Function pipeUntilClose

src/mcp/proxy.ts:504–537

* Pipe stdin → socket and socket → stdout. Resolves once either end closes * so the process can exit. Note: we deliberately do NOT use * `process.stdin.pipe(socket)` because pipe propagates 'end' onto the * downstream, which would close the socket prematurely if stdin happens to * end early — th

(socket: net.Socket)

 * end early — the MCP spec allows it to stay open across reconnects.
 */
function pipeUntilClose(socket: net.Socket): Promise<void> {
  return new Promise((resolve) => {
    let resolved = false;
    const done = () => { if (!resolved) { resolved = true; resolve(); } };

    process.stdin.on('data', (chunk) => {
      try { socket.write(chunk); } catch { /* socket may have errored — close path catches it */ }
    });
    process.stdin.on('end', () => {
      try { socket.end(); } catch { /* ignore */ }
      done();
    });
    // 'close' and 'error' both tear down: a socket-backed stdin can fail with
    // an 'error' (ECONNRESET/hangup) rather than a clean close; destroying it
    // stops a hung fd from busy-spinning the event loop (#799).
    const teardown = () => {
      try { process.stdin.destroy(); } catch { /* ignore */ }
      try { socket.destroy(); } catch { /* ignore */ }
      done();
    };
    process.stdin.on('close', teardown);
    process.stdin.on('error', teardown);

    socket.on('data', (chunk) => {
      try { process.stdout.write(chunk); } catch { /* ignore */ }
    });
    socket.on('end', () => done());
    socket.on('close', () => done());
    socket.on('error', (err) => {
      process.stderr.write(`[CodeGraph MCP] daemon socket error: ${err.message}\n`);
      done();
    });
  });
}

/**
 * PPID watchdog mirroring the one in `MCPServer.start` — kills the proxy if