Files
codex/codex-rs/app-server-client
Michael Bolin 8fea372c77 Fix remote app-server shutdown race (#18936)
## Why

A Mac Bazel CI run saw `remote_notifications_arrive_over_websocket` fail
during shutdown with `remote app-server shutdown channel is closed`
(https://app.buildbuddy.io/invocation/9dac05d6-ae20-40f9-b627-fca6e91cf127).
The remote websocket worker can legitimately finish while `shutdown()`
is waiting for the shutdown acknowledgement: after the test server sends
a notification and exits, the worker may deliver the required disconnect
event, observe that the caller has dropped the event receiver, and exit
before it sends the shutdown one-shot.

That state is already terminal cleanup, not a failed shutdown, so
callers should not see a `BrokenPipe` from the acknowledgement channel.

## What Changed

- Treat a closed remote shutdown acknowledgement as an already-exited
worker while still propagating websocket close errors when the worker
returns them.
- Added a deterministic regression test for the interleaving where the
shutdown command is received and the worker exits before replying.

## Verification

- `cargo test -p codex-app-server-client`
- New test:
`remote::tests::shutdown_tolerates_worker_exit_after_command_is_queued`
2026-04-22 02:41:19 +00:00
..

codex-app-server-client

Shared in-process app-server client used by conversational CLI surfaces:

  • codex-exec
  • codex-tui

Purpose

This crate centralizes startup and lifecycle management for an in-process codex-app-server runtime, so CLI clients do not need to duplicate:

  • app-server bootstrap and initialize handshake
  • in-memory request/event transport wiring
  • lifecycle orchestration around caller-provided startup identity
  • graceful shutdown behavior

Startup identity

Callers pass both the app-server SessionSource and the initialize client_info.name explicitly when starting the facade.

That keeps thread metadata (for example in thread/list and thread/read) aligned with the originating runtime without baking TUI/exec-specific policy into the shared client layer.

Transport model

The in-process path uses typed channels:

  • client -> server: ClientRequest / ClientNotification
  • server -> client: InProcessServerEvent
    • ServerRequest
    • ServerNotification
    • LegacyNotification

JSON serialization is still used at external transport boundaries (stdio/websocket), but the in-process hot path is typed.

Typed requests still receive app-server responses through the JSON-RPC result envelope internally. That is intentional: the in-process path is meant to preserve app-server semantics while removing the process boundary, not to introduce a second response contract.

Bootstrap behavior

The client facade starts an already-initialized in-process runtime, but thread bootstrap still follows normal app-server flow:

  • caller sends thread/start or thread/resume
  • app-server returns the immediate typed response
  • richer session metadata may arrive later as a SessionConfigured legacy event

Surfaces such as TUI and exec may therefore need a short bootstrap phase where they reconcile startup response data with later events.

Backpressure and shutdown

  • Queues are bounded and use DEFAULT_IN_PROCESS_CHANNEL_CAPACITY by default.
  • Full queues return explicit overload behavior instead of unbounded growth.
  • shutdown() performs a bounded graceful shutdown and then aborts if timeout is exceeded.

If the client falls behind on event consumption, the worker emits InProcessServerEvent::Lagged and may reject pending server requests so approval flows do not hang indefinitely behind a saturated queue.