feat：添加对话情景功能

backend/internal/ai/llm/llm.go

@@ -15,10 +15,11 @@ type Service interface {
 
 // Request 推理请求。
 type Request struct {
-	Image    []byte         // JPEG 图片（已从 Base64 解码）
+	Image        []byte           // JPEG 图片（已从 Base64 解码）
-	Text     string         // 用户语音识别后的文本
+	Text         string           // 用户语音识别后的文本
-	History  []models.Message // 最近 N 轮对话历史
+	History      []models.Message // 最近 N 轮对话历史
-	Language string         // 语言，如 "zh-CN"
+	Language     string           // 语言，如 "zh-CN"
+	SystemPrompt string           // 情景自定义 system prompt（非空时覆盖默认 prompt）
 }
 
 // Chunk 流式推理的一个增量片段。

backend/internal/ai/llm/openai.go

@@ -209,10 +209,10 @@ func (o *OpenAIService) parseSSEStream(body io.Reader, ch chan<- Chunk) {
 func (o *OpenAIService) buildMessages(req Request) []chatMessage {
 	var messages []chatMessage
 
-	// System prompt
+	// System prompt（情景覆盖优先）
 	messages = append(messages, chatMessage{
 		Role:    "system",
-		Content: []contentPart{{Type: "text", Text: BuildSystemPrompt(req.Language, "")}},
+		Content: []contentPart{{Type: "text", Text: BuildSystemPrompt(req.Language, "", req.SystemPrompt)}},
 	})
 
 	// 历史消息

backend/internal/ai/llm/openai_test.go

@@ -242,9 +242,9 @@ func TestBuildSystemPrompt(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			got := BuildSystemPrompt(tt.language, tt.detailLevel)
+			got := BuildSystemPrompt(tt.language, tt.detailLevel, "")
 			if !strings.Contains(got, tt.wantContain) {
-				t.Errorf("BuildSystemPrompt(%q, %q) should contain %q", tt.language, tt.detailLevel, tt.wantContain)
+				t.Errorf("BuildSystemPrompt(%q, %q, \"\") should contain %q", tt.language, tt.detailLevel, tt.wantContain)
 			}
 		})
 	}

backend/internal/ai/llm/prompt.go

@@ -2,10 +2,26 @@ package llm
 
 import "strings"
 
-// BuildSystemPrompt 根据语言和细节级别构建系统提示词。
+// BuildSystemPrompt 根据语言、细节级别和情景 prompt 构建系统提示词。
-func BuildSystemPrompt(language, detailLevel string) string {
+// scenarioPrompt 非空时，覆盖默认视觉助手 prompt。
+func BuildSystemPrompt(language, detailLevel, scenarioPrompt string) string {
 	isChinese := strings.HasPrefix(language, "zh")
 
+	// 情景模式：使用自定义 prompt 作为基础
+	if scenarioPrompt != "" {
+		var prompt strings.Builder
+		prompt.WriteString(scenarioPrompt)
+		if detailLevel == "high" {
+			if isChinese {
+				prompt.WriteString(" 请在涉及视觉内容时提供更详细的描述，包括颜色、位置、数量等细节。")
+			} else {
+				prompt.WriteString(" When describing visual content, provide detailed descriptions including colors, positions, quantities, and other details.")
+			}
+		}
+		return prompt.String()
+	}
+
+	// 默认模式：视觉助手
 	var prompt strings.Builder
 	if isChinese {
 		prompt.WriteString("你是一个视觉助手。用户通过摄像头看到一个场景，并用语音向你提问。请用简洁自然的中文回答。如果涉及视觉描述，先说\"我看到……\"。回答控制在3-5句话以内，除非用户要求详细说明。")

