aether-acp-utils 0.5.2

Agent Client Protocol (ACP) utilities for the Aether AI agent framework
Documentation
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#![cfg(feature = "websocket")]

use acp_utils::client::{AcpEvent, connect_acp_client};
use acp_utils::testing::{idle_notification, initialize_request, initialize_response, running_notification};
use acp_utils::websocket::WebSocketTransport;
use agent_client_protocol::schema::ProtocolVersion;
use agent_client_protocol::schema::v2::{
    ContentBlock, ContentChunk, CreateElicitationRequest, CreateElicitationResponse, ElicitationAction,
    ElicitationFormMode, ElicitationSchema, ElicitationSessionScope, InitializeRequest, PromptRequest, PromptResponse,
    SessionUpdate, StateUpdate, StopReason, TextContent, UpdateSessionNotification,
};
use agent_client_protocol::{self as acp, Agent, Client, HandleDispatchFrom, NullRun, V2Builder};
use futures::{FutureExt, SinkExt, StreamExt};
use std::time::Duration;
use tokio::io::{DuplexStream, duplex};
use tokio::net::TcpListener;
use tokio::task::{LocalSet, spawn_local};
use tokio_tungstenite::tungstenite::Message;
use tokio_tungstenite::tungstenite::client::IntoClientRequest;
use tokio_tungstenite::tungstenite::handshake::server::Request;
use tokio_tungstenite::tungstenite::http::header::InvalidHeaderValue;
use tokio_tungstenite::tungstenite::protocol::{
    Role, WebSocketConfig,
    frame::{
        Frame,
        coding::{Data, OpCode},
    },
};
use tokio_tungstenite::{WebSocketStream, accept_hdr_async_with_config, connect_async};

#[tokio::test]
async fn acp_over_websocket_with_elicitation() -> Result<(), TestError> {
    LocalSet::new()
        .run_until(async {
            let (server, client) = SocketPairBuilder::default().build().await;
            let agent = streaming_elicitation_agent(&["hello ", "world"]);
            let server_task = spawn_local(agent.connect_to(WebSocketTransport::new(server)));
            let mut client = connect_acp_client(WebSocketTransport::new(client), initialize_request()).await?;

            let handle = client.handle.clone();
            let prompt = spawn_local(async move {
                handle.prompt(PromptRequest::new("session", vec![ContentBlock::Text(TextContent::new("hi"))])).await
            });

            let Some(AcpEvent::SessionUpdate(notification)) = client.event_rx.recv().await else {
                return Err(TestError::Unexpected("expected running update"));
            };
            assert!(matches!(notification.update, SessionUpdate::StateUpdate(StateUpdate::Running(_))));

            for expected in ["hello ", "world"] {
                let Some(AcpEvent::SessionUpdate(notification)) = client.event_rx.recv().await else {
                    return Err(TestError::Unexpected("expected streamed update"));
                };
                let SessionUpdate::AgentMessageChunk(chunk) = notification.update else {
                    return Err(TestError::Unexpected("expected agent message chunk"));
                };
                assert_eq!(chunk.content, ContentBlock::Text(TextContent::new(expected)));
                assert_eq!(chunk.message_id.0.as_ref(), "message-1");
            }

            let Some(AcpEvent::ElicitationRequest { responder, .. }) = client.event_rx.recv().await else {
                return Err(TestError::Unexpected("expected elicitation request"));
            };

            responder.respond(CreateElicitationResponse::new(ElicitationAction::Decline))?;
            prompt.await??;
            let Some(AcpEvent::SessionUpdate(notification)) = client.event_rx.recv().await else {
                return Err(TestError::Unexpected("expected idle update"));
            };
            assert_eq!(notification.update, idle_notification("session", Some(StopReason::EndTurn)).update);
            drop(client);
            server_task.abort();
            let _ = server_task.await;
            Ok(())
        })
        .await
}

