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SSE client transport: tolerate return of RPC responses in POST requests. #445

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Merged
merged 4 commits into from
May 23, 2025
Merged

SSE client transport: tolerate return of RPC responses in POST requests. #445

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7eea3e2
SSE client transport: handle return of RPC responses in POST requests.
eiriktsarpalis May 22, 2025
7232559
Remove accidental change.
eiriktsarpalis May 22, 2025
6ad87a9
Address feedback
eiriktsarpalis May 23, 2025
95d787b
Remove unused namespace.
eiriktsarpalis May 23, 2025
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14 changes: 3 additions & 11 deletions src/ModelContextProtocol/Client/SseClientSessionTransport.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -92,26 +92,18 @@ public override async Task SendMessageAsync(
StreamableHttpClientSessionTransport.CopyAdditionalHeaders(httpRequestMessage.Headers, _options.AdditionalHeaders);
var response = await _httpClient.SendAsync(httpRequestMessage, cancellationToken).ConfigureAwait(false);

response.EnsureSuccessStatusCode();

var responseContent = await response.Content.ReadAsStringAsync(cancellationToken).ConfigureAwait(false);

if (string.IsNullOrEmpty(responseContent) || responseContent.Equals("accepted", StringComparison.OrdinalIgnoreCase))
{
LogAcceptedPost(Name, messageId);
}
else
if (!response.IsSuccessStatusCode)
{
if (_logger.IsEnabled(LogLevel.Trace))
{
LogRejectedPostSensitive(Name, messageId, responseContent);
LogRejectedPostSensitive(Name, messageId, await response.Content.ReadAsStringAsync(cancellationToken).ConfigureAwait(false));
}
else
{
LogRejectedPost(Name, messageId);
}

throw new InvalidOperationException("Failed to send message");
response.EnsureSuccessStatusCode();
}
}

Expand Down
30 changes: 27 additions & 3 deletions tests/ModelContextProtocol.AspNetCore.Tests/SseIntegrationTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -58,6 +58,22 @@ public async Task ConnectAndReceiveMessage_InMemoryServer_WithFullEndpointEventU
Assert.True(true);
}

[Fact]
public async Task ConnectAndReceiveMessage_ServerReturningJsonInPostRequest()
{
await using var app = Builder.Build();
MapAbsoluteEndpointUriMcp(app, respondInJson: true);

await app.StartAsync(TestContext.Current.CancellationToken);

await using var mcpClient = await ConnectMcpClientAsync();

// Send a test message through POST endpoint
await mcpClient.SendNotificationAsync("test/message", new Envelope { Message = "Hello, SSE!" }, serializerOptions: JsonContext.Default.Options, cancellationToken: TestContext.Current.CancellationToken);

Assert.True(true);
}

[Fact]
public async Task ConnectAndReceiveNotification_InMemoryServer()
{
Expand Down Expand Up @@ -220,7 +236,7 @@ public async Task EmptyAdditionalHeadersKey_Throws_InvalidOperationException()
Assert.Equal("Failed to add header '' with value '' from AdditionalHeaders.", ex.Message);
}

private static void MapAbsoluteEndpointUriMcp(IEndpointRouteBuilder endpoints)
private static void MapAbsoluteEndpointUriMcp(IEndpointRouteBuilder endpoints, bool respondInJson = false)
{
var loggerFactory = endpoints.ServiceProvider.GetRequiredService<ILoggerFactory>();
var optionsSnapshot = endpoints.ServiceProvider.GetRequiredService<IOptions<McpServerOptions>>();
Expand Down Expand Up @@ -267,7 +283,7 @@ private static void MapAbsoluteEndpointUriMcp(IEndpointRouteBuilder endpoints)
await Results.BadRequest("Session not started.").ExecuteAsync(context);
return;
}
var message = (JsonRpcMessage?)await context.Request.ReadFromJsonAsync(McpJsonUtilities.DefaultOptions.GetTypeInfo(typeof(JsonRpcMessage)), context.RequestAborted);
var message = await context.Request.ReadFromJsonAsync<JsonRpcMessage>(McpJsonUtilities.DefaultOptions, context.RequestAborted);
if (message is null)
{
await Results.BadRequest("No message in request body.").ExecuteAsync(context);
Expand All @@ -276,7 +292,15 @@ private static void MapAbsoluteEndpointUriMcp(IEndpointRouteBuilder endpoints)

await session.OnMessageReceivedAsync(message, context.RequestAborted);
context.Response.StatusCode = StatusCodes.Status202Accepted;
await context.Response.WriteAsync("Accepted");

if (respondInJson)
{
await context.Response.WriteAsJsonAsync(message, McpJsonUtilities.DefaultOptions, cancellationToken: context.RequestAborted);
}
else
{
await context.Response.WriteAsync("Accepted");
}
});
}

Expand Down
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