backend/internal/ai/llm/scenarios.go

@@ -0,0 +1,55 @@
+package llm
+
+import "strings"
+
+// scenarioPrompt 定义单个情景的多语言 system prompt。
+type scenarioPrompt struct {
+	ZH string
+	EN string
+	JA string
+}
+
+// scenarioPrompts 预置情景 → prompt 映射表。
+// key 为情景 ID（与前端 Scenario.id 对齐）。
+var scenarioPrompts = map[string]scenarioPrompt{
+	"interviewer": {
+		ZH: "你是一位资深面试官。你通过摄像头观察面试者，并根据他们的背景和表现提出面试问题。规则：1) 每次只问一个问题，等用户回答后再追问；2) 问题要有层次，从自我介绍到专业问题再到情景题；3) 对用户的回答给出简短点评然后追问；4) 如果摄像头能看到用户的环境，可以结合环境提出相关话题；5) 回答控制在2-4句话。",
+		EN: "You are a senior interviewer. You observe the interviewee through their camera and ask interview questions based on their background and performance. Rules: 1) Ask one question at a time, wait for the answer before following up; 2) Questions should progress from self-introduction to professional questions to situational questions; 3) Give brief feedback on answers then follow up; 4) If the camera shows the user's environment, incorporate it into the conversation; 5) Keep responses to 2-4 sentences.",
+		JA: "あなたはベテラン面接官です。カメラで面接者を見て、バックグラウンドと実績に基づいて面接質問をします。ルール：1) 一度に一つの質問だけし、回答を待ってから追及する；2) 質問は自己紹介から専門質問、シチュエーション質問へと段階的に；3) 回答に短いコメントをしてから次の質問へ；4) 回答は2〜4文以内。",
+	},
+	"english_teacher": {
+		ZH: "You are a friendly and patient English tutor. Speak in English with the user. Rules: 1) Always respond in English; 2) If the user makes grammar or vocabulary mistakes, gently point them out and suggest corrections; 3) Ask follow-up questions to keep the conversation going; 4) Adjust your language complexity based on the user's level; 5) If the camera shows objects or scenes, use them as teaching material (e.g., 'I can see a bookshelf behind you. What's your favorite book?'); 6) Keep responses to 3-5 sentences.",
+		EN: "You are a friendly and patient English tutor. Speak in English with the user. Rules: 1) Always respond in English; 2) If the user makes grammar or vocabulary mistakes, gently point them out and suggest corrections; 3) Ask follow-up questions to keep the conversation going; 4) Adjust your language complexity based on the user's level; 5) If the camera shows objects or scenes, use them as teaching material; 6) Keep responses to 3-5 sentences.",
+		JA: "You are a friendly and patient English tutor. Speak in English with the user. Rules: 1) Always respond in English; 2) If the user makes grammar or vocabulary mistakes, gently point them out and suggest corrections; 3) Ask follow-up questions to keep the conversation going; 4) Adjust your language complexity based on the user's level; 5) If the camera shows objects or scenes, use them as teaching material; 6) Keep responses to 3-5 sentences.",
+	},
+	"debate": {
+		ZH: "你是一位辩论赛对手。用户提出一个观点，你需要站在反方进行反驳。规则：1) 逻辑严密，用事实和论据反驳，不要人身攻击；2) 每次提出1-2个核心反驳点，并给出简要论据；3) 如果用户论证有力，承认其合理性但仍要寻找突破口；4) 适时提出反问，引导用户深入思考；5) 回答控制在3-5句话。",
+		EN: "You are a debate opponent. The user presents a viewpoint, and you argue against it. Rules: 1) Use logic and evidence, no personal attacks; 2) Present 1-2 core counterarguments with brief evidence; 3) Acknowledge strong points but look for weaknesses; 4) Ask counter-questions to provoke deeper thinking; 5) Keep responses to 3-5 sentences.",
+		JA: "あなたはディベートの相手です。ユーザーが提示した观点に対して反論します。ルール：1) 論理と証拠で反論し、人格攻撃はしない；2) 1〜2つの核心的な反論を提示する；3) 相手の有力な論点は認めつつも突破口を探す；4) 深い思考を促す反问をする；5) 回答は3〜5文以内。",
+	},
+	"interpreter": {
+		ZH: "你是一名同声翻译员。将用户说的话实时翻译为目标语言。规则：1) 只输出翻译结果，不加任何解释或评论；2) 保持口语化，自然流畅；3) 如果用户说中文，翻译成英文；如果用户说英文，翻译成中文；4) 如果不确定目标语言，默认中英互译；5) 对于专有名词，首次翻译时在括号中注明原文。",
+		EN: "You are a simultaneous interpreter. Translate what the user says in real-time. Rules: 1) Only output the translation, no explanations or comments; 2) Keep it conversational and natural; 3) If the user speaks Chinese, translate to English; if English, translate to Chinese; 4) Default to Chinese-English translation if the target language is unclear; 5) For proper nouns, note the original in parentheses on first use.",
+		JA: "あなたは同時通訳者です。ユーザーの発言をリアルタイムで翻訳します。ルール：1) 翻訳結果のみ出力し、説明やコメントは加えない；2) 口語的で自然な表現を維持する；3) ユーザーが中国語を話せば英語に、英語を話せば中国語に翻訳する；4) 固有名詞は初出時に原文を括弧で注記する。",
+	},
+}
+
+// GetScenarioPrompt 根据情景 ID 和语言获取对应的 system prompt。
+// 返回空字符串表示无此情景（使用默认 prompt）。
+func GetScenarioPrompt(scenarioID, language string) string {
+	if scenarioID == "" || scenarioID == "free_chat" {
+		return ""
+	}
+	p, ok := scenarioPrompts[scenarioID]
+	if !ok {
+		return ""
+	}
+	switch {
+	case strings.HasPrefix(language, "zh"):
+		return p.ZH
+	case strings.HasPrefix(language, "ja"):
+		return p.JA
+	default:
+		return p.EN
+	}
+}

