Files
codex/codex-rs/app-server-client
Eric Traut 92fb848065 Allow large remote app-server resume responses (#19920)
## Why

Remote TUI resume uses the app-server websocket client. That client
inherited tungstenite's default `16 MiB` frame limit, so a large saved
session could make `thread/resume` return a single JSON-RPC response
frame that the client rejected before the TUI could deserialize or
render it.

Fixes #19837

## What Changed

- Configure the remote app-server websocket client with a bounded `128
MiB` max frame/message size.
- Preserve the concrete remote worker exit reason when completing
pending requests after a transport/read failure instead of replacing it
with a generic channel-closed error.
- Add a regression test that sends a single `>16 MiB` JSON-RPC response
frame and verifies the typed request succeeds.

Note: This isn't a perfect fix. It really just moves the limit to a much
larger value. I looked at a bunch of other potential fixes (both
server-side and client-side), and they all involved significant
complexity, had backward-compatibility impact, or impacted performance
of common use cases. This simple fix should address the vast majority of
remote use cases.

## Verification

I reproed the problem locally using a long rollout. Verified that fix
addresses connection drop.
2026-04-27 22:44:10 -07:00
..

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.