github
diff --git a/‎.github/workflows/rust-sdk-tests.yml‎
Lines changed: 3 additions & 1 deletion b/‎.github/workflows/rust-sdk-tests.yml‎
Lines changed: 3 additions & 1 deletion
diff --git a/‎rust/Cargo.lock‎
Lines changed: 10 additions & 0 deletions b/‎rust/Cargo.lock‎
Lines changed: 10 additions & 0 deletions
diff --git a/‎rust/Cargo.toml‎
Lines changed: 1 addition & 0 deletions b/‎rust/Cargo.toml‎
Lines changed: 1 addition & 0 deletions
diff --git a/‎rust/src/jsonrpc.rs‎
Lines changed: 19 additions & 3 deletions b/‎rust/src/jsonrpc.rs‎
Lines changed: 19 additions & 3 deletions
diff --git a/‎rust/src/lib.rs‎
Lines changed: 166 additions & 33 deletions b/‎rust/src/lib.rs‎
Lines changed: 166 additions & 33 deletions
@@ -94,10 +94,12 @@ jobs:
         run: pwsh.exe -Command "Write-Host 'PowerShell ready'"
 
       - name: cargo test
+        timeout-minutes: 90
         env:
+          RUST_E2E_CONCURRENCY: 4
           COPILOT_HMAC_KEY: ${{ secrets.COPILOT_DEVELOPER_CLI_INTEGRATION_HMAC_KEY }}
           COPILOT_CLI_PATH: ${{ steps.setup-copilot.outputs.cli-path }}
-        run: cargo test --features test-support
+        run: cargo test --features test-support -- --test-threads=4 --nocapture
 
   # Validates the `embedded-cli` build path on all three supported
   # platforms. This is the only place `build.rs` actually runs (the
 
@@ -51,6 +51,7 @@ parking_lot = "0.12"
 regex = "1"
 sha2 = { version = "0.10", optional = true }
 getrandom = "0.2"
+uuid = { version = "1", default-features = false, features = ["v4"] }
 zstd = { version = "0.13", optional = true }
 
 [dev-dependencies]
 
@@ -3,11 +3,12 @@ use std::sync::Arc;
 use std::sync::atomic::{AtomicU64, Ordering};
 use std::time::Instant;
 
-use parking_lot::RwLock;
+use parking_lot::{Mutex, RwLock};
 use serde::{Deserialize, Serialize};
 use serde_json::Value;
 use tokio::io::{AsyncBufReadExt, AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt, BufReader};
 use tokio::sync::{broadcast, mpsc, oneshot};
+use tokio::task::JoinHandle;
 use tracing::{Instrument, debug, error, warn};
 
 use crate::{Error, ProtocolError};
@@ -184,6 +185,8 @@ pub struct JsonRpcClient {
     pending_requests: Arc<RwLock<HashMap<u64, oneshot::Sender<JsonRpcResponse>>>>,
     notification_tx: broadcast::Sender<JsonRpcNotification>,
     request_tx: mpsc::UnboundedSender<JsonRpcRequest>,
+    read_task: Mutex<Option<JoinHandle<()>>>,
+    write_task: Mutex<Option<JoinHandle<()>>>,
 }
 
 impl JsonRpcClient {
@@ -202,22 +205,24 @@ impl JsonRpcClient {
         let (write_tx, write_rx) = mpsc::unbounded_channel::<WriteCommand>();
 
         let writer_span = tracing::error_span!("jsonrpc_write_loop");
-        tokio::spawn(Self::write_loop(writer, write_rx).instrument(writer_span));
+        let write_task = tokio::spawn(Self::write_loop(writer, write_rx).instrument(writer_span));
 
         let client = Self {
             request_id: AtomicU64::new(1),
             write_tx,
             pending_requests: Arc::new(RwLock::new(HashMap::new())),
             notification_tx,
             request_tx,
+            read_task: Mutex::new(None),
+            write_task: Mutex::new(Some(write_task)),
         };
 
         let pending_requests = client.pending_requests.clone();
         let notification_tx_clone = client.notification_tx.clone();
         let request_tx_clone = client.request_tx.clone();
         let reader_span = tracing::error_span!("jsonrpc_read_loop");
 
