diff --git a/packages/server/src/routes/sessions.ts b/packages/server/src/routes/sessions.ts
index 741fcf3..09b3d7d 100644
--- a/packages/server/src/routes/sessions.ts
+++ b/packages/server/src/routes/sessions.ts
@@ -6,7 +6,12 @@
 
 import { Hono } from 'hono';
 import { getSessionManager } from '../session/manager.js';
-import { CreateSessionInputSchema, type ToolCallInfo, type MergedMessage } from '../types.js';
+import {
+  CreateSessionInputSchema,
+  type ToolCallInfo,
+  type MergedMessage,
+  type MessagePart,
+} from '../types.js';
 
 export const sessionsRouter = new Hono();
 
@@ -163,13 +168,40 @@ sessionsRouter.get('/:id/messages', async (c) => {
     for (const msgInfo of messageInfos) {
       const parts = await PartStorage.getByIds(msgInfo.id, msgInfo.partIds);
 
-      // 提取文本内容
+      // 转换 Parts 为前端格式（保持顺序）
+      const messageParts: MessagePart[] = parts
+        .filter((p) => p.type === 'text' || p.type === 'tool' || p.type === 'reasoning')
+        .map((p): MessagePart => {
+          if (p.type === 'text') {
+            return { type: 'text', id: p.id, text: p.text ?? '' };
+          }
+          if (p.type === 'reasoning') {
+            return { type: 'reasoning', id: p.id, text: p.text ?? '' };
+          }
+          // tool
+          const state = p.state!;
+          const startTime = state.time?.start;
+          const endTime = state.time?.end;
+          return {
+            type: 'tool',
+            id: p.id,
+            toolCallId: p.toolCallId ?? '',
+            toolName: p.toolName ?? '',
+            status: state.status,
+            arguments: state.input ?? {},
+            result: state.status === 'completed' ? state.output : undefined,
+            error: state.status === 'error' ? state.error : undefined,
+            duration: startTime && endTime ? endTime - startTime : undefined,
+          };
+        });
+
+      // 兼容字段：提取文本内容
       const textContent = parts
         .filter((p) => p.type === 'text')
         .map((p) => p.text ?? '')
         .join('');
 
-      // 提取工具调用
+      // 兼容字段：提取工具调用
       const toolCalls: ToolCallInfo[] = parts
         .filter((p) => p.type === 'tool' && p.state)
         .map((p) => {
@@ -191,8 +223,9 @@ sessionsRouter.get('/:id/messages', async (c) => {
         id: msgInfo.id,
         sessionId: msgInfo.sessionId,
         role: msgInfo.role,
-        content: textContent,
         timestamp: new Date(msgInfo.createdAt).toISOString(),
+        parts: messageParts,
+        content: textContent || undefined,
         toolCalls: toolCalls.length > 0 ? toolCalls : undefined,
       });
     }
diff --git a/packages/server/src/types.ts b/packages/server/src/types.ts
index 92023ec..7563bd9 100644
--- a/packages/server/src/types.ts
+++ b/packages/server/src/types.ts
@@ -188,7 +188,7 @@ export interface SSEEvent {
   };
 }
 
-// ============ 合并消息相关 (API 层消息合并) ============
+// ============ 消息 Parts 相关 ============
 
 /**
  * 工具调用状态
@@ -196,7 +196,45 @@ export interface SSEEvent {
 export type ToolCallStatus = 'pending' | 'running' | 'completed' | 'error';
 
 /**
- * 工具调用信息（合并后）
+ * 文本 Part
+ */
+export interface TextMessagePart {
+  type: 'text';
+  id: string;
+  text: string;
+}
+
+/**
+ * 工具调用 Part
+ */
+export interface ToolMessagePart {
+  type: 'tool';
+  id: string;
+  toolCallId: string;
+  toolName: string;
+  status: ToolCallStatus;
+  arguments: Record<string, unknown>;
+  result?: unknown;
+  error?: string;
+  duration?: number;
+}
+
+/**
+ * 推理 Part
+ */
+export interface ReasoningMessagePart {
+  type: 'reasoning';
+  id: string;
+  text: string;
+}
+
+/**
+ * 消息 Part 联合类型
+ */
+export type MessagePart = TextMessagePart | ToolMessagePart | ReasoningMessagePart;
+
+/**
+ * 工具调用信息（兼容字段，合并后）
  */
 export interface ToolCallInfo {
   id: string;
@@ -205,25 +243,27 @@ export interface ToolCallInfo {
   status: ToolCallStatus;
   result?: unknown;
   error?: string;
-  duration?: number; // 执行时长 ms
+  duration?: number;
 }
 
