diff --git a/Docs/api-client.md b/Docs/api-client.md
index cd030d2..6c9eed9 100644
--- a/Docs/api-client.md
+++ b/Docs/api-client.md
@@ -23,7 +23,7 @@
 |---|------|------|------|:---:|------|
 | 1 | `/api/v1/auth/login` | POST | 否 | ✅ | `{username,password}` → `{data:{token,expiresAt,role}}`（24h，role=owner） |
 | 2 | `/api/v1/health` | GET | 否 | ✅ | 健康检查 `{data:{status:"ok"}}` |
-| 3 | `/api/v1/chat` | POST | JWT | ✅ | `{text,image?,deviceId?,stream?}` → `{data:{reply}}`；`stream:true` 时经 WS 触发流式。`image` 为 base64 data: URI 或 http(s) URL，入视觉路由（design/06）——**真视觉需配 `LLM_VISION_MODEL`/凭据，无凭据时降级为主模型直接看图或视觉·OCR 工具文本描述**；`deviceId` 为**客户端生成的具体端标识**（design/16 §4.5，如 `web:chrome:a1b2c3`，可选），落库到消息、便于主人知道从哪个端发来。**会话编排（design/15）**：非流式且该会话「正忙」时**不阻塞**，返回 `202` `{data:{queued:true,queueDepth}}`（稍后按上下文续接）；待处理队列满时返回 `409` `{error:{code:"chat_busy"}}` |
+| 3 | `/api/v1/chat` | POST | JWT | ✅ | `{text,image?,deviceId?,mode?,stream?}` → `{data:{reply}}`；`stream:true` 时经 WS 触发流式。`image` 为 base64 data: URI 或 http(s) URL，入视觉路由（design/06）——**真视觉需配 `LLM_VISION_MODEL`/凭据，无凭据时降级为主模型直接看图或视觉·OCR 工具文本描述**；`deviceId` 为**客户端生成的具体端标识**（design/16 §4.5，如 `web:chrome:a1b2c3`，可选），落库到消息、便于主人知道从哪个端发来；`mode` 为**行为模式**（design/01 §3 / design/16 §5.1，如 `chat`/`code`/`home`/`docs`/…，可选），随该轮次落库——IM 恒 `chat`、缺省回落 `chat`，供前端按模式渲染气泡（仅 `chat` 才解析 `<p>` 拆气泡）。**会话编排（design/15）**：非流式且该会话「正忙」时**不阻塞**，返回 `202` `{data:{queued:true,queueDepth}}`（稍后按上下文续接）；待处理队列满时返回 `409` `{error:{code:"chat_busy"}}` |
 | 4 | `/api/v1/sessions` | GET | JWT | ✅ | `{data:[session...]}`。**会话持久化（design/16）**：注入 HistoryStore 后返回持久化会话元数据 `{data:[{id,type("main"|"sub"),title?,createdAt}]}`（主会话 `id="web"` 恒在首位，次级 `web:<uuid>`）；未注入时退化回渠道会话列表 |
 | 5 | `/api/v1/sessions` | POST | JWT(owner/admin) | ✅ | **新建次级会话** → `201 {data:{sessionId}}`（`sessionId="web:<uuid>"`）；未注入 HistoryStore 回 `501 not_implemented` |
 | 6 | `/api/v1/sessions/{id}/messages` | GET | JWT(owner/admin) | ✅ | **热分页拉历史**：`?limit=&before=&platform=` 默认 `limit=50`（上限 200）、`before`=上一页最旧 `createdAt`（毫秒），按时间倒序 `{data:[{id,sessionId,role,content,mode?,mood?,image?,thinking?,platform?,deviceId?,senderName?,createdAt}]}`；`platform` 为**可选**来源平台过滤（design/16 §4.4）——Web 端不传（=全量共享主会话），IM 适配器传**本平台**（如 `telegram`）只拉本渠道消息；`deviceId` 为**客户端具体端标识**（design/16 §4.5，如 `web:chrome:a1b2c3` / `weixin-ilink:conf0:wx_uid`）；`senderName` 为**第三方发送者昵称**（design/16 §4.6，群聊/陌生人私聊消息带，主人私聊为空，`omitempty`）；非法 `limit`/`before` 回 `400`；未注入 HistoryStore 回 `501` |
@@ -204,6 +204,7 @@
 - 语音：上行 `voice_input`（base64 音频或已转写 text），下行 `voice_output`（合成音频 base64 + text）。
 
