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Martin Au-Yeung ee46c5ba0e Negotiate MCP extensions per app-server session (#36910 )

## Why

App-server clients need to advertise structured MCP extension settings, including supported MCP App UI MIME types, rather than only opting into OpenAI form elicitation with a boolean.

## What changed

- Add an `extensions` map to initialize capabilities and preserve `mcpServerOpenaiFormElicitation` as a legacy alias for `openai/form`.
- Capture the declared extension profile when a thread is started, resumed, or forked, propagate it to subagents, and advertise it to downstream MCP servers during initialization.
- Keep the profile stable for the lifetime of the loaded session instead of changing it on later turns or direct tool calls.

## Testing

- Cover extension conversion, downstream MCP initialization, session isolation, legacy form support, and subagent inheritance.

GitOrigin-RevId: fbcedbb74ce788e574b0f884a4c45c4cedb9de54

2026-08-04 15:23:43 +00:00

src

Negotiate MCP extensions per app-server session (#36910 )

2026-08-04 15:23:43 +00:00

BUILD.bazel

fix(bazel) add missing app-server-client BUILD.bazel (#14027 )

2026-03-09 03:42:54 +00:00

Cargo.toml

Add support for UDS in codex --remote (#22414 )

2026-05-12 21:17:20 -07:00

README.md

Add in-process app server and wire up exec to use it (#14005 )

2026-03-08 18:43:55 -06:00

README.md

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.