Class MCPSession

src/mcp/session.ts:106–350

 * (direct mode) or per socket connection (daemon mode).
 */
export class MCPSession {
  private clientSupportsRoots = false;
  /** From the initialize handshake — attributes usage rollups to the agent host. */
  private clientInfo: ClientInfo | undefined;
  private rootsAttempted = false;
  private resolvePromise: Promise<void> | null = null;
  private explicitProjectPath: string | null;

  constructor(
    private transport: JsonRpcTransport,
    private engine: MCPEngine,
    opts: MCPSessionOptions = {},
  ) {
    this.explicitProjectPath = opts.explicitProjectPath ?? null;
  }

  /**
   * Start handling messages from the transport. Returns immediately — the
   * session lives for as long as the transport is open.
   */
  start(): void {
    this.transport.start(this.handleMessage.bind(this));
  }

  /**
   * Tear down the session. Does NOT touch the engine (the engine may serve
   * other sessions) or call `process.exit` (the daemon decides when to exit).
   */
  stop(): void {
    this.transport.stop();
  }

  /** Underlying transport — exposed for daemon-side close hooks. */
  getTransport(): JsonRpcTransport {
    return this.transport;
  }

  private async handleMessage(message: JsonRpcRequest | JsonRpcNotification): Promise<void> {
    const isRequest = 'id' in message;
    switch (message.method) {
      case 'initialize':
        if (isRequest) await this.handleInitialize(message as JsonRpcRequest);
        break;
      case 'initialized':
        // Notification that client has finished initialization — no action needed.
        break;
      case 'tools/list':
        if (isRequest) await this.handleToolsList(message as JsonRpcRequest);
        break;
      case 'tools/call':
        if (isRequest) await this.handleToolsCall(message as JsonRpcRequest);
        break;
      case 'ping':
        if (isRequest) this.transport.sendResult((message as JsonRpcRequest).id, {});
        break;
      case 'resources/list':
        // We expose no MCP resources, but some clients (opencode, Codex) probe
        // for them on connect; reply with an empty list instead of a