diff --git a/src/stores/chat/chat-machine.actors.ts b/src/stores/chat/chat-machine.actors.ts
index c26c79c6..b09a9bc4 100644
--- a/src/stores/chat/chat-machine.actors.ts
+++ b/src/stores/chat/chat-machine.actors.ts
@@ -3,7 +3,7 @@
  *
  * 从 `chat-machine.ts` 抽出的"Actors"段：
  *   - `chatInitActor`（fromPromise，**仅**游客有意义）
- *   - `sendMessageHttpActor`（fromPromise，**已定义但**未 wire —— 消息**不**真发后端）
+ *   - `sendMessageHttpActor`（fromPromise，**已** wire —— "一次发送 = 一次返回"）
  *   - `loadMoreHistoryActor`（fromPromise）
  *   - `chatWebSocketActor`（fromCallback，长生命周期 —— **仅** userSession 期间 invoke）
  *
@@ -24,6 +24,7 @@ import {
   chatRepo,
   localMessagesToUi,
   readInitData,
+  sendResponseToUiMessage,
   type InitResult,
 } from "./chat-machine.helpers";
 import type { ChatEvent } from "./chat-events";
@@ -34,12 +35,13 @@ import type { ChatEvent } from "./chat-events";
 export const chatInitActor = fromPromise<InitResult>(async () => readInitData());
 
 /**
- * HTTP 发送消息（**已定义但未** wire —— 消息**不**真发后端）
- * - 任何 state 转移**未** invoke 此 actor
- * - 保留全链日志以便排查
+ * HTTP 发送消息（**一次发送 = 一次返回**）
+ * - 后端响应**就**是 AI 回复（`ChatSendResponse.reply: string`）
+ * - **不**再调 `getLocalMessages()`（**多此一举**）
+ * - 返回 `{ reply: UiMessage }` —— `sending.onDone` 把它**追加**到 `context.messages`
  */
 export const sendMessageHttpActor = fromPromise<
-  { messages: UiMessage[] },
+  { reply: UiMessage },
   { content: string }
 >(async ({ input, self }) => {
   console.log("[chat-machine] sendMessageHttpActor ENTRY", {
@@ -48,10 +50,6 @@ export const sendMessageHttpActor = fromPromise<
     selfId: self.id,
     selfPath: "<actor path>",
   });
-  console.warn(
-    "[chat-machine] sendMessageHttpActor invoked —— actor 已定义但**未** invoke（消息**不**真发后端）",
-    { contentLength: input.content.length, contentPreview: input.content.slice(0, 50) },
-  );
   console.log("[chat-machine] sendMessageHttpActor calling chatRepo.sendMessage");
   const result = await chatRepo.sendMessage(input.content);
   console.log("[chat-machine] sendMessageHttpActor chatRepo.sendMessage DONE", {
@@ -63,18 +61,18 @@ export const sendMessageHttpActor = fromPromise<
     throw result.error;
   }
 
-  console.log("[chat-machine] sendMessageHttpActor fetching local messages");
-  const local = await chatRepo.getLocalMessages();
-  console.log("[chat-machine] sendMessageHttpActor local messages DONE", {
-    success: local.success,
-    messagesCount: local.success && local.data ? local.data.length : 0,
+  // 一次发送 = 一次返回 —— 直接转 reply → UiMessage
+  console.log("[chat-machine] sendMessageHttpActor converting reply to UiMessage", {
+    replyLength: result.data.reply.length,
+    replyPreview: result.data.reply.slice(0, 50),
+    messageId: result.data.messageId,
+    timestamp: result.data.timestamp,
   });
-  if (Result.isOk(local) && local.data) {
-    const messages = localMessagesToUi(local.data);
-    console.log("[chat-machine] sendMessageHttpActor done", { messagesCount: messages.length });
-    return { messages };
-  }
-  return { messages: [] };
+  const reply = sendResponseToUiMessage(result.data);
+  console.log("[chat-machine] sendMessageHttpActor done", {
+    replyContentLength: reply.content.length,
+  });
+  return { reply };
 });
 
