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Charlie Marsh 0bc73bbeb1 Add opt-in protocol discovery for local stdio MCP servers (#57210 )

## Why

Stdio servers without `CODEX_MCP_PROTOCOL_VERSION` use the legacy handshake, even when they support MCP `2026-07-28`.

## What changed

- Add the disabled-by-default `mcp_connection_sharing` feature to enable discovery for eligible local stdio servers.
- Recover from failed or late discovery with a fresh handshake when needed, waiting for the previous helper to release resources before restarting.
- Retain a working legacy connection when an upgrade attempt fails for the same account, except on authentication errors.
- Keep tool catalogs separate by protocol and invalidate legacy catalogs when discovery negotiates the modern protocol.

## Testing

Add regression coverage for failed and late discovery, legacy fallback, protocol-specific catalog reuse, message limits, and Windows descendant cleanup.

GitOrigin-RevId: 36c675ef3b81d32fccf06ccbddda2312cfe602c9

2026-10-26 19:37:06 +00:00

src

Add opt-in protocol discovery for local stdio MCP servers (#57210 )

2026-10-26 19:37:06 +00:00

tests

Use descriptor-safe helpers for executable test fixtures (#50018 )

2026-10-01 15:57:03 +00:00

BUILD.bazel

feat: add support for building with Bazel (#8875 )

2026-01-09 11:09:43 -08:00

Cargo.toml

Use descriptor-safe helpers for executable test fixtures (#50018 )

2026-10-01 15:57:03 +00:00

README.md

Prefer just test over cargo test in docs (#23910 )

2026-05-22 16:58:14 +00:00

README.md

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