Remove batching support from StreamableHttpServerTransport (#372)

src/ModelContextProtocol/Protocol/Transport/StreamClientSessionTransport.cs

@@ -70,7 +70,7 @@ internal class StreamClientSessionTransport : TransportBase
             id = messageWithId.Id.ToString();
         }
 
-        var json = JsonSerializer.Serialize(message, McpJsonUtilities.DefaultOptions.GetTypeInfo(typeof(JsonRpcMessage)));
+        var json = JsonSerializer.Serialize(message, McpJsonUtilities.JsonContext.Default.JsonRpcMessage);
 
         using var _ = await _sendLock.LockAsync(cancellationToken).ConfigureAwait(false);
         try

src/ModelContextProtocol/Protocol/Transport/StreamableHttpPostTransport.cs

@@ -32,7 +32,9 @@ internal sealed class StreamableHttpPostTransport(ChannelWriter<JsonRpcMessage>?
         // The incomingChannel is null to handle the potential client GET request to handle unsolicited JsonRpcMessages.
         if (incomingChannel is not null)
         {
-            await OnPostBodyReceivedAsync(httpBodies.Input, cancellationToken).ConfigureAwait(false);
+            var message = await JsonSerializer.DeserializeAsync(httpBodies.Input.AsStream(),
+                McpJsonUtilities.JsonContext.Default.JsonRpcMessage, cancellationToken).ConfigureAwait(false);
+            await OnMessageReceivedAsync(message, cancellationToken).ConfigureAwait(false);
         }
 
         if (_pendingRequests.Count == 0)
@@ -72,24 +74,6 @@ internal sealed class StreamableHttpPostTransport(ChannelWriter<JsonRpcMessage>?
         }
     }
 
-    private async ValueTask OnPostBodyReceivedAsync(PipeReader streamableHttpRequestBody, CancellationToken cancellationToken)
-    {
-        if (!await IsJsonArrayAsync(streamableHttpRequestBody, cancellationToken).ConfigureAwait(false))
-        {
-            var message = await JsonSerializer.DeserializeAsync(streamableHttpRequestBody.AsStream(), McpJsonUtilities.JsonContext.Default.JsonRpcMessage, cancellationToken).ConfigureAwait(false);
-            await OnMessageReceivedAsync(message, cancellationToken).ConfigureAwait(false);
-        }
-        else
-        {
-            // Batched JSON-RPC message
-            var messages = JsonSerializer.DeserializeAsyncEnumerable(streamableHttpRequestBody.AsStream(), McpJsonUtilities.JsonContext.Default.JsonRpcMessage, cancellationToken).ConfigureAwait(false);
-            await foreach (var message in messages.WithCancellation(cancellationToken))
-            {
-                await OnMessageReceivedAsync(message, cancellationToