app-server: add Unix socket transport (#18255)

## Summary
- add unix:// app-server transport backed by the shared codex-uds crate
- reuse the websocket connection loop for axum and tungstenite-backed
streams
- add codex app-server proxy to bridge stdio clients to the control
socket
- tolerate Windows UDS backends that report a missing rendezvous path as
connection refused before binding

## Tests
- cargo test -p codex-app-server
control_socket_acceptor_forwards_websocket_text_messages_and_pings
- cargo test -p codex-app-server
- just fmt
- just fix -p codex-app-server
- git -c core.fsmonitor=false diff --check

codex-rs/app-server/src/lib.rs

@@ -31,6 +31,7 @@ use crate::transport::OutboundConnectionState;
 use crate::transport::TransportEvent;
 use crate::transport::auth::policy_from_settings;
 use crate::transport::route_outgoing_envelope;
+use crate::transport::start_control_socket_acceptor;
 use crate::transport::start_remote_control;
 use crate::transport::start_stdio_connection;
 use crate::transport::start_websocket_acceptor;
@@ -93,6 +94,7 @@ mod transport;
 pub use crate::error_code::INPUT_TOO_LARGE_ERROR_CODE;
 pub use crate::error_code::INVALID_PARAMS_ERROR_CODE;
 pub use crate::transport::AppServerTransport;
+pub use crate::transport::app_server_control_socket_path;
 pub use crate::transport::auth::AppServerWebsocketAuthArgs;
 pub use crate::transport::auth::AppServerWebsocketAuthSettings;
 pub use crate::transport::auth::WebsocketAuthCliMode;
@@ -542,7 +544,7 @@ pub async fn run_main_with_transport(
     let graceful_signal_restart_enabled = !single_client_mode;
     let mut app_server_client_name_rx = None;
 
-    match transport {
+    match &transport {
         AppServerTransport::Stdio => {
             let (stdio_client_name_tx, stdio_client_name_rx) = oneshot::channel::<String>();
             app_server_client_name_rx = Some(stdio_client_name_rx);
@@ -553,9 +555,18 @@ pub async fn run_main_with_transport(
             )
             .await?;
         }
+        AppServerTransport::UnixSocket { socket_path } => {
+            let accept_handle = start_control_socket_acceptor(
+                socket_path.clone(),
+                transport_event_tx.clone(),
+                transport_shutdown_token.clone(),
+            )
+            .await?;
+            transport_accept_handles.push(accept_handle);
+        }
         AppServerTransport::WebSocket { bind_address } => {
             let accept_handle = start_websocket_acceptor(
-                bind_address,
+                *bind_address,
                 transport_event_tx.clone(),
                 transport_shutdown_token.clone(),
                 policy_from_settings(&auth)?,
@@ -660,7 +671,7 @@ pub async fn run_main_with_transport(
             config_warnings,
             session_source,
             auth_manager,
-            rpc_transport: analytics_rpc_transport(transport),
+            rpc_transport: analytics_rpc_transport(&transport),
             remote_control_handle: Some(remote_control_handle),
         }));
         let mut thread_created_rx = processor.thread_created_receiver();
@@ -772,7 +783,7 @@ pub async fn run_main_with_transport(
                                             .process_request(
                                                 connection_id,
                                                 request,
-                                                transport,
+                                                &transport,
                                                 Arc::clone(&connection_state.session),
                                             )
                                             .await;
@@ -892,12 +903,12 @@ pub async fn run_main_with_transport(
     Ok(())
 }
 
-fn analytics_rpc_transport(transport: AppServerTransport) -> AppServerRpcTransport {
+fn analytics_rpc_transport(transport: &AppServerTransport) -> AppServerRpcTransport {
     match transport {
         AppServerTransport::Stdio => AppServerRpcTransport::Stdio,
-        AppServerTransport::WebSocket { .. } | AppServerTransport::Off => {
-            AppServerRpcTransport::Websocket
-        }
+        AppServerTransport::UnixSocket { .. }
+        | AppServerTransport::WebSocket { .. }
+        | AppServerTransport::Off => AppServerRpcTransport::Websocket,
     }
 }