Transport

AGUI.Client separates the chat client from the wire protocol with IAGUITransport. AGUIChatClient builds a RunAgentInput, passes it to the transport, and consumes the resulting AG-UI BaseEvent stream.

using AGUI.Abstractions;
using AGUI.Client;

IAGUITransport

IAGUITransport has a single method:

public interface IAGUITransport
{
    IAsyncEnumerable<BaseEvent> SendAsync(
        RunAgentInput input,
        CancellationToken cancellationToken);
}

The input contains the AG-UI thread id, run id, message history, tools, state, context, forwarded properties, and any resume entries for interrupted runs. The output is the ordered AG-UI event stream described in the event reference.

HTTP transport

The AGUIChatClientOptions(HttpClient, endpoint) constructor creates the built-in HTTP transport internally:

using AGUI.Client;
using Microsoft.Extensions.AI;

using HttpClient httpClient = new();
IChatClient client = new AGUIChatClient(new(httpClient, "https://api.example.com/agent"));

The built-in transport sends the request as an HTTP POST whose body is the serialized RunAgentInput. The response is read as Server-Sent Events, and each SSE item is deserialized as a BaseEvent.

AGUIHttpTransport is the built-in HTTP+SSE implementation used by the AGUIChatClientOptions(HttpClient, endpoint) constructor. Most applications do not need to instantiate a transport directly.

Custom transports

Implement IAGUITransport when you want to test without a server or use a different transport. Then pass the implementation to AGUIChatClient.

using System.Runtime.CompilerServices;
using AGUI.Abstractions;
using AGUI.Client;
using Microsoft.Extensions.AI;

public sealed class InMemoryAGUITransport : IAGUITransport
{
    public List<RunAgentInput> Requests { get; } = [];

    public async IAsyncEnumerable<BaseEvent> SendAsync(
        RunAgentInput input,
        [EnumeratorCancellation] CancellationToken cancellationToken)
    {
        Requests.Add(input);
        await Task.Yield();

        string threadId = string.IsNullOrEmpty(input.ThreadId) ? "thread_1" : input.ThreadId;
        string runId = string.IsNullOrEmpty(input.RunId) ? "run_1" : input.RunId;

        yield return new RunStartedEvent { ThreadId = threadId, RunId = runId };
        yield return new TextMessageStartEvent { MessageId = "msg_1", Role = AGUIRoles.Assistant };
        yield return new TextMessageContentEvent { MessageId = "msg_1", Delta = "Hello from AG-UI" };
        yield return new TextMessageEndEvent { MessageId = "msg_1" };
        yield return new RunFinishedEvent { ThreadId = threadId, RunId = runId };
    }
}

IAGUITransport transport = new InMemoryAGUITransport();
IChatClient client = new AGUIChatClient(new() { Transport = transport });

Event conversion

The transport returns AG-UI protocol events. AGUIChatClient then converts them to ChatResponseUpdate values:

RUN_STARTED establishes the AG-UI thread id and run id.
Text message events become streamed text updates.
Tool call events become MEAI function call content.
Interrupt outcomes become ToolApprovalRequestContent or InterruptRequestContent.
RUN_ERROR is surfaced as an exception.

ResponseId on each update corresponds to the AG-UI run id. The client clears ConversationId before yielding updates so callers continue sending full message history to stateless AG-UI servers.

Cancellation

SendAsync receives the caller’s CancellationToken. Custom transports should observe it while sending the request and while producing events:

public async IAsyncEnumerable<BaseEvent> SendAsync(
    RunAgentInput input,
    [EnumeratorCancellation] CancellationToken cancellationToken)
{
    cancellationToken.ThrowIfCancellationRequested();

    await Task.Delay(TimeSpan.FromMilliseconds(10), cancellationToken);
    yield return new RunStartedEvent { ThreadId = input.ThreadId, RunId = input.RunId };

    cancellationToken.ThrowIfCancellationRequested();
    yield return new RunFinishedEvent { ThreadId = input.ThreadId, RunId = input.RunId };
}

​Transport

​IAGUITransport

​HTTP transport

​Custom transports

​Event conversion

​Cancellation

​Related references

Transport

IAGUITransport

HTTP transport

Custom transports

Event conversion

Cancellation

Related references