feat: 添加系统命令支持 (:clear)

- 新增系统命令模块 (core/system-commands)
  - 支持 :clear/:cls/:c 清空对话历史
  - 命令注册表支持别名
  - 可扩展的命令执行器

- Server 端支持
  - 新增 /api/system-commands API
  - WebSocket 处理系统命令消息
  - 会话清空 API 端点

- UI 端支持
  - 新增 SystemCommandMenu 组件
  - 输入 : 时显示命令建议菜单
  - 键盘导航和选择
  - 底部提示添加 : 快捷键

packages/core/src/index.ts

@@ -150,6 +150,25 @@ export type {
   CommandOperationResult,
 } from './commands/index.js';
 
+// System Commands (: 前缀)
+export {
+  getSystemCommandRegistry,
+  resetSystemCommandRegistry,
+  SystemCommandExecutor,
+  isSystemCommand,
+  parseSystemCommand,
+  executeSystemCommand,
+  initializeSystemCommands,
+  builtinSystemCommands,
+} from './system-commands/index.js';
+export type {
+  SystemCommand,
+  SystemCommandContext,
+  SystemCommandResult,
+  SystemCommandAction,
+  SystemCommandInput,
+} from './system-commands/index.js';
+
 // Checkpoint
 export {
   CheckpointManager,

packages/core/src/system-commands/builtin/clear.ts

@@ -0,0 +1,22 @@
+/**
+ * :clear 系统命令
+ *
+ * 清空当前会话的历史记录
+ */
+
+import type { SystemCommand } from '../types.js';
+
+export const clearCommand: SystemCommand = {
+  name: 'clear',
+  description: '清空当前会话的历史记录',
+  aliases: ['cls', 'c'],
+  execute: async (_context) => {
+    // 实际的清空操作由 Server 层处理
+    // 这里只返回操作指令
+    return {
+      success: true,
+      message: '会话已清空',
+      action: { type: 'clear_messages' },
+    };
+  },
+};

packages/core/src/system-commands/builtin/index.ts

@@ -0,0 +1,15 @@
+/**
+ * 内置系统命令
+ */
+
+import type { SystemCommand } from '../types.js';
+import { clearCommand } from './clear.js';
+
+/**
+ * 所有内置系统命令
+ */
+export const builtinSystemCommands: SystemCommand[] = [
+  clearCommand,
+];
+
+export { clearCommand };

packages/core/src/system-commands/executor.ts

@@ -0,0 +1,135 @@
+/**
+ * System Command 执行器
+ *
+ * 解析和执行系统命令
+ */
+
+import type {
+  SystemCommandContext,
+  SystemCommandInput,
+  SystemCommandResult,
+} from './types.js';
+import { getSystemCommandRegistry } from './registry.js';
+
+/**
+ * System Command 执行器
+ */
+export class SystemCommandExecutor {
+  /**
+   * 检查输入是否为系统命令
+   */
+  static isSystemCommand(input: string): boolean {
+    return input.trim().startsWith(':');
+  }
+
+  /**
+   * 解析系统命令输入
+   */
+  static parseInput(input: string): SystemCommandInput | null {
+    const trimmed = input.trim();
+
+    if (!trimmed.startsWith(':')) {
+      return null;
+    }
+
+    // 移除 : 前缀
+    const content = trimmed.slice(1);
+
+    // 分割命令和参数
+    const spaceIndex = content.indexOf(' ');
+
+    if (spaceIndex === -1) {
+      return {
+        command: content.toLowerCase(),
+        arguments: '',
+        args: [],
+      };
+    }
+
+    const command = content.slice(0, spaceIndex).toLowerCase();
+    const argsString = content.slice(spaceIndex + 1).trim();
+
+    return {
+      command,
+      arguments: argsString,
+      args: argsString ? argsString.split(/\s+/) : [],
+    };
+  }
+
+  /**
+   * 执行系统命令
+   */
+  static async execute(
+    input: string,
+    context: Partial<SystemCommandContext> = {}
+  ): Promise<SystemCommandResult> {
+    const parsed = this.parseInput(input);
+
+    if (!parsed) {
+      return {
+        success: false,
+        error: '无效的系统命令格式',
+      };
+    }
+
+    const registry = getSystemCommandRegistry();
+    const command = registry.get(parsed.command);
+
+    if (!command) {
+      // 列出可用命令作为提示
+      const available = registry
+        .list()
+        .map((c) => `:${c.name}`)
+        .join(', ');
+
+      return {
+        success: false,
+        error: `未知的系统命令: :${parsed.command}`,
+        message: available ? `可用的系统命令: ${available}` : undefined,
+      };
+    }
+
+    try {
+      const result = await command.execute({
+        arguments: parsed.arguments,
+        args: parsed.args,
+        sessionId: context.sessionId,
+        workdir: context.workdir,
+      });
+
+      return result;
+    } catch (error) {
+      return {
+        success: false,
+        error:
+          error instanceof Error ? error.message : '系统命令执行失败',
+      };
+    }
+  }
+}
+
+/**
+ * 便捷函数：检查是否为系统命令
+ */
+export function isSystemCommand(input: string): boolean {
+  return SystemCommandExecutor.isSystemCommand(input);
+}
+
+/**
+ * 便捷函数：解析系统命令
+ */
+export function parseSystemCommand(
+  input: string
+): SystemCommandInput | null {
+  return SystemCommandExecutor.parseInput(input);
+}
+
+/**
+ * 便捷函数：执行系统命令
+ */
+export async function executeSystemCommand(
+  input: string,
+  context?: Partial<SystemCommandContext>
+): Promise<SystemCommandResult> {
+  return SystemCommandExecutor.execute(input, context);
+}

