 0000000..8a01b60
--- /dev/null
+++ b/src/components/layout/locale-context.tsx
@@ -0,0 +1,11 @@
+"use client";
+
+import { createContext, useContext } from "react";
+import type { Locale } from "@/lib/i18n";
+
+export const LocaleContext = createContext<Locale>("zh-Hans");
+export function useRouteLocale() { return useContext(LocaleContext); }
+
+export function LocaleProvider({ locale, children }: { locale: Locale; children: React.ReactNode }) {
+  return <LocaleContext.Provider value={locale}>{children}</LocaleContext.Provider>;
+}
diff --git a/src/components/layout/locale-url-sync.tsx b/src/components/layout/locale-url-sync.tsx
new file mode 100644
index 0000000..ad89f54
--- /dev/null
+++ b/src/components/layout/locale-url-sync.tsx
@@ -0,0 +1,16 @@
+"use client";
+
+import { useEffect } from "react";
+import { usePathname, useSearchParams } from "next/navigation";
+import { applyLocale, getInitialLocale } from "@/lib/i18n";
+
+export function LocaleUrlSync() {
+  const pathname = usePathname();
+  const searchParams = useSearchParams();
+
+  useEffect(() => {
+    applyLocale(getInitialLocale());
+  }, [pathname, searchParams]);
+
+  return null;
+}
diff --git a/src/components/layout/page-breadcrumb.tsx b/src/components/layout/page-breadcrumb.tsx
index 1474b74..e0f45d2 100644
--- a/src/components/layout/page-breadcrumb.tsx
+++ b/src/components/layout/page-breadcrumb.tsx
@@ -1,4 +1,10 @@
+"use client";
+
+import { useRouteLocale } from "@/components/layout/locale-context";
+
 import Link from "next/link";
+import { useEffect, useState } from "react";
+import { getInitialLocale, withLocale, type Locale } from "@/lib/i18n";
 
 export function PageBreadcrumb({
   items,
@@ -7,12 +13,21 @@ export function PageBreadcrumb({
   items: Array<{ label: string; href?: string }>;
   ariaLabel?: string;
 }) {
+  const [locale, setLocale] = useState<Locale>(useRouteLocale());
+
+  useEffect(() => {
+    const syncLocale = () => setLocale(getInitialLocale());
+    syncLocale();
+    window.addEventListener("kr-locale-change", syncLocale);
+    return () => window.removeEventListener("kr-locale-change", syncLocale);
+  }, []);
+
   return (
     <nav className="page-breadcrumb" aria-label={ariaLabel}>
       {items.map((item, index) => (
         <span className="page-breadcrumb-item" key={`${item.label}-${index}`}>
           {index > 0 && <span className="page-breadcrumb-separator" aria-hidden="true">›</span>}
-          {item.href ? <Link href={item.href}>{item.label}</Link> : <span>{item.label}</span>}
+          {item.href ? <Link href={withLocale(item.href, locale)}>{item.label}</Link> : <span>{item.label}</span>}
         </span>
       ))}
     </nav>
diff --git a/src/components/layout/site-document.tsx b/src/components/layout/site-document.tsx
new file mode 100644
index 0000000..a0c18f7
--- /dev/null
+++ b/src/components/layout/site-document.tsx
@@ -0,0 +1,93 @@
+import type { Metadata, Viewport } from "next";
+import { Suspense } from "react";
+import "@/app/globals.css";
+import type { Locale } from "@/lib/i18n";
+import { LocaleProvider } from "@/components/layout/locale-context";
+import { SiteFooter } from "@/components/layout/site-footer";
+import { SiteHeader } from "@/components/layout/site-header";
+import { LocaleUrlSync } from "@/components/layout/locale-url-sync";
+
+export const metadata: Metadata = {
+  title: {
+    default: "基沃托斯铁道公团 KivotosRailway",
+    template: "%s | 基沃托斯铁道公团 KivotosRailway",
+  },
+  description: "Kivotos Railway website",
+  icons: {
+    icon: "/icon/icon.svg",
+  },
+};
+
+export const viewport: Viewport = {
+  width: "device-width",
+  initialScale: 1,
+};
+
+export default function RootLayout({
+  children,
+  locale = "zh-Hans",
+}: Readonly<{ children: React.ReactNode; locale?: Locale }>) {
+  return (
+    <html lang={locale} suppressHydrationWarning>
+      <head>
+        {/* Run during HTML parsing, before the body can paint. */}
+        <script
+          id="theme-preference"
+          dangerouslySetInnerHTML={{ __html: `(() => {
+            const isTheme = (value) => value === 'light' || value === 'system' || value === 'dark';
+            let preference = 'system';
+            try {
+              const cookieTheme = document.cookie.split(';').map((entry) => entry.trim()).find((entry) => entry.startsWith('kr-theme='))?.slice('kr-theme='.length);
+              const savedTheme = isTheme(cookieTheme) ? cookieTheme : localStorage.getItem('kr-theme');
+              if (isTheme(savedTheme)) preference = savedTheme;
+            } catch {}
+            const theme = preference === 'system' ? (matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light') : preference;
+            document.documentElement.dataset.theme = theme;
+            document.documentElement.style.colorScheme = theme;
+          })();` }}
+        />
+        <script
+          id="locale-canonicalization"
+          dangerouslySetInnerHTML={{ __html: `(() => {
+            const canonicalLocale = (value) => {
+              const language = value?.toLowerCase().replaceAll('_', '-');
+              if (!language) return null;
+              if (/^zh(?:-|$)/.test(language)) return /^zh-(tw|hk|mo)(-|$)|-hant(?:-|$)/.test(language) ? 'zh-Hant' : 'zh-Hans';
+              if (/^en(?:-|$)/.test(language)) return 'en';
+              if (/^(ja|jp)(?:-|$)/.test(language)) return 'jp';
+              return null;
+            };
+            const parts = location.pathname.split('/');
+            const firstSegment = parts[1];
+            const pathLocale = canonicalLocale(firstSegment);
+            const isUnknownLanguagePath = !pathLocale && /^[a-z]{2,3}(?:-[a-z0-9]+)*$/i.test(firstSegment ?? '');
+            let locale = pathLocale;
+            if (!locale) {
+              try { locale = canonicalLocale(localStorage.getItem('kr-locale')); } catch {}
+            }
+            if (!locale) {
+              for (const language of navigator.languages?.length ? navigator.languages : [navigator.language]) {
+                locale = canonicalLocale(language);
+                if (locale) break;
+              }
+            }
+            locale ??= 'en';
+            const path = pathLocale || isUnknownLanguagePath ? '/' + parts.slice(2).join('/') : location.pathname;
+            const normalizedPath = path.replace(/\\/$/, '');
+            const destination = '/' + locale + normalizedPath + '/';
+            const search = new URLSearchParams(location.search);
+            search.delete('lang');
+            const canonicalUrl = destination + (search.size ? '?' + search : '') + location.hash;
+            if (location.pathname + location.search + location.hash !== canonicalUrl) location.replace(canonicalUrl);
+          })();` }}
+        />
+      </head>
+      <body>
+        <LocaleProvider locale={locale}>
+        <Suspense fallback={null}><LocaleUrlSync /></Suspense>
+        <SiteHeader />{children}<SiteFooter />
+        </LocaleProvider>
+      </body>
+    </html>
+  );
+}
diff --git a/src/components/layout/site-footer.tsx b/src/components/layout/site-footer.tsx
index ee30605..f69fefe 100644
--- a/src/components/layout/site-footer.tsx
+++ b/src/components/layout/site-footer.tsx
@@ -1,8 +1,10 @@
 "use client";
 
+import { useRouteLocale } from "@/components/layout/locale-context";
+
 import Image from "next/image";
 import { useEffect, useState } from "react";
-import { applyLocale, getInitialLocale, getLocaleMessages, type Locale } from "@/lib/i18n";
+import { applyLocale, getInitialLocale, withLocale, getLocaleMessages, type Locale } from "@/lib/i18n";
 import { ThemeToggle } from "@/components/layout/theme-toggle";
 
 const footerColumnHrefs = [
@@ -18,7 +20,7 @@ function isIcpVisibleHost(hostname: string) {
 }
 
 export function SiteFooter() {
-  const [locale, setLocale] = useState<Locale>("zh-CN");
+  const [locale, setLocale] = useState<Locale>(useRouteLocale());
   const [showIcp, setShowIcp] = useState(false);
 