 ## 5. 变更记录
+- `v0.20`（**A3 消息 mode 落库**）：`POST /api/v1/chat` 与 `ws.chat` 上行新增**可选 `mode`**（行为模式，design/01 §3 / design/16 §5.1）。后端把每条持久化消息的 `Mode` **真实写入**（IM 路径恒 `chat`；Web 路径经 ctx 透传本轮 `mode`，缺省回落 `chat`；恢复/续接路径沿用发起轮次的 `mode`），消息 DTO、`message_persisted`、`channel_persisted` 的 `mode` 不再恒空，供前端按模式渲染气泡（**仅 `chat` 解析 `<p>` 拆气泡**，其它模式原样整条）。
 - `v0.19`（**百炼声音复刻 create_voice + TTS instruction 情绪驱动，主 TTS 用昔涟复刻音色**）：`POST /api/v1/audio/voice-clone`（**新增**，owner-only + 审计，body `{url:"<公网参考音频URL>", prefix?}` → `{data:{voiceId}}`）——走后端 `voice.DashscopeCloner`（百炼 `voice-enrollment` create_voice，`POST {base}/services/audio/tts/customization`，`input{action:create_voice, target_model:VOICE_TTS_MODEL, prefix, url}`，**只收公网 URL 不收 base64**，返回 `output.voice_id`；**URL 不打日志不写审计**）。`POST /api/v1/audio/speech` 新增**可选 `instruction`**（per-request 情绪/语气指令，如 `"语气开朗俏皮，像女朋友撒娇"`），经 ctx 透传给 TTS adapter；**只对复刻/设计音色生效**（`cosyvoice-v3-flash` 复刻音色可任意指令；系统音色 `longxiaochun_v3` 需固定格式，服务端 `canInstruct` 判定后**永不发送**）。config 新增 `VOICE_TTS_INSTRUCTION`（默认 `""`）、`VOICE_CLONE_PREFIX`（默认 `cyrene`，≤10 字母/数字）；`voice.Chain`/`voice.Service` 新增 `CloneVoice`，`VoiceCloner` 接口（cloud rung 提供；未配 cloud 回 `voice_unavailable`）。**⚠️ 真建昔涟音色仍待主人提供公网参考音频 URL（当前无）**，且 CosyVoice 声音复刻仅华北2北京地域（确认 key 地域）；TTS instruction 用现有复刻音色或先仅单测请求体，避免改系统音色行为。
 - `v0.18`（**后端语音接通阿里百炼 STT + TTS 主链路**）：`POST /api/v1/audio/transcribe`（**新增**，owner + 审计，body `{audio,format?,deviceId?}` → `{data:{text}}`，走 STT）；`POST /api/v1/audio/speech`（**新增**，owner + 审计，body `{text,voice?,format?}` → 音频字节 `audio/<format>`，走 TTS）——**REST 语音源**，原生/移动端经它绕开 WS 4KB 帧限上传/获取音频；WS `voice_input` 上行新增 **`deviceId`**（随语音轮次落库，design/16 §4.5）。后端 `internal/runtime/multimodal/voice` 的 cloud rung 由空 endpoint stub 改为**真实百炼 adapter**：STT `qwen-audio-3.0-asr-flash`（base64 原始字节→文本）、TTS `cosyvoice-v3-flash`（按 `voice_id` 合成，取非流式返回的 24h 音频 URL 下载字节）。**实测**（`DASHSCOPE_API_KEY` 实跑）：TTS「你好，我是昔涟」→ 106124 字节 wav；把该 wav 喂给 STT → 文本「你好，我是西联。」（TTS 发音把「昔涟」读得近似「西联」，STT 识别正确）；语音链 (cloud→…→silent) 返回真实字节/文本。**已实测修正**：`cosyvoice-v3.5-plus`/`longxiaochun`（v2 音色）走 HTTP `SpeechSynthesizer` 会回 `418`（引擎拒绝），改用 **`cosyvoice-v3-flash` + `longxiaochun_v3`**（v3 音色，各模型音色不可混用）。**声音复刻（响昔涟音色）仍待**：需参考音频（公网 URL）在百炼建自定义音色后把 `voice_id` 填入 `VOICE_TTS_VOICE_ID`（本项目不做 create_voice）。config 新增 `DASHSCOPE_BASE_URL`/`VOICE_STT_\*`/`VOICE_TTS_\*`（`VOICE_TTS_SAMPLE_RATE` 默认 24000）。
 - `v0.17`（系统设置安全与存储：吊销全部 API key / 轮换 JWT 密钥 / 备份 / 恢复，design/11 §4 + design/10 §3 模块14）：新增 `POST /api/v1/admin/system/{revoke-keys,rotate-jwt,backup,restore}`（均 **owner-only** + 审计）。`revoke-keys` 走 `auth.APIKey.RevokeAll()`（清空 key 表，返回 `{revoked:n}`）；`rotate-jwt` 走 `auth.JWTService.RotateSecret`（≥32 位，**新密钥不回显/不落日志**，现有 token 立即失效）；`backup` 用 SQLite `VACUUM INTO` 快照到 `<dataDir>/backup-<ts>.db`（含已提交 WAL 内容）返回 `{path,size}`；`restore` 先校验路径在 dataDir 内（**`filepath.Rel` 防路径穿越**，逃逸回 `400`）→ **先自动备份当前 DB** → 替换 DB 文件 → 返回 `{restored:true,backup,note:"需重启后生效"}`（运行进程持有 DB 句柄，热替换需重启可见）。gateway 新增 `Deps.DatabasePath`（composition root 传入实际打开的 SQLite 路径）。`编辑环境变量 / 重启服务 / 检查更新` 仍为后置，未实现、不伪造。
diff --git a/internal/services/channelbridge/channelbridge_test.go b/internal/services/channelbridge/channelbridge_test.go
index c239c60..c1fd9d3 100644
--- a/internal/services/channelbridge/channelbridge_test.go
+++ b/internal/services/channelbridge/channelbridge_test.go
@@ -315,14 +315,17 @@ func TestOwnerPrivatePersistsToMainSessionWithPlatform(t *testing.T) {
 	if len(recs) != 2 {
 		t.Fatalf("appends = %d, want 2 (user + assistant)", len(recs))
 	}
-	// Both land on the main web session and carry the channel platform + adapter.
+	// Both land on the main web session and carry the channel platform + adapter,
+	// and IM messages are always persisted in chat mode (design/16 §5.1).
 	if recs[0].SessionID != history.MainSessionID || recs[0].Role != history.RoleUser ||
-		recs[0].Content != "hello" || recs[0].Platform != "telegram" || recs[0].AdapterID != "telegram" {
-		t.Fatalf("user record = %+v, want web/telegram/hello/telegram", recs[0])
+		recs[0].Content != "hello" || recs[0].Platform != "telegram" || recs[0].AdapterID != "telegram" ||
+		recs[0].Mode != "chat" {
+		t.Fatalf("user record = %+v, want web/telegram/hello/telegram/chat", recs[0])
 	}
 	if recs[1].SessionID != history.MainSessionID || recs[1].Role != history.RoleAssistant ||
-		recs[1].Content != "微信回复" || recs[1].Platform != "telegram" || recs[1].AdapterID != "telegram" {
-		t.Fatalf("assistant record = %+v, want web/telegram/微信回复/telegram", recs[1])
+		recs[1].Content != "微信回复" || recs[1].Platform != "telegram" || recs[1].AdapterID != "telegram" ||
+		recs[1].Mode != "chat" {
+		t.Fatalf("assistant record = %+v, want web/telegram/微信回复/telegram/chat", recs[1])
 	}
 	// Every persisted message was handed to the broadcast hook.
 	if len(persisted) != 2 {
@@ -414,6 +417,10 @@ func TestGroupMessageNotPersistedToMainSession(t *testing.T) {
 		if rec.Platform != "telegram" {
 			t.Fatalf("record[%d] Platform = %q, want telegram", i, rec.Platform)
 		}
+		// Isolated IM messages are still chat-mode (design/16 §5.1).
+		if rec.Mode != "chat" {
+			t.Fatalf("record[%d] Mode = %q, want chat", i, rec.Mode)
+		}
 	}
 	if chat.sessionID != "sess-g" {
 		t.Fatalf("group loop session id = %q, want sess-g", chat.sessionID)
diff --git a/internal/services/channelbridge/persist.go b/internal/services/channelbridge/persist.go
index a45e791..907c61d 100644
--- a/internal/services/channelbridge/persist.go
+++ b/internal/services/channelbridge/persist.go
@@ -14,6 +14,10 @@ import (
 // without a refresh. Kept separate from channelbridge.go so the bridge's inbound
 // pipeline file stays under the module size bound.
 