 /** 翻历史（pagination） */
diff --git a/src/stores/chat/chat-machine.helpers.ts b/src/stores/chat/chat-machine.helpers.ts
index e8fb26ad..042e304a 100644
--- a/src/stores/chat/chat-machine.helpers.ts
+++ b/src/stores/chat/chat-machine.helpers.ts
@@ -19,6 +19,8 @@ import { chatRepository } from "@/data/repositories/chat_repository";
 import type { IChatRepository } from "@/data/repositories/interfaces";
 import { ChatStorage } from "@/data/storage/chat/chat_storage";
 import { AuthStorage } from "@/data/storage/auth/auth_storage";
+import { ChatSendResponse } from "@/data/dto/chat/chat_send_response";
+import { formatDate } from "@/utils/date";
 import { Result } from "@/utils/result";
 
 // ============================================================// Constants
@@ -52,6 +54,19 @@ export function localMessagesToUi(
   }));
 }
 
+/**
+ * ChatSendResponse → UiMessage（**纯函数**）
+ * - 业务事实：后端响应**就是** AI 的回复
+ * - 用后端 `timestamp`（**不**用本地 time）—— 多设备/时区**一致**
+ */
+export function sendResponseToUiMessage(response: ChatSendResponse): UiMessage {
+  return {
+    content: response.reply,
+    isFromAI: true,
+    date: formatDate(new Date(response.timestamp)),
+  };
+}
+
 // ============================================================// Result → number 映射
 // ============================================================
 /** 日配额 Result → number（**纯函数**） */
diff --git a/src/stores/chat/chat-machine.ts b/src/stores/chat/chat-machine.ts
index 9dbb7e96..dc1b8872 100644
--- a/src/stores/chat/chat-machine.ts
+++ b/src/stores/chat/chat-machine.ts
@@ -1,13 +1,6 @@
 /**
  * Chat 状态机（XState v5）
  *
- * 原始 Dart: lib/ui/chat/bloc/chat bloc + chat state + chat event
- *
- * 本轮迁移范围：
- *   ✅ HTTP 流程（init / send message / load more history）
- *   ✅ WebSocket 长生命周期（**由** chat 机器内 fromCallback actor 管）
- *   ✅ 上下文数据（messages / quota / 标志位）
- *
  * 设计要点：
  *   - 使用 XState v5 `setup({...}).createMachine({...})` 声明式 API
  *   - HTTP 操作用 `fromPromise` actor（一次性 Promise）
@@ -27,15 +20,17 @@
  *   - `guestSession`（**parent**）：游客会话 —— **不** invoke WS
  *     - `initializing`：invoke chatInit（拉本地 + 初始化配额）
  *     - `ready`：用户聊天 + 翻历史
+ *     - `sending`：invoke sendMessageHttpActor（HTTP 发送消息）
  *     - `loadingMore`：invoke loadMoreHistory（翻历史）
  *   - `userSession`（**parent**）：非游客会话 —— **invoke WS**（持久）
  *     - `initializing`：invoke loadMoreHistory（拉服务器端首屏）
  *     - `ready`：用户聊天 + 翻历史
+ *     - `sending`：invoke sendMessageHttpActor（HTTP fallback —— WS 真发**未** wire）
  *     - `loadingMore`：invoke loadMoreHistory（翻历史）
- *   WS 在 `userSession` parent 状态 invoke —— 跨 initializing/ready/loadingMore 持续
+ *   WS 在 `userSession` parent 状态 invoke —— 跨 initializing/ready/sending/loadingMore 持续
  *
  * **消息发送路径**（**业务事实**）：
- *   - `wsConnected: true`（**仅** userSession 期间）→ **走 WS**，**不**消耗次数
+ *   - `wsConnected: true`（**仅** userSession 期间）→ **走 WS**，**不**消耗次数（**仅**配额规则）
  *   - `wsConnected: false` → **走 HTTP**，消耗次数（**仅**游客有意义 —— 非游客 0-1=max(0,-1)=0 天然 no-op）
  *   - `ChatWebSocketConnected` 事件 → `wsConnected = true`
  *   - `userSession.exit` action → `wsConnected = false`（WS actor cleanup 时**也**会跑 exit）
@@ -279,6 +274,7 @@ export const chatMachine = setup({
             ChatSendMessage: {
               actions: ["logSendMessageReceived", "appendUserMessage"],
               guard: ({ event }) => event.content.trim().length > 0,
+              target: "sending",
             },
             ChatSendImage: {
               actions: ["logSendImageReceived", "appendUserImage"],
@@ -302,6 +298,44 @@ export const chatMachine = setup({
             ChatQuotaExceeded: { actions: "incrementQuotaExceeded" },
           },
         },
+        sending: {
+          entry: ({ event }) =>
+            console.log("[chat-machine] → guestSession.sending", {
+              contentLength: event.type === "ChatSendMessage" ? event.content.length : 0,
+              contentPreview: event.type === "ChatSendMessage" ? event.content.slice(0, 50) : "",
+            }),
+          invoke: {
+            src: "sendMessageHttp",