   useEffect(() => {
@@ -77,7 +79,7 @@ export function SiteFooter() {
                 <h3>{group.title}</h3>
                 <ul>
                   {group.links.map((link, linkIndex) => (
-                    <li key={`column-${groupIndex}-link-${linkIndex}`}><a href={footerColumnHrefs[groupIndex][linkIndex]}>{link}</a></li>
+                    <li key={`column-${groupIndex}-link-${linkIndex}`}><a href={withLocale(footerColumnHrefs[groupIndex][linkIndex], locale)}>{link}</a></li>
                   ))}
                 </ul>
               </div>
@@ -100,7 +102,7 @@ export function SiteFooter() {
         <div className="site-footer-meta">
           <div className="site-footer-legal-row">
             {messages.footer.legal.map((item, itemIndex) => (
-              <a key={`legal-${itemIndex}`} href={footerLegalHrefs[itemIndex]}>{item}</a>
+              <a key={`legal-${itemIndex}`} href={withLocale(footerLegalHrefs[itemIndex], locale)}>{item}</a>
             ))}
           </div>
           <p className="site-footer-description">{messages.footer.description}</p>
diff --git a/src/components/layout/site-header.tsx b/src/components/layout/site-header.tsx
index 61052ed..6f11753 100644
--- a/src/components/layout/site-header.tsx
+++ b/src/components/layout/site-header.tsx
@@ -1,18 +1,20 @@
 "use client";
 
+import { useRouteLocale } from "@/components/layout/locale-context";
+
 import Link from "next/link";
 import Image from "next/image";
 import { useEffect, useState } from "react";
-import { applyLocale, getInitialLocale, getLocaleMessages, localeLabels, locales, localeShortLabels, type Locale } from "@/lib/i18n";
+import { applyLocale, getInitialLocale, withLocale, withoutLocale, getLocaleMessages, localeLabels, locales, localeShortLabels, type Locale } from "@/lib/i18n";
 
 export function SiteHeader() {
-  const [locale, setLocale] = useState<Locale>("zh-CN");
+  const [locale, setLocale] = useState<Locale>(useRouteLocale());
   const [menuOpen, setMenuOpen] = useState(false);
 
   useEffect(() => {
     const updateDocumentTitle = (nextLocale: Locale) => {
       const messages = getLocaleMessages(nextLocale);
-      const pathname = window.location.pathname;
+      const pathname = withoutLocale(window.location.pathname).replace(/\/$/, "") || "/";
       const currentTitle = document.title.split(" | ")[0];
       const pageLabel = pathname === "/"
         ? ""
@@ -54,7 +56,7 @@ export function SiteHeader() {
 
   return (
     <header className="site-header">
-      <Link className="site-logo" href="/" aria-label={`Kivotos Railway ${localeLabels[locale]}`}>
+      <Link className="site-logo" href={withLocale("/", locale)} aria-label={`Kivotos Railway ${localeLabels[locale]}`}>
         <Image
           className="site-logo-image"
           src="/icon/kivotosrailway.svg"
@@ -68,7 +70,7 @@ export function SiteHeader() {
         {messages.header.nav.map((label, index) => {
           const href = ["/", "/news", "/railway", "/about", "/members"][index] ?? "/";
           return (
-            <Link key={href} href={href} onClick={() => setMenuOpen(false)}>
+            <Link key={href} href={withLocale(href, locale)} onClick={() => setMenuOpen(false)}>
               {label}
             </Link>
           );
diff --git a/src/components/layout/theme-toggle.tsx b/src/components/layout/theme-toggle.tsx
index 1bb75d8..9939d32 100644
--- a/src/components/layout/theme-toggle.tsx
+++ b/src/components/layout/theme-toggle.tsx
@@ -1,5 +1,7 @@
 "use client";
 
+import { useRouteLocale } from "@/components/layout/locale-context";
+
 import Image from "next/image";
 import { useEffect, useState } from "react";
 import { getInitialLocale, getLocaleMessages, type Locale } from "@/lib/i18n";
@@ -43,7 +45,7 @@ function applyTheme(preference: ThemePreference) {
 
 export function ThemeToggle() {
   const [themePreference, setThemePreference] = useState<ThemePreference>("system");
-  const [locale, setLocale] = useState<Locale>("zh-CN");
+  const [locale, setLocale] = useState<Locale>(useRouteLocale());
 
   useEffect(() => {
     const syncTheme = () => {
diff --git a/src/components/news/news-detail-client.tsx b/src/components/news/news-detail-client.tsx
index e7d5f54..8dd3466 100644
--- a/src/components/news/news-detail-client.tsx
+++ b/src/components/news/news-detail-client.tsx
@@ -1,17 +1,19 @@
 "use client";
 