+// modeChat is the behavior mode written for every IM-persisted message: IM carries
+// chat text alone (design/02 §1 单向回流), so no other mode ever applies there.
+const modeChat = "chat"
+
 // SetOnPersisted wires (or replaces) the transport hook called after an
 // owner-private message is persisted into the main web session. The gateway is
 // built after the bridge in the composition root, so the hook is attached post-New
@@ -60,7 +64,7 @@ func (b *Bridge) persistToMain(ctx context.Context, role, content, platform, dev
 		return
 	}
 	full, err := b.history.AppendFull(ctx, history.Message{
-		SessionID: history.MainSessionID, Role: role, Content: content, Platform: platform, DeviceID: deviceID, AdapterID: adapterID,
+		SessionID: history.MainSessionID, Role: role, Content: content, Platform: platform, DeviceID: deviceID, AdapterID: adapterID, Mode: modeChat,
 	})
 	if err != nil {
 		b.log.Warn("persist main session", "err", err, "role", role, "platform", platform, "device_id", deviceID, "adapter", adapterID)
@@ -85,7 +89,7 @@ func (b *Bridge) persistIsolated(ctx context.Context, role, content, deviceID st
 	}
 	full, err := b.history.AppendFull(ctx, history.Message{
 		SessionID: sess.SessionID, Role: role, Content: content, Platform: platform,
-		DeviceID: deviceID, SenderName: senderName, AdapterID: adapterID,
+		DeviceID: deviceID, SenderName: senderName, AdapterID: adapterID, Mode: modeChat,
 	})
 	if err != nil {
 		b.log.Warn("persist isolated session", "err", err, "role", role,
diff --git a/internal/services/gateway/extra_test.go b/internal/services/gateway/extra_test.go
index ae0c863..b35f04a 100644
--- a/internal/services/gateway/extra_test.go
+++ b/internal/services/gateway/extra_test.go
@@ -348,6 +348,33 @@ func TestChatStreamMode(t *testing.T) {
 	}
 }
 
