Cache executor metadata from initialization (#40343)

## What changed

- Include `environmentInfo` in the exec-server `initialize` response and seed the Rust client's metadata cache from it.
- Fall back to one lazy `environment/info` request when connecting to older servers that omit initialization metadata, then share the cached result across client clones and session recovery.
- Keep app-server `environment/info` requests uncached so they continue to probe the executor.

## Testing

- Cover initialization metadata, the legacy-server fallback, shared caching, accepted WebSocket environments, and repeated uncached app-server probes.

GitOrigin-RevId: 380132d9db183998d73e8c6b0954e4d70c7e8406

codex-rs/exec-server/README.md

@@ -153,9 +153,22 @@ Request params:
 Response:
 
 ```json
-{}
+{
+  "sessionId": "00000000-0000-4000-8000-000000000001",
+  "environmentInfo": {
+    "shell": { "name": "bash", "path": "/bin/bash" },
+    "cwd": "file:///workspace"
+  }
+}
 ```
 
+`environmentInfo` contains the same executor metadata returned by
+`environment/info`, so clients can use it without a second request.
+
+Rust clients cache this metadata for the client's lifetime, including session
+resumption. If initialization omits it, the first metadata request fetches and
+caches `environment/info`.
+
 ### `initialized`
 
 Handshake acknowledgement notification sent by the client after a successful
@@ -429,7 +442,7 @@ Initialize:
 
 ```json
 {"id":1,"method":"initialize","params":{"clientName":"example-client"}}
-{"id":1,"result":{}}
+{"id":1,"result":{"sessionId":"00000000-0000-4000-8000-000000000001","environmentInfo":{"shell":{"name":"bash","path":"/bin/bash"},"cwd":"file:///tmp"}}}
 {"method":"initialized","params":{}}
 ```
 

codex-rs/exec-server/src/client.rs

@@ -264,6 +264,8 @@ struct Inner {
     // Keep admission shared while recovered transports finish older requests.
     rpc_inbound_request_slots: Arc<Semaphore>,
     session_id: OnceLock<String>,
+    /// Caches metadata from initialization or the first successful info request for this client's lifetime.
+    environment_info: OnceCell<EnvironmentInfo>,
     reconnect_strategy: Option<ExecServerReconnectStrategy>,
 }
 
@@ -765,7 +767,18 @@ impl ExecServerClient {
         self.call(EXEC_METHOD, &params).await
     }
 
+    /// Returns cached executor metadata, fetching it lazily if initialization omitted it.
     pub async fn environment_info(&self) -> Result<EnvironmentInfo, ExecServerError> {
+        self.inner
+            .environment_info
+            .get_or_try_init(|| self.force_environment_info())
+            .await
+            .cloned()
+    }
+
+    /// Fetches executor metadata over RPC without reading or updating the cache.
+    // TODO: Remove after app-server migrates off this call.
+    pub async fn force_environment_info(&self) -> Result<EnvironmentInfo, ExecServerError> {
         let rpc_client = self.rpc_client().await?;
         map_rpc_call_result(
             rpc_client
@@ -1117,6 +1130,7 @@ impl ExecServerClient {
             http_body_stream_next_id: AtomicU64::new(1),
             rpc_inbound_request_slots: Arc::new(Semaphore::new(MAX_IN_FLIGHT_SERVER_CALLS)),
             session_id,
+            environment_info: OnceCell::new(),
             reconnect_strategy,
         });
         let client = Self {
@@ -1127,7 +1141,13 @@ impl ExecServerClient {
         // before initialize returns. Drain them immediately so a burst cannot
         // fill the bounded event channel and block the initialize response.
         client.spawn_rpc_reader(&rpc_client, events_rx);
-        client.initialize_rpc(&rpc_client, options).await?;
+        let initialize_response = client.initialize_rpc(&rpc_client, options).await?;
+        if let Some(info) = initialize_response.environment_info {
+            assert!(
+                client.inner.environment_info.set(info).is_ok(),
+                "new client metadata cache must be empty"
+            );
+        }
         Ok(client)
     }
 