packages/core/src/system-commands/index.ts

@@ -0,0 +1,46 @@
+/**
+ * System Commands 模块
+ *
+ * 提供系统命令（: 前缀）的所有功能导出
+ */
+
+// 类型
+export type {
+  SystemCommand,
+  SystemCommandContext,
+  SystemCommandResult,
+  SystemCommandAction,
+  SystemCommandInput,
+} from './types.js';
+
+// 注册表
+export {
+  SystemCommandRegistry,
+  getSystemCommandRegistry,
+  resetSystemCommandRegistry,
+} from './registry.js';
+
+// 执行器
+export {
+  SystemCommandExecutor,
+  isSystemCommand,
+  parseSystemCommand,
+  executeSystemCommand,
+} from './executor.js';
+
+// 内置命令
+export { builtinSystemCommands, clearCommand } from './builtin/index.js';
+
+// 初始化函数
+import { getSystemCommandRegistry } from './registry.js';
+import { builtinSystemCommands } from './builtin/index.js';
+
+/**
+ * 初始化系统命令注册表
+ *
+ * 注册所有内置系统命令
+ */
+export function initializeSystemCommands(): void {
+  const registry = getSystemCommandRegistry();
+  registry.registerAll(builtinSystemCommands);
+}

packages/core/src/system-commands/registry.ts

@@ -0,0 +1,99 @@
+/**
+ * System Command 注册表
+ *
+ * 管理所有系统命令的注册和查找
+ */
+
+import type { SystemCommand } from './types.js';
+
+/**
+ * System Command 注册表
+ */
+export class SystemCommandRegistry {
+  private commands = new Map<string, SystemCommand>();
+  private aliases = new Map<string, string>();
+
+  /**
+   * 注册系统命令
+   */
+  register(command: SystemCommand): void {
+    this.commands.set(command.name, command);
+
+    // 注册别名
+    if (command.aliases) {
+      for (const alias of command.aliases) {
+        this.aliases.set(alias, command.name);
+      }
+    }
+  }
+
+  /**
+   * 批量注册系统命令
+   */
+  registerAll(commands: SystemCommand[]): void {
+    for (const command of commands) {
+      this.register(command);
+    }
+  }
+
+  /**
+   * 获取系统命令
+   */
+  get(name: string): SystemCommand | undefined {
+    // 先尝试直接查找
+    const command = this.commands.get(name);
+    if (command) {
+      return command;
+    }
+
+    // 再尝试别名查找
+    const aliasTarget = this.aliases.get(name);
+    if (aliasTarget) {
+      return this.commands.get(aliasTarget);
+    }
+
+    return undefined;
+  }
+
+  /**
+   * 检查命令是否存在
+   */
+  has(name: string): boolean {
+    return this.commands.has(name) || this.aliases.has(name);
+  }
+
+  /**
+   * 获取所有命令
+   */
+  list(): SystemCommand[] {
+    return Array.from(this.commands.values());
+  }
+
+  /**
+   * 清空注册表
+   */
+  clear(): void {
+    this.commands.clear();
+    this.aliases.clear();
+  }
+}
+
+// 全局单例
+let globalRegistry: SystemCommandRegistry | null = null;
+
+/**
+ * 获取全局 System Command 注册表
+ */
+export function getSystemCommandRegistry(): SystemCommandRegistry {
+  if (!globalRegistry) {
+    globalRegistry = new SystemCommandRegistry();
+  }
+  return globalRegistry;
+}
+
+/**
+ * 重置全局注册表（用于测试）
+ */
+export function resetSystemCommandRegistry(): void {
+  globalRegistry = null;
+}

packages/core/src/system-commands/types.ts

@@ -0,0 +1,74 @@
+/**
+ * System Command 系统类型定义
+ *
+ * System Command 是以 : 开头的系统操作命令。
+ * 与普通 Command 不同，System Command 不调用 Agent，
+ * 而是直接执行系统操作（如清空会话、切换模型等）。
+ */
+
+/**
+ * System Command 定义
+ */
+export interface SystemCommand {
+  /** 命令名称（不含 : 前缀） */
+  name: string;
+  /** 命令描述 */
+  description: string;
+  /** 命令别名 */
+  aliases?: string[];
+  /** 执行函数 */
+  execute: (context: SystemCommandContext) => Promise<SystemCommandResult>;
+}
+
+/**
+ * System Command 执行上下文
+ */
+export interface SystemCommandContext {
+  /** 原始参数字符串 */
+  arguments: string;
+  /** 解析后的参数数组 */
+  args: string[];
+  /** 当前会话 ID */
+  sessionId?: string;
+  /** 当前工作目录 */
+  workdir?: string;
+}
+
+/**
+ * System Command 执行结果
+ */
+export interface SystemCommandResult {
+  /** 是否成功 */
+  success: boolean;
+  /** 返回消息（显示给用户） */
+  message?: string;
+  /** 错误信息 */
+  error?: string;
+  /** 附加数据 */
+  data?: Record<string, unknown>;
+  /** 特殊操作指令 */
+  action?: SystemCommandAction;
+}
+
+/**
+ * System Command 操作指令
+ *
+ * 用于通知前端执行特定操作
+ */
+export type SystemCommandAction =
+  | { type: 'clear_messages' }
+  | { type: 'new_session'; sessionId?: string }
+  | { type: 'switch_model'; model: string }
+  | { type: 'reload' };
+
+/**
+ * System Command 输入解析结果
+ */
+export interface SystemCommandInput {
+  /** 命令名称（不含 : 前缀） */
+  command: string;
+  /** 原始参数字符串 */
+  arguments: string;
+  /** 解析后的参数数组 */
+  args: string[];
+}

