Class MCPServer

src/mcp/index.ts:181–446

 * daemon at start time.
 */
export class MCPServer {
  private projectPath: string | null;
  // Direct-mode-only state. In daemon mode the per-connection sessions live
  // inside the Daemon class; in proxy mode there is no session at all.
  private session: MCPSession | null = null;
  private engine: MCPEngine | null = null;
  private daemon: Daemon | null = null;
  private ppidWatchdog: ReturnType<typeof setInterval> | null = null;
  // Worker-thread liveness watchdog (#850). Long-lived modes only; SIGKILLs the
  // process if the main thread wedges in a non-yielding sync loop.
  private livenessWatchdog: WatchdogHandle | null = null;
  // PPID watchdog baseline — captured at construction so we always have a
  // baseline, even if start() runs after a fork-style reparent.
  private originalPpid: number = process.ppid;
  private hostPpid: number | null = parseHostPpid(process.env[HOST_PPID_ENV]);
  // Idempotency guard for stop().
  private stopped = false;
  private mode: 'unstarted' | 'direct' | 'proxy' | 'daemon' = 'unstarted';

  constructor(projectPath?: string) {
    this.projectPath = projectPath || null;
  }

  /**
   * Start the MCP server.
   *
   * Decision order:
   *   1. `CODEGRAPH_NO_DAEMON=1` → direct mode (unchanged pre-#411 behavior).
   *   2. `CODEGRAPH_DAEMON_INTERNAL=1` → we ARE the detached daemon; listen.
   *   3. No `.codegraph/` reachable → direct mode (the daemon's lockfile and
   *      socket both live under `.codegraph/`).
   *   4. Otherwise connect to (or spawn) the shared daemon and proxy to it.
   *
   * On any unexpected failure in step 4 we transparently fall back to direct
   * mode — a misbehaving daemon must never block a session from starting.
   */
  async start(): Promise<void> {
    // Long-lived process (direct / proxy / daemon alike): flush buffered
    // telemetry opportunistically. Fire-and-forget + unref'd — adds nothing
    // to the handshake path and never keeps the process alive.
    getTelemetry().startInterval();

    // The detached daemon process itself. Checked before the opt-out so the
    // daemon honors the same env it was spawned with (it never sets NO_DAEMON).
    if (daemonInternalSet()) {
      return this.startDaemonProcess();
    }

    // Direct mode if the user opted out. Setting the env var is sufficient to
    // get the pre-#411 single-process behavior.
    if (daemonOptOutSet()) {
      return this.startDirect('CODEGRAPH_NO_DAEMON set');
    }

    const root = resolveDaemonRoot(this.projectPath);
    if (!root) {
      // No initialized project found — daemon mode has nowhere to put its
      // socket. The fresh-checkout / outside-project case; behave as before.