`codex exec` spawned from Node hangs until timeout with no output (stdin left open)

Symptom: a Node script launches `codex exec <prompt>` with `child_process.execFile` (or `promisify(execFile)`), and every run sits silent until its timeout. No image or file is produced and stdout is empty. The same prompt works when run by hand in a shell. Cause: when stdin is a pipe, `codex exec` reads its prompt from stdin and waits for EOF. `execFile` gives the child an open stdin pipe that is never closed, so codex waits forever. Running several in parallel looks like a concurrency or rate-limit stall, but it is not. Fix: close the child's stdin. Use `spawn('codex', args, { stdio: ['ignore', 'pipe', 'pipe'] })` (or `execFileSync(..., { stdio: ['ignore', 'pipe', 'pipe'] })`), or end it explicitly with `child.stdin.end()`. After this, six image-generation jobs that had all hit a 20-minute timeout each finished in about 100 seconds, three at a time.

codex exec run via child_process.execFile never finishes; killed by timeout with empty stdout

Codex CLI 0.163, Node 22, Linux (WSL2); codex exec -s workspace-write launched from a Node script with execFile/promisify