+func TestChatRequestPersistsMode(t *testing.T) {
+	t.Parallel()
+	hist := &fakeHistory{}
+	_, ts, jwt := buildEnv(t, cfgDefault(), Deps{
+		Loop:    &stubRunner{res: &loop.Result{Text: "回复", StopReason: "stop"}},
+		History: hist,
+	})
+	tok := signAny(t, jwt, "acct", auth.RoleOwner)
+	// The REST body carries the client's behavior mode (design/16 §5.1); the
+	// orchestrator persists both the user turn and the assistant reply under it.
+	resp, body := doReq(t, http.MethodPost, ts.URL+"/api/v1/chat",
+		map[string]any{"sessionId": "web", "text": "改代码", "mode": "code"}, tok)
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("status = %d, want 200 (body=%s)", resp.StatusCode, body)
+	}
+	recs := hist.records()
+	if len(recs) != 2 {
+		t.Fatalf("appends = %d, want 2 (user + assistant)", len(recs))
+	}
+	if recs[0].Role != history.RoleUser || recs[0].Mode != "code" {
+		t.Fatalf("user record = %+v, want role=user mode=code", recs[0])
+	}
+	if recs[1].Role != history.RoleAssistant || recs[1].Mode != "code" {
+		t.Fatalf("assistant record = %+v, want role=assistant mode=code", recs[1])
+	}
+}
+
 func TestChatDefaultsSessionToWeb(t *testing.T) {
 	t.Parallel()
 	cr := &captureRunner{res: &loop.Result{Text: "ok", Steps: 1, StopReason: "stop"}}
@@ -882,6 +909,37 @@ func TestHubStreamChat(t *testing.T) {
 	}
 }
 
+func TestHubStreamChatPersistsMode(t *testing.T) {
+	t.Parallel()
+	hist := &fakeHistory{}
+	hb := newTestHub(&stubRunner{res: &loop.Result{Text: "hi", StopReason: "stop"}}, nil)
+	hb.orchestrator = NewOrchestrator(OrchestratorOptions{
+		Run: func(context.Context, string, []model.Message, loop.SessionEnv) (*loop.Result, error) {
+			return &loop.Result{Text: "hi", StopReason: "stop"}, nil
+		},
+		History: hist,
+	})
+	// The ws.chat payload carries the client's behavior mode (design/16 §5.1);
+	// streamChat threads it into the orchestrator, which persists both the user
+	// turn and the assistant reply under it.
+	hb.streamChat(context.Background(), map[string]any{"sessionId": "web", "text": "改代码", "mode": "code"})
+
+	deadline := time.Now().Add(2 * time.Second)
+	for time.Now().Before(deadline) && len(hist.records()) < 2 {
+		time.Sleep(time.Millisecond)
+	}
+	recs := hist.records()
+	if len(recs) != 2 {
+		t.Fatalf("appends = %d, want 2 (user + assistant)", len(recs))
+	}
+	if recs[0].Role != history.RoleUser || recs[0].Mode != "code" {
+		t.Fatalf("user record = %+v, want role=user mode=code", recs[0])
+	}
+	if recs[1].Role != history.RoleAssistant || recs[1].Mode != "code" {
+		t.Fatalf("assistant record = %+v, want role=assistant mode=code", recs[1])
+	}
+}
+
 func TestHubBroadcastStream(t *testing.T) {
 	t.Parallel()
 	hb := newTestHub(nil, nil)
diff --git a/internal/services/gateway/rest.go b/internal/services/gateway/rest.go
index f3532c5..d0d1aa0 100644
--- a/internal/services/gateway/rest.go
+++ b/internal/services/gateway/rest.go
@@ -72,11 +72,15 @@ type loginResponse struct {
 // loop routes it through the vision/OCR tool or the main model (design/06 §0).
 // DeviceID is the client-produced identifier of the sending browser/device
 // (design/16 §4.5), e.g. "web:chrome:a1b2c3"; it is optional and persisted as-is.
+// Mode is the behavior mode the client sent the turn in (design/01 §3, design/16
+// §5.1); it is optional and persisted per message for bubble rendering, falling
+// back to "chat" when omitted.
 type chatRequest struct {
 	SessionID string `json:"sessionId"`
 	Text      string `json:"text"`
 	Image     string `json:"image,omitempty"`
 	DeviceID  string `json:"deviceId,omitempty"`
+	Mode      string `json:"mode,omitempty"`
 	Stream    bool   `json:"stream"`
 }
 