 /**
- * 消息格式（存储层已经是 2-message 格式，无需 API 层合并）
+ * 消息格式（包含有序 Parts）
  *
  * 只有 user 和 assistant 两种角色：
  * - user: 用户输入
- * - assistant: AI 回复（包含文本和工具调用）
+ * - assistant: AI 回复（包含文本和工具调用，按原始顺序）
  */
 export interface MergedMessage {
   id: string;
   sessionId: string;
   role: 'user' | 'assistant';
-  content: string;
   timestamp: string;
+  /** 有序的消息内容 Parts */
+  parts: MessagePart[];
+  /** 所有文本拼接（兼容字段） */
+  content?: string;
+  /** 所有工具调用（兼容字段） */
   toolCalls?: ToolCallInfo[];
-  hasReasoning?: boolean;
-  reasoning?: string;
   metadata?: {
     model?: string;
     stepCount?: number;
diff --git a/packages/ui/src/api/types.ts b/packages/ui/src/api/types.ts
index 34f50e6..de6a729 100644
--- a/packages/ui/src/api/types.ts
+++ b/packages/ui/src/api/types.ts
@@ -29,19 +29,62 @@ export interface ToolCallInfo {
   duration?: number; // 执行时长 ms
 }
 
+// ============ 消息 Parts 相关 ============
+
+/**
+ * 文本 Part
+ */
+export interface TextMessagePart {
+  type: 'text';
+  id: string;
+  text: string;
+}
+
+/**
+ * 工具调用 Part
+ */
+export interface ToolMessagePart {
+  type: 'tool';
+  id: string;
+  toolCallId: string;
+  toolName: string;
+  status: ToolCallStatus;
+  arguments: Record<string, unknown>;
+  result?: unknown;
+  error?: string;
+  duration?: number;
+}
+
+/**
+ * 推理 Part
+ */
+export interface ReasoningMessagePart {
+  type: 'reasoning';
+  id: string;
+  text: string;
+}
+
+/**
+ * 消息 Part 联合类型
+ */
+export type MessagePart = TextMessagePart | ToolMessagePart | ReasoningMessagePart;
+
 /**
  * 消息格式（存储层已经是 2-message 格式，无需 API 层合并）
  *
  * 只有 user 和 assistant 两种角色：
  * - user: 用户输入
- * - assistant: AI 回复（包含文本和工具调用）
+ * - assistant: AI 回复（包含文本和工具调用，按原始顺序）
  */
 export interface Message {
   id: string;
   role: 'user' | 'assistant';
-  content: string;
   timestamp: string;
-  /** 工具调用列表 */
+  /** 有序的消息内容 Parts */
+  parts: MessagePart[];
+  /** 所有文本拼接（兼容字段） */
+  content?: string;
+  /** 所有工具调用（兼容字段） */
   toolCalls?: ToolCallInfo[];
   /** 是否包含推理过程 */
   hasReasoning?: boolean;
diff --git a/packages/ui/src/components/ChatMessage.tsx b/packages/ui/src/components/ChatMessage.tsx
index 388a34b..33a4675 100644
--- a/packages/ui/src/components/ChatMessage.tsx
+++ b/packages/ui/src/components/ChatMessage.tsx
@@ -20,7 +20,7 @@ import { useState, forwardRef } from 'react';
 import { cn } from '../utils/cn';
 import { fadeInUp, smoothTransition } from '../utils/animations';
 import { Markdown } from './Markdown';
-import type { Message, ToolCallInfo, ToolCallStatus } from '../api/types.js';
+import type { Message, ToolCallInfo, ToolCallStatus, ToolMessagePart } from '../api/types.js';
 
