diff --git a/.unipi/docs/specs/2026-05-25-frontend-backend-api-requirements.md b/.unipi/docs/specs/2026-05-25-frontend-backend-api-requirements.md
index e1f9c90..b53eb26 100644
--- a/.unipi/docs/specs/2026-05-25-frontend-backend-api-requirements.md
+++ b/.unipi/docs/specs/2026-05-25-frontend-backend-api-requirements.md
@@ -15,7 +15,7 @@ status: draft
 - API base：前端通过 `VITE_API_URL` 指向后端；本地可同源 `/api`。
 - 上传文件可通过 `/uploads/...` 或完整 URL 返回；前端会用 `assetUrl()` 处理相对路径。
 - 所有时间字段使用 ISO 8601 字符串，例如 `2026-05-24T14:42:00.000Z`。
-- 语言字段：`zh` / `en` / `ja` / `ko` / `vi` / `id` / `ms`；默认语言为 `en`。中文只有简体 `zh`，没有繁体中文。
+- 语言字段：`zh-CN` / `en` / `ja` / `ko` / `vi` / `id` / `ms`；默认语言为 `en`。中文只有简体 `zh-CN`，没有繁体中文。
 - 错误格式：非 2xx + text/plain 或 JSON 均可；前端会显示错误文本。
 - Admin 接口需要 `Authorization: Bearer <token>`。
 
@@ -57,7 +57,7 @@ type Post = {
   id: string;
   categoryId: number;
   categorySlug: string;
-  language: "zh" | "en" | "ja" | "ko" | "vi" | "id" | "ms";
+  language: "zh-CN" | "en" | "ja" | "ko" | "vi" | "id" | "ms";
   text?: string;
   attachments: Attachment[];
   isRecommended: boolean;
@@ -449,7 +449,7 @@ Request:
 ```ts
 type UpsertPostPayload = {
   categoryId: number;
-  language: "zh" | "en" | "ja" | "ko" | "vi" | "id" | "ms";
+  language: "zh-CN" | "en" | "ja" | "ko" | "vi" | "id" | "ms";
   text?: string;
   attachments: Attachment[];
   isPublic: boolean;
diff --git a/.unipi/docs/specs/2026-05-25-posts-api-contract.md b/.unipi/docs/specs/2026-05-25-posts-api-contract.md
index 7f084eb..477fc37 100644
--- a/.unipi/docs/specs/2026-05-25-posts-api-contract.md
+++ b/.unipi/docs/specs/2026-05-25-posts-api-contract.md
@@ -33,7 +33,7 @@ type Post = {
   id: string;
   categoryId: number;
   categorySlug: string;
-  language: string; // "zh" | "en" | "ja" | "ko" | "vi" | "id" | "ms"
+  language: string; // "zh-CN" | "en" | "ja" | "ko" | "vi" | "id" | "ms"
   text?: string; // 可选，纯文本/图说；前端做 https → 链接自动识别
   attachments: Attachment[]; // 0~N；text-only post 时为 []
   isRecommended: boolean;
@@ -72,7 +72,7 @@ Query 参数：
 | `lang`     | 是   | UI 语言；后端可据此选择不同语言版本的 `text`                                       |
 | `category` | 否   | category slug；不传 = 全部分类                                                     |
 | `type`     | 否   | `all` / `image` / `video` / `pdf` / `ppt` / `text` / `link` / `archive`；语义见 §3 |
-| `language` | 否   | 资源语言：`zh` / `en` / `ja` / `ko` / `vi` / `id` / `ms`                           |
+| `language` | 否   | 资源语言：`zh-CN` / `en` / `ja` / `ko` / `vi` / `id` / `ms`                        |
 | `cursor`   | 否   | 上一次返回的 `nextCursor`；不传 = 第一页                                           |
 | `limit`    | 否   | 默认 20，最大 50                                                                   |
 
diff --git a/README.md b/README.md
index c909612..2eee7a4 100644
--- a/README.md
+++ b/README.md
@@ -68,7 +68,7 @@ src/
   App.tsx                  # public app + optional admin routes
   AppAdminOnly.tsx         # admin-only app entry
   api.ts                   # fetch helpers and shared API types
-  i18n.tsx                 # zh / en / ja / ko / vi / id / ms dictionary
+  i18n.tsx                 # zh-CN / en / ja / ko / vi / id / ms dictionary
   adminPaths.ts            # admin UI prefix logic
   adminRouteTree.tsx       # admin routes
   components/              # reusable public components
diff --git a/src/admin/useAdminT.ts b/src/admin/useAdminT.ts