packages/server/src/agent/adapter.ts

@@ -643,3 +643,16 @@ export function submitUserInput(toolCallId: string, answer: string): boolean {
   const userInputWaiter = getUserInputWaiter();
   return userInputWaiter.submitInput(toolCallId, answer);
 }
+
+/**
+ * 清空 Agent 的对话历史（内存中）
+ *
+ * 用于系统命令 :clear
+ */
+export function clearAgentHistory(sessionId: string): void {
+  const agent = agentCache.get(sessionId);
+  if (agent) {
+    agent.clearHistory();
+    console.log(`[Agent] Cleared history for session ${sessionId}`);
+  }
+}

packages/server/src/agent/index.ts

@@ -17,6 +17,8 @@ export {
   compressContext,
   // 用户输入响应
   submitUserInput,
+  // 系统命令支持
+  clearAgentHistory,
   // 类型导出
   type TokenUsage,
   type CompressionResult,

packages/server/src/index.ts

@@ -9,7 +9,7 @@ import { cors } from 'hono/cors';
 import { logger } from 'hono/logger';
 import { createBunWebSocket } from 'hono/bun';
 
-import { sessionsRouter, toolsRouter, configRouter, filesRouter, commandsRouter, mcpRouter, hooksRouter, agentsRouter, checkpointsRouter, providersRouter, servicesRouter, contextRouter, lspRouter } from './routes/index.js';
+import { sessionsRouter, toolsRouter, configRouter, filesRouter, commandsRouter, mcpRouter, hooksRouter, agentsRouter, checkpointsRouter, providersRouter, servicesRouter, contextRouter, lspRouter, systemCommandsRouter } from './routes/index.js';
 import {
   handleWebSocket,
   handleWebSocketMessage,
@@ -90,6 +90,7 @@ api.route('/checkpoints', checkpointsRouter);
 api.route('/providers', providersRouter);
 api.route('/services', servicesRouter);
 api.route('/lsp', lspRouter);
+api.route('/system-commands', systemCommandsRouter);
 
 // 上下文压缩相关（挂载到根路径，内部路由包含 /sessions/:id/context）
 api.route('/', contextRouter);

packages/server/src/routes/index.ts

@@ -17,3 +17,4 @@ export { providersRouter } from './providers.js';
 export { servicesRouter } from './services.js';
 export { contextRouter } from './context.js';
 export { lspRouter } from './lsp.js';
+export { systemCommandsRouter } from './system-commands.js';

packages/server/src/routes/sessions.ts

@@ -104,6 +104,47 @@ sessionsRouter.delete('/:id', async (c) => {
   });
 });
 
+/**
+ * POST /sessions/:id/clear - 清空会话消息
+ *
+ * 删除会话的所有消息和相关数据，但保留会话本身
+ */
+sessionsRouter.post('/:id/clear', async (c) => {
+  const id = c.req.param('id');
+
+  if (!sessionManager.exists(id)) {
+    return c.json(
+      {
+        success: false,
+        error: 'Session not found',
+      },
+      404
+    );
+  }
+
+  try {
+    // 删除会话的所有消息
+    await MessageStorage.removeBySession(id);
+
+    // 重置会话状态
+    sessionManager.updateStatus(id, 'idle');
+
+    return c.json({
+      success: true,
+      message: 'Session messages cleared',
+    });
+  } catch (error) {
+    console.error('[Sessions] Failed to clear messages:', error);
+    return c.json(
+      {
+        success: false,
+        error: error instanceof Error ? error.message : 'Failed to clear messages',
+      },
+      500
+    );
+  }
+});
+
 /**
  * GET /sessions/:id/messages - 获取会话消息
  *

packages/server/src/routes/system-commands.ts

@@ -0,0 +1,57 @@
+/**
+ * System Commands API Routes
+ *
+ * 系统命令（: 前缀）相关的 REST API
+ */
+
+import { Hono } from 'hono';
+import { getSystemCommandRegistry } from '@ai-assistant/core';
+
+export const systemCommandsRouter = new Hono();
+
+/**
+ * GET /system-commands - 列出所有系统命令
+ */
+systemCommandsRouter.get('/', (c) => {
+  const registry = getSystemCommandRegistry();
+  const commands = registry.list();
+
+  return c.json({
+    success: true,
+    data: {
+      commands: commands.map((cmd) => ({
+        name: cmd.name,
+        description: cmd.description,
+        aliases: cmd.aliases || [],
+      })),
+    },
+  });
+});
+
+/**
+ * GET /system-commands/:name - 获取单个系统命令
+ */
+systemCommandsRouter.get('/:name', (c) => {
+  const name = c.req.param('name');
+  const registry = getSystemCommandRegistry();
+  const command = registry.get(name);
+
+  if (!command) {
+    return c.json(
+      {
+        success: false,
+        error: 'System command not found',
+      },
+      404
+    );
+  }
+
+  return c.json({
+    success: true,
+    data: {
+      name: command.name,
+      description: command.description,
+      aliases: command.aliases || [],
+    },
+  });
+});

packages/server/src/types.ts

@@ -82,7 +82,7 @@ export type AgentModeType = 'build' | 'plan';
 