-        tokio::spawn(
+        let read_task = tokio::spawn(
             async move {
                 Self::read_loop(
                     reader,
@@ -229,10 +234,21 @@ impl JsonRpcClient {
             }
             .instrument(reader_span),
         );
+        *client.read_task.lock() = Some(read_task);
 
         client
     }
 
+    pub(crate) fn force_close(&self) {
+        if let Some(task) = self.read_task.lock().take() {
+            task.abort();
+        }
+        if let Some(task) = self.write_task.lock().take() {
+            task.abort();
+        }
+        self.pending_requests.write().clear();
+    }
+
     /// Writer-actor task. Owns the `AsyncWrite`, drains the command queue,
     /// and writes each frame atomically (header + body + flush) before
     /// signaling the ack.
 
@@ -267,6 +267,15 @@ pub enum SessionError {
     /// non-empty.
     #[error("invalid SessionFsConfig: {0}")]
     InvalidSessionFsConfig(String),
+
+    /// The CLI returned a different session ID than the one the SDK registered.
+    #[error("CLI returned session ID {returned} after SDK registered {requested}")]
+    SessionIdMismatch {
+        /// Session ID registered by the SDK before the RPC was sent.
+        requested: SessionId,
+        /// Session ID returned by the CLI.
+        returned: SessionId,
+    },
 }
 
 /// How the SDK communicates with the CLI server.
@@ -873,6 +882,7 @@ struct ClientInner {
     state: parking_lot::Mutex<ConnectionState>,
     lifecycle_tx: broadcast::Sender<SessionLifecycleEvent>,
     on_list_models: Option<Arc<dyn ListModelsHandler>>,
+    models_cache: parking_lot::Mutex<Arc<tokio::sync::OnceCell<Vec<Model>>>>,
     session_fs_configured: bool,
     on_get_trace_context: Option<Arc<dyn TraceContextProvider>>,
     /// Token sent in the `connect` handshake. Auto-generated when the
@@ -900,6 +910,24 @@ impl Client {
         if let Some(cfg) = &options.session_fs {
             validate_session_fs_config(cfg)?;
         }
+        // Auth options only make sense when the SDK spawns the CLI; with an
+        // external server, the server manages its own auth.
+        if matches!(options.transport, Transport::External { .. }) {
+            if options.github_token.is_some() {
+                return Err(Error::InvalidConfig(
+                    "github_token cannot be used with Transport::External \
+                     (external server manages its own auth)"
+                        .to_string(),
+                ));
+            }
+            if options.use_logged_in_user == Some(true) {
+                return Err(Error::InvalidConfig(
+                    "use_logged_in_user cannot be used with Transport::External \
+                     (external server manages its own auth)"
+                        .to_string(),
+                ));
+            }
+        }
         // Validate token + transport combination. Stdio cannot use a
         // connection token; auto-generate a UUID when the SDK spawns
         // its own CLI in TCP mode and no explicit token was set.
@@ -1138,6 +1166,7 @@ impl Client {
                 state: parking_lot::Mutex::new(ConnectionState::Connected),
                 lifecycle_tx: broadcast::channel(256).0,
                 on_list_models,
+                models_cache: parking_lot::Mutex::new(Arc::new(tokio::sync::OnceCell::new())),
                 session_fs_configured,
                 on_get_trace_context,
                 effective_connection_token,
@@ -1752,10 +1781,17 @@ impl Client {
     /// When [`ClientOptions::on_list_models`] is set, returns the handler's
     /// result without making a `models.list` RPC. Otherwise queries the CLI.
     pub async fn list_models(&self) -> Result<Vec<Model>, Error> {
-        if let Some(handler) = &self.inner.on_list_models {
-            return handler.list_models().await;
-        }
-        Ok(self.rpc().models().list().await?.models)
+        let cache = self.inner.models_cache.lock().clone();
+        let models = cache
+            .get_or_try_init(|| async {
+                if let Some(handler) = &self.inner.on_list_models {
+                    handler.list_models().await
+                } else {
+                    Ok(self.rpc().models().list().await?.models)
+                }
+            })
+            .await?;
+        Ok(models.clone())
     }
 
