core-agent-ide/codex-rs/app-server-client/README.md
Eric Traut da3689f0ef
Add in-process app server and wire up exec to use it (#14005)
This is a subset of PR #13636. See that PR for a full overview of the
architectural change.

This PR implements the in-process app server and modifies the
non-interactive "exec" entry point to use the app server.

---------

Co-authored-by: Felipe Coury <felipe.coury@gmail.com>
2026-03-08 18:43:55 -06:00

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Markdown

# 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.