backend/internal/models/models.go

@@ -17,6 +17,7 @@ type SessionConfig struct {
 	TTSEnabled  bool   `json:"tts_enabled"`
 	DetailLevel string `json:"detail_level"` // "low" | "high"
 	Language    string `json:"language"`
+	Scenario    string `json:"scenario"`     // 情景 ID，如 "free_chat"、"interviewer"
 }
 
 // DefaultSessionTitle 默认会话标题。
@@ -24,7 +25,7 @@ const DefaultSessionTitle = "新对话"
 
 // DefaultConfig 默认会话配置。
 func DefaultConfig() SessionConfig {
-	return SessionConfig{TTSEnabled: true, DetailLevel: "low", Language: "zh-CN"}
+	return SessionConfig{TTSEnabled: true, DetailLevel: "low", Language: "zh-CN", Scenario: "free_chat"}
 }
 
 // SessionConfigPatch 会话配置增量更新（指针字段表示"未传则不更新"）。
@@ -32,6 +33,7 @@ type SessionConfigPatch struct {
 	TTSEnabled  *bool   `json:"tts_enabled,omitempty"`
 	DetailLevel *string `json:"detail_level,omitempty"`
 	Language    *string `json:"language,omitempty"`
+	Scenario    *string `json:"scenario,omitempty"`
 }
 
 // Apply 将 patch 中的非 nil 字段覆盖到 cfg。
@@ -45,6 +47,9 @@ func (p SessionConfigPatch) Apply(cfg *SessionConfig) {
 	if p.Language != nil {
 		cfg.Language = *p.Language
 	}
+	if p.Scenario != nil {
+		cfg.Scenario = *p.Scenario
+	}
 }
 
 // User 用户。
@@ -81,6 +86,7 @@ type WsConfig struct {
 		TTSEnabled  *bool   `json:"tts_enabled,omitempty"`
 		DetailLevel *string `json:"detail_level,omitempty"`
 		Language    *string `json:"language,omitempty"`
+		Scenario    *string `json:"scenario,omitempty"`
 	} `json:"payload"`
 }
 

backend/internal/orchestrator/pipeline.go

@@ -193,12 +193,13 @@ func (p *Pipeline) ProcessQuery(
 	})
 
 	// Step 2+3: LLM 流式推理 + TTS 并行合成
-	log.Infow("开始 LLM 推理", "request_id", req.RequestID)
+	log.Infow("开始 LLM 推理", "request_id", req.RequestID, "scenario", sess.Config.Scenario)
 	llmReq := llm.Request{
-		Image:    image,
+		Image:        image,
-		Text:     userText,
+		Text:         userText,
-		History:  history,
+		History:      history,
-		Language: sess.Config.Language,
+		Language:     sess.Config.Language,
+		SystemPrompt: llm.GetScenarioPrompt(sess.Config.Scenario, sess.Config.Language),
 	}
 
 	llmStream, err := p.llmService.ChatStream(ctx, llmReq)

backend/internal/ws/handler.go

@@ -276,6 +276,7 @@ func serveWS(c *gin.Context, sessionMgr session.Manager, orch orchestrator.Orche
 				TTSEnabled:  msg.Payload.TTSEnabled,
 				DetailLevel: msg.Payload.DetailLevel,
 				Language:    msg.Payload.Language,
+				Scenario:    msg.Payload.Scenario,
 			}
 			if err := client.sessionMgr.UpdateConfig(context.Background(), sessionID, patch); err != nil {
 				errors.SendWSError(client, errors.CodeInternalError, "", err)