     /// Invoke [`ClientOptions::on_get_trace_context`] when configured,
@@ -1828,6 +1864,7 @@ impl Client {
 
         let child = self.inner.child.lock().take();
         *self.inner.state.lock() = ConnectionState::Disconnected;
+        *self.inner.models_cache.lock() = Arc::new(tokio::sync::OnceCell::new());
         if let Some(mut child) = child
             && let Err(e) = child.kill().await
         {
@@ -1879,10 +1916,12 @@ impl Client {
         {
             error!(pid = ?pid, error = %e, "failed to send kill signal");
         }
+        self.inner.rpc.force_close();
         // Drop all session channels so any awaiters see a closed channel
         // instead of waiting for responses that will never arrive.
         self.inner.router.clear();
         *self.inner.state.lock() = ConnectionState::Disconnected;
+        *self.inner.models_cache.lock() = Arc::new(tokio::sync::OnceCell::new());
     }
 
     /// Subscribe to lifecycle events.
@@ -2405,43 +2444,137 @@ mod tests {
             policy: None,
             supported_reasoning_efforts: Vec::new(),
         };
-        let handler = Arc::new(CountingHandler {
+        let handler: Arc<dyn ListModelsHandler> = Arc::new(CountingHandler {
             calls: Arc::clone(&calls),
             models: vec![model.clone()],
         });
 
-        // We can't call list_models() through Client::start without a CLI, but we
-        // can exercise the override path by directly constructing a Client whose
-        // inner has the handler set. This is the same dispatch path as the real
-        // call; from_streams's None default is replaced via inner construction.
-        let inner = ClientInner {
-            child: parking_lot::Mutex::new(None),
-            rpc: {
-                let (req_tx, _req_rx) = mpsc::unbounded_channel();
-                let (notif_tx, _notif_rx) = broadcast::channel(16);
-                let (read_pipe, _write_pipe) = tokio::io::duplex(64);
-                let (_unused_read, write_pipe) = tokio::io::duplex(64);
-                JsonRpcClient::new(write_pipe, read_pipe, notif_tx, req_tx)
-            },
-            cwd: PathBuf::from("."),
-            request_rx: parking_lot::Mutex::new(None),
-            notification_tx: broadcast::channel(16).0,
-            router: router::SessionRouter::new(),
-            negotiated_protocol_version: OnceLock::new(),
-            state: parking_lot::Mutex::new(ConnectionState::Connected),
-            lifecycle_tx: broadcast::channel(16).0,
-            on_list_models: Some(handler),
-            session_fs_configured: false,
-            on_get_trace_context: None,
-            effective_connection_token: None,
-        };
-        let client = Client {
-            inner: Arc::new(inner),
-        };
+        let client = client_with_list_models_handler(handler);
 