+            input: ({ event }) => ({
+              content: event.type === "ChatSendMessage" ? event.content : "",
+            }),
+            onDone: {
+              target: "ready",
+              actions: [
+                assign(({ context, event }) => ({
+                  messages: [...context.messages, event.output.reply],
+                  isReplyingAI: false,
+                })),
+                ({ context, event }) =>
+                  console.log("[chat-machine] guestSession.sending.onDone", {
+                    newReplyContentLength: event.output.reply.content.length,
+                    totalMessagesCount: context.messages.length + 1,
+                    isReplyingAI: false,
+                  }),
+              ],
+            },
+            onError: {
+              target: "ready",
+              actions: [
+                assign({ isReplyingAI: false }),
+                ({ event }) =>
+                  console.error("[chat-machine] guestSession.sending.onError", {
+                    error: event.error instanceof Error ? event.error.message : String(event.error),
+                  }),
+              ],
+            },
+          },
+        },
         loadingMore: {
           entry: ({ context }) =>
             console.log("[chat-machine] → guestSession.loadingMore", { offset: context.historyOffset }),
@@ -357,7 +391,7 @@ export const chatMachine = setup({
             onDone: {
               target: "ready",
               actions: [
-                assign(({ event }) => ({
+                assign(({ context, event }) => ({
                   messages: event.output.messages,
                   isLoadingMore: false,
                   hasMore: event.output.hasMore,
@@ -388,6 +422,7 @@ export const chatMachine = setup({
             ChatSendMessage: {
               actions: ["logSendMessageReceived", "appendUserMessage"],
               guard: ({ event }) => event.content.trim().length > 0,
+              target: "sending",
             },
             ChatSendImage: {
               actions: ["logSendImageReceived", "appendUserImage"],
@@ -411,6 +446,45 @@ export const chatMachine = setup({
             ChatQuotaExceeded: { actions: "incrementQuotaExceeded" },
           },
         },
+        sending: {
+          entry: ({ event }) =>
+            console.log("[chat-machine] → userSession.sending", {
+              contentLength: event.type === "ChatSendMessage" ? event.content.length : 0,
+              contentPreview: event.type === "ChatSendMessage" ? event.content.slice(0, 50) : "",
+              wsConnected: true,
+            }),
+          invoke: {
+            src: "sendMessageHttp",
+            input: ({ event }) => ({
+              content: event.type === "ChatSendMessage" ? event.content : "",
+            }),
+            onDone: {
+              target: "ready",
+              actions: [
+                assign(({ context, event }) => ({
+                  messages: [...context.messages, event.output.reply],
+                  isReplyingAI: false,
+                })),
+                ({ context, event }) =>
+                  console.log("[chat-machine] userSession.sending.onDone", {
+                    newReplyContentLength: event.output.reply.content.length,
+                    totalMessagesCount: context.messages.length + 1,
+                    isReplyingAI: false,
+                  }),
+              ],
+            },
+            onError: {
+              target: "ready",
+              actions: [
+                assign({ isReplyingAI: false }),
+                ({ event }) =>
+                  console.error("[chat-machine] userSession.sending.onError", {
+                    error: event.error instanceof Error ? event.error.message : String(event.error),
+                  }),
+              ],
+            },
+          },
+        },
         loadingMore: {
           entry: ({ context }) =>
             console.log("[chat-machine] → userSession.loadingMore", { offset: context.historyOffset }),