#[tokio::test]
#[allow(clippy::result_large_err)]
async fn caller_established_socket_supports_acp_initialization() -> Result<(), TestError> {
    LocalSet::new()
        .run_until(Box::pin(async {
            let listener = TcpListener::bind("127.0.0.1:0").await?;
            let endpoint = format!("ws://{}/custom/path?session=example", listener.local_addr()?);
            let server = spawn_local(async move {
                let (stream, _) = listener.accept().await?;
                let socket = accept_hdr_async_with_config(
                    stream,
                    |request: &Request, response| {
                        assert_eq!(request.uri().path_and_query().unwrap().as_str(), "/custom/path?session=example");
                        assert_eq!(request.headers()["origin"], "https://example.com");
                        assert_eq!(request.headers()["x-aws-proxy-auth"], "secret");
                        assert_eq!(request.headers()["x-aws-proxy-port"], "8081");
                        assert_eq!(
                            request.headers().get_all("x-custom").iter().collect::<Vec<_>>(),
                            vec!["first", "second"]
                        );
                        assert_eq!(request.headers()["x-empty"], "");
                        Ok(response)
                    },
                    None,
                )
                .await?;
                test_agent().connect_to(WebSocketTransport::new(socket)).await.map_err(TestError::from)
            });
            let mut request = endpoint.into_client_request()?;
            request.headers_mut().insert("x-aws-proxy-auth", "secret".parse()?);
            request.headers_mut().insert("x-aws-proxy-port", "8081".parse()?);
            request.headers_mut().insert("origin", "https://example.com".parse()?);
            request.headers_mut().append("x-custom", "first".parse()?);
            request.headers_mut().append("x-custom", "second".parse()?);
            request.headers_mut().insert("x-empty", "".parse()?);
            let (socket, _) = connect_async(request).await?;
            let client = Client
                .v2()
                .connect_with(WebSocketTransport::new(socket), async |cx| {
                    let response = cx.send_request(initialize_request()).block_task().await?;
                    assert_eq!(response.protocol_version, ProtocolVersion::V2);
                    Ok(())
                })
                .await;
            client?;
            let error = server.await?.expect_err("SDK foreground completion drops the socket");
            assert!(format!("{error:?}").contains("without closing handshake"), "{error:?}");
            Ok(())
        }))
        .await
}

#[tokio::test]
async fn final_response_is_not_lost_when_close_is_already_buffered() -> Result<(), TestError> {
    LocalSet::new()
        .run_until(async {
            let (mut server, client_socket) = SocketPairBuilder::default().build().await;
            let peer = spawn_local(async move {
                let request = receive_json(&mut server).await?;
                let response =
                    serde_json::json!({"jsonrpc": "2.0", "id": request["id"], "result": {"protocolVersion": 2, "info": {"name": "test-agent", "version": "0.0.0"}}});
                server.feed(Message::Text(response.to_string().into())).await?;
                server.feed(Message::Close(None)).await?;
                server.flush().await?;
                while server
                    .next()
                    .await
                    .is_some_and(|message| matches!(message, Ok(Message::Ping(_) | Message::Pong(_))))
                {}
                Ok::<_, TestError>(())
            });
            let client =
                connect_acp_client(WebSocketTransport::new(client_socket), initialize_request())
                    .await;
            assert!(client.is_ok(), "last response must be delivered before EOF");
            peer.await??;
            Ok(())
        })
        .await
}

#[tokio::test]
async fn final_turn_and_replay_events_are_delivered_before_buffered_close() -> Result<(), TestError> {
    use acp::schema::v2::ResumeSessionRequest;
    use acp_utils::client::AcpEvent;

    LocalSet::new()
        .run_until(async {
            for replay in [false, true] {
                let (mut client, peer) = SocketPairBuilder::default()
                    .before_response(idle_notification("session", Some(StopReason::EndTurn)))
                    .after_response(running_notification("session"))
                    .build_closing_agent()
                    .await?;
                if replay {
                    client.handle.resume_session_with_replay(ResumeSessionRequest::new("session", "/tmp")).await?;
                    assert!(matches!(client.event_rx.recv().await, Some(AcpEvent::SessionUpdate(notification))
                    if *notification == idle_notification("session", Some(StopReason::EndTurn))));
                } else {
                    client.handle.prompt(PromptRequest::new("session", vec![])).await?;
                    assert!(matches!(client.event_rx.recv().await, Some(AcpEvent::SessionUpdate(notification))
                    if notification.update == idle_notification("session", Some(StopReason::EndTurn)).update));
                }
                assert!(matches!(client.event_rx.recv().await, Some(AcpEvent::SessionUpdate(notification))
                if notification.update == running_notification("session").update));
                assert!(matches!(client.event_rx.recv().await, Some(AcpEvent::ConnectionClosed)));
                assert!(client.event_rx.recv().await.is_none());
                peer.await??;
            }
            Ok(())
        })
        .await
}

#[tokio::test]
async fn burst_and_replay_updates_survive_backpressure_and_buffered_close() -> Result<(), TestError> {
    use acp::schema::v2::ResumeSessionRequest;