 // 客户端发送的消息
 export interface ClientMessage {
-  type: 'message' | 'cancel' | 'tool_response' | 'permission_response' | 'config_update' | 'mode_switch' | 'user_input_response';
+  type: 'message' | 'cancel' | 'tool_response' | 'permission_response' | 'config_update' | 'mode_switch' | 'user_input_response' | 'system_command';
   sessionId: string;
   payload?: {
     content?: string;
@@ -122,7 +122,9 @@ export interface ServerMessage {
     | 'subagent:end'        // 子 Agent 执行结束
     | 'subagent:stream'     // 子 Agent 流式输出
     | 'subagent:tool_start' // 子 Agent 工具调用开始
-    | 'subagent:tool_end';  // 子 Agent 工具调用结束
+    | 'subagent:tool_end'   // 子 Agent 工具调用结束
+    // 系统命令响应
+    | 'system_command_result'; // 系统命令执行结果
   sessionId: string;
   payload?: unknown;
 }

packages/server/src/ws.ts

@@ -6,9 +6,18 @@
 
 import type { WSContext } from 'hono/ws';
 import { getSessionManager } from './session/manager.js';
-import { processMessage, cancelProcessing, getOrCreateAgent, submitUserInput } from './agent/index.js';
+import { processMessage, cancelProcessing, getOrCreateAgent, submitUserInput, clearAgentHistory } from './agent/index.js';
 import { handlePermissionResponse, setSessionAutoApprove } from './permission/handler.js';
 import type { ClientMessage, ServerMessage } from './types.js';
+import {
+  isSystemCommand,
+  executeSystemCommand,
+  initializeSystemCommands,
+  MessageStorage,
+} from '@ai-assistant/core';
+
+// 初始化系统命令
+initializeSystemCommands();
 
 // 存储活跃的 WebSocket 连接
 const connections: Map<string, Set<WSContext>> = new Map();
@@ -109,6 +118,12 @@ export async function handleWebSocketMessage(
         const agentMode = message.payload?.agentMode as 'build' | 'plan' | undefined;
         const autoApprove = message.payload?.autoApprove as boolean | undefined;
 
+        // 检测系统命令（: 前缀）
+        if (isSystemCommand(content)) {
+          await handleSystemCommand(sessionId, content);
+          break;
+        }
+
         // 将 @filepath 转换为 ./filepath 格式（方便 AI 识别为文件路径）
         content = content.replace(/@([\w./-]+)/g, './$1');
 
@@ -281,3 +296,45 @@ export function getConnectionStats(): { sessions: number; connections: number }
     connections: totalConnections,
   };
 }
+
+/**
+ * 处理系统命令（: 前缀）
+ */
+async function handleSystemCommand(sessionId: string, content: string): Promise<void> {
+  const sessionManager = getSessionManager();
+
+  console.log(`[WS] System command: ${content}`);
+
+  // 执行系统命令
+  const result = await executeSystemCommand(content, { sessionId });
+
+  // 处理特殊操作
+  if (result.success && result.action) {
+    switch (result.action.type) {
+      case 'clear_messages': {
+        // 清空存储的消息
+        await MessageStorage.removeBySession(sessionId);
+
+        // 清空 Agent 内存中的对话历史
+        clearAgentHistory(sessionId);
+
+        // 重置会话状态
+        sessionManager.updateStatus(sessionId, 'idle');
+        break;
+      }
+      // 可以在这里添加其他操作类型的处理
+    }
+  }
+
+  // 发送结果给客户端
+  broadcastToSession(sessionId, {
+    type: 'system_command_result',
+    sessionId,
+    payload: {
+      success: result.success,
+      message: result.message,
+      error: result.error,
+      action: result.action,
+    },
+  });
+}

packages/ui/src/api/client.ts

@@ -53,6 +53,9 @@ import type {
   // LSP types
   LSPServer,
   DiagnosticsResponse,
+  // System Commands types
+  SystemCommandListResponse,
+  SystemCommandInfo,
 } from './types.js';
 
 // Re-export types
@@ -145,6 +148,9 @@ export type {
   SingleFileDiagnosticsResponse,
   AllFilesDiagnosticsResponse,
   DiagnosticsResponse,
+  // System Commands types
+  SystemCommandInfo,
+  SystemCommandListResponse,
 } from './types.js';
 
 // API Configuration
@@ -368,6 +374,29 @@ export async function deleteCommand(
   return request('DELETE', `/commands/${encodeURIComponent(name)}`);
 }
 
+// ============ System Commands API (: 前缀) ============
+
+/**
+ * 获取所有系统命令列表
+ */
+export async function listSystemCommands(): Promise<{
+  success: boolean;
+  data: SystemCommandListResponse;
+}> {
+  return request('GET', '/system-commands');
+}
+
+/**
+ * 获取单个系统命令
+ */
+export async function getSystemCommand(name: string): Promise<{
+  success: boolean;
+  data?: SystemCommandInfo;
+  error?: string;
+}> {
+  return request('GET', `/system-commands/${encodeURIComponent(name)}`);
+}
+
 // ============ MCP API ============
 