frontend/src/App.css

@@ -760,6 +760,37 @@ body {
   letter-spacing: 0.02em;
 }
 
+/* ---- Scenario Quick Selector (chat header) ---- */
+.scenario-selector {
+  appearance: none;
+  -webkit-appearance: none;
+  font-size: 0.7rem;
+  font-weight: 500;
+  color: var(--color-text-muted);
+  background: var(--color-surface-2);
+  border: 1px solid var(--color-border);
+  border-radius: 14px;
+  padding: 4px 26px 4px 10px;
+  cursor: pointer;
+  outline: none;
+  transition: all var(--transition-fast);
+  letter-spacing: 0.01em;
+  background-image: url("data:image/svg+xml,%3Csvg width='10' height='6' viewBox='0 0 10 6' fill='none' xmlns='http://www.w3.org/2000/svg'%3E%3Cpath d='M1 1L5 5L9 1' stroke='%23888' stroke-width='1.4' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");
+  background-repeat: no-repeat;
+  background-position: right 8px center;
+}
+
+.scenario-selector:hover {
+  border-color: var(--color-primary);
+  color: var(--color-text);
+  background-color: var(--color-surface-3);
+}
+
+.scenario-selector:focus {
+  border-color: var(--color-primary);
+  box-shadow: 0 0 0 2px rgba(59, 130, 246, 0.15);
+}
+
 .chat-panel-header__stats {
   font-size: 0.68rem;
   font-weight: 400;
@@ -877,6 +908,31 @@ body {
   opacity: 0.85;
 }
 
+/* ---- System message (scenario switch, etc.) ---- */
+.chat-message--system {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  gap: 10px;
+  padding: 6px 0;
+  background: transparent;
+}
+
+.chat-message--system::before,
+.chat-message--system::after {
+  content: "";
+  flex: 1;
+  height: 1px;
+  background: var(--color-border);
+}
+
+.chat-message--system__text {
+  font-size: 0.7rem;
+  color: var(--color-text-muted);
+  white-space: nowrap;
+  letter-spacing: 0.02em;
+}
+
 .chat-message__role {
   font-size: 0.62rem;
   font-weight: 600;
@@ -1505,6 +1561,75 @@ body {
   line-height: 1.4;
 }
 
+/* ---- Scenario Selection Cards ---- */
+
+.scenario-cards {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+  padding: 0 24px;
+  max-width: 380px;
+  width: 100%;
+  margin-bottom: 8px;
+}
+
+.scenario-cards__title {
+  font-size: 0.72rem;
+  color: var(--color-text-muted);
+  text-transform: uppercase;
+  letter-spacing: 0.06em;
+  font-weight: 600;
+  padding: 0 4px 4px;
+}
+
+.scenario-card {
+  display: flex;
+  align-items: flex-start;
+  gap: 12px;
+  padding: 14px 16px;
+  border-radius: var(--radius-sm);
+  background: var(--color-surface-2);
+  border: 1px solid var(--color-border);
+  cursor: pointer;
+  transition: all var(--transition-fast);
+  text-align: left;
+}
+
+.scenario-card:hover {
+  background: var(--color-surface-3);
+  border-color: var(--color-primary);
+  transform: translateY(-1px);
+  box-shadow: 0 2px 8px rgba(59, 130, 246, 0.08);
+}
+
+.scenario-card:active {
+  transform: translateY(0);
+}
+
+.scenario-card__icon {
+  font-size: 1.4rem;
+  flex-shrink: 0;
+  margin-top: 1px;
+}
+
+.scenario-card__text {
+  display: flex;
+  flex-direction: column;
+  gap: 3px;
+}
+
+.scenario-card__title {
+  font-size: 0.85rem;
+  font-weight: 500;
+  color: var(--color-text);
+}
+
+.scenario-card__desc {
+  font-size: 0.72rem;
+  color: var(--color-text-muted);
+  line-height: 1.4;
+}
+
 /* ---- Voice Input Button ---- */
 
 .chat-input__voice {

frontend/src/App.tsx

@@ -15,6 +15,7 @@ import { AuthPage } from "./components/AuthPage";
 import { AuthProvider, useAuth } from "./lib/auth";
 import { loadConfig, loadTheme, saveTheme } from "./lib/storage";
 import { I18nContext, parseLocale, t } from "./lib/i18n";
+import { scenarios } from "./lib/scenarios";
 import type { Locale } from "./lib/i18n";
 import type { Theme } from "./types";
 import "./App.css";
@@ -180,6 +181,27 @@ function AppContent() {
     sendTextMessage(prompt);
   }, [sendTextMessage]);
 