         let result = client.list_models().await.unwrap();
         assert_eq!(result.len(), 1);
         assert_eq!(result[0].id, "byok-gpt-4");
         assert_eq!(calls.load(Ordering::SeqCst), 1);
     }
+
+    #[tokio::test]
+    async fn list_models_serializes_concurrent_cache_misses() {
+        use std::sync::atomic::{AtomicUsize, Ordering};
+
+        struct SlowCountingHandler {
+            calls: Arc<AtomicUsize>,
+            models: Vec<Model>,
+        }
+        #[async_trait]
+        impl ListModelsHandler for SlowCountingHandler {
+            async fn list_models(&self) -> Result<Vec<Model>, Error> {
+                self.calls.fetch_add(1, Ordering::SeqCst);
+                tokio::time::sleep(std::time::Duration::from_millis(25)).await;
+                Ok(self.models.clone())
+            }
+        }
+
+        let calls = Arc::new(AtomicUsize::new(0));
+        let model = Model {
+            billing: None,
+            capabilities: ModelCapabilities {
+                limits: None,
+                supports: None,
+            },
+            default_reasoning_effort: None,
+            id: "single-flight-model".into(),
+            name: "Single Flight Model".into(),
+            policy: None,
+            supported_reasoning_efforts: Vec::new(),
+        };
+        let handler: Arc<dyn ListModelsHandler> = Arc::new(SlowCountingHandler {
+            calls: Arc::clone(&calls),
+            models: vec![model],
+        });
+        let client = client_with_list_models_handler(handler);
+
+        let (first, second) = tokio::join!(client.list_models(), client.list_models());
+        assert_eq!(first.unwrap()[0].id, "single-flight-model");
+        assert_eq!(second.unwrap()[0].id, "single-flight-model");
+        assert_eq!(calls.load(Ordering::SeqCst), 1);
+    }
+
+    #[tokio::test]
+    async fn cancelled_create_session_unregisters_pending_session() {
+        let (client_write, _server_read) = tokio::io::duplex(8192);
+        let (_server_write, client_read) = tokio::io::duplex(8192);
+        let client = Client::from_streams(client_read, client_write, std::env::temp_dir()).unwrap();
+        let handle = tokio::spawn({
+            let client = client.clone();
+            async move { client.create_session(SessionConfig::default()).await }
+        });
+
+        wait_for_pending_session_registration(&client).await;
+        handle.abort();
+        let _ = handle.await;
+
+        assert!(client.inner.router.session_ids().is_empty());
+        client.force_stop();
+    }
+
+    #[tokio::test]
+    async fn cancelled_resume_session_unregisters_pending_session() {
+        let (client_write, _server_read) = tokio::io::duplex(8192);
+        let (_server_write, client_read) = tokio::io::duplex(8192);
+        let client = Client::from_streams(client_read, client_write, std::env::temp_dir()).unwrap();
+        let session_id = SessionId::new("resume-cancel-test");
+        let handle = tokio::spawn({
+            let client = client.clone();
+            async move {
+                client
+                    .resume_session(ResumeSessionConfig::new(session_id))
+                    .await
+            }
+        });
+
+        wait_for_pending_session_registration(&client).await;
+        handle.abort();
+        let _ = handle.await;
+
+        assert!(client.inner.router.session_ids().is_empty());
+        client.force_stop();
+    }
+
+    fn client_with_list_models_handler(handler: Arc<dyn ListModelsHandler>) -> Client {
+        Client {
+            inner: Arc::new(ClientInner {
+                child: parking_lot::Mutex::new(None),
+                rpc: {
+                    let (req_tx, _req_rx) = mpsc::unbounded_channel();
+                    let (notif_tx, _notif_rx) = broadcast::channel(16);
+                    let (read_pipe, _write_pipe) = tokio::io::duplex(64);
+                    let (_unused_read, write_pipe) = tokio::io::duplex(64);
+                    JsonRpcClient::new(write_pipe, read_pipe, notif_tx, req_tx)
+                },
+                cwd: PathBuf::from("."),
+                request_rx: parking_lot::Mutex::new(None),
+                notification_tx: broadcast::channel(16).0,
+                router: router::SessionRouter::new(),
+                negotiated_protocol_version: OnceLock::new(),
+                state: parking_lot::Mutex::new(ConnectionState::Connected),
+                lifecycle_tx: broadcast::channel(16).0,
+                on_list_models: Some(handler),
+                models_cache: parking_lot::Mutex::new(Arc::new(tokio::sync::OnceCell::new())),
+                session_fs_configured: false,
+                on_get_trace_context: None,
+                effective_connection_token: None,
+            }),
+        }
+    }
+
+    async fn wait_for_pending_session_registration(client: &Client) {
+        let deadline = tokio::time::Instant::now() + std::time::Duration::from_secs(1);
+        while client.inner.router.session_ids().is_empty() {
+            assert!(
+                tokio::time::Instant::now() < deadline,
+                "session was not registered"
+            );
+            tokio::time::sleep(std::time::Duration::from_millis(10)).await;
+        }
+    }
 }