Merge pull request #1147 from QwenLM/mingholy/feat/cli-sdk-stage-2

Custom tools support via SDK controlled MCP servers

packages/core/src/config/config.test.ts

@@ -63,6 +63,7 @@ vi.mock('../tools/tool-registry', () => {
   ToolRegistryMock.prototype.registerTool = vi.fn();
   ToolRegistryMock.prototype.discoverAllTools = vi.fn();
   ToolRegistryMock.prototype.getAllTools = vi.fn(() => []); // Mock methods if needed
+  ToolRegistryMock.prototype.getAllToolNames = vi.fn(() => []);
   ToolRegistryMock.prototype.getTool = vi.fn();
   ToolRegistryMock.prototype.getFunctionDeclarations = vi.fn(() => []);
   return { ToolRegistry: ToolRegistryMock };

packages/core/src/config/config.ts

@@ -46,6 +46,7 @@ import { ExitPlanModeTool } from '../tools/exitPlanMode.js';
 import { GlobTool } from '../tools/glob.js';
 import { GrepTool } from '../tools/grep.js';
 import { LSTool } from '../tools/ls.js';
+import type { SendSdkMcpMessage } from '../tools/mcp-client.js';
 import { MemoryTool, setGeminiMdFilename } from '../tools/memoryTool.js';
 import { ReadFileTool } from '../tools/read-file.js';
 import { ReadManyFilesTool } from '../tools/read-many-files.js';
@@ -239,9 +240,18 @@ export class MCPServerConfig {
     readonly targetAudience?: string,
     /* targetServiceAccount format: <service-account-name>@<project-num>.iam.gserviceaccount.com */
     readonly targetServiceAccount?: string,
+    // SDK MCP server type - 'sdk' indicates server runs in SDK process
+    readonly type?: 'sdk',
   ) {}
 }
 
+/**
+ * Check if an MCP server config represents an SDK server
+ */
+export function isSdkMcpServerConfig(config: MCPServerConfig): boolean {
+  return config.type === 'sdk';
+}
+
 export enum AuthProviderType {
   DYNAMIC_DISCOVERY = 'dynamic_discovery',
   GOOGLE_CREDENTIALS = 'google_credentials',
@@ -360,6 +370,17 @@ function normalizeConfigOutputFormat(
   }
 }
 
+/**
+ * Options for Config.initialize()
+ */
+export interface ConfigInitializeOptions {
+  /**
+   * Callback for sending MCP messages to SDK servers via control plane.
+   * Required for SDK MCP server support in SDK mode.
+   */
+  sendSdkMcpMessage?: SendSdkMcpMessage;
+}
+
 export class Config {
   private sessionId: string;
   private sessionData?: ResumedSessionData;
@@ -599,8 +620,9 @@ export class Config {
 
   /**
    * Must only be called once, throws if called again.
+   * @param options Optional initialization options including sendSdkMcpMessage callback
    */
-  async initialize(): Promise<void> {
+  async initialize(options?: ConfigInitializeOptions): Promise<void> {
     if (this.initialized) {
       throw Error('Config was already initialized');
     }
@@ -619,7 +641,9 @@ export class Config {
       this.subagentManager.loadSessionSubagents(this.sessionSubagents);
     }
 
-    this.toolRegistry = await this.createToolRegistry();
+    this.toolRegistry = await this.createToolRegistry(
+      options?.sendSdkMcpMessage,
+    );
 
     await this.geminiClient.initialize();
 
@@ -1261,8 +1285,14 @@ export class Config {
     return this.subagentManager;
   }
 
-  async createToolRegistry(): Promise<ToolRegistry> {
-    const registry = new ToolRegistry(this, this.eventEmitter);
+  async createToolRegistry(
+    sendSdkMcpMessage?: SendSdkMcpMessage,
+  ): Promise<ToolRegistry> {
+    const registry = new ToolRegistry(
+      this,
+      this.eventEmitter,
+      sendSdkMcpMessage,
+    );
 
     const coreToolsConfig = this.getCoreTools();
     const excludeToolsConfig = this.getExcludeTools();
@@ -1347,6 +1377,7 @@ export class Config {
     }
 
     await registry.discoverAllTools();
+    console.debug('ToolRegistry created', registry.getAllToolNames());
     return registry;
   }
 }

packages/core/src/index.ts

@@ -102,7 +102,9 @@ export * from './tools/shell.js';
 export * from './tools/web-search/index.js';
 export * from './tools/read-many-files.js';
 export * from './tools/mcp-client.js';
+export * from './tools/mcp-client-manager.js';
 export * from './tools/mcp-tool.js';
+export * from './tools/sdk-control-client-transport.js';
 export * from './tools/task.js';
 export * from './tools/todoWrite.js';
 export * from './tools/exitPlanMode.js';