+import { useRouteLocale } from "@/components/layout/locale-context";
+
 import Link from "next/link";
 import { useEffect, useState } from "react";
 import type { NewsItem } from "@/data/news";
-import { getAiTranslationNotice, getInitialLocale, getLocaleMessages, type Locale } from "@/lib/i18n";
+import { getAiTranslationNotice, getInitialLocale, withLocale, getLocaleMessages, type Locale } from "@/lib/i18n";
 import { markdownToHtml } from "@/lib/markdown";
 import { PageBreadcrumb } from "@/components/layout/page-breadcrumb";
 import { NewsShare } from "@/components/news/news-share";
 
 export function NewsDetailClient({ catalog, slug }: { catalog: Record<Locale, NewsItem[]>; slug: string }) {
-  const [locale, setLocale] = useState<Locale>("zh-CN");
+  const [locale, setLocale] = useState<Locale>(useRouteLocale());
   const messages = getLocaleMessages(locale);
-  const item = catalog[locale].find((entry) => entry.slug === slug) ?? catalog["zh-CN"].find((entry) => entry.slug === slug);
+  const item = catalog[locale].find((entry) => entry.slug === slug) ?? catalog["zh-Hans"].find((entry) => entry.slug === slug);
 
   useEffect(() => {
     const syncLocale = () => setLocale(getInitialLocale());
@@ -24,16 +26,16 @@ export function NewsDetailClient({ catalog, slug }: { catalog: Record<Locale, Ne
     };
   }, []);
 
-  if (!item) return <main className="news-detail-page"><div className="news-detail-inner"><p>未找到该文章。</p><Link href="/news">{messages.common.backToNews}</Link></div></main>;
+  if (!item) return <main className="news-detail-page"><div className="news-detail-inner"><p>未找到该文章。</p><Link href={withLocale("/news", locale)}>{messages.common.backToNews}</Link></div></main>;
 
   return <main className="news-detail-page">
     <div className="news-detail-inner">
-      <Link href="/news" className="back-link">← {messages.common.backToNews}</Link>
+      <Link href={withLocale("/news", locale)} className="back-link">← {messages.common.backToNews}</Link>
       <article className="news-detail-card">
         <p className="news-detail-tag">{item.category}</p>
         <h1>{item.title}</h1>
         <time>{item.date}</time>
-        {locale !== "zh-CN" && (
+        {locale !== "zh-Hans" && (
           <div className="news-detail-ai-banner" aria-label="AI translated content">
             {getAiTranslationNotice(locale)}
           </div>
diff --git a/src/components/news/news-list.tsx b/src/components/news/news-list.tsx
index 9af3a5e..1f0a97a 100644
--- a/src/components/news/news-list.tsx
+++ b/src/components/news/news-list.tsx
@@ -1,15 +1,17 @@
 "use client";
 
+import { useRouteLocale } from "@/components/layout/locale-context";
+
 import Link from "next/link";
 import { useEffect, useState } from "react";
 import type { NewsItem } from "@/data/news";
-import { getInitialLocale, getLocaleMessages, type Locale } from "@/lib/i18n";
+import { getInitialLocale, withLocale, getLocaleMessages, type Locale } from "@/lib/i18n";
 
 const ITEMS_PER_PAGE = 12;
 
 export function NewsList({ catalog }: { catalog: Record<Locale, NewsItem[]> }) {
   const [activeCategory, setActiveCategory] = useState<string | null>(null);
-  const [locale, setLocale] = useState<Locale>("zh-CN");
+  const [locale, setLocale] = useState<Locale>(useRouteLocale());
   const [currentPage, setCurrentPage] = useState(1);
   const messages = getLocaleMessages(locale);
   const news = catalog[locale];
@@ -88,7 +90,7 @@ export function NewsList({ catalog }: { catalog: Record<Locale, NewsItem[]> }) {
       <div className="news-list-grid">
         {paginatedNews.map((item) => (
           <article key={item.id} className="news-list-card">
-            <Link href={item.href} className="news-list-link">
+            <Link href={withLocale(item.href, locale)} className="news-list-link">
               <div className="news-list-cover" style={{ backgroundImage: `url(${item.cover})` }} />
               <div className="news-list-meta">
                 <span className="news-list-tag">{item.category}</span>
diff --git a/src/components/news/news-page-heading.tsx b/src/components/news/news-page-heading.tsx
index 0d2324e..de33cdb 100644
--- a/src/components/news/news-page-heading.tsx
+++ b/src/components/news/news-page-heading.tsx
@@ -1,10 +1,12 @@
 "use client";
 