 interface ChatMessageProps {
   message: Message;
@@ -32,11 +32,61 @@ export const ChatMessage = forwardRef<HTMLDivElement, ChatMessageProps>(
     const [copied, setCopied] = useState(false);
 
     const handleCopy = async () => {
-      await navigator.clipboard.writeText(message.content);
+      await navigator.clipboard.writeText(message.content ?? '');
       setCopied(true);
       setTimeout(() => setCopied(false), 2000);
     };
 
+    // 渲染消息内容 - 使用 parts 保持原始顺序
+    const renderContent = () => {
+      // 优先使用 parts 数组（保持原始顺序）
+      if (message.parts && message.parts.length > 0) {
+        return (
+          <div className="message-content text-gray-200 space-y-3">
+            {message.parts.map((part) => {
+              switch (part.type) {
+                case 'text':
+                  if (!part.text) return null;
+                  return isUser ? (
+                    <div key={part.id} className="whitespace-pre-wrap break-words">
+                      {part.text}
+                    </div>
+                  ) : (
+                    <Markdown key={part.id} content={part.text} />
+                  );
+                case 'tool':
+                  return <ToolPartItem key={part.id} part={part} />;
+                case 'reasoning':
+                  return (
+                    <div key={part.id} className="text-gray-400 italic border-l-2 border-gray-600 pl-3">
+                      {part.text}
+                    </div>
+                  );
+                default:
+                  return null;
+              }
+            })}
+          </div>
+        );
+      }
+
+      // 回退：使用旧的 content + toolCalls 字段
+      return (
+        <>
+          {!isUser && message.toolCalls && message.toolCalls.length > 0 && (
+            <ToolCallsDisplay toolCalls={message.toolCalls} />
+          )}
+          <div className="message-content text-gray-200">
+            {isUser ? (
+              <div className="whitespace-pre-wrap break-words">{message.content ?? ''}</div>
+            ) : (
+              <Markdown content={message.content ?? ''} />
+            )}
+          </div>
+        </>
+      );
+    };
+
     return (
       <motion.div
         ref={ref}
@@ -71,19 +121,7 @@ export const ChatMessage = forwardRef<HTMLDivElement, ChatMessageProps>(
               {copied ? <Check size={14} className="text-green-500" /> : <Copy size={14} />}
             </button>
           </div>
-          {/* 工具调用显示 */}
-          {!isUser && message.toolCalls && message.toolCalls.length > 0 && (
-            <ToolCallsDisplay toolCalls={message.toolCalls} />
-          )}
-          <div className="message-content text-gray-200">
-            {isUser ? (
-              // 用户消息：保持原样显示
-              <div className="whitespace-pre-wrap break-words">{message.content}</div>
-            ) : (
-              // AI 消息：Markdown 渲染
-              <Markdown content={message.content} />
-            )}
-          </div>
+          {renderContent()}
         </div>
       </motion.div>
     );
@@ -154,6 +192,96 @@ export function TypingIndicator() {
 