packages/core/src/tools/mcp-client-manager.ts

@@ -5,6 +5,7 @@
  */
 
 import type { Config, MCPServerConfig } from '../config/config.js';
+import { isSdkMcpServerConfig } from '../config/config.js';
 import type { ToolRegistry } from './tool-registry.js';
 import type { PromptRegistry } from '../prompts/prompt-registry.js';
 import {
@@ -12,6 +13,7 @@ import {
   MCPDiscoveryState,
   populateMcpServerCommand,
 } from './mcp-client.js';
+import type { SendSdkMcpMessage } from './mcp-client.js';
 import { getErrorMessage } from '../utils/errors.js';
 import type { EventEmitter } from 'node:events';
 import type { WorkspaceContext } from '../utils/workspaceContext.js';
@@ -31,6 +33,7 @@ export class McpClientManager {
   private readonly workspaceContext: WorkspaceContext;
   private discoveryState: MCPDiscoveryState = MCPDiscoveryState.NOT_STARTED;
   private readonly eventEmitter?: EventEmitter;
+  private readonly sendSdkMcpMessage?: SendSdkMcpMessage;
 
   constructor(
     mcpServers: Record<string, MCPServerConfig>,
@@ -40,6 +43,7 @@ export class McpClientManager {
     debugMode: boolean,
     workspaceContext: WorkspaceContext,
     eventEmitter?: EventEmitter,
+    sendSdkMcpMessage?: SendSdkMcpMessage,
   ) {
     this.mcpServers = mcpServers;
     this.mcpServerCommand = mcpServerCommand;
@@ -48,6 +52,7 @@ export class McpClientManager {
     this.debugMode = debugMode;
     this.workspaceContext = workspaceContext;
     this.eventEmitter = eventEmitter;
+    this.sendSdkMcpMessage = sendSdkMcpMessage;
   }
 
   /**
@@ -71,6 +76,11 @@ export class McpClientManager {
     this.eventEmitter?.emit('mcp-client-update', this.clients);
     const discoveryPromises = Object.entries(servers).map(
       async ([name, config]) => {
+        // For SDK MCP servers, pass the sendSdkMcpMessage callback
+        const sdkCallback = isSdkMcpServerConfig(config)
+          ? this.sendSdkMcpMessage
+          : undefined;
+
         const client = new McpClient(
           name,
           config,
@@ -78,6 +88,7 @@ export class McpClientManager {
           this.promptRegistry,
           this.workspaceContext,
           this.debugMode,
+          sdkCallback,
         );
         this.clients.set(name, client);
 

packages/core/src/tools/mcp-client.ts

@@ -13,6 +13,7 @@ import { StreamableHTTPClientTransport } from '@modelcontextprotocol/sdk/client/
 import type { Transport } from '@modelcontextprotocol/sdk/shared/transport.js';
 import type {
   GetPromptResult,
+  JSONRPCMessage,
   Prompt,
 } from '@modelcontextprotocol/sdk/types.js';
 import {
@@ -22,10 +23,11 @@ import {
 } from '@modelcontextprotocol/sdk/types.js';
 import { parse } from 'shell-quote';
 import type { Config, MCPServerConfig } from '../config/config.js';
-import { AuthProviderType } from '../config/config.js';
+import { AuthProviderType, isSdkMcpServerConfig } from '../config/config.js';
 import { GoogleCredentialProvider } from '../mcp/google-auth-provider.js';
 import { ServiceAccountImpersonationProvider } from '../mcp/sa-impersonation-provider.js';
 import { DiscoveredMCPTool } from './mcp-tool.js';
+import { SdkControlClientTransport } from './sdk-control-client-transport.js';
 
 import type { FunctionDeclaration } from '@google/genai';
 import { mcpToTool } from '@google/genai';
@@ -42,6 +44,14 @@ import type {
 } from '../utils/workspaceContext.js';
 import type { ToolRegistry } from './tool-registry.js';
 