+import { useRouteLocale } from "@/components/layout/locale-context";
+
 import { useEffect, useState } from "react";
 import { getInitialLocale, getLocaleMessages, type Locale } from "@/lib/i18n";
 
 export function NewsPageHeading() {
-  const [locale, setLocale] = useState<Locale>("zh-CN");
+  const [locale, setLocale] = useState<Locale>(useRouteLocale());
   useEffect(() => {
     const sync = () => setLocale(getInitialLocale());
     sync();
diff --git a/src/components/news/news-share.tsx b/src/components/news/news-share.tsx
index 1b4dfc6..3c9f092 100644
--- a/src/components/news/news-share.tsx
+++ b/src/components/news/news-share.tsx
@@ -1,11 +1,13 @@
 "use client";
 
+import { useRouteLocale } from "@/components/layout/locale-context";
+
 import { useEffect, useState } from "react";
 import { getInitialLocale, getLocaleMessages, type Locale } from "@/lib/i18n";
 
 export function NewsShare({ title }: { title: string }) {
   const [copied, setCopied] = useState(false);
-  const [locale, setLocale] = useState<Locale>("zh-CN");
+  const [locale, setLocale] = useState<Locale>(useRouteLocale());
   const messages = getLocaleMessages(locale);
 
   useEffect(() => {
diff --git a/src/components/policy/policy-page-content.tsx b/src/components/policy/policy-page-content.tsx
index 0b350b1..9afe7d4 100644
--- a/src/components/policy/policy-page-content.tsx
+++ b/src/components/policy/policy-page-content.tsx
@@ -1,5 +1,7 @@
 "use client";
 
+import { useRouteLocale } from "@/components/layout/locale-context";
+
 import { useEffect, useState } from "react";
 import { getAiTranslationNotice, getInitialLocale, getLocaleMessages, type Locale } from "@/lib/i18n";
 import type { PolicyDocument } from "@/data/policy";
@@ -8,9 +10,9 @@ import { PageBreadcrumb } from "@/components/layout/page-breadcrumb";
 type PolicyCatalog = Partial<Record<Locale, PolicyDocument>>;
 
 export function PolicyPageContent({ catalog }: { catalog: PolicyCatalog }) {
-  const [locale, setLocale] = useState<Locale>("zh-CN");
-  const document = catalog[locale] ?? catalog["zh-CN"];
-  const isTranslated = locale !== "zh-CN" && Boolean(catalog[locale]);
+  const [locale, setLocale] = useState<Locale>(useRouteLocale());
+  const document = catalog[locale] ?? catalog["zh-Hans"];
+  const isTranslated = locale !== "zh-Hans" && Boolean(catalog[locale]);
   const messages = getLocaleMessages(locale);
 
   useEffect(() => {
diff --git a/src/components/status/http-status-page.tsx b/src/components/status/http-status-page.tsx
index ffb31df..4f75f58 100644
--- a/src/components/status/http-status-page.tsx
+++ b/src/components/status/http-status-page.tsx
@@ -1,13 +1,15 @@
 "use client";
 
+import { useRouteLocale } from "@/components/layout/locale-context";
+
 import Image from "next/image";
 import { useEffect, useState } from "react";
-import { getInitialLocale, type Locale } from "@/lib/i18n";
+import { getInitialLocale, withLocale, type Locale } from "@/lib/i18n";
 
 export type HttpStatusCode = 403 | 404 | 500 | 502 | 503 | 504;
 
 const statusMessages: Record<Locale, Record<HttpStatusCode, string>> = {
-  "zh-CN": {
+  "zh-Hans": {
     403: "你没有权限访问此页面",
     404: "人与人的悲欢不尽相同",
     500: "服务器遇到了一点问题",
@@ -15,7 +17,7 @@ const statusMessages: Record<Locale, Record<HttpStatusCode, string>> = {
     503: "服务暂时不可用",
     504: "服务响应超时",
   },
-  "zh-TW": {
+  "zh-Hant": {
     403: "你沒有權限存取此頁面",
     404: "人與人的悲歡並不相同",
     500: "伺服器遇到了一點問題",
@@ -31,7 +33,7 @@ const statusMessages: Record<Locale, Record<HttpStatusCode, string>> = {
     503: "The service is temporarily unavailable",
     504: "The service took too long to respond",
   },
-  ja: {
+  jp: {
     403: "このページにアクセスする権限がありません",
     404: "人それぞれ、喜びも悲しみも違う",
     500: "サーバーで問題が発生しました",
@@ -42,10 +44,10 @@ const statusMessages: Record<Locale, Record<HttpStatusCode, string>> = {
 };
 