 /**

packages/ui/src/api/types.ts

@@ -291,6 +291,23 @@ export interface CommandContent {
   sourcePath?: string;
 }
 
+// ============ System Commands (: 前缀) 相关 ============
+
+/** 系统命令信息 */
+export interface SystemCommandInfo {
+  /** 命令名称（不含 : 前缀） */
+  name: string;
+  /** 命令描述 */
+  description: string;
+  /** 命令别名 */
+  aliases: string[];
+}
+
+/** 系统命令列表响应 */
+export interface SystemCommandListResponse {
+  commands: SystemCommandInfo[];
+}
+
 // ============ MCP 相关 ============
 
 /** MCP 服务器状态类型 */

packages/ui/src/components/ChatInput.tsx

@@ -3,6 +3,7 @@
  *
  * 支持响应式：responsive=true 时适配移动端键盘和触摸操作
  * 支持斜杠命令：输入 / 时显示命令菜单
+ * 支持系统命令：输入 : 时显示系统命令菜单
  * 支持文件提及：输入 @ 时显示文件搜索菜单
  */
 
@@ -11,10 +12,12 @@ import { Square, Sparkles } from 'lucide-react';
 import { motion } from 'framer-motion';
 import clsx from 'clsx';
 import { CommandMenu, type CommandMenuItem } from './CommandMenu.js';
+import { SystemCommandMenu, type SystemCommandMenuItem } from './SystemCommandMenu.js';
 import { FileMenu, type FileMenuItem } from './FileMenu.js';
 import { FileMentionTag } from './FileMentionTag.js';
 import { AgentModeSelector, type AgentModeType } from './AgentModeSelector.js';
 import { useCommands } from '../hooks/useCommands.js';
+import { useSystemCommands } from '../hooks/useSystemCommands.js';
 import { useFileMention } from '../hooks/useFileMention.js';
 
 interface ChatInputProps {
@@ -54,6 +57,8 @@ export function ChatInput({
   const [input, setInput] = useState('');
   const [showCommandMenu, setShowCommandMenu] = useState(false);
   const [selectedCommandIndex, setSelectedCommandIndex] = useState(0);
+  const [showSystemCommandMenu, setShowSystemCommandMenu] = useState(false);
+  const [selectedSystemCommandIndex, setSelectedSystemCommandIndex] = useState(0);
   const textareaRef = useRef<HTMLTextAreaElement>(null);
 
   // 命令系统
@@ -63,6 +68,13 @@ export function ChatInput({
     filterCommands,
   } = useCommands({ autoLoad: enableCommands });
 
+  // 系统命令系统
+  const {
+    filteredCommands: filteredSystemCommands,
+    isLoading: systemCommandsLoading,
+    filterCommands: filterSystemCommands,
+  } = useSystemCommands({ autoLoad: enableCommands });
+
   // 文件提及系统
   const {
     isOpen: showFileMenu,
@@ -130,17 +142,41 @@ export function ChatInput({
     [enableCommands, filterCommands]
   );
 
+  // 检测系统命令输入
+  const checkSystemCommandTrigger = useCallback(
+    (value: string) => {
+      if (!enableCommands) return;
+
+      // 检测是否在输入系统命令
+      // 条件：以 : 开头，且 : 后面没有空格（还在输入命令名）
+      const colonMatch = value.match(/^:(\S*)$/);
+
+      if (colonMatch) {
+        const query = colonMatch[1]; // : 后面的内容
+        setShowSystemCommandMenu(true);
+        setSelectedSystemCommandIndex(0);
+        filterSystemCommands(query);
+      } else {
+        setShowSystemCommandMenu(false);
+      }
+    },
+    [enableCommands, filterSystemCommands]
+  );
+
   // 处理输入变化
   const handleInputChange = (e: React.ChangeEvent<HTMLTextAreaElement>) => {
     const value = e.target.value;
     const cursorPos = e.target.selectionStart;
     setInput(value);
 
-    // 检查命令触发
+    // 检查斜杠命令触发
     checkCommandTrigger(value);
 
+    // 检查系统命令触发
+    checkSystemCommandTrigger(value);
+
     // 检查文件提及触发（只在非命令输入模式下）
-    if (enableFileMention && !value.startsWith('/')) {
+    if (enableFileMention && !value.startsWith('/') && !value.startsWith(':')) {
       checkFileTrigger(value, cursorPos);
     } else {
       closeFileMenu();
@@ -189,12 +225,28 @@ export function ChatInput({
     setShowCommandMenu(false);
   }, []);
 
+  // 选择系统命令
+  const handleSystemCommandSelect = useCallback((command: SystemCommandMenuItem) => {
+    // 直接发送系统命令
+    setInput(`:${command.name}`);
+    setShowSystemCommandMenu(false);
+
+    // 聚焦输入框
+    textareaRef.current?.focus();
+  }, []);
+
+  // 关闭系统命令菜单
+  const handleSystemCommandMenuClose = useCallback(() => {
+    setShowSystemCommandMenu(false);
+  }, []);
+
   const handleSubmit = () => {
     const trimmed = input.trim();
     if (!trimmed || isLoading || disabled) return;
 