+/**
+ * Callback type for sending MCP messages to SDK servers via control plane
+ */
+export type SendSdkMcpMessage = (
+  serverName: string,
+  message: JSONRPCMessage,
+) => Promise<JSONRPCMessage>;
+
 export const MCP_DEFAULT_TIMEOUT_MSEC = 10 * 60 * 1000; // default to 10 minutes
 
 export type DiscoveredMCPPrompt = Prompt & {
@@ -92,6 +102,7 @@ export class McpClient {
     private readonly promptRegistry: PromptRegistry,
     private readonly workspaceContext: WorkspaceContext,
     private readonly debugMode: boolean,
+    private readonly sendSdkMcpMessage?: SendSdkMcpMessage,
   ) {
     this.client = new Client({
       name: `qwen-cli-mcp-client-${this.serverName}`,
@@ -189,7 +200,12 @@ export class McpClient {
   }
 
   private async createTransport(): Promise<Transport> {
-    return createTransport(this.serverName, this.serverConfig, this.debugMode);
+    return createTransport(
+      this.serverName,
+      this.serverConfig,
+      this.debugMode,
+      this.sendSdkMcpMessage,
+    );
   }
 
   private async discoverTools(cliConfig: Config): Promise<DiscoveredMCPTool[]> {
@@ -501,6 +517,7 @@ export function populateMcpServerCommand(
  * @param mcpServerName The name identifier for this MCP server
  * @param mcpServerConfig Configuration object containing connection details
  * @param toolRegistry The registry to register discovered tools with
+ * @param sendSdkMcpMessage Optional callback for SDK MCP servers to route messages via control plane.
  * @returns Promise that resolves when discovery is complete
  */
 export async function connectAndDiscover(
@@ -511,6 +528,7 @@ export async function connectAndDiscover(
   debugMode: boolean,
   workspaceContext: WorkspaceContext,
   cliConfig: Config,
+  sendSdkMcpMessage?: SendSdkMcpMessage,
 ): Promise<void> {
   updateMCPServerStatus(mcpServerName, MCPServerStatus.CONNECTING);
 
@@ -521,6 +539,7 @@ export async function connectAndDiscover(
       mcpServerConfig,
       debugMode,
       workspaceContext,
+      sendSdkMcpMessage,
     );
 
     mcpClient.onerror = (error) => {
@@ -744,6 +763,7 @@ export function hasNetworkTransport(config: MCPServerConfig): boolean {
  *
  * @param mcpServerName The name of the MCP server, used for logging and identification.
  * @param mcpServerConfig The configuration specifying how to connect to the server.
+ * @param sendSdkMcpMessage Optional callback for SDK MCP servers to route messages via control plane.
  * @returns A promise that resolves to a connected MCP `Client` instance.
  * @throws An error if the connection fails or the configuration is invalid.
  */
@@ -752,6 +772,7 @@ export async function connectToMcpServer(
   mcpServerConfig: MCPServerConfig,
   debugMode: boolean,
   workspaceContext: WorkspaceContext,
+  sendSdkMcpMessage?: SendSdkMcpMessage,
 ): Promise<Client> {
   const mcpClient = new Client({
     name: 'qwen-code-mcp-client',
@@ -808,6 +829,7 @@ export async function connectToMcpServer(
       mcpServerName,
       mcpServerConfig,
       debugMode,
+      sendSdkMcpMessage,
     );
     try {
       await mcpClient.connect(transport, {
@@ -1172,7 +1194,21 @@ export async function createTransport(
   mcpServerName: string,
   mcpServerConfig: MCPServerConfig,
   debugMode: boolean,
+  sendSdkMcpMessage?: SendSdkMcpMessage,
 ): Promise<Transport> {
+  if (isSdkMcpServerConfig(mcpServerConfig)) {
+    if (!sendSdkMcpMessage) {
+      throw new Error(
+        `SDK MCP server '${mcpServerName}' requires sendSdkMcpMessage callback`,
+      );
+    }
+    return new SdkControlClientTransport({
+      serverName: mcpServerName,
+      sendMcpMessage: sendSdkMcpMessage,
+      debugMode,
+    });
+  }
+
   if (
     mcpServerConfig.authProviderType ===
     AuthProviderType.SERVICE_ACCOUNT_IMPERSONATION