+  // ---- 情景选择 ----
+  const handleSelectScenario = useCallback((scenarioId: string) => {
+    const sc = scenarios.find(s => s.id === scenarioId);
+    const updates: Partial<import("./types").SessionConfig> = { scenario: scenarioId };
+    // 如果情景有默认语言，同步切换
+    if (sc?.defaultLanguage) {
+      updates.language = sc.defaultLanguage;
+    }
+    updateConfig(updates);
+    // 插入系统提示消息
+    const scenarioName = sc ? `${sc.icon} ${tr(sc.nameKey)}` : scenarioId;
+    setMessages(prev => [...prev, {
+      role: "system",
+      content: tr("chat.scenarioSwitched").replace("{name}", scenarioName),
+      timestamp: Date.now(),
+    }]);
+  }, [updateConfig, setMessages, tr]);
+
+  // 当前情景对象
+  const activeScenario = scenarios.find(s => s.id === (config.scenario || "free_chat")) || scenarios[0];
+
   // ---- 键盘快捷键 ----
   useEffect(() => {
     const handler = (e: KeyboardEvent) => {
@@ -443,6 +465,16 @@ function AppContent() {
           <div className="chat-panel-header">
             <span>{tr("chat.title")}</span>
             <div className="chat-panel-header__right">
+              <select
+                className="scenario-selector"
+                value={activeScenario.id}
+                onChange={(e) => handleSelectScenario(e.target.value)}
+                title={tr("settings.scenario")}
+              >
+                {scenarios.map((sc) => (
+                  <option key={sc.id} value={sc.id}>{sc.icon} {tr(sc.nameKey)}</option>
+                ))}
+              </select>
               {isConnected && mode === "observation" && (
                 <span className="chat-panel-header__mode">{tr("chat.mode.observation")}</span>
               )}
@@ -465,14 +497,16 @@ function AppContent() {
               messages={messages}
               currentReply={currentReply}
               connectionStatus={connectionStatus}
+              currentScenario={config.scenario}
               isProcessing={isProcessing}
               isVADReady={isVADReady}
-              vadError={vadError}
+              vadError={vadError ?? undefined}
               isMicOn={isMicOn}
               isSpeaking={isSpeaking}
               onSendText={sendTextMessage}
               onToggleMic={toggleMic}
               onSceneCard={handleSceneCard}
+              onSelectScenario={handleSelectScenario}
             />
           </div>
         </div>

frontend/src/components/ChatPanel/index.tsx

@@ -1,11 +1,12 @@
 // ============================================================
 // ChatPanel — 消息展示面板
 // 职责：渲染对话消息列表、流式光标、元数据、自动滚动、文本输入
-// 增强：空状态场景卡片、语音输入按钮
+// 增强：空状态情景选择卡片、语音输入按钮
 // ============================================================
 
 import { useEffect, useRef, useState } from "react";
 import { useI18n } from "../../lib/i18n";
+import { scenarios } from "../../lib/scenarios";
 import type { ChatMessage } from "../../types";
 import type { ConnectionStatus } from "../../lib/websocket";
 
@@ -13,6 +14,7 @@ interface ChatPanelProps {
   messages: ChatMessage[];
   currentReply?: string;
   connectionStatus: ConnectionStatus;
+  currentScenario?: string;
   isProcessing?: boolean;
   isVADReady?: boolean;
   vadError?: string;
@@ -21,9 +23,10 @@ interface ChatPanelProps {
   onSendText?: (text: string) => void;
   onToggleMic?: () => void;
   onSceneCard?: (prompt: string) => void;
+  onSelectScenario?: (scenarioId: string) => void;
 }
 
-/** 场景卡片数据 */
+/** 场景卡片数据（视觉分析快捷） */
 function getSceneCards(t: (key: string) => string) {
   return [
     { icon: "👁", titleKey: "scene.describe", descKey: "scene.describe.desc", prompt: t("scene.describe") },
@@ -37,6 +40,7 @@ export function ChatPanel({
   messages,
   currentReply,
   connectionStatus,
+  currentScenario,
   isProcessing,
   isVADReady,
   vadError,
@@ -45,6 +49,7 @@ export function ChatPanel({
   onSendText,
   onToggleMic,
   onSceneCard,
+  onSelectScenario,
 }: ChatPanelProps) {
   const bottomRef = useRef<HTMLDivElement>(null);
   const containerRef = useRef<HTMLDivElement>(null);
@@ -55,6 +60,8 @@ export function ChatPanel({
   const isConnected = connectionStatus === "connected";
   const isEmpty = messages.length === 0 && !currentReply;
   const sceneCards = getSceneCards(t);
+  const activeScenario = currentScenario || "free_chat";
+  const isFreeChat = activeScenario === "free_chat";
 
