diff --git a/server/app/api/v1/legal.py b/server/app/api/v1/legal.py
index 0a16e2c..d6cf918 100644
--- a/server/app/api/v1/legal.py
+++ b/server/app/api/v1/legal.py
@@ -7,7 +7,13 @@ from fastapi.responses import HTMLResponse
 from pydantic import BaseModel, HttpUrl
 
 from app.core.config import get_settings
-from app.legal_docs import PRIVACY_POLICY_MD, TERMS_OF_USE_MD, choose_content_by_lang, render_as_simple_html
+from app.legal_docs import (
+    PRIVACY_POLICY_MD,
+    TERMS_OF_USE_MD,
+    choose_content_by_lang,
+    render_as_simple_html,
+    split_bilingual_markdown,
+)
 
 
 router = APIRouter(prefix="/v1/legal", tags=["legal"])
@@ -64,6 +70,7 @@ Dear Mama｜技術支援
 
 # 当前多语言仅支持 EN / TC（繁体）
 ResolvedLang = Literal["en", "tc"]
+BILINGUAL_CONTENT_LANGUAGE = "en, zh-Hant"
 
 
 class LegalLinksResponse(BaseModel):
@@ -132,6 +139,18 @@ def _normalize_internal_url(request: Request, url: str, internal_path: str) -> s
     return _join_base_url(str(request.base_url), internal_path)
 
 
+def _build_bilingual_content(text: str) -> str:
+    """
+    固定输出双语协议内容：EN 在前，TC 在后。
+    若缺少 TC，则仅返回 EN。
+    """
+
+    en, tc = split_bilingual_markdown(text)
+    if not tc:
+        return en
+    return f"{en}\n\n---\n{tc}"
+
+
 @router.get("/links", response_model=LegalLinksResponse)
 async def get_legal_links(request: Request) -> LegalLinksResponse:
     """
@@ -156,11 +175,18 @@ async def get_privacy_policy(request: Request) -> HTMLResponse:
     """
 
     accept_language = request.headers.get("accept-language")
-    lang = _resolve_lang(accept_language)
-    content, resolved = choose_content_by_lang(PRIVACY_POLICY_MD, lang)
-    title = "Dear Mama | Privacy Policy" if resolved == "en" else "Dear Mama｜隱私權政策"
-    page = render_as_simple_html(title=title, content=content)
-    return HTMLResponse(content=page, headers={"Content-Language": "en" if resolved == "en" else "zh-Hant"})
+    if accept_language:
+        lang = _resolve_lang(accept_language)
+        content, resolved = choose_content_by_lang(PRIVACY_POLICY_MD, lang)
+        title = "Dear Mama | Privacy Policy" if resolved == "en" else "Dear Mama｜隱私權政策"
+        html_lang = "en" if resolved == "en" else "zh-Hant"
+        page = render_as_simple_html(title=title, content=content, html_lang=html_lang)
+        return HTMLResponse(content=page, headers={"Content-Language": html_lang})
+
+    content = _build_bilingual_content(PRIVACY_POLICY_MD)
+    title = "Dear Mama | Privacy Policy / 隱私權政策"
+    page = render_as_simple_html(title=title, content=content, html_lang="en")
+    return HTMLResponse(content=page, headers={"Content-Language": BILINGUAL_CONTENT_LANGUAGE})
 
 
 @router.get("/terms", response_class=HTMLResponse)
@@ -170,11 +196,18 @@ async def get_terms_of_use(request: Request) -> HTMLResponse:
     """
 
     accept_language = request.headers.get("accept-language")
-    lang = _resolve_lang(accept_language)
-    content, resolved = choose_content_by_lang(TERMS_OF_USE_MD, lang)
-    title = "Dear Mama – Terms of Use" if resolved == "en" else "Dear Mama 使用條款"
-    page = render_as_simple_html(title=title, content=content)
-    return HTMLResponse(content=page, headers={"Content-Language": "en" if resolved == "en" else "zh-Hant"})
+    if accept_language:
+        lang = _resolve_lang(accept_language)
+        content, resolved = choose_content_by_lang(TERMS_OF_USE_MD, lang)
+        title = "Dear Mama – Terms of Use" if resolved == "en" else "Dear Mama 使用條款"
+        html_lang = "en" if resolved == "en" else "zh-Hant"
+        page = render_as_simple_html(title=title, content=content, html_lang=html_lang)
+        return HTMLResponse(content=page, headers={"Content-Language": html_lang})
+
+    content = _build_bilingual_content(TERMS_OF_USE_MD)
+    title = "Dear Mama – Terms of Use / 使用條款"
+    page = render_as_simple_html(title=title, content=content, html_lang="en")
+    return HTMLResponse(content=page, headers={"Content-Language": BILINGUAL_CONTENT_LANGUAGE})
 
