## 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`
codex-app-server-client
Shared in-process app-server client used by conversational CLI surfaces:
codex-execcodex-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:
InProcessServerEventServerRequestServerNotificationLegacyNotification
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/startorthread/resume - app-server returns the immediate typed response
- richer session metadata may arrive later as a
SessionConfiguredlegacy 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_CAPACITYby 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.