@@ -129,7 +133,7 @@ func (s *Server) handleChat(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	if req.Stream {
-		s.publishChatStream(r.Context(), req.SessionID, req.Text, req.Image, req.DeviceID)
+		s.publishChatStream(r.Context(), req.SessionID, req.Text, req.Image, req.DeviceID, req.Mode)
 		writeJSON(w, http.StatusOK, map[string]any{"stream": true})
 		return
 	}
@@ -144,7 +148,7 @@ func (s *Server) handleChat(w http.ResponseWriter, r *http.Request) {
 	// it binds the full-access env: memory read+write, unchanged behavior.
 	msgs := userChatMessages(req.Text, req.Image)
 	if s.hub.orchestrator != nil {
-		sr, res := s.hub.orchestrator.SubmitSync(withDeviceID(r.Context(), req.DeviceID), req.SessionID, msgs, loop.OwnerEnv())
+		sr, res := s.hub.orchestrator.SubmitSync(withMode(withDeviceID(r.Context(), req.DeviceID), req.Mode), req.SessionID, msgs, loop.OwnerEnv())
 		if !sr.Accepted {
 			if sr.PendingFull {
 				writeError(w, apperr.Wrap(apperr.ErrConflict, "chat_busy", "会话正忙，待处理消息已满"))
diff --git a/internal/services/gateway/session_orchestrator.go b/internal/services/gateway/session_orchestrator.go
index 7a73f53..833a27a 100644
--- a/internal/services/gateway/session_orchestrator.go
+++ b/internal/services/gateway/session_orchestrator.go
@@ -130,11 +130,14 @@ type sessionState struct {
 // pendingMsg is one queued user turn. It carries its own env so a resume runs
 // under the same memory-isolation boundary the message arrived with, plus the
 // client deviceID of the originating turn (design/16 §4.5) so the resumed
-// assistant reply is tagged with the same client that sent the message.
+// assistant reply is tagged with the same client that sent the message, and the
+// turn's behavior mode (design/16 §5.1) so the resumed reply is persisted under
+// the same mode as the user message that started it.
 type pendingMsg struct {
 	messages []model.Message
 	env      loop.SessionEnv
 	deviceID string
+	mode     string
 	at       time.Time
 }
 
@@ -219,6 +222,7 @@ func (o *Orchestrator) submitInternal(ctx context.Context, sessionID string, mes
 		o.states[sessionID] = st
 	}
 	deviceID := deviceIDFrom(ctx)
+	msgMode := modeFrom(ctx)
 	if st.mode != ModeIdle {
 		if len(st.pending) >= o.maxPending {
 			mode := st.mode
@@ -226,11 +230,11 @@ func (o *Orchestrator) submitInternal(ctx context.Context, sessionID string, mes
 			o.emitState(sessionID, EventPendingFull, map[string]any{"sessionId": sessionID, "mode": mode, "max": o.maxPending})
 			return SubmitResult{PendingFull: true}, nil
 		}
-		st.pending = append(st.pending, pendingMsg{messages: messages, env: env, deviceID: deviceID, at: time.Now()})
+		st.pending = append(st.pending, pendingMsg{messages: messages, env: env, deviceID: deviceID, mode: msgMode, at: time.Now()})
 		depth := len(st.pending)
 		mode := st.mode
 		o.mu.Unlock()
-		o.persistUserMessages(ctx, sessionID, messages, deviceID)
+		o.persistUserMessages(ctx, sessionID, messages, deviceID, msgMode)
 		o.emitState(sessionID, EventPendingAck, map[string]any{"sessionId": sessionID, "mode": mode, "queueDepth": depth})
 		return SubmitResult{Accepted: true, Pending: true, QueueDepth: depth}, nil
 	}
@@ -244,32 +248,32 @@ func (o *Orchestrator) submitInternal(ctx context.Context, sessionID string, mes
 	o.mu.Unlock()
 
 	o.emitState(sessionID, EventSessionBusy, map[string]any{"sessionId": sessionID, "mode": ModeThinking})
-	o.persistUserMessages(ctx, sessionID, messages, deviceID)
+	o.persistUserMessages(ctx, sessionID, messages, deviceID, msgMode)
 
 	if sync {
 		res, err := o.run(runCtx, sessionID, messages, env)
 		if err != nil {
 			o.log.Error("orchestrator turn", "err", err, "session", sessionID)
 		}
-		_ = o.completeTurn(sessionID, gen, res, err, deviceID)
+		_ = o.completeTurn(sessionID, gen, res, err, deviceID, msgMode)
 		return SubmitResult{Accepted: true, Immediate: true, Err: err}, res
 	}
 