index 81904cf..39fb670 100644
--- a/src/admin/useAdminT.ts
+++ b/src/admin/useAdminT.ts
@@ -3,5 +3,5 @@ import { tLang } from "../i18n";
 
 /** Admin area always uses Chinese, independent of site language. */
 export function useAdminT() {
-  return useCallback((key: string) => tLang("zh", key), []);
+  return useCallback((key: string) => tLang("zh-CN", key), []);
 }
diff --git a/src/components/messageStream/MessageStream.tsx b/src/components/messageStream/MessageStream.tsx
index b473f27..e938473 100644
--- a/src/components/messageStream/MessageStream.tsx
+++ b/src/components/messageStream/MessageStream.tsx
@@ -26,7 +26,7 @@ export function MessageStream({ scope }: MessageStreamProps) {
   const { items, isLoading, error, hasMore, loadMore, reset } =
     usePostStream(params);
   const groups = useGroupedByDay(items, lang);
-  const retryLabel = lang === "zh" ? "重试" : "Retry";
+  const retryLabel = lang === "zh-CN" ? "重试" : "Retry";
 
   const sentinelRef = useRef<HTMLDivElement>(null);
   const hasMoreRef = useRef(hasMore);
diff --git a/src/components/messageStream/hooks/useGroupedByDay.test.ts b/src/components/messageStream/hooks/useGroupedByDay.test.ts
index 487c1c4..6c33ee5 100644
--- a/src/components/messageStream/hooks/useGroupedByDay.test.ts
+++ b/src/components/messageStream/hooks/useGroupedByDay.test.ts
@@ -8,7 +8,7 @@ function makePost(id: string, isoDate: string): Post {
     id,
     categoryId: 1,
     categorySlug: "x",
-    language: "zh",
+    language: "zh-CN",
     attachments: [],
     isRecommended: false,
     publishedAt: isoDate,
@@ -25,7 +25,7 @@ describe("useGroupedByDay", () => {
       makePost("c", "2026-02-28T01:00:00.000Z"),
       makePost("d", "2026-05-16T12:00:00.000Z"),
     ];
-    const { result } = renderHook(() => useGroupedByDay(posts, "zh"));
+    const { result } = renderHook(() => useGroupedByDay(posts, "zh-CN"));
     expect(result.current.length).toBeGreaterThanOrEqual(2);
     const allIds = result.current.flatMap((g) => g.items.map((p) => p.id));
     expect(allIds).toEqual(["a", "b", "c", "d"]);
@@ -47,7 +47,7 @@ describe("useGroupedByDay", () => {
   });
 
   it("returns empty array for empty input", () => {
-    const { result } = renderHook(() => useGroupedByDay([], "zh"));
+    const { result } = renderHook(() => useGroupedByDay([], "zh-CN"));
     expect(result.current).toEqual([]);
   });
 });
diff --git a/src/components/messageStream/hooks/useGroupedByDay.ts b/src/components/messageStream/hooks/useGroupedByDay.ts
index 2837a99..02fb618 100644
--- a/src/components/messageStream/hooks/useGroupedByDay.ts
+++ b/src/components/messageStream/hooks/useGroupedByDay.ts
@@ -35,10 +35,10 @@ function dayLabel(iso: string, lang: string): string {
     a.getMonth() === b.getMonth() &&
     a.getDate() === b.getDate();
   if (isSameDay(d, today)) {
-    return lang === "zh" ? "今天" : "Today";
+    return lang === "zh-CN" ? "今天" : "Today";
   }
   if (isSameDay(d, yesterday)) {
-    return lang === "zh" ? "昨天" : "Yesterday";
+    return lang === "zh-CN" ? "昨天" : "Yesterday";
   }
   return new Intl.DateTimeFormat(localeFor(lang), {
     month: "long",
diff --git a/src/i18n.tsx b/src/i18n.tsx
index 9fb7869..7a00e17 100644
--- a/src/i18n.tsx
+++ b/src/i18n.tsx
@@ -6,7 +6,7 @@ import React, {
   useState,
 } from "react";
 
-export type Lang = "zh" | "en" | "ja" | "ko" | "vi" | "id" | "ms";