@@ -1740,6 +1760,7 @@ mod tests {
     use crate::protocol::EXEC_OUTPUT_DELTA_METHOD;
     use crate::protocol::EXEC_READ_METHOD;
     use crate::protocol::EXEC_WRITE_METHOD;
+    use crate::protocol::EnvironmentInfo;
     use crate::protocol::ExecClosedNotification;
     use crate::protocol::ExecExitedNotification;
     use crate::protocol::ExecOutputDeltaNotification;
@@ -1796,6 +1817,7 @@ mod tests {
                     id: initialize.id,
                     result: serde_json::to_value(InitializeResponse {
                         session_id: "trace-test".to_string(),
+                        environment_info: None,
                     })
                     .expect("initialize response should serialize"),
                 }),
@@ -1942,6 +1964,21 @@ mod tests {
         websocket: &mut WebSocketStream<TcpStream>,
         session_id: &str,
         expected_resume_session_id: Option<&str>,
+    ) {
+        complete_websocket_initialize_with_environment_info(
+            websocket,
+            session_id,
+            expected_resume_session_id,
+            /*environment_info*/ None,
+        )
+        .await;
+    }
+
+    async fn complete_websocket_initialize_with_environment_info(
+        websocket: &mut WebSocketStream<TcpStream>,
+        session_id: &str,
+        expected_resume_session_id: Option<&str>,
+        environment_info: Option<EnvironmentInfo>,
     ) {
         let initialize = read_jsonrpc_websocket(websocket).await;
         let request = match initialize {
@@ -1961,6 +1998,7 @@ mod tests {
                 id: request.id,
                 result: serde_json::to_value(InitializeResponse {
                     session_id: session_id.to_string(),
+                    environment_info,
                 })
                 .expect("initialize response should serialize"),
             }),
@@ -2184,6 +2222,7 @@ mod tests {
                     id: request.id,
                     result: serde_json::to_value(InitializeResponse {
                         session_id: "session-1".to_string(),
+                        environment_info: None,
                     })
                     .expect("initialize response should serialize"),
                 }),
@@ -2329,6 +2368,7 @@ mod tests {
                     id: request.id,
                     result: serde_json::to_value(InitializeResponse {
                         session_id: "session-1".to_string(),
+                        environment_info: None,
                     })
                     .expect("initialize response should serialize"),
                 }),
@@ -2397,6 +2437,61 @@ mod tests {
         server.await.expect("server task should finish");
     }
 
+    #[test_case::test_case(Some(EnvironmentInfo::local()); "from_initialize")]
+    #[test_case::test_case(None; "legacy_server")]
+    #[tokio::test]
+    async fn environment_info_is_cached(
+        initial_environment_info: Option<EnvironmentInfo>,
+    ) -> anyhow::Result<()> {
+        let listener = TcpListener::bind("127.0.0.1:0").await?;
+        let websocket_url = format!("ws://{}", listener.local_addr()?);
+        let expected_info = initial_environment_info
+            .clone()
+            .unwrap_or_else(EnvironmentInfo::local);
+        let server_info = expected_info.clone();
+        let server = tokio::spawn(async move {
+            let mut websocket = accept_websocket(&listener).await;
+            complete_websocket_initialize_with_environment_info(
+                &mut websocket,
+                "session-1",
+                /*expected_resume_session_id*/ None,
+                initial_environment_info.clone(),
+            )
+            .await;
+            if initial_environment_info.is_none() {
+                let JSONRPCMessage::Request(request) = read_jsonrpc_websocket(&mut websocket).await
+                else {
+                    panic!("expected environment info request");
+                };
+                assert_eq!(request.method, "environment/info");
+                write_jsonrpc_websocket(
+                    &mut websocket,
+                    JSONRPCMessage::Response(JSONRPCResponse {
+                        id: request.id,
+                        result: serde_json::to_value(server_info)
+                            .expect("environment info should serialize"),
+                    }),
+                )
+                .await;
+            }
+        });
+        let client = ExecServerClient::connect_websocket(RemoteExecServerConnectArgs {
+            websocket_url,
+            client_name: "metadata-test".to_string(),
+            connect_timeout: Duration::from_secs(1),
+            initialize_timeout: Duration::from_secs(1),
+            resume_session_id: None,
+            http_client_factory: HttpClientFactory::new(OutboundProxyPolicy::ReqwestDefault),
+        })
+        .await?;
+
+        assert_eq!(client.environment_info().await?, expected_info);
+        server.await?;
+        // The server is gone, so a cloned client must use the shared cache.
+        assert_eq!(client.clone().environment_info().await?, expected_info);
+        Ok(())
+    }
+
     #[tokio::test]
     async fn remote_websocket_client_resumes_session() {
         let listener = TcpListener::bind("127.0.0.1:0")
@@ -2615,6 +2710,7 @@ mod tests {
                     id: request.id,
                     result: serde_json::to_value(InitializeResponse {
                         session_id: "session-1".to_string(),
+                        environment_info: None,
                     })
                     .expect("initialize response should serialize"),
                 }),
@@ -2932,6 +3028,7 @@ mod tests {
                     id: request.id,
                     result: serde_json::to_value(InitializeResponse {
                         session_id: "session-1".to_string(),
+                        environment_info: None,
                     })
                     .expect("initialize response should serialize"),
                 }),

codex-rs/exec-server/src/environment.rs

@@ -889,6 +889,7 @@ impl Environment {
     }
 
     /// Returns environment information from the selected execution/filesystem environment.
+    /// Remote metadata is cached for the current client's lifetime.
     #[tracing::instrument(
         name = "exec_server.environment.info",
         skip_all,
@@ -901,6 +902,20 @@ impl Environment {
         }
     }
 