-	go o.goTurn(sessionID, gen, messages, env, runCtx, cancel, deviceID)
+	go o.goTurn(sessionID, gen, messages, env, runCtx, cancel, deviceID, msgMode)
 	return SubmitResult{Accepted: true, Immediate: true}, nil
 }
 
 // goTurn runs a single turn on a background goroutine and, when it finishes,
 // hands the outcome to completeTurn so the orchestrator can resume the queue.
 // deviceID tags the persistent assistant reply with the client that sent the turn
-// (design/16 §4.5).
-func (o *Orchestrator) goTurn(sessionID string, gen uint64, messages []model.Message, env loop.SessionEnv, ctx context.Context, cancel context.CancelFunc, deviceID string) {
+// (design/16 §4.5) and mode with the turn's behavior mode (design/16 §5.1).
+func (o *Orchestrator) goTurn(sessionID string, gen uint64, messages []model.Message, env loop.SessionEnv, ctx context.Context, cancel context.CancelFunc, deviceID, mode string) {
 	defer cancel()
 	res, err := o.run(ctx, sessionID, messages, env)
 	if err != nil && ctx.Err() == nil {
 		o.log.Error("orchestrator turn", "err", err, "session", sessionID)
 	}
-	_ = o.completeTurn(sessionID, gen, res, err, deviceID)
+	_ = o.completeTurn(sessionID, gen, res, err, deviceID, mode)
 }
 
 // completeTurn runs after a turn settles (either it finished, errored, or was
@@ -278,9 +282,10 @@ func (o *Orchestrator) goTurn(sessionID string, gen uint64, messages []model.Mes
 // message "remembers" the prior context instead of starting from a blank slate
 // (design/15 §2.2: incremental, not full replay). A stale generation (an
 // interrupt or a newer top-level turn superseded this one) is a no-op.
-// deviceID is the originating turn's client id, used to tag the persisted reply.
-func (o *Orchestrator) completeTurn(sessionID string, gen uint64, res *loop.Result, runErr error, deviceID string) error {
-	o.persistAssistantReply(sessionID, res, deviceID)
+// deviceID is the originating turn's client id and mode its behavior mode, both
+// used to tag the persisted reply (design/16 §4.5, §5.1).
+func (o *Orchestrator) completeTurn(sessionID string, gen uint64, res *loop.Result, runErr error, deviceID, mode string) error {
+	o.persistAssistantReply(sessionID, res, deviceID, mode)
 	o.mu.Lock()
 	st := o.states[sessionID]
 	if st == nil || st.gen != gen {
@@ -305,7 +310,7 @@ func (o *Orchestrator) completeTurn(sessionID string, gen uint64, res *loop.Resu
 		o.mu.Unlock()
 
 		o.emitState(sessionID, EventPendingDrain, map[string]any{"sessionId": sessionID, "mode": ModeThinking, "queueDepth": depth})
-		go o.goTurn(sessionID, gen, resume, env, runCtx, cancel, next.deviceID)
+		go o.goTurn(sessionID, gen, resume, env, runCtx, cancel, next.deviceID, next.mode)
 		return nil
 	}
 