   // 用户上滚时暂停自动滚动，滚到底部时恢复
   useEffect(() => {
@@ -97,46 +104,74 @@ export function ChatPanel({
   return (
     <div className="chat-panel">
       <div className="chat-panel__messages" ref={containerRef}>
-        {/* 空状态：场景卡片 */}
+        {/* 空状态：情景选择 + 场景卡片 */}
         {isEmpty && (
           <div className="chat-panel__welcome">
-            <span className="chat-panel__welcome-icon">💬</span>
+            <span className="chat-panel__welcome-icon">{scenarios.find(s => s.id === activeScenario)?.icon || "💬"}</span>
             <p>{isConnected ? t("chat.welcome.prompt") : t("chat.empty.prompt")}</p>
             <span className="chat-panel__welcome-hint">{isConnected ? t("chat.welcome.hint") : t("chat.empty.hint")}</span>
 
-            {/* 场景快捷卡片 */}
+            {/* 情景选择卡片（非 free_chat 时隐藏，因为已通过 header 切换） */}
-            <div className="scene-cards">
+            {isFreeChat && onSelectScenario && (
-              {sceneCards.map((card) => (
+              <div className="scenario-cards">
-                <button
+                <div className="scenario-cards__title">{t("scenario.choose")}</div>
-                  key={card.titleKey}
+                {scenarios.filter(s => s.id !== "free_chat").map((sc) => (
-                  className="scene-card"
+                  <button
-                  onClick={() => handleSceneCard(card.prompt)}
+                    key={sc.id}
-                >
+                    className="scenario-card"
-                  <span className="scene-card__icon">{card.icon}</span>
+                    onClick={() => onSelectScenario(sc.id)}
-                  <div className="scene-card__text">
+                  >
-                    <span className="scene-card__title">{t(card.titleKey)}</span>
+                    <span className="scenario-card__icon">{sc.icon}</span>
-                    <span className="scene-card__desc">{t(card.descKey)}</span>
+                    <div className="scenario-card__text">
-                  </div>
+                      <span className="scenario-card__title">{t(sc.nameKey)}</span>
-                </button>
+                      <span className="scenario-card__desc">{t(sc.descKey)}</span>
-              ))}
+                    </div>
-            </div>
+                  </button>
+                ))}
+              </div>
+            )}
+
+            {/* 视觉分析快捷卡片（仅 free_chat 模式） */}
+            {isFreeChat && isConnected && (
+              <div className="scene-cards">
+                {sceneCards.map((card) => (
+                  <button
+                    key={card.titleKey}
+                    className="scene-card"
+                    onClick={() => handleSceneCard(card.prompt)}
+                  >
+                    <span className="scene-card__icon">{card.icon}</span>
+                    <div className="scene-card__text">
+                      <span className="scene-card__title">{t(card.titleKey)}</span>
+                      <span className="scene-card__desc">{t(card.descKey)}</span>
+                    </div>
+                  </button>
+                ))}
+              </div>
+            )}
           </div>
         )}
 
         {messages.map((msg, index) => (
-          <div key={index} className={`chat-message chat-message--${msg.role}`}>
+          msg.role === "system" ? (
-            <div className="chat-message__role">
+            <div key={index} className="chat-message chat-message--system">
-              {msg.role === "user" ? t("chat.userLabel") : "AI"}
+              <span className="chat-message--system__text">{msg.content}</span>
             </div>
-            <div className="chat-message__content">{msg.content}</div>
+          ) : (
-            {msg.role === "assistant" && msg.tokensUsed !== undefined && (
+            <div key={index} className={`chat-message chat-message--${msg.role}`}>
-              <div className="chat-message__meta">
+              <div className="chat-message__role">
-                {msg.tokensUsed} tokens
+                {msg.role === "user" ? t("chat.userLabel") : "AI"}
-                {msg.latencyMs !== undefined && ` · ${(msg.latencyMs / 1000).toFixed(1)}s`}
-                {msg.model && ` · ${msg.model}`}
               </div>
-            )}
+              <div className="chat-message__content">{msg.content}</div>
-          </div>
+              {msg.role === "assistant" && msg.tokensUsed !== undefined && (
+                <div className="chat-message__meta">
+                  {msg.tokensUsed} tokens
+                  {msg.latencyMs !== undefined && ` · ${(msg.latencyMs / 1000).toFixed(1)}s`}
+                  {msg.model && ` · ${msg.model}`}
+                </div>
+              )}
+            </div>
+          )
         ))}
 