-    // 关闭菜单
+    // 关闭所有菜单
     setShowCommandMenu(false);
+    setShowSystemCommandMenu(false);
     closeFileMenu();
 
     onSend(trimmed);
@@ -222,7 +274,7 @@ export function ChatInput({
       }
     }
 
-    // 命令菜单处理
+    // 斜杠命令菜单处理
     if (showCommandMenu && filteredCommands.length > 0) {
       if (['ArrowUp', 'ArrowDown', 'Tab', 'Escape'].includes(e.key)) {
         // 这些键由 CommandMenu 处理，阻止默认行为
@@ -238,6 +290,22 @@ export function ChatInput({
       }
     }
 
+    // 系统命令菜单处理
+    if (showSystemCommandMenu && filteredSystemCommands.length > 0) {
+      if (['ArrowUp', 'ArrowDown', 'Tab', 'Escape'].includes(e.key)) {
+        // 这些键由 SystemCommandMenu 处理，阻止默认行为
+        return;
+      }
+      if (e.key === 'Enter' && !e.shiftKey) {
+        // Enter 选择系统命令
+        e.preventDefault();
+        if (filteredSystemCommands[selectedSystemCommandIndex]) {
+          handleSystemCommandSelect(filteredSystemCommands[selectedSystemCommandIndex]);
+        }
+        return;
+      }
+    }
+
     // Enter 发送，Shift+Enter 换行
     if (e.key === 'Enter' && !e.shiftKey) {
       e.preventDefault();
@@ -252,7 +320,7 @@ export function ChatInput({
         responsive ? 'p-3 md:p-4 safe-area-pb' : 'p-4'
       )}
     >
-      {/* Command Menu */}
+      {/* Command Menu (斜杠命令) */}
       {enableCommands && (
         <CommandMenu
           commands={filteredCommands}
@@ -265,6 +333,19 @@ export function ChatInput({
         />
       )}
 
+      {/* System Command Menu (系统命令) */}
+      {enableCommands && (
+        <SystemCommandMenu
+          commands={filteredSystemCommands}
+          isOpen={showSystemCommandMenu}
+          selectedIndex={selectedSystemCommandIndex}
+          onSelect={handleSystemCommandSelect}
+          onClose={handleSystemCommandMenuClose}
+          onSelectedIndexChange={setSelectedSystemCommandIndex}
+          isLoading={systemCommandsLoading}
+        />
+      )}
+
       {/* File Menu */}
       {enableFileMention && (
         <FileMenu
@@ -382,6 +463,10 @@ export function ChatInput({
               <kbd className="px-1.5 py-0.5 rounded bg-surface-subtle text-fg-muted font-mono text-[10px]">/</kbd>
               <span>commands</span>
             </span>
+            <span className="flex items-center gap-1">
+              <kbd className="px-1.5 py-0.5 rounded bg-surface-subtle text-fg-muted font-mono text-[10px]">:</kbd>
+              <span>system</span>
+            </span>
             <span className="flex items-center gap-1">
               <kbd className="px-1.5 py-0.5 rounded bg-surface-subtle text-fg-muted font-mono text-[10px]">@</kbd>
               <span>files</span>