packages/core/src/tools/sdk-control-client-transport.ts

@@ -0,0 +1,163 @@
+/**
+ * @license
+ * Copyright 2025 Qwen Team
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * SdkControlClientTransport - MCP Client transport for SDK MCP servers
+ *
+ * This transport enables CLI's MCP client to connect to SDK MCP servers
+ * through the control plane. Messages are routed:
+ *
+ * CLI MCP Client → SdkControlClientTransport → sendMcpMessage() →
+ * control_request (mcp_message) → SDK → control_response → onmessage → CLI
+ *
+ * Unlike StdioClientTransport which spawns a subprocess, this transport
+ * communicates with SDK MCP servers running in the SDK process.
+ */
+
+import type { JSONRPCMessage } from '@modelcontextprotocol/sdk/types.js';
+
+/**
+ * Callback to send MCP messages to SDK via control plane
+ * Returns the MCP response from the SDK
+ */
+export type SendMcpMessageCallback = (
+  serverName: string,
+  message: JSONRPCMessage,
+) => Promise<JSONRPCMessage>;
+
+export interface SdkControlClientTransportOptions {
+  serverName: string;
+  sendMcpMessage: SendMcpMessageCallback;
+  debugMode?: boolean;
+}
+
+/**
+ * MCP Client Transport for SDK MCP servers
+ *
+ * Implements the @modelcontextprotocol/sdk Transport interface to enable
+ * CLI's MCP client to connect to SDK MCP servers via the control plane.
+ */
+export class SdkControlClientTransport {
+  private serverName: string;
+  private sendMcpMessage: SendMcpMessageCallback;
+  private debugMode: boolean;
+  private started = false;
+
+  // Transport interface callbacks
+  onmessage?: (message: JSONRPCMessage) => void;
+  onerror?: (error: Error) => void;
+  onclose?: () => void;
+
+  constructor(options: SdkControlClientTransportOptions) {
+    this.serverName = options.serverName;
+    this.sendMcpMessage = options.sendMcpMessage;
+    this.debugMode = options.debugMode ?? false;
+  }
+
+  /**
+   * Start the transport
+   * For SDK transport, this just marks it as ready - no subprocess to spawn
+   */
+  async start(): Promise<void> {
+    if (this.started) {
+      return;
+    }
+
+    this.started = true;
+
+    if (this.debugMode) {
+      console.error(
+        `[SdkControlClientTransport] Started for server '${this.serverName}'`,
+      );
+    }
+  }
+
+  /**
+   * Send a message to the SDK MCP server via control plane
+   *
+   * Routes the message through the control plane and delivers
+   * the response via onmessage callback.
+   */
+  async send(message: JSONRPCMessage): Promise<void> {
+    if (!this.started) {
+      throw new Error(
+        `SdkControlClientTransport (${this.serverName}) not started. Call start() first.`,
+      );
+    }
+
+    if (this.debugMode) {
+      console.error(
+        `[SdkControlClientTransport] Sending message to '${this.serverName}':`,
+        JSON.stringify(message),
+      );
+    }
+
+    try {
+      // Send message to SDK and wait for response
+      const response = await this.sendMcpMessage(this.serverName, message);
+
+      if (this.debugMode) {
+        console.error(
+          `[SdkControlClientTransport] Received response from '${this.serverName}':`,
+          JSON.stringify(response),
+        );
+      }
+
+      // Deliver response via onmessage callback
+      if (this.onmessage) {
+        this.onmessage(response);
+      }
+    } catch (error) {
+      if (this.debugMode) {
+        console.error(
+          `[SdkControlClientTransport] Error sending to '${this.serverName}':`,
+          error,
+        );
+      }
+
+      if (this.onerror) {
+        this.onerror(error instanceof Error ? error : new Error(String(error)));
+      }
+
+      throw error;
+    }
+  }
+
+  /**
+   * Close the transport
+   */
+  async close(): Promise<void> {
+    if (!this.started) {
+      return;
+    }
+
+    this.started = false;
+
+    if (this.debugMode) {
+      console.error(
+        `[SdkControlClientTransport] Closed for server '${this.serverName}'`,
+      );
+    }
+
+    if (this.onclose) {
+      this.onclose();
+    }
+  }
+
+  /**
+   * Check if transport is started
+   */
+  isStarted(): boolean {
+    return this.started;
+  }
+
+  /**
+   * Get server name
+   */
+  getServerName(): string {
+    return this.serverName;
+  }
+}

packages/core/src/tools/tool-registry.ts

@@ -16,6 +16,7 @@ import type { Config } from '../config/config.js';
 import { spawn } from 'node:child_process';
 import { StringDecoder } from 'node:string_decoder';
 import { connectAndDiscover } from './mcp-client.js';
+import type { SendSdkMcpMessage } from './mcp-client.js';
 import { McpClientManager } from './mcp-client-manager.js';
 import { DiscoveredMCPTool } from './mcp-tool.js';
 import { parse } from 'shell-quote';
@@ -173,7 +174,11 @@ export class ToolRegistry {
   private config: Config;
   private mcpClientManager: McpClientManager;
 
-  constructor(config: Config, eventEmitter?: EventEmitter) {
+  constructor(
+    config: Config,
+    eventEmitter?: EventEmitter,
+    sendSdkMcpMessage?: SendSdkMcpMessage,
+  ) {
     this.config = config;
     this.mcpClientManager = new McpClientManager(
       this.config.getMcpServers() ?? {},
@@ -183,6 +188,7 @@ export class ToolRegistry {
       this.config.getDebugMode(),
       this.config.getWorkspaceContext(),
       eventEmitter,
+      sendSdkMcpMessage,
     );
   }