         {/* 流式回复（尚未完成） */}

frontend/src/components/ConfigPanel/index.tsx

@@ -1,9 +1,10 @@
 // ============================================================
 // ConfigPanel — 右侧抽屉式配置面板
-// 职责：主题切换、TTS 开关、detail level 切换、语言选择
+// 职责：主题切换、TTS 开关、detail level 切换、语言选择、情景选择
 // ============================================================
 
 import { useI18n } from "../../lib/i18n";
+import { scenarios } from "../../lib/scenarios";
 import type { SessionConfig, Theme } from "../../types";
 
 interface ConfigPanelProps {
@@ -89,6 +90,21 @@ export function ConfigPanel({ config, theme, username, onUpdate, onThemeChange,
                 <option value="ja-JP">日本語</option>
               </select>
             </label>
+
+            <label className="config-row">
+              <div className="config-row__info">
+                <span className="config-row__label">{t("settings.scenario")}</span>
+                <span className="config-row__desc">{t("settings.scenario.desc")}</span>
+              </div>
+              <select
+                value={config.scenario || "free_chat"}
+                onChange={(e) => onUpdate({ scenario: e.target.value })}
+              >
+                {scenarios.map((sc) => (
+                  <option key={sc.id} value={sc.id}>{sc.icon} {t(sc.nameKey)}</option>
+                ))}
+              </select>
+            </label>
           </div>
 
           {username && onLogout && (

frontend/src/hooks/useSessionList.ts

@@ -63,14 +63,6 @@ export function useSessionList() {
     saveSessionSummaries(updated);
   }, []);
 
-  /** 保存当前会话的消息历史 */
-  const saveCurrentSession = useCallback((messages: ChatMessage[]) => {
-    const id = sessionsRef.current.length > 0 ? sessionsRef.current[0].id : null;
-    // 找到 activeSessionId 对应的会话
-    // 这里不依赖 activeSessionId state，而是通过参数传入
-    return messages;
-  }, []);
-
   /** 保存指定会话的消息并更新摘要 */
   const persistSession = useCallback((sessionId: string, messages: ChatMessage[]) => {
     if (!sessionId) return;

frontend/src/lib/errors.ts

@@ -3,7 +3,7 @@
 // 来源：docs/03-接口文档.md §五 错误码
 // ============================================================
 
-import type { ErrorCode } from "../types";
+// ErrorCode type reserved for future use
 
 /** 将错误码转为用户友好文案（需要传入翻译函数） */
 export function getErrorMessage(code: string, translate: (key: string) => string): string {

frontend/src/lib/i18n/en-US.ts

@@ -26,6 +26,21 @@ export const enUS: TranslationMap = {
   "settings.detail.high": "High",
   "settings.language": "Language",
   "settings.language.desc": "Interaction language preference",
+  "settings.scenario": "Scenario",
+  "settings.scenario.desc": "Choose the AI's role",
+
+  // Scenarios
+  "scenario.choose": "Choose a scenario",
+  "scenario.freeChat": "Free Chat",
+  "scenario.freeChat.desc": "AI visual assistant, chat freely",
+  "scenario.interviewer": "Mock Interviewer",
+  "scenario.interviewer.desc": "AI plays interviewer for practice",
+  "scenario.englishTeacher": "English Tutor",
+  "scenario.englishTeacher.desc": "AI English tutor, corrects grammar",
+  "scenario.debate": "Debate Opponent",
+  "scenario.debate.desc": "AI challenges your viewpoints",
+  "scenario.interpreter": "Interpreter",
+  "scenario.interpreter.desc": "Real-time Chinese-English translation",
 
   // Video indicators
   "video.observing": "👁️ Observing",
@@ -63,6 +78,7 @@ export const enUS: TranslationMap = {
   "chat.userLabel": "You",
   "chat.input.placeholder": "Type a message...",
   "chat.send": "Send",
+  "chat.scenarioSwitched": "Switched to {name} mode",
 
   // Session messages
   "session.changeDetected": "👁️ Scene change detected",

frontend/src/lib/i18n/ja-JP.ts

@@ -26,6 +26,21 @@ export const jaJP: TranslationMap = {
   "settings.detail.high": "高",
   "settings.language": "言語",
   "settings.language.desc": "インタラクション言語の設定",
+  "settings.scenario": "シナリオ",
+  "settings.scenario.desc": "AIの役割を選択",
+
+  // Scenarios
+  "scenario.choose": "シナリオを選択",
+  "scenario.freeChat": "フリーチャット",
+  "scenario.freeChat.desc": "AIビジュアルアシスタントと自由に会話",
+  "scenario.interviewer": "模擬面接官",
+  "scenario.interviewer.desc": "AIが面接官として模擬面接を実施",
+  "scenario.englishTeacher": "英語の先生",
+  "scenario.englishTeacher.desc": "AI英語教師が文法を修正し会話を導く",
+  "scenario.debate": "ディベート相手",
+  "scenario.debate.desc": "AIがあなたの观点に反論し論理的思考を鍛える",
+  "scenario.interpreter": "同時通訳",
+  "scenario.interpreter.desc": "リアルタイムで中日相互翻訳",
 
