fixup Codex MCP handling problem (connection closed: initialize response / transport closed)

mcp-stdio-jsonrpc-guard.mjs

#!/usr/bin/env node
'use strict';

import { spawn } from 'node:child_process';
import { createInterface } from 'node:readline';

if (process.argv.length < 3) {
  console.error('Usage: mcp-stdio-jsonrpc-guard <command...>');
  process.exit(1);
}

// Build a POSIX-safe command string for sh -lc
const args = process.argv.slice(2);
const command = args.length === 1
  ? args[0]
  : args.map((s) => s === '' ? "''" : `'${String(s).replace(/'/g, `'\\''`)}'`).join(' ');

const child = spawn('sh', ['-lc', command], {
  stdio: ['pipe', 'pipe', 'pipe'],
  env: process.env,
  cwd: process.cwd(),
  windowsHide: false,
  shell: false,
});

// stdin -> child stdin
process.stdin.pipe(child.stdin);

// child stderr -> parent stderr (verbatim)
child.stderr.pipe(process.stderr);

// child stdout -> line filter via readline: JSON lines -> stdout (with patch), others -> stderr
const stdout = createInterface({
  input: child.stdout,
  crlfDelay: Infinity,
});

stdout.on('line', (line) => {
  const trimmed = line.trim();
  if (!trimmed) {
    process.stderr.write(line + '\n');
    return;
  }

  try {
    let out = line; // preserve original text by default
    let msg = JSON.parse(trimmed);

    // Patch: move params.message -> params.data when method matches and data is absent
    // https://github.com/openai/codex/issues/5671
    if (msg && typeof msg === 'object' && msg.method === 'notifications/message' && msg.params) {
      const p = msg.params;
      if (Object.prototype.hasOwnProperty.call(p, 'message') && !('data' in p)) {
        msg.params = { ...p, data: p.message };
        delete msg.params.message;
        out = JSON.stringify(msg);
      }
    }

    process.stdout.write(out + '\n');
  } catch {
    process.stderr.write(line + '\n');
  }
});

// forward common signals to child
[
  'SIGINT', 'SIGTERM', 'SIGHUP', 'SIGQUIT', 'SIGUSR1', 'SIGUSR2', 'SIGPIPE', 'SIGBREAK'
].forEach(sig => process.on(sig, () => child.kill(sig)));

// ensure child is cleaned up if parent exits
process.on('exit', () => {
  try { child.kill(); } catch {}
});

// mirror child exit status
child.on('exit', (code, signal) => {
  if (signal) {
    try {
      process.kill(process.pid, signal);
    } catch {
      process.exit(128);
    }
  } else {
    process.exit(code ?? 0);
  }
});

child.on('error', (err) => {
  console.error(`Failed to start "${cmd}": ${err.message}`);
  process.exit(127);
});