 
 @router.get("/support", response_class=HTMLResponse)
@@ -184,9 +217,16 @@ async def get_support_page(request: Request) -> HTMLResponse:
     """
 
     accept_language = request.headers.get("accept-language")
-    lang = _resolve_lang(accept_language)
-    content, resolved = choose_content_by_lang(SUPPORT_MD, lang)
-    title = "Dear Mama | Technical Support" if resolved == "en" else "Dear Mama｜技術支援"
-    page = render_as_simple_html(title=title, content=content)
-    return HTMLResponse(content=page, headers={"Content-Language": "en" if resolved == "en" else "zh-Hant"})
+    if accept_language:
+        lang = _resolve_lang(accept_language)
+        content, resolved = choose_content_by_lang(SUPPORT_MD, lang)
+        title = "Dear Mama | Technical Support" if resolved == "en" else "Dear Mama｜技術支援"
+        html_lang = "en" if resolved == "en" else "zh-Hant"
+        page = render_as_simple_html(title=title, content=content, html_lang=html_lang)
+        return HTMLResponse(content=page, headers={"Content-Language": html_lang})
+
+    content = _build_bilingual_content(SUPPORT_MD)
+    title = "Dear Mama | Technical Support / 技術支援"
+    page = render_as_simple_html(title=title, content=content, html_lang="en")
+    return HTMLResponse(content=page, headers={"Content-Language": BILINGUAL_CONTENT_LANGUAGE})
 
diff --git a/server/app/legal_docs.py b/server/app/legal_docs.py
index ebf9b1b..42ffddc 100644
--- a/server/app/legal_docs.py
+++ b/server/app/legal_docs.py
@@ -265,7 +265,7 @@ def choose_content_by_lang(text: str, lang: ResolvedLang) -> tuple[str, Resolved
     return en, "en"
 
 
-def render_as_simple_html(title: str, content: str) -> str:
+def render_as_simple_html(title: str, content: str, html_lang: str = "en") -> str:
     """
     将文本以简单 HTML 的方式展示（使用 pre 保留换行并自动换行）。
     不做 Markdown 渲染，避免引入额外依赖，确保“最小可用、必有内容”。
@@ -273,8 +273,9 @@ def render_as_simple_html(title: str, content: str) -> str:
 
     safe_title = html.escape(title)
     safe_content = html.escape(content)
+    safe_lang = html.escape(html_lang or "en")
     return f"""<!doctype html>
-<html lang="en">
+<html lang="{safe_lang}">
   <head>
     <meta charset="utf-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1" />
diff --git a/spec_kit/overview.md b/spec_kit/overview.md
index f8e9649..57f4c59 100644
--- a/spec_kit/overview.md
+++ b/spec_kit/overview.md
@@ -203,6 +203,8 @@
     - `GET /v1/legal/privacy`
     - `GET /v1/legal/terms`
     - `GET /v1/legal/support`（技术支持页面，提供审核可用的公开支持信息）
+  - 协议展示策略调整：`/v1/legal/privacy`、`/v1/legal/terms`、`/v1/legal/support` 在携带 `Accept-Language` 时按语言单语展示（EN/TC），缺省时展示 EN + TC（EN 在前、TC 在后）
+  - 协议页面语义修复：HTML 根节点 `lang` 属性不再写死，改为随页面实际语言输出（单语 en/zh-Hant；双语默认 en）
   - 客户端新增协议接口封装 `client/src/services/legalApi.ts`
   - 客户端工程化：新增统一 HTTP 封装 `client/src/utils/http.ts`（baseURL/超时/JSON/统一错误），并将 `legalApi.ts` / `recoApi.ts` 接入
   - 客户端接入两处入口：`app/(splash)/splash.tsx`、`components/home/ProfileModal.tsx`