 // ============ 工具调用显示组件 ============
 
+/**
+ * 单个工具 Part 项（用于 parts 数组渲染）
+ */
+interface ToolPartItemProps {
+  part: ToolMessagePart;
+}
+
+function ToolPartItem({ part }: ToolPartItemProps) {
+  const [expanded, setExpanded] = useState(false);
+  const hasDetails =
+    Object.keys(part.arguments).length > 0 ||
+    part.result !== undefined ||
+    part.error !== undefined;
+
+  return (
+    <div className="border border-gray-700 rounded-lg overflow-hidden bg-gray-800/30">
+      {/* 头部：工具名称、状态、时长 */}
+      <button
+        onClick={() => hasDetails && setExpanded(!expanded)}
+        className={cn(
+          'w-full flex items-center gap-2 px-3 py-2 text-sm',
+          hasDetails && 'hover:bg-gray-700/50 cursor-pointer',
+          !hasDetails && 'cursor-default'
+        )}
+      >
+        <Wrench size={14} className="text-gray-400 flex-shrink-0" />
+        <span className="font-mono text-gray-200 flex-1 text-left truncate">
+          {part.toolName}
+        </span>
+        {getStatusIcon(part.status)}
+        {part.duration && (
+          <span className="text-xs text-gray-500">{formatDuration(part.duration)}</span>
+        )}
+        {hasDetails && (
+          <span className="text-gray-500">
+            {expanded ? <ChevronDown size={14} /> : <ChevronRight size={14} />}
+          </span>
+        )}
+      </button>
+
+      {/* 展开的详情 */}
+      <AnimatePresence>
+        {expanded && hasDetails && (
+          <motion.div
+            initial={{ height: 0, opacity: 0 }}
+            animate={{ height: 'auto', opacity: 1 }}
+            exit={{ height: 0, opacity: 0 }}
+            transition={{ duration: 0.2 }}
+            className="border-t border-gray-700 overflow-hidden"
+          >
+            <div className="px-3 py-2 space-y-2 text-xs">
+              {/* 参数 */}
+              {Object.keys(part.arguments).length > 0 && (
+                <div>
+                  <div className="text-gray-500 mb-1">Arguments:</div>
+                  <pre className="bg-gray-900 rounded p-2 overflow-x-auto text-gray-300 max-h-48 overflow-y-auto">
+                    {JSON.stringify(part.arguments, null, 2)}
+                  </pre>
+                </div>
+              )}
+
+              {/* 结果 */}
+              {part.result !== undefined && (
+                <div>
+                  <div className="text-gray-500 mb-1">Result:</div>
+                  <pre className="bg-gray-900 rounded p-2 overflow-x-auto text-green-300 max-h-48 overflow-y-auto">
+                    {typeof part.result === 'string'
+                      ? part.result
+                      : JSON.stringify(part.result, null, 2)}
+                  </pre>
+                </div>
+              )}
+
+              {/* 错误 */}
+              {part.error && (
+                <div>
+                  <div className="text-red-400 mb-1">Error:</div>
+                  <pre className="bg-gray-900 rounded p-2 overflow-x-auto text-red-300 max-h-48 overflow-y-auto">
+                    {part.error}
+                  </pre>
+                </div>
+              )}
+            </div>
+          </motion.div>
+        )}
+      </AnimatePresence>
+    </div>
+  );
+}
+
 /**
  * 获取工具状态图标
  */
diff --git a/packages/ui/src/hooks/useChat.ts b/packages/ui/src/hooks/useChat.ts
index 125cffc..4d9a94b 100644
--- a/packages/ui/src/hooks/useChat.ts
+++ b/packages/ui/src/hooks/useChat.ts
@@ -123,11 +123,13 @@ export function useChat({ sessionId, onError, onSessionNotFound, onSessionUpdate
 
           case 'done':
             setState((prev) => {
+              const content = message.payload?.content || prev.streamingContent;
               const newMessage: Message = {
                 id: message.payload?.id || `assistant-${Date.now()}-${Math.random().toString(36).slice(2, 9)}`,
                 role: 'assistant',
-                content: message.payload?.content || prev.streamingContent,
                 timestamp: message.payload?.timestamp || new Date().toISOString(),
+                parts: [{ type: 'text', id: `text-${Date.now()}`, text: content }],
+                content,
               };
               return {
                 ...prev,
@@ -141,11 +143,13 @@ export function useChat({ sessionId, onError, onSessionNotFound, onSessionUpdate
           case 'message_received':
             // 用户消息已确认 - 构建完整的消息对象
             setState((prev) => {
+              const content = message.payload?.content || '';
               const userMessage: Message = {
                 id: `user-${Date.now()}-${Math.random().toString(36).slice(2, 9)}`,
                 role: 'user',
-                content: message.payload?.content || '',
                 timestamp: new Date().toISOString(),
+                parts: [{ type: 'text', id: `text-${Date.now()}`, text: content }],
+                content,
               };
               return {
                 ...prev,