    LocalSet::new()
        .run_until(async {
            for replay in [false, true] {
                let updates: Vec<_> = (0..2048)
                    .map(|index| {
                        UpdateSessionNotification::new(
                            "session",
                            SessionUpdate::AgentMessageChunk(ContentChunk::new(
                                ContentBlock::Text(TextContent::new(index.to_string())),
                                "message-1",
                            )),
                        )
                    })
                    .collect();
                let mut builder = SocketPairBuilder::default().buffer_capacity(1024 * 1024);
                for update in &updates[..1024] {
                    builder = builder.before_response(update.clone());
                }
                for update in &updates[1024..] {
                    builder = builder.after_response(update.clone());
                }
                let (mut client, peer) = builder.build_closing_agent().await?;
                if replay {
                    client.handle.resume_session_with_replay(ResumeSessionRequest::new("session", "/tmp")).await?;
                } else {
                    client.handle.prompt(PromptRequest::new("session", vec![])).await?;
                }
                for expected in updates {
                    let Some(AcpEvent::SessionUpdate(notification)) = client.event_rx.recv().await else {
                        return Err(TestError::Unexpected("burst lost a session update"));
                    };
                    assert_eq!(*notification, expected);
                }
                assert!(matches!(client.event_rx.recv().await, Some(AcpEvent::ConnectionClosed)));
                peer.await??;
            }
            Ok(())
        })
        .await
}

#[tokio::test]
async fn invalid_utf8_terminates_the_connection() -> Result<(), TestError> {
    LocalSet::new()
        .run_until(async {
            let (server, mut client) = SocketPairBuilder::default().build().await;
            let task = spawn_local(Agent.v2().connect_to(WebSocketTransport::new(server)));
            client.send(Message::Frame(Frame::message(vec![0xff], OpCode::Data(Data::Text), true))).await?;
            assert!(task.await?.is_err());
            Ok(())
        })
        .await
}

#[tokio::test(start_paused = true)]
async fn idle_connection_sends_periodic_keepalive_pings() -> Result<(), TestError> {
    LocalSet::new()
        .run_until(async {
            let (server, mut client) = SocketPairBuilder::default().build().await;
            let task = spawn_local(Agent.v2().connect_to(WebSocketTransport::new(server)));
            tokio::task::yield_now().await;

            for _ in 0..4 {
                assert!(client.next().now_or_never().is_none());
                tokio::time::advance(Duration::from_secs(20)).await;
                tokio::task::yield_now().await;
                assert!(matches!(client.next().now_or_never(), Some(Some(Ok(Message::Ping(_))))));
                client.flush().await?;
                tokio::task::yield_now().await;
            }

            task.abort();
            let _ = task.await;
            Ok(())
        })
        .await
}

#[tokio::test]
async fn transport_closes_cleanly_when_peer_component_finishes_first() -> Result<(), TestError> {
    LocalSet::new()
        .run_until(async {
            for _ in 0..40 {
                let (mut server, client_socket) = SocketPairBuilder::default().build().await;
                let peer = spawn_local(async move {
                    let message = receive_message(&mut server).await?;
                    assert!(matches!(message, Message::Close(_)), "expected transport-initiated close");
                    while server.next().await.is_some() {}
                    Ok::<_, TestError>(())
                });
                let result =
                    acp::ConnectTo::<Client>::connect_to(WebSocketTransport::new(client_socket), ImmediatePeer).await;
                let peer_result = peer.await?;
                result?;
                peer_result?;
            }
            Ok(())
        })
        .await
}

struct ImmediatePeer;

impl acp::ConnectTo<Agent> for ImmediatePeer {
    fn connect_to(self, _client: impl acp::ConnectTo<Client>) -> impl Future<Output = Result<(), acp::Error>> {
        std::future::ready(Ok(()))
    }
}

#[derive(Default)]
struct SocketPairBuilder {
    buffer_capacity: Option<usize>,
    server_config: Option<WebSocketConfig>,
    client_config: Option<WebSocketConfig>,
    before_response: Vec<UpdateSessionNotification>,
    after_response: Vec<UpdateSessionNotification>,
}

impl SocketPairBuilder {
    fn buffer_capacity(mut self, capacity: usize) -> Self {
        self.buffer_capacity = Some(capacity);
        self
    }

    fn before_response(mut self, update: UpdateSessionNotification) -> Self {
        self.before_response.push(update);
        self
    }

    fn after_response(mut self, update: UpdateSessionNotification) -> Self {
        self.after_response.push(update);
        self
    }