 const backLabels: Record<Locale, string> = {
-  "zh-CN": "回到上一页",
-  "zh-TW": "回到上一頁",
+  "zh-Hans": "回到上一页",
+  "zh-Hant": "回到上一頁",
   en: "Go back",
-  ja: "前のページに戻る",
+  jp: "前のページに戻る",
 };
 
 function parseLocalizedMessages(source: string): Partial<Record<Locale, string[]>> {
@@ -53,7 +55,7 @@ function parseLocalizedMessages(source: string): Partial<Record<Locale, string[]
   let locale: Locale | null = null;
 
   for (const line of source.split(/\r?\n/)) {
-    const localeMatch = line.match(/^(zh-CN|zh-TW|en|ja):\s*$/);
+    const localeMatch = line.match(/^(zh-Hans|zh-Hant|en|jp):\s*$/);
     if (localeMatch) {
       locale = localeMatch[1] as Locale;
       messages[locale] = [];
@@ -68,7 +70,7 @@ function parseLocalizedMessages(source: string): Partial<Record<Locale, string[]
 }
 
 export function HttpStatusPage({ code }: { code: HttpStatusCode }) {
-  const [locale, setLocale] = useState<Locale>("zh-CN");
+  const [locale, setLocale] = useState<Locale>(useRouteLocale());
   const [randomMessages, setRandomMessages] = useState<Partial<Record<Locale, string[]>>>({});
   const [randomMessage, setRandomMessage] = useState<string | null>(null);
 
@@ -93,7 +95,7 @@ export function HttpStatusPage({ code }: { code: HttpStatusCode }) {
   }, [code]);
 
   useEffect(() => {
-    const messages = randomMessages[locale] ?? randomMessages["zh-CN"];
+    const messages = randomMessages[locale] ?? randomMessages["zh-Hans"];
     if (!messages?.length) return;
     setRandomMessage(messages[Math.floor(Math.random() * messages.length)]);
   }, [locale, randomMessages]);
@@ -103,7 +105,7 @@ export function HttpStatusPage({ code }: { code: HttpStatusCode }) {
       window.history.back();
       return;
     }
-    window.location.assign("/");
+    window.location.assign(withLocale("/", locale));
   };
 
   return (
diff --git a/src/data/news/index.ts b/src/data/news/index.ts
index fb12c69..2b3b939 100644
--- a/src/data/news/index.ts
+++ b/src/data/news/index.ts
@@ -1,6 +1,6 @@
 import fs from "fs/promises";
 import path from "path";
-import type { Locale } from "@/lib/i18n";
+import { localeContentDirectory, type Locale } from "@/lib/i18n";
 import { markdownToHtml } from "@/lib/markdown";
 import { imageMap } from "@/lib/image-map.generated";
 
@@ -95,7 +95,7 @@ function normalizeNewsItem(fileName: string, raw: NewsFrontmatter, body: string)
 }
 
 async function readNewsList(locale: Locale): Promise<NewsItem[]> {
-  const directory = path.join(process.cwd(), "src", "data", "news", "posts", locale);
+  const directory = path.join(process.cwd(), "src", "data", "news", "posts", localeContentDirectory[locale]);
 
   try {
     const files = (await fs.readdir(directory))
@@ -123,15 +123,15 @@ async function readNewsList(locale: Locale): Promise<NewsItem[]> {
   }
 }
 
-export async function getNewsList(locale: Locale = "zh-CN"): Promise<NewsItem[]> {
+export async function getNewsList(locale: Locale = "zh-Hans"): Promise<NewsItem[]> {
   const items = await readNewsList(locale);
-  return locale === "zh-CN" || items.length > 0 ? items : readNewsList("zh-CN");
+  return locale === "zh-Hans" || items.length > 0 ? items : readNewsList("zh-Hans");
 }
 
 export async function getNewsCatalog(): Promise<Record<Locale, NewsItem[]>> {
-  const source = await readNewsList("zh-CN");
-  const entries = await Promise.all((["zh-CN", "zh-TW", "en", "ja"] as Locale[]).map(async (locale) => {
-    if (locale === "zh-CN") return [locale, source] as const;
+  const source = await readNewsList("zh-Hans");
+  const entries = await Promise.all((["zh-Hans", "zh-Hant", "en", "jp"] as Locale[]).map(async (locale) => {
+    if (locale === "zh-Hans") return [locale, source] as const;
 
     const translated = await readNewsList(locale);
     const bySlug = new Map(translated.map((item) => [item.slug, item]));
@@ -140,12 +140,12 @@ export async function getNewsCatalog(): Promise<Record<Locale, NewsItem[]>> {
   return Object.fromEntries(entries) as Record<Locale, NewsItem[]>;
 }
 