+export type Lang = "zh-CN" | "en" | "ja" | "ko" | "vi" | "id" | "ms";
 
 type Dict = Record<string, string>;
 
@@ -82,7 +82,7 @@ const zhDict: Dict = {
   walletMissingProjectId:
     "请配置 VITE_WALLETCONNECT_PROJECT_ID（Reown Cloud），否则无法使用 WalletConnect/扫码。",
   walletSetupNeeded: "钱包扫码未启用（请在服务器配置环境变量）",
-  lang_zh: "中文",
+  lang_zh_CN: "中文",
   lang_en: "English",
   lang_ja: "日本語",
   lang_ko: "한국어",
@@ -208,7 +208,7 @@ const enDict: Dict = {
   walletMissingProjectId:
     "Set VITE_WALLETCONNECT_PROJECT_ID (free on Reown Cloud). Required for WalletConnect / QR login.",
   walletSetupNeeded: "Wallet QR login disabled (set env on server)",
-  lang_zh: "Chinese",
+  lang_zh_CN: "Chinese",
   lang_en: "English",
   lang_ja: "Japanese",
   lang_ko: "Korean",
@@ -262,8 +262,8 @@ const enDict: Dict = {
 };
 
 const languageNames: Record<Lang, Dict> = {
-  zh: {
-    lang_zh: "中文",
+  "zh-CN": {
+    lang_zh_CN: "中文",
     lang_en: "English",
     lang_ja: "日本語",
     lang_ko: "한국어",
@@ -272,7 +272,7 @@ const languageNames: Record<Lang, Dict> = {
     lang_ms: "Bahasa Melayu",
   },
   en: {
-    lang_zh: "Chinese",
+    lang_zh_CN: "Chinese",
     lang_en: "English",
     lang_ja: "Japanese",
     lang_ko: "Korean",
@@ -281,7 +281,7 @@ const languageNames: Record<Lang, Dict> = {
     lang_ms: "Malay",
   },
   ja: {
-    lang_zh: "中国語",
+    lang_zh_CN: "中国語",
     lang_en: "英語",
     lang_ja: "日本語",
     lang_ko: "韓国語",
@@ -290,7 +290,7 @@ const languageNames: Record<Lang, Dict> = {
     lang_ms: "マレー語",
   },
   ko: {
-    lang_zh: "중국어",
+    lang_zh_CN: "중국어",
     lang_en: "영어",
     lang_ja: "일본어",
     lang_ko: "한국어",
@@ -299,7 +299,7 @@ const languageNames: Record<Lang, Dict> = {
     lang_ms: "말레이어",
   },
   vi: {
-    lang_zh: "Tiếng Trung",
+    lang_zh_CN: "Tiếng Trung",
     lang_en: "Tiếng Anh",
     lang_ja: "Tiếng Nhật",
     lang_ko: "Tiếng Hàn",
@@ -308,7 +308,7 @@ const languageNames: Record<Lang, Dict> = {
     lang_ms: "Tiếng Mã Lai",
   },
   id: {
-    lang_zh: "Bahasa Tionghoa",
+    lang_zh_CN: "Bahasa Tionghoa",
     lang_en: "Bahasa Inggris",
     lang_ja: "Bahasa Jepang",
     lang_ko: "Bahasa Korea",
@@ -317,7 +317,7 @@ const languageNames: Record<Lang, Dict> = {
     lang_ms: "Bahasa Melayu",
   },
   ms: {
-    lang_zh: "Bahasa Cina",
+    lang_zh_CN: "Bahasa Cina",
     lang_en: "Bahasa Inggeris",
     lang_ja: "Bahasa Jepun",
     lang_ko: "Bahasa Korea",
@@ -328,7 +328,7 @@ const languageNames: Record<Lang, Dict> = {
 };
 
 const dict: Record<Lang, Dict> = {
-  zh: { ...zhDict, ...languageNames.zh },
+  "zh-CN": { ...zhDict, ...languageNames["zh-CN"] },
   en: { ...enDict, ...languageNames.en },
   ja: { ...enDict, ...languageNames.ja },
   ko: { ...enDict, ...languageNames.ko },
@@ -351,9 +351,9 @@ const LANG_KEY = "ark_lang";
 export function I18nProvider({ children }: { children: React.ReactNode }) {
   const [lang, setLangState] = useState<Lang>(() => {
     const s = localStorage.getItem(LANG_KEY);
-    if (s === "zh-CN" || s === "zh-TW") return "zh";
+    if (s === "zh" || s === "zh-TW") return "zh-CN";
     if (
-      s === "zh" ||
+      s === "zh-CN" ||
       s === "en" ||
       s === "ja" ||
       s === "ko" ||
@@ -383,5 +383,5 @@ export function useI18n() {
 }
 
 export function langQuery(lang: Lang) {
-  return lang === "zh" ? "zh-CN" : lang;
