Files
codex/codex-rs/utils/pty
Charlie Marsh 88b498ded4 Route Linux PTY launches through the process setup helper (#47617)
## Why

PTY launches need to establish a controlling terminal and reset signal state. Extend the Linux process setup helper to perform this work in a fresh, single-threaded process image without forking the application when the native helper is available.

## What changed

- Add a PTY setup mode and support caller-owned stdout and stderr descriptors so all three standard streams use the PTY slave.
- Use the helper for eligible Linux PTY launches, including launches with explicitly preserved descriptors, and wait for child exit asynchronously.
- Preserve portable PTY behavior for `PATH` lookup, custom `argv[0]`, missing working directories, default `SHELL`, stdin EOF, and signal exit status.
- Retain compatibility fallbacks and release the initial PTY descriptors before allocating a portable replacement.

## Testing

Add regression tests for controlling-terminal setup without forking, portable signal exit status, and successful fallback under file-descriptor pressure. Resolve the Python test executable to an absolute path to exercise the helper path.

GitOrigin-RevId: 4b07ce68aa33c5b79548581e221caf5953b0eda1
2026-09-23 18:36:48 +00:00
..

codex-utils-pty

Lightweight helpers for spawning interactive processes either under a PTY (pseudo terminal) or regular pipes. The public API is minimal and mirrors both backends so callers can switch based on their needs (e.g., enabling or disabling TTY).

API surface

  • spawn_pty_process(program, args, cwd, env, arg0, size) → SpawnedProcess
  • spawn_pipe_process(program, args, cwd, env, arg0) → SpawnedProcess
  • spawn_pipe_process_no_stdin(program, args, cwd, env, arg0) → SpawnedProcess
  • combine_output_receivers(stdout_rx, stderr_rx) → broadcast::Receiver<Vec<u8>>
  • conpty_supported() → bool (Windows only; always true elsewhere)
  • TerminalSize { rows, cols } selects PTY dimensions in character cells.
  • ProcessHandle exposes:
    • writer_sender() → mpsc::Sender<Vec<u8>> (stdin)
    • resize(TerminalSize)
    • close_stdin()
    • has_exited(), exit_code(), terminate()
  • SpawnedProcess bundles session, stdout_rx, stderr_rx, and exit_rx (oneshot exit code).

Usage examples

use std::collections::HashMap;
use std::path::Path;
use codex_utils_pty::combine_output_receivers;
use codex_utils_pty::spawn_pty_process;
use codex_utils_pty::TerminalSize;

# tokio_test::block_on(async {
let env_map: HashMap<String, String> = std::env::vars().collect();
let spawned = spawn_pty_process(
    "bash",
    &["-lc".into(), "echo hello".into()],
    Path::new("."),
    &env_map,
    &None,
    TerminalSize::default(),
).await?;

let writer = spawned.session.writer_sender();
writer.send(b"exit\n".to_vec()).await?;

// Collect output until the process exits.
let mut output_rx = combine_output_receivers(spawned.stdout_rx, spawned.stderr_rx);
let mut collected = Vec::new();
while let Ok(chunk) = output_rx.try_recv() {
    collected.extend_from_slice(&chunk);
}
let exit_code = spawned.exit_rx.await.unwrap_or(-1);
# let _ = (collected, exit_code);
# anyhow::Ok(())
# });

Swap in spawn_pipe_process for a non-TTY subprocess; the rest of the API stays the same. Use spawn_pipe_process_no_stdin to force stdin closed (commands that read stdin will see EOF immediately).

Tests

Unit tests live in src/lib.rs and cover both backends (PTY Python REPL and pipe-based stdin roundtrip). Run with:

just test -p codex-utils-pty --no-capture