-export async function getNewsBySlug(slug: string, locale: Locale = "zh-CN"): Promise<NewsItem | null> {
+export async function getNewsBySlug(slug: string, locale: Locale = "zh-Hans"): Promise<NewsItem | null> {
   const items = await getNewsList(locale);
   return items.find((item) => item.slug === slug) ?? null;
 }
 
-export async function getLatestNews(locale: Locale = "zh-CN") {
+export async function getLatestNews(locale: Locale = "zh-Hans") {
   const items = await getNewsList(locale);
   return items.slice(0, 3);
 }
diff --git a/src/data/policy/index.ts b/src/data/policy/index.ts
index 7578c0b..88384e9 100644
--- a/src/data/policy/index.ts
+++ b/src/data/policy/index.ts
@@ -1,6 +1,6 @@
 import fs from "fs/promises";
 import path from "path";
-import type { Locale } from "@/lib/i18n";
+import { localeContentDirectory, type Locale } from "@/lib/i18n";
 import { parseFrontmatter } from "@/data/news";
 import { markdownToHtml } from "@/lib/markdown";
 
@@ -21,7 +21,7 @@ function isPolicySlug(slug: string): slug is PolicySlug {
 }
 
 async function readPolicy(slug: PolicySlug, locale: Locale): Promise<PolicyDocument | null> {
-  const filePath = path.join(process.cwd(), "src", "data", "policy", locale, `${slug}.md`);
+  const filePath = path.join(process.cwd(), "src", "data", "policy", localeContentDirectory[locale], `${slug}.md`);
 
   try {
     const body = await fs.readFile(filePath, "utf-8");
@@ -38,7 +38,7 @@ async function readPolicy(slug: PolicySlug, locale: Locale): Promise<PolicyDocum
       translationLabel,
       body: content,
       html: markdownToHtml(content),
-      markdownFile: `src/data/policy/${locale}/${slug}.md`,
+      markdownFile: `src/data/policy/${localeContentDirectory[locale]}/${slug}.md`,
     };
   } catch {
     return null;
@@ -49,7 +49,7 @@ export async function getPolicyCatalog(slug: string): Promise<Partial<Record<Loc
   if (!isPolicySlug(slug)) return {};
 
   const entries = await Promise.all(
-    (["zh-CN", "zh-TW", "en", "ja"] as Locale[]).map(async (locale) => [locale, await readPolicy(slug, locale)] as const),
+    (["zh-Hans", "zh-Hant", "en", "jp"] as Locale[]).map(async (locale) => [locale, await readPolicy(slug, locale)] as const),
   );
 
   return Object.fromEntries(entries.filter(([, document]) => document)) as Partial<Record<Locale, PolicyDocument>>;
@@ -57,4 +57,4 @@ export async function getPolicyCatalog(slug: string): Promise<Partial<Record<Loc
 
 export function getPolicySlugs() {
   return policySlugs.map((slug) => ({ slug }));
-}
\ No newline at end of file
+}
diff --git a/src/lib/i18n.ts b/src/lib/i18n.ts
index cc5320d..c50dce7 100644
--- a/src/lib/i18n.ts
+++ b/src/lib/i18n.ts
@@ -3,28 +3,67 @@ import zhTW from "@/locales/zh-TW.json";
 import en from "@/locales/en.json";
 import ja from "@/locales/ja.json";
 
-export const locales = ["zh-CN", "zh-TW", "en", "ja"] as const;
+export const locales = ["zh-Hans", "zh-Hant", "en", "jp"] as const;
 export type Locale = (typeof locales)[number];
 