diff --git a/internal/services/gateway/session_orchestrator_test.go b/internal/services/gateway/session_orchestrator_test.go
index ed6daa8..3e077c3 100644
--- a/internal/services/gateway/session_orchestrator_test.go
+++ b/internal/services/gateway/session_orchestrator_test.go
@@ -240,6 +240,45 @@ func TestSubmitPersistsUserAndAssistant(t *testing.T) {
 	if recs[1].SessionID != "web" || recs[1].Role != history.RoleAssistant || recs[1].Content == "" {
 		t.Fatalf("assistant record = %+v", recs[1])
 	}
+	// No mode on the ctx → both fall back to "chat" (design/16 §5.1).
+	for i, rec := range recs {
+		if rec.Mode != "chat" {
+			t.Fatalf("record[%d] Mode = %q, want chat fallback", i, rec.Mode)
+		}
+	}
+}
+
+func TestSubmitPersistsMessageMode(t *testing.T) {
+	t.Parallel()
+	run := newGatedRunner(1)
+	hist := &fakeHistory{}
+	o := NewOrchestrator(OrchestratorOptions{
+		Run:     run.Run,
+		Log:     slog.Default(),
+		History: hist,
+	})
+	run.tickets <- struct{}{}
+	// The HTTP/WS boundary threads the client's behavior mode through ctx
+	// (design/01 §3, design/16 §5.1); both the user turn and the assistant reply
+	// must be persisted under that mode.
+	ctx := withMode(context.Background(), "code")
+	sr, res := o.SubmitSync(ctx, "web", []model.Message{userMsg("改代码")}, loop.OwnerEnv())
+	if !sr.Accepted || !sr.Immediate {
+		t.Fatalf("submit = %+v, want Accepted+Immediate", sr)
+	}
+	if res == nil {
+		t.Fatal("sync result is nil")
+	}
+	recs := hist.records()
+	if len(recs) != 2 {
+		t.Fatalf("appends = %d, want 2 (user + assistant)", len(recs))
+	}
+	if recs[0].Mode != "code" {
+		t.Fatalf("user Mode = %q, want code", recs[0].Mode)
+	}
+	if recs[1].Mode != "code" {
+		t.Fatalf("assistant Mode = %q, want code", recs[1].Mode)
+	}
 }
 
 func TestSubmitPersistsDeviceID(t *testing.T) {
diff --git a/internal/services/gateway/session_persist.go b/internal/services/gateway/session_persist.go
index df5879f..08bcbf0 100644
--- a/internal/services/gateway/session_persist.go
+++ b/internal/services/gateway/session_persist.go
@@ -13,14 +13,47 @@ import (
 // turn settles. Both are silent no-ops when no history store is wired, so the
 // orchestrator runs unchanged without a store (tests / an unwired gateway).
 
+// modeChat is the behavior mode persisted when a turn carries none (design/01 §3,
+// design/16 §5.1). It is also the only mode the IM paths ever write, because IM
+// carries chat text alone.
+const modeChat = "chat"
+
+// modeOrDefault returns mode, or modeChat when the caller supplied none, so a
+// persisted message never carries an empty behavior mode (design/16 §5.1).
+func modeOrDefault(mode string) string {
+	if mode == "" {
+		return modeChat
+	}
+	return mode
+}
+
+// messageModeContextKey is the context key carrying a turn's behavior mode
+// (design/01 §3, design/16 §5.1) from the HTTP/WS boundary into the orchestrator's
+// persistence, so each persisted message is tagged with the mode it was sent in.
+type messageModeContextKey struct{}
+
+// withMode returns a context carrying mode so the orchestrator can tag the
+// persisted user message and assistant reply. An empty mode is a no-op (the
+// persistence layer falls back to modeChat).
+func withMode(ctx context.Context, mode string) context.Context {
+	return context.WithValue(ctx, messageModeContextKey{}, mode)
+}
+
+// modeFrom returns the behavior mode carried by ctx, or "" when none was set.
+func modeFrom(ctx context.Context) string {
+	v, _ := ctx.Value(messageModeContextKey{}).(string)
+	return v
+}
+
 // persistUserMessages writes each RoleUser message of a submitted turn to the
 // history store so the raw user stream is durable before the turn resolves, then
 // notifies the transport so every browser of the same account can append it
 // without a manual refresh (design/16 §3.3, §4.2). deviceID tags the message with
-// the sending client (design/16 §4.5). It is a no-op when no history store is
-// wired. Rejected turns (empty, pending-full) never reach it, so nothing vacuous
-// is persisted.
-func (o *Orchestrator) persistUserMessages(ctx context.Context, sessionID string, messages []model.Message, deviceID string) {
+// the sending client (design/16 §4.5) and mode is the behavior mode the turn was
+// sent in (design/16 §5.1), falling back to modeChat when empty. It is a no-op
+// when no history store is wired. Rejected turns (empty, pending-full) never
+// reach it, so nothing vacuous is persisted.
+func (o *Orchestrator) persistUserMessages(ctx context.Context, sessionID string, messages []model.Message, deviceID, mode string) {
 	if o.history == nil {
 		return
 	}
@@ -32,7 +65,7 @@ func (o *Orchestrator) persistUserMessages(ctx context.Context, sessionID string
 		if text == "" && image == "" {
 			continue
 		}
-		full, err := o.history.AppendFull(ctx, history.Message{SessionID: sessionID, Role: history.RoleUser, Content: text, Image: image, DeviceID: deviceID})
+		full, err := o.history.AppendFull(ctx, history.Message{SessionID: sessionID, Role: history.RoleUser, Content: text, Image: image, DeviceID: deviceID, Mode: modeOrDefault(mode)})
 		if err != nil {
 			o.log.Error("orchestrator persist user", "err", err, "session", sessionID, "device_id", deviceID)
 			continue
@@ -43,15 +76,16 @@ func (o *Orchestrator) persistUserMessages(ctx context.Context, sessionID string
 
