Function runProxy

src/mcp/proxy.ts:83–123

(
  socketPath: string,
  expectedVersion: string = CodeGraphPackageVersion,
)

 * price of never silently running a stale daemon against newer client code.)
 */
export async function runProxy(
  socketPath: string,
  expectedVersion: string = CodeGraphPackageVersion,
): Promise<ProxyResult> {
  // POSIX: refuse to connect to a stale socket file that points at no
  // listening process. `fs.existsSync` is a cheap pre-check; a real
  // ECONNREFUSED below catches the rare "exists but unbound" race.
  if (process.platform !== 'win32' && !fs.existsSync(socketPath)) {
    return { outcome: 'fallback-needed', reason: 'socket file missing' };
  }

  const socket = net.createConnection(socketPath);
  socket.setEncoding('utf8');

  const hello = await readHelloLine(socket).catch((err) => {
    socket.destroy();
    return new Error(String(err));
  });
  if (hello instanceof Error) {
    return { outcome: 'fallback-needed', reason: hello.message };
  }

  if (hello.codegraph !== expectedVersion) {
    process.stderr.write(
      `[CodeGraph MCP] Found a daemon on ${socketPath} but version (${hello.codegraph}) ` +
      `differs from ours (${expectedVersion}); falling back to direct mode.\n`
    );
    socket.destroy();
    return { outcome: 'fallback-needed', reason: 'version mismatch' };
  }

  logAttachedDaemon(socketPath, hello);

  sendClientHello(socket);
  startPpidWatchdog(socket);
  await pipeUntilClose(socket);
  // Host disconnected (or the daemon went away). The proxy's only job is the
  // pipe; exit now so we don't linger — process.stdin's 'data' listener would
  // otherwise keep the event loop alive and leave a zombie launcher behind.
  process.exit(0);
}

/**
 * Connect to a daemon at `socketPath` and verify its hello (exact version match).