+// Content storage retains its original names; public URLs use script subtags.
+export const localeContentDirectory: Record<Locale, string> = {
+  "zh-Hans": "zh-CN", "zh-Hant": "zh-TW", en: "en", jp: "ja",
+};
+
+export function matchLocale(value: string | null): Locale | null {
+  const language = value?.toLowerCase().replaceAll("_", "-");
+  if (!language) return null;
+  if (/^zh(?:-|$)/.test(language)) {
+    if (language.includes("-hant")) return "zh-Hant";
+    if (language.includes("-hans")) return "zh-Hans";
+    return /^zh-(tw|hk|mo)(-|$)/.test(language) ? "zh-Hant" : "zh-Hans";
+  }
+  if (/^en(?:-|$)/.test(language)) return "en";
+  if (/^(ja|jp)(?:-|$)/.test(language)) return "jp";
+  return null;
+}
+
+export function getPathLocale(pathname: string): Locale | null {
+  return matchLocale(pathname.split("/")[1]);
+}
+
+export function withoutLocale(pathname: string): string {
+  return getPathLocale(pathname) ? `/${pathname.split("/").slice(2).join("/")}` : pathname;
+}
+
+export function isLocale(value: string | null | undefined): value is Locale {
+  return locales.some((locale) => locale === value);
+}
+
+export function withLocale(href: string, locale: Locale): string {
+  if (!href.startsWith("/") || href.startsWith("//")) return href;
+  const url = new URL(href, "https://locale.invalid");
+  const path = withoutLocale(url.pathname).replace(/\/$/, "");
+  url.pathname = `/${locale}${path}/`;
+  url.searchParams.delete("lang");
+  return `${url.pathname}${url.search}${url.hash}`;
+}
+
 export const localeLabels: Record<Locale, string> = {
-  "zh-CN": "简体中文",
-  "zh-TW": "繁體中文",
+  "zh-Hans": "简体中文",
+  "zh-Hant": "繁體中文",
   en: "English",
-  ja: "日本語",
+  jp: "日本語",
 };
 
 export const localeShortLabels: Record<Locale, string> = {
-  "zh-CN": "简",
-  "zh-TW": "繁",
+  "zh-Hans": "简",
+  "zh-Hant": "繁",
   en: "EN",
-  ja: "JP",
+  jp: "JP",
 };
 
 export const translations = {
-  "zh-CN": zhCN,
-  "zh-TW": zhTW,
+  "zh-Hans": zhCN,
+  "zh-Hant": zhTW,
   en,
-  ja,
+  jp: ja,
 } as const;
 
 export function applyLocale(locale: Locale) {
@@ -32,23 +71,38 @@ export function applyLocale(locale: Locale) {
 
   if (!locales.includes(locale)) return;
 
-  window.localStorage.setItem("kr-locale", locale);
+  const href = `${window.location.pathname}${window.location.search}${window.location.hash}`;
+  const localizedHref = withLocale(href, locale);
+  try {
+    window.localStorage.setItem("kr-locale", locale);
+  } catch { /* The URL remains the source of truth when storage is unavailable. */ }
+  if (href !== localizedHref) {
+    window.location.replace(localizedHref);
+    return;
+  }
   document.documentElement.lang = locale;
   document.documentElement.setAttribute("data-locale", locale);
   window.dispatchEvent(new CustomEvent("kr-locale-change", { detail: { locale } }));
 }
 
 export function getInitialLocale(): Locale {
-  if (typeof window === "undefined") return "zh-CN";
+  if (typeof window === "undefined") return "zh-Hans";
 
-  const saved = window.localStorage.getItem("kr-locale") as Locale | null;
-  if (saved && locales.includes(saved)) return saved;
+  const pathLocale = getPathLocale(window.location.pathname);
+  if (pathLocale) return pathLocale;
+  const urlLocale = matchLocale(new URLSearchParams(window.location.search).get("lang"));
+  if (urlLocale) return urlLocale;
 
-  const browserLanguage = navigator.language.toLowerCase();
-  if (browserLanguage.startsWith("zh-tw") || browserLanguage.startsWith("zh-hk")) return "zh-TW";
-  if (browserLanguage.startsWith("en")) return "en";
-  if (browserLanguage.startsWith("ja")) return "ja";
-  return "zh-CN";
+  try {
+    const saved = matchLocale(window.localStorage.getItem("kr-locale"));
+    if (saved) return saved;
+  } catch { /* Fall back to the browser language. */ }
+
+  for (const language of navigator.languages?.length ? navigator.languages : [navigator.language]) {
+    const locale = matchLocale(language);
+    if (locale) return locale;
+  }
+  return "en";
 }
 
 export function getLocaleMessages(locale: Locale) {
@@ -56,7 +110,7 @@ export function getLocaleMessages(locale: Locale) {
 }
 
 export function getAiTranslationNotice(locale: Locale) {
-  if (locale === "zh-TW") {
+  if (locale === "zh-Hant") {
     return "此文章由 AI 從簡體中文翻譯而成，如有任何歧義，以簡體中文版本為準。";
   }