+  return lang;
 }
diff --git a/src/i18nLanguages.ts b/src/i18nLanguages.ts
index 261ad1d..c5997d3 100644
--- a/src/i18nLanguages.ts
+++ b/src/i18nLanguages.ts
@@ -1,7 +1,7 @@
 import type { Lang } from "./i18n";
 
 export const LANG_OPTIONS: { code: Lang; label: string }[] = [
-  { code: "zh", label: "中文" },
+  { code: "zh-CN", label: "中文" },
   { code: "en", label: "English" },
   { code: "ja", label: "日本語" },
   { code: "ko", label: "한국어" },
@@ -12,6 +12,7 @@ export const LANG_OPTIONS: { code: Lang; label: string }[] = [
 
 export function languageLabel(t: (key: string) => string, code: string) {
   if (!code) return t("filterLanguageAll");
-  const label = t(`lang_${code}`);
-  return label === `lang_${code}` ? code : label;
+  const key = `lang_${code.replace("-", "_")}`;
+  const label = t(key);
+  return label === key ? code : label;
 }
diff --git a/src/mocks/mockPosts.ts b/src/mocks/mockPosts.ts
index 7193286..8e86149 100644
--- a/src/mocks/mockPosts.ts
+++ b/src/mocks/mockPosts.ts
@@ -31,7 +31,7 @@ export const MOCK_POSTS: Post[] = [
     id: "p-001",
     categoryId: 1,
     categorySlug: "project",
-    language: "zh",
+    language: "zh-CN",
     attachments: [
       {
         id: "a-001",
@@ -55,7 +55,7 @@ export const MOCK_POSTS: Post[] = [
     id: "p-002",
     categoryId: 1,
     categorySlug: "project",
-    language: "zh",
+    language: "zh-CN",
     attachments: [
       {
         id: "a-002",
@@ -79,7 +79,7 @@ export const MOCK_POSTS: Post[] = [
     id: "p-013",
     categoryId: 1,
     categorySlug: "project",
-    language: "zh",
+    language: "zh-CN",
     attachments: [
       {
         id: "a-013",
@@ -100,7 +100,7 @@ export const MOCK_POSTS: Post[] = [
     id: "p-003",
     categoryId: 2,
     categorySlug: "guide",
-    language: "zh",
+    language: "zh-CN",
     attachments: [
       {
         id: "a-003",
@@ -121,7 +121,7 @@ export const MOCK_POSTS: Post[] = [
     id: "p-004",
     categoryId: 2,
     categorySlug: "guide",
-    language: "zh",
+    language: "zh-CN",
     attachments: [
       {
         id: "a-004",
@@ -142,7 +142,7 @@ export const MOCK_POSTS: Post[] = [
     id: "p-005",
     categoryId: 3,
     categorySlug: "data",
-    language: "zh",
+    language: "zh-CN",
     text:
       "📊 ARK DeFAI 各大平台现已上线 🔥\n\n" +
       "🔷 市场数据平台\n" +
@@ -163,7 +163,7 @@ export const MOCK_POSTS: Post[] = [
     id: "p-006",
     categoryId: 3,
     categorySlug: "data",
-    language: "zh",
+    language: "zh-CN",
     text:
       "📌 收取协议固定 2.5% 手续费。\n\n" +
       "🔷 贡献值合约\n0x7736b5B84cADDB7661D250D10e60E31F3C905c99\n📌 用于新贡献值机制的 USDT 购买与资金流向管理（通缩销毁 / 储备 RBS）",
@@ -178,7 +178,7 @@ export const MOCK_POSTS: Post[] = [
     id: "p-007",
     categoryId: 4,
     categorySlug: "videos",
-    language: "zh",
+    language: "zh-CN",
     text: "ARK 山东·东营社区 招商复盘·势位重塑\n🔥 ARK DeFai 相位偏移锁死增值弧度。质能裂变诱发认知风暴，海岱动能正于中原合围！🚀",
     attachments: [
       {
@@ -204,7 +204,7 @@ export const MOCK_POSTS: Post[] = [
     id: "p-008",
     categoryId: 5,
     categorySlug: "poster",
-    language: "zh",
+    language: "zh-CN",
     attachments: [
       {
         id: "a-008",
@@ -228,7 +228,7 @@ export const MOCK_POSTS: Post[] = [
     id: "p-009",
     categoryId: 5,
     categorySlug: "poster",
-    language: "zh",
+    language: "zh-CN",
     attachments: [
       {
         id: "a-009",