packages/ui/src/components/SystemCommandMenu.tsx

@@ -0,0 +1,228 @@
+/**
+ * System Command Menu Component
+ *
+ * 系统命令（: 前缀）选择菜单，支持键盘导航
+ */
+
+import { useEffect, useRef } from 'react';
+import { motion, AnimatePresence } from 'framer-motion';
+import { Settings, Trash2, RefreshCw } from 'lucide-react';
+import clsx from 'clsx';
+
+export interface SystemCommandMenuItem {
+  name: string;
+  description: string;
+  aliases?: string[];
+}
+
+interface SystemCommandMenuProps {
+  /** 命令列表 */
+  commands: SystemCommandMenuItem[];
+  /** 是否显示 */
+  isOpen: boolean;
+  /** 当前选中索引 */
+  selectedIndex: number;
+  /** 选择命令回调 */
+  onSelect: (command: SystemCommandMenuItem) => void;
+  /** 关闭菜单回调 */
+  onClose: () => void;
+  /** 选中索引变化回调 */
+  onSelectedIndexChange: (index: number) => void;
+  /** 是否正在加载 */
+  isLoading?: boolean;
+}
+
+// 根据命令名称获取图标
+function getCommandIcon(name: string) {
+  switch (name) {
+    case 'clear':
+      return <Trash2 size={14} className="text-red-400" />;
+    case 'reload':
+      return <RefreshCw size={14} className="text-blue-400" />;
+    default:
+      return <Settings size={14} className="text-purple-400" />;
+  }
+}
+
+export function SystemCommandMenu({
+  commands,
+  isOpen,
+  selectedIndex,
+  onSelect,
+  onClose,
+  onSelectedIndexChange,
+  isLoading = false,
+}: SystemCommandMenuProps) {
+  const menuRef = useRef<HTMLDivElement>(null);
+  const selectedRef = useRef<HTMLButtonElement>(null);
+
+  // 滚动选中项到可见区域
+  useEffect(() => {
+    if (isOpen && selectedRef.current) {
+      selectedRef.current.scrollIntoView({
+        block: 'nearest',
+        behavior: 'smooth',
+      });
+    }
+  }, [selectedIndex, isOpen]);
+
+  // 键盘导航
+  useEffect(() => {
+    if (!isOpen) return;
+
+    const handleKeyDown = (e: KeyboardEvent) => {
+      switch (e.key) {
+        case 'ArrowDown':
+          e.preventDefault();
+          onSelectedIndexChange(
+            selectedIndex < commands.length - 1 ? selectedIndex + 1 : 0
+          );
+          break;
+        case 'ArrowUp':
+          e.preventDefault();
+          onSelectedIndexChange(
+            selectedIndex > 0 ? selectedIndex - 1 : commands.length - 1
+          );
+          break;
+        case 'Enter':
+          e.preventDefault();
+          if (commands[selectedIndex]) {
+            onSelect(commands[selectedIndex]);
+          }
+          break;
+        case 'Escape':
+          e.preventDefault();
+          onClose();
+          break;
+        case 'Tab':
+          e.preventDefault();
+          if (commands[selectedIndex]) {
+            onSelect(commands[selectedIndex]);
+          }
+          break;
+      }
+    };
+
+    document.addEventListener('keydown', handleKeyDown);
+    return () => document.removeEventListener('keydown', handleKeyDown);
+  }, [isOpen, commands, selectedIndex, onSelect, onClose, onSelectedIndexChange]);
+
+  return (
+    <AnimatePresence>
+      {isOpen && (
+        <motion.div
+          ref={menuRef}
+          initial={{ opacity: 0, y: 8, scale: 0.96 }}
+          animate={{ opacity: 1, y: 0, scale: 1 }}
+          exit={{ opacity: 0, y: 8, scale: 0.96 }}
+          transition={{ duration: 0.15 }}
+          className="absolute bottom-full left-0 right-0 mb-2 mx-4 md:mx-0 z-50"
+        >
+          <div className="bg-surface-subtle border border-line rounded-lg shadow-xl overflow-hidden max-h-64 overflow-y-auto">
+            {/* Header */}
+            <div className="px-3 py-2 border-b border-line bg-surface-subtle/80 sticky top-0">
+              <div className="flex items-center gap-2 text-xs text-fg-muted">
+                <Settings size={12} />
+                <span>System Commands</span>
+                {commands.length > 0 && (
+                  <span className="text-fg-subtle">({commands.length})</span>
+                )}
+              </div>
+            </div>
+
+            {/* Loading */}
+            {isLoading && commands.length === 0 && (
+              <div className="px-3 py-4 text-center text-fg-muted text-sm">
+                Loading system commands...
+              </div>
+            )}
+
+            {/* Empty state */}
+            {!isLoading && commands.length === 0 && (
+              <div className="px-3 py-4 text-center text-fg-muted text-sm">
+                No system commands found
+              </div>
+            )}
+
+            {/* Command list */}
+            {commands.length > 0 && (
+              <div className="py-1">
+                {commands.map((command, index) => (
+                  <button
+                    key={command.name}
+                    ref={index === selectedIndex ? selectedRef : null}
+                    onClick={() => onSelect(command)}
+                    onMouseEnter={() => onSelectedIndexChange(index)}
+                    className={clsx(
+                      'w-full px-3 py-2 flex items-start gap-3 text-left transition-colors',
+                      index === selectedIndex
+                        ? 'bg-primary-600/20'
+                        : 'hover:bg-surface-muted/50'
+                    )}
+                  >
+                    {/* Icon */}
+                    <div className="mt-0.5">{getCommandIcon(command.name)}</div>
+
+                    {/* Content */}
+                    <div className="flex-1 min-w-0">
+                      <div className="flex items-center gap-2">
+                        <span
+                          className={clsx(
+                            'font-mono text-sm',
+                            index === selectedIndex
+                              ? 'text-primary-300'
+                              : 'text-fg-secondary'
+                          )}
+                        >
+                          :{command.name}
+                        </span>
+                        {command.aliases && command.aliases.length > 0 && (
+                          <span className="text-[10px] text-fg-subtle">
+                            ({command.aliases.map((a) => `:${a}`).join(', ')})
+                          </span>
+                        )}
+                      </div>
+                      {command.description && (
+                        <p className="text-xs text-fg-muted mt-0.5 truncate">
+                          {command.description}
+                        </p>
+                      )}
+                    </div>
+
+                    {/* Keyboard hint */}
+                    {index === selectedIndex && (
+                      <div className="flex items-center gap-1 text-[10px] text-fg-subtle">
+                        <kbd className="px-1 py-0.5 bg-surface-muted rounded">
+                          Enter
+                        </kbd>
+                      </div>
+                    )}
+                  </button>
+                ))}
+              </div>
+            )}
+
+            {/* Footer hint */}
+            <div className="px-3 py-1.5 border-t border-line bg-surface-subtle/80 sticky bottom-0">
+              <div className="flex items-center gap-3 text-[10px] text-fg-subtle">
+                <span>
+                  <kbd className="px-1 py-0.5 bg-surface-muted rounded mr-1">↑</kbd>
+                  <kbd className="px-1 py-0.5 bg-surface-muted rounded">↓</kbd>
+                  {' '}navigate
+                </span>
+                <span>
+                  <kbd className="px-1 py-0.5 bg-surface-muted rounded">Tab</kbd>
+                  {' '}select
+                </span>
+                <span>
+                  <kbd className="px-1 py-0.5 bg-surface-muted rounded">Esc</kbd>
+                  {' '}close
+                </span>
+              </div>
+            </div>
+          </div>
+        </motion.div>
+      )}
+    </AnimatePresence>
+  );
+}

