### Overview
This PR adds the first piece of tracing for app-server JSON-RPC
requests.
There are two main changes:
- JSON-RPC requests can now take an optional W3C trace context at the
top level via a `trace` field (`traceparent` / `tracestate`).
- app-server now creates a dedicated request span for every inbound
JSON-RPC request in `MessageProcessor`, and uses the request-level trace
context as the parent when present.
For compatibility with existing flows, app-server still falls back to
the TRACEPARENT env var when there is no request-level traceparent.
This PR is intentionally scoped to the app-server boundary. In a
followup, we'll actually propagate trace context through the async
handoff into core execution spans like run_turn, which will make
app-server traces much more useful.
### Spans
A few details on the app-server span shape:
- each inbound request gets its own server span
- span/resource names are based on the JSON-RPC method (`initialize`,
`thread/start`, `turn/start`, etc.)
- spans record transport (stdio vs websocket), request id, connection
id, and client name/version when available
- `initialize` stores client metadata in session state so later requests
on the same connection can reuse it
## Summary
- add graceful websocket app-server restart on Ctrl-C by draining until
no assistant turns are running
- stop the websocket acceptor and disconnect existing connections once
the drain condition is met
- add a websocket integration test that verifies Ctrl-C waits for an
in-flight turn before exit
## Verification
- `cargo check -p codex-app-server --quiet`
- `cargo test -p codex-app-server --test all
suite::v2::connection_handling_websocket`
- I (maxj) tested remote and local Codex.app
---------
Co-authored-by: Codex <noreply@openai.com>
Reapply "Add app-server transport layer with websocket support" with
additional fixes from https://github.com/openai/codex/pull/11313/changes
to avoid deadlocking.
This reverts commit 47356ff83c.
## Summary
To avoid deadlocking when queues are full, we maintain separate tokio
tasks dedicated to incoming vs outgoing event handling
- split the app-server main loop into two tasks in
`run_main_with_transport`
- inbound handling (`transport_event_rx`)
- outbound handling (`outgoing_rx` + `thread_created_rx`)
- separate incoming and outgoing websocket tasks
## Validation
Integration tests, testing thoroughly e2e in codex app w/ >10 concurrent
requests
<img width="1365" height="979" alt="Screenshot 2026-02-10 at 2 54 22 PM"
src="https://github.com/user-attachments/assets/47ca2c13-f322-4e5c-bedd-25859cbdc45f"
/>
---------
Co-authored-by: jif-oai <jif@openai.com>
- Adds --listen <URL> to codex app-server with two listen modes:
- stdio:// (default, existing behavior)
- ws://IP:PORT (new websocket transport)
- Refactors message routing to be connection-aware:
- Tracks per-connection session state (initialize/experimental
capability)
- Routes responses/errors to the originating connection
- Broadcasts server notifications/requests to initialized connections
- Updates initialization semantics to be per connection (not
process-global), and updates app-server docs accordingly.
- Adds websocket accept/read/write handling (JSON-RPC per text frame,
ping/pong handling, connection lifecycle events).
Testing
- Unit tests for transport URL parsing and targeted response/error
routing.
- New websocket integration test validating:
- per-connection initialization requirements
- no cross-connection response leakage
- same request IDs on different connections route independently.