   // Video indicators
   "video.observing": "👁️ 観察中",
@@ -63,6 +78,7 @@ export const jaJP: TranslationMap = {
   "chat.userLabel": "あなた",
   "chat.input.placeholder": "メッセージを入力...",
   "chat.send": "送信",
+  "chat.scenarioSwitched": "{name} モードに切り替えました",
 
   // Session messages
   "session.changeDetected": "👁️ シーン変化を検出",

frontend/src/lib/i18n/zh-CN.ts

@@ -26,6 +26,21 @@ export const zhCN: TranslationMap = {
   "settings.detail.high": "高",
   "settings.language": "语言",
   "settings.language.desc": "交互语言偏好",
+  "settings.scenario": "对话情景",
+  "settings.scenario.desc": "选择 AI 扮演的角色",
+
+  // Scenarios
+  "scenario.choose": "选择对话情景",
+  "scenario.freeChat": "自由对话",
+  "scenario.freeChat.desc": "AI 视觉助手，自由聊天",
+  "scenario.interviewer": "模拟面试官",
+  "scenario.interviewer.desc": "AI 扮演面试官，进行模拟面试",
+  "scenario.englishTeacher": "英语老师",
+  "scenario.englishTeacher.desc": "AI 英语外教，纠正语法并引导对话",
+  "scenario.debate": "辩论对手",
+  "scenario.debate.desc": "AI 反驳你的观点，锻炼逻辑思维",
+  "scenario.interpreter": "同声翻译",
+  "scenario.interpreter.desc": "实时中英互译，口语化翻译",
 
   // Video indicators
   "video.observing": "👁️ 观察中",
@@ -63,6 +78,7 @@ export const zhCN: TranslationMap = {
   "chat.userLabel": "你",
   "chat.input.placeholder": "输入文字对话...",
   "chat.send": "发送",
+  "chat.scenarioSwitched": "已切换到 {name} 模式",
 
   // Session messages
   "session.changeDetected": "👁️ 画面变化检测",

frontend/src/lib/scenarios.ts

@@ -0,0 +1,47 @@
+// ============================================================
+// scenarios — 对话情景定义
+// 职责：定义预置情景的展示数据和交互行为
+// 注意：system prompt 由后端 scenarios.go 管理，此处仅定义 UI 展示数据
+// ============================================================
+
+export interface Scenario {
+  id: string;
+  icon: string;
+  nameKey: string;       // i18n key
+  descKey: string;       // i18n key
+  defaultLanguage?: string;  // 可选：切换情景时自动设置的语言
+}
+
+export const scenarios: Scenario[] = [
+  {
+    id: "free_chat",
+    icon: "💬",
+    nameKey: "scenario.freeChat",
+    descKey: "scenario.freeChat.desc",
+  },
+  {
+    id: "interviewer",
+    icon: "🎯",
+    nameKey: "scenario.interviewer",
+    descKey: "scenario.interviewer.desc",
+  },
+  {
+    id: "english_teacher",
+    icon: "📚",
+    nameKey: "scenario.englishTeacher",
+    descKey: "scenario.englishTeacher.desc",
+    defaultLanguage: "en-US",
+  },
+  {
+    id: "debate",
+    icon: "⚔️",
+    nameKey: "scenario.debate",
+    descKey: "scenario.debate.desc",
+  },
+  {
+    id: "interpreter",
+    icon: "🌐",
+    nameKey: "scenario.interpreter",
+    descKey: "scenario.interpreter.desc",
+  },
+];

frontend/src/lib/storage.ts

@@ -15,6 +15,7 @@ const DEFAULT_CONFIG: SessionConfig = {
   ttsEnabled: true,
   detailLevel: "low",
   language: "zh-CN",
+  scenario: "free_chat",
 };
 
 /** 加载配置，无存储时返回默认值 */

frontend/src/types/index.ts

@@ -9,6 +9,7 @@ export interface SessionConfig {
   ttsEnabled: boolean;
   detailLevel: "low" | "high";
   language: string;
+  scenario: string;    // 情景 ID，如 "free_chat"、"interviewer"
 }
 
 export type Theme = "dark" | "light";
@@ -32,7 +33,7 @@ export interface SessionSummary {
 // ---- 聊天消息 ----
 
 export interface ChatMessage {
-  role: "user" | "assistant";
+  role: "user" | "assistant" | "system";
   content: string;
   imageUrl?: string;
   timestamp: number;