@@ -252,7 +252,7 @@ export const MOCK_POSTS: Post[] = [
     id: "p-010",
     categoryId: 6,
     categorySlug: "meeting",
-    language: "zh",
+    language: "zh-CN",
     text: "📌 ARK DeFAI 方舟晨间时刻\n\n🧠 会议主题：市场概况交流 & 市场问题讨论。\n🕙 会议时间：3月1日（日）10:00\n🎬 直播腾讯会议链接：https://meeting.tencent.com/l/G718S4Sedm38",
     attachments: [
       {
@@ -277,7 +277,7 @@ export const MOCK_POSTS: Post[] = [
     id: "p-011",
     categoryId: 5,
     categorySlug: "poster",
-    language: "zh",
+    language: "zh-CN",
     attachments: [
       {
         id: "a-011a",
@@ -323,7 +323,7 @@ export const MOCK_POSTS: Post[] = [
     id: "p-012",
     categoryId: 5,
     categorySlug: "poster",
-    language: "zh",
+    language: "zh-CN",
     attachments: Array.from({ length: 7 }).map((_, i) => ({
       id: `a-012-${i}`,
       kind: "image" as const,
diff --git a/src/pages/admin/AdminResourceForm.tsx b/src/pages/admin/AdminResourceForm.tsx
index 2993a12..735b538 100644
--- a/src/pages/admin/AdminResourceForm.tsx
+++ b/src/pages/admin/AdminResourceForm.tsx
@@ -37,7 +37,7 @@ export function AdminResourceForm() {
   const [title, setTitle] = useState("");
   const [description, setDescription] = useState("");
   const [rtype, setRtype] = useState<string>("image");
-  const [language, setLanguage] = useState("zh");
+  const [language, setLanguage] = useState("zh-CN");
   const [categoryId, setCategoryId] = useState(1);
   const [coverImage, setCoverImage] = useState("");
   const [fileUrl, setFileUrl] = useState("");
@@ -66,7 +66,7 @@ export function AdminResourceForm() {
         setTitle(r.title || "");
         setDescription(r.description || "");
         setRtype(r.type || "image");
-        setLanguage(r.language || "zh");
+        setLanguage(r.language || "zh-CN");
         setCategoryId(r.categoryId || 1);
         setCoverImage(r.coverImage || "");
         setFileUrl(r.fileUrl || "");
@@ -183,7 +183,7 @@ export function AdminResourceForm() {
             value={language}
             onChange={(e) => setLanguage(e.target.value)}
           >
-            <option value="zh">{t("lang_zh")}</option>
+            <option value="zh-CN">{t("lang_zh_CN")}</option>
             <option value="en">{t("lang_en")}</option>
             <option value="ja">{t("lang_ja")}</option>
             <option value="ko">{t("lang_ko")}</option>
diff --git a/src/resourceTypeLabels.test.ts b/src/resourceTypeLabels.test.ts
index 54b4e6f..4188551 100644
--- a/src/resourceTypeLabels.test.ts
+++ b/src/resourceTypeLabels.test.ts
@@ -12,7 +12,7 @@ const t = (key: string) =>
     type_image: "图片",
     type_video: "视频",
     type_music: "音乐",
-    lang_zh: "中文",
+    lang_zh_CN: "中文",
     lang_en: "English",
     lang_ja: "日本語",
   })[key] ?? key;
diff --git a/src/resourceTypeLabels.ts b/src/resourceTypeLabels.ts
index 348cf75..70a4786 100644
--- a/src/resourceTypeLabels.ts
+++ b/src/resourceTypeLabels.ts
@@ -34,8 +34,10 @@ export function resourceLanguageLabel(
 ): string {
   const lc = langCode.trim().toLowerCase();
   const normalized =
-    lc === "zh-cn" || lc === "zh-tw" || lc === "zh-hans" ? "zh" : lc;
-  const key = `lang_${normalized}`;
+    lc === "zh" || lc === "zh-cn" || lc === "zh-tw" || lc === "zh-hans"
+      ? "zh-CN"
+      : lc;
+  const key = `lang_${normalized.replace("-", "_")}`;
   const label = t(key);
   return label !== key ? label : langCode.trim();
 }