 // persistAssistantReply writes the final assistant text of a settled turn to the
 // history store, then notifies the transport (design/16 §3.3, §4.2). deviceID tags
-// the reply with the client that sent the turn (design/16 §4.5). It is a no-op
-// when no history store is wired or the turn produced no text (interrupted/errored
-// turns leave res nil). The write runs under a fresh background context so a
-// canceled turn context never aborts it.
-func (o *Orchestrator) persistAssistantReply(sessionID string, res *loop.Result, deviceID string) {
+// the reply with the client that sent the turn (design/16 §4.5) and mode is the
+// behavior mode of that turn (design/16 §5.1), falling back to modeChat when
+// empty. It is a no-op when no history store is wired or the turn produced no text
+// (interrupted/errored turns leave res nil). The write runs under a fresh
+// background context so a canceled turn context never aborts it.
+func (o *Orchestrator) persistAssistantReply(sessionID string, res *loop.Result, deviceID, mode string) {
 	if o.history == nil || res == nil || res.Text == "" {
 		return
 	}
-	full, err := o.history.AppendFull(context.Background(), history.Message{SessionID: sessionID, Role: history.RoleAssistant, Content: res.Text, DeviceID: deviceID})
+	full, err := o.history.AppendFull(context.Background(), history.Message{SessionID: sessionID, Role: history.RoleAssistant, Content: res.Text, DeviceID: deviceID, Mode: modeOrDefault(mode)})
 	if err != nil {
 		o.log.Error("orchestrator persist assistant", "err", err, "session", sessionID, "device_id", deviceID)
 		return
diff --git a/internal/services/gateway/ws_hub.go b/internal/services/gateway/ws_hub.go
index cc3c442..1d23bc3 100644
--- a/internal/services/gateway/ws_hub.go
+++ b/internal/services/gateway/ws_hub.go
@@ -235,9 +235,10 @@ func (h *hub) streamChat(ctx context.Context, payload any) {
 	// The Web main session is the owner's private conversation (JWT = owner), so
 	// it binds the full-access env: memory read+write, unchanged behavior.
 	msgs := userChatMessages(req.Text, req.Image)
-	// Thread the client's deviceID into the orchestrator via ctx so both the
-	// persisted user turn and the assistant reply are tagged (design/16 §4.5).
-	ctx = withDeviceID(ctx, req.DeviceID)
+	// Thread the client's deviceID and behavior mode into the orchestrator via ctx
+	// so both the persisted user turn and the assistant reply are tagged
+	// (design/16 §4.5, §5.1).
+	ctx = withMode(withDeviceID(ctx, req.DeviceID), req.Mode)
 	if h.orchestrator != nil {
 		_ = h.orchestrator.Submit(ctx, req.SessionID, msgs, loop.OwnerEnv())
 		return
@@ -312,6 +313,10 @@ type chatStreamRequest struct {
 	// (design/16 §4.5), e.g. "web:chrome:a1b2c3"; it is optional and persisted
 	// alongside the message so the agent knows which end the owner is chatting from.
 	DeviceID string `json:"deviceId,omitempty"`
+	// Mode is the behavior mode the client sent the turn in (design/01 §3,
+	// design/16 §5.1); it is optional and persisted per message, falling back to
+	// "chat" when omitted.
+	Mode string `json:"mode,omitempty"`
 }
 
 // handleWS upgrades /ws/chat after authenticating the JWT from the query token or
@@ -439,13 +444,14 @@ func (c *wsConn) enqueueJSON(ev wsEvent) {
 }
 
 // publishChatStream publishes a ws.chat streaming trigger (REST stream mode).
-// deviceID is the sending browser/device id carried on the payload so the ws.chat
-// consumer can tag the persisted turn (design/16 §4.5).
-func (s *Server) publishChatStream(ctx context.Context, sessionID, text, image, deviceID string) {
+// deviceID is the sending browser/device id and mode the behavior mode the client
+// sent the turn in, both carried on the payload so the ws.chat consumer can tag
+// the persisted turn (design/16 §4.5, §5.1).
+func (s *Server) publishChatStream(ctx context.Context, sessionID, text, image, deviceID, mode string) {
 	if s.bus == nil {
 		return
 	}
-	_ = s.bus.Publish(ctx, wsChatSubject, map[string]any{"sessionId": sessionID, "text": text, "image": image, "deviceId": deviceID})
+	_ = s.bus.Publish(ctx, wsChatSubject, map[string]any{"sessionId": sessionID, "text": text, "image": image, "deviceId": deviceID, "mode": mode})
 }
 
 // wsToken extracts the JWT from the ?token= query or the Authorization header.