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Keep AutoDetect channel open after provisional SSE failure (#1768)

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Copilot-Session: c0e71f8e-9302-4c6b-835d-223dec24d37d
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Pranav Senthilnathan 2026-07-29 12:31:53 -07:00 • committed by GitHub
commit f8e9e1d23f
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1 changed files with 127 additions and 3 deletions
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110
tests/ModelContextProtocol.Tests/Transport/HttpClientTransportAutoDetectTests.cs
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@ -2,6 +2,7 @@ using ModelContextProtocol.Client;
using ModelContextProtocol.Protocol;
using ModelContextProtocol.Tests.Utils;
using Microsoft.Extensions.Logging;
using System.IO.Pipelines;
using System.Net;
namespace ModelContextProtocol.Tests.Transport;
@ -163,6 +164,115 @@ public class HttpClientTransportAutoDetectTests(ITestOutputHelper testOutputHelp
Assert.NotNull(session);
}
[Fact]
public async Task AutoDetectMode_WhenProvisionalSseFails_LeavesSharedMessageChannelOpen()
{
var options = new HttpClientTransportOptions
{
Endpoint = new Uri("http://localhost"),
TransportMode = HttpTransportMode.AutoDetect,
Name = "AutoDetect shared channel test client"
};
using var mockHttpHandler = new MockHttpHandler();
using var httpClient = new HttpClient(mockHttpHandler);
await using var transport = new HttpClientTransport(options, httpClient, LoggerFactory);
var streamableHttpPostCount = 0;
mockHttpHandler.RequestHandler = request =>
{
if (request.Method == HttpMethod.Get)
{
return Task.FromResult(new HttpResponseMessage(HttpStatusCode.MethodNotAllowed));
}
if (request.Method == HttpMethod.Post && ++streamableHttpPostCount == 1)
{
return Task.FromResult(new HttpResponseMessage(HttpStatusCode.NotFound)
{
Content = new StringContent("Invalid session ID"),
});
}
return Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
{
Content = new StringContent(
"{\"jsonrpc\":\"2.0\",\"id\":2,\"result\":{\"protocolVersion\":\"2025-11-25\",\"capabilities\":{},\"serverInfo\":{\"name\":\"test\",\"version\":\"1.0\"}}}",
System.Text.Encoding.UTF8,
"application/json"),
});
};
await using var session = await transport.ConnectAsync(TestContext.Current.CancellationToken);
await Assert.ThrowsAsync<HttpRequestException>(() =>
session.SendMessageAsync(
new JsonRpcRequest { Method = RequestMethods.ServerDiscover, Id = new RequestId(1) },
TestContext.Current.CancellationToken));
await session.SendMessageAsync(
new JsonRpcRequest { Method = RequestMethods.Initialize, Id = new RequestId(2) },
TestContext.Current.CancellationToken);
var response = await session.MessageReader.ReadAsync(TestContext.Current.CancellationToken);
Assert.Equal(new RequestId(2), Assert.IsType<JsonRpcResponse>(response).Id);
}
[Fact]
public async Task AutoDetectMode_WhenAdoptedSseDisconnects_CompletesSharedMessageChannel()
{
var options = new HttpClientTransportOptions
{
Endpoint = new Uri("http://localhost"),
TransportMode = HttpTransportMode.AutoDetect,
Name = "AutoDetect adopted SSE test client"
};
using var mockHttpHandler = new MockHttpHandler();
using var httpClient = new HttpClient(mockHttpHandler);
await using var transport = new HttpClientTransport(options, httpClient, LoggerFactory);
var ssePipe = new Pipe();
var postCount = 0;
await ssePipe.Writer.WriteAsync(
System.Text.Encoding.UTF8.GetBytes("event: endpoint\r\ndata: /sse-endpoint\r\n\r\n"),
TestContext.Current.CancellationToken);
mockHttpHandler.RequestHandler = request =>
{
if (request.Method == HttpMethod.Get)
{
var content = new StreamContent(ssePipe.Reader.AsStream());
content.Headers.ContentType = new("text/event-stream");
return Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK) { Content = content });
}
if (request.Method == HttpMethod.Post && ++postCount == 1)
{
return Task.FromResult(new HttpResponseMessage(HttpStatusCode.NotFound)
{
Content = new StringContent("Streamable HTTP not supported"),
});
}
return Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK));
};
await using var session = await transport.ConnectAsync(TestContext.Current.CancellationToken);
await session.SendMessageAsync(
new JsonRpcRequest { Method = RequestMethods.Initialize, Id = new RequestId(1) },
TestContext.Current.CancellationToken);
await ssePipe.Writer.CompleteAsync();
var exception = await Assert.ThrowsAsync<ClientTransportClosedException>(
async () => await session.MessageReader.Completion.WaitAsync(
TestConstants.DefaultTimeout,
TestContext.Current.CancellationToken));
Assert.IsType<HttpClientCompletionDetails>(exception.Details);
}
// Regression test for https://github.com/modelcontextprotocol/csharp-sdk/issues/1526
// When Streamable HTTP returns 415 (e.g. wrong Content-Type) and the SSE fallback also fails
// (e.g. a Streamable-HTTP-only server returns 405 to the GET), the surfaced exception must