+    /// Fetches uncached metadata, connecting or waiting for recovery as needed.
+    // TODO: Remove after app-server migrates off of force_environment_info.
+    #[tracing::instrument(
+        name = "exec_server.environment.force_info",
+        skip_all,
+        fields(remote = self.is_remote())
+    )]
+    pub async fn force_info(&self) -> Result<EnvironmentInfo, ExecServerError> {
+        match &self.remote_client {
+            Some(client) => client.get().await?.force_environment_info().await,
+            None => Ok(EnvironmentInfo::local()),
+        }
+    }
+
     /// Reads selected executor-local configuration fields for this environment.
     pub async fn read_environment_config(
         &self,

codex-rs/exec-server/src/remote_file_system_path_uri_tests.rs

@@ -614,6 +614,7 @@ async fn complete_websocket_initialize(websocket: &mut WebSocketStream<TcpStream
             id: request.id,
             result: serde_json::to_value(InitializeResponse {
                 session_id: "session-1".to_string(),
+                environment_info: None,
             })
             .expect("initialize response should serialize"),
         }),

codex-rs/exec-server/src/server/handler.rs

@@ -156,7 +156,10 @@ impl ExecServerHandler {
             .session
             .lock()
             .unwrap_or_else(std::sync::PoisonError::into_inner) = Some(session);
-        Ok(InitializeResponse { session_id })
+        Ok(InitializeResponse {
+            session_id,
+            environment_info: Some(EnvironmentInfo::local()),
+        })
     }
 
     pub(crate) fn initialized(&self) -> Result<(), String> {

codex-rs/exec-server/tests/accepted_websocket.rs

@@ -8,6 +8,7 @@ use axum::extract::State;
 use axum::extract::WebSocketUpgrade;
 use axum::response::IntoResponse;
 use axum::routing::any;
+use codex_exec_server::EnvironmentInfo;
 use codex_exec_server::EnvironmentManager;
 use codex_exec_server::EnvironmentObservedStatus;
 use codex_exec_server::EnvironmentStatus;
@@ -77,6 +78,25 @@ async fn accepted_websocket_rejects_initial_resume_session_id() -> Result<()> {
     Ok(())
 }
 
+#[tokio::test]
+async fn accepted_websocket_environment_info_uses_initialization_metadata() -> Result<()> {
+    let (websocket_url, mut accepted_sockets, server_task) = start_acceptor().await?;
+    let (_socket, manager) =
+        connect_executor(&websocket_url, &mut accepted_sockets, "session-1").await?;
+    let environment = manager
+        .default_environment()
+        .context("accepted environment")?;
+
+    assert_eq!(
+        timeout(TEST_TIMEOUT, environment.info()).await??,
+        EnvironmentInfo::local()
+    );
+
+    server_task.abort();
+    let _ = server_task.await;
+    Ok(())
+}
+
 #[tokio::test]
 async fn accepted_websocket_environment_is_ready_immediately() -> Result<()> {
     let (websocket_url, mut accepted_sockets, server_task) = start_acceptor().await?;
@@ -430,6 +450,7 @@ where
             id,
             result: serde_json::to_value(InitializeResponse {
                 session_id: session_id.to_string(),
+                environment_info: Some(EnvironmentInfo::local()),
             })?,
         }),
     )

codex-rs/exec-server/tests/http_client.rs

@@ -1440,6 +1440,7 @@ impl JsonRpcPeer {
             request.id,
             InitializeResponse {
                 session_id: "session-1".to_string(),
+                environment_info: None,
             },
         )
         .await?;

codex-rs/exec-server/tests/initialize.rs

@@ -1,5 +1,6 @@
 mod common;
 
+use codex_exec_server::EnvironmentInfo;
 use codex_exec_server::InitializeParams;
 use codex_exec_server::InitializeResponse;
 use codex_exec_server_protocol::JSONRPCError;
@@ -31,6 +32,10 @@ async fn exec_server_accepts_initialize() -> anyhow::Result<()> {
     assert_eq!(id, initialize_id);
     let initialize_response: InitializeResponse = serde_json::from_value(result)?;
     Uuid::parse_str(&initialize_response.session_id)?;
+    assert_eq!(
+        initialize_response.environment_info,
+        Some(EnvironmentInfo::local())
+    );
 
     server.shutdown().await?;
     Ok(())

codex-rs/exec-server/tests/relay.rs

@@ -277,9 +277,11 @@ async fn pending_noise_environment_connects_and_reconnects_after_ready_report()
         second_reconnected_websocket,
         Arc::new(Mutex::new(Vec::new())),
     ));
-    let recovered_info = timeout(TEST_TIMEOUT, environment.info())
-        .await
-        .context("pending Noise environment should reconnect")??;
+    assert_eq!(
+        next_connection_state(&mut connection_state).await?,
+        EnvironmentConnectionState::Connected
+    );
+    let recovered_info = environment.info().await?;
 
     assert_eq!(recovered_info, initial_info);
     assert_eq!(
@@ -287,10 +289,6 @@ async fn pending_noise_environment_connects_and_reconnects_after_ready_report()
         selected_capability_roots
     );
     assert_eq!(provider.calls(), 2);
-    assert_eq!(
-        next_connection_state(&mut connection_state).await?,
-        EnvironmentConnectionState::Connected
-    );
     registry.verify().await;
 
     second_relay.abort();