    async fn build_closing_agent(
        mut self,
    ) -> Result<(acp_utils::client::AcpClient, tokio::task::JoinHandle<Result<(), TestError>>), TestError> {
        use serde_json::json;

        let before = std::mem::take(&mut self.before_response);
        let after = std::mem::take(&mut self.after_response);
        let (mut server, client_socket) = self.build().await;
        let peer = spawn_local(async move {
            let init = receive_json(&mut server).await?;
            let response = json!({"jsonrpc": "2.0", "id": init["id"], "result": initialize_response()});
            server.send(Message::Text(response.to_string().into())).await?;
            let request = receive_json(&mut server).await?;
            let notification = |update| json!({"jsonrpc": "2.0", "method": "session/update", "params": update});
            let response = json!({"jsonrpc": "2.0", "id": request["id"], "result": {}});
            for message in
                before.into_iter().map(notification).chain([response]).chain(after.into_iter().map(notification))
            {
                server.feed(Message::Text(message.to_string().into())).await?;
            }
            server.feed(Message::Close(None)).await?;
            server.flush().await?;
            while server.next().await.is_some_and(|message| matches!(message, Ok(Message::Ping(_) | Message::Pong(_))))
            {
            }
            Ok(())
        });
        let client = connect_acp_client(WebSocketTransport::new(client_socket), initialize_request()).await?;
        Ok((client, peer))
    }

    async fn build(self) -> (WebSocketStream<DuplexStream>, WebSocketStream<DuplexStream>) {
        let (server, client) = duplex(self.buffer_capacity.unwrap_or(64 * 1024));
        tokio::join!(
            WebSocketStream::from_raw_socket(server, Role::Server, self.server_config),
            WebSocketStream::from_raw_socket(client, Role::Client, self.client_config),
        )
    }
}

#[derive(Debug, thiserror::Error)]
enum TestError {
    #[error(transparent)]
    Client(#[from] acp_utils::client::AcpClientError),
    #[error(transparent)]
    Acp(#[from] acp::Error),
    #[error(transparent)]
    WebSocket(#[from] tokio_tungstenite::tungstenite::Error),
    #[error(transparent)]
    Io(#[from] std::io::Error),
    #[error(transparent)]
    Join(#[from] tokio::task::JoinError),
    #[error(transparent)]
    Json(#[from] serde_json::Error),
    #[error(transparent)]
    Header(#[from] InvalidHeaderValue),
    #[error("{0}")]
    Unexpected(&'static str),
}

async fn receive_message(socket: &mut WebSocketStream<DuplexStream>) -> Result<Message, TestError> {
    Ok(socket.next().await.ok_or(TestError::Unexpected("socket closed before expected message"))??)
}

async fn receive_json(socket: &mut WebSocketStream<DuplexStream>) -> Result<serde_json::Value, TestError> {
    let Message::Text(text) = receive_message(socket).await? else {
        return Err(TestError::Unexpected("expected JSON text message"));
    };
    Ok(serde_json::from_str(&text)?)
}

fn test_agent() -> V2Builder<Agent, impl HandleDispatchFrom<Client>, NullRun> {
    Agent.v2().on_receive_request(
        async |_: InitializeRequest, responder, _cx| responder.respond(initialize_response()),
        acp::on_receive_request!(),
    )
}

fn streaming_elicitation_agent(
    chunks: &'static [&'static str],
) -> V2Builder<Agent, impl HandleDispatchFrom<Client>, NullRun> {
    test_agent().on_receive_request(
        async move |request: PromptRequest, responder, cx| {
            responder.respond(PromptResponse::new())?;
            cx.send_notification(running_notification(request.session_id.clone()))?;
            for &text in chunks {
                cx.send_notification(UpdateSessionNotification::new(
                    request.session_id.clone(),
                    SessionUpdate::AgentMessageChunk(ContentChunk::new(
                        ContentBlock::Text(TextContent::new(text)),
                        "message-1",
                    )),
                ))?;
            }
            let input = CreateElicitationRequest::new(
                ElicitationFormMode::new(
                    ElicitationSessionScope::new(request.session_id.clone()),
                    ElicitationSchema::new(),
                ),
                "Continue?",
            );
            let connection = cx.clone();
            cx.spawn(async move {
                let response = connection.send_request(input).block_task().await?;
                assert_eq!(response.action, ElicitationAction::Decline);
                connection.send_notification(idle_notification(request.session_id, Some(StopReason::EndTurn)))
            })?;
            Ok(())
        },
        acp::on_receive_request!(),
    )
}