packages/ui/src/hooks/useChat.ts

@@ -564,6 +564,33 @@ export function useChat({ sessionId, onError, onSessionNotFound, onSessionUpdate
             }, 1000);
             break;
           }
+
+          // ============ 系统命令结果 ============
+
+          case 'system_command_result': {
+            const payload = message.payload as {
+              success: boolean;
+              message?: string;
+              error?: string;
+              action?: { type: string };
+            };
+
+            // 处理清空消息操作
+            if (payload.success && payload.action?.type === 'clear_messages') {
+              setState((prev) => ({
+                ...prev,
+                messages: [],
+                streamingMessage: null,
+                isLoading: false,
+              }));
+            }
+
+            // 如果有错误，通过 onError 回调通知
+            if (!payload.success && payload.error) {
+              onErrorRef.current?.(new Error(payload.error));
+            }
+            break;
+          }
         }
       } catch {
         // 忽略解析错误
@@ -693,6 +720,23 @@ export function useChat({ sessionId, onError, onSessionNotFound, onSessionUpdate
     [sessionId]
   );
 
+  // 清空会话消息（系统命令 :clear）
+  const clearMessages = useCallback(() => {
+    if (!wsRef.current || wsRef.current.readyState !== WebSocket.OPEN) {
+      onErrorRef.current?.(new Error('WebSocket not connected'));
+      return;
+    }
+
+    // 发送 :clear 系统命令
+    wsRef.current.send(
+      JSON.stringify({
+        type: 'message',
+        sessionId,
+        payload: { content: ':clear' },
+      })
+    );
+  }, [sessionId]);
+
   // 回答问题（ask_user_question 工具）
   const answerQuestion = useCallback(
     (questionPartId: string, answers: string[]) => {
@@ -813,5 +857,6 @@ export function useChat({ sessionId, onError, onSessionNotFound, onSessionUpdate
     setAgentMode,
     setAutoApprove,
     answerQuestion,
+    clearMessages,
   };
 }

packages/ui/src/hooks/useSystemCommands.ts

@@ -0,0 +1,112 @@
+/**
+ * System Commands Hook
+ *
+ * 管理系统命令（: 前缀）的加载和过滤
+ */
+
+import { useState, useEffect, useCallback, useRef } from 'react';
+import { listSystemCommands } from '../api/client.js';
+import type { SystemCommandInfo } from '../api/types.js';
+
+interface UseSystemCommandsOptions {
+  /** 是否在挂载时自动加载命令列表 */
+  autoLoad?: boolean;
+}
+
+interface UseSystemCommandsState {
+  /** 所有系统命令列表 */
+  commands: SystemCommandInfo[];
+  /** 过滤后的命令列表 */
+  filteredCommands: SystemCommandInfo[];
+  /** 是否正在加载 */
+  isLoading: boolean;
+  /** 错误信息 */
+  error: string | null;
+}
+
+export function useSystemCommands(options: UseSystemCommandsOptions = {}) {
+  const { autoLoad = true } = options;
+
+  const [state, setState] = useState<UseSystemCommandsState>({
+    commands: [],
+    filteredCommands: [],
+    isLoading: false,
+    error: null,
+  });
+
+  const loadedRef = useRef(false);
+
+  // 加载系统命令列表
+  const loadCommands = useCallback(async () => {
+    if (state.isLoading) return;
+
+    setState((prev) => ({ ...prev, isLoading: true, error: null }));
+
+    try {
+      const result = await listSystemCommands();
+      if (result.success) {
+        setState({
+          commands: result.data.commands,
+          filteredCommands: result.data.commands,
+          isLoading: false,
+          error: null,
+        });
+      } else {
+        setState((prev) => ({
+          ...prev,
+          isLoading: false,
+          error: 'Failed to load system commands',
+        }));
+      }
+    } catch (error) {
+      setState((prev) => ({
+        ...prev,
+        isLoading: false,
+        error: error instanceof Error ? error.message : 'Unknown error',
+      }));
+    }
+  }, [state.isLoading]);
+
+  // 搜索/过滤系统命令
+  const filterCommands = useCallback(
+    (query: string) => {
+      // 空查询显示所有命令
+      if (!query.trim()) {
+        setState((prev) => ({
+          ...prev,
+          filteredCommands: prev.commands,
+        }));
+        return;
+      }
+
+      // 本地过滤
+      const queryLower = query.toLowerCase();
+      const localFiltered = state.commands.filter(
+        (cmd) =>
+          cmd.name.toLowerCase().includes(queryLower) ||
+          cmd.description?.toLowerCase().includes(queryLower) ||
+          cmd.aliases?.some((alias) => alias.toLowerCase().includes(queryLower))
+      );
+
+      setState((prev) => ({
+        ...prev,
+        filteredCommands: localFiltered,
+      }));
+    },
+    [state.commands]
+  );
+
+  // 自动加载
+  useEffect(() => {
+    if (autoLoad && !loadedRef.current) {
+      loadedRef.current = true;
+      loadCommands();
+    }
+  }, [autoLoad, loadCommands]);
+
+  return {
+    ...state,
+    loadCommands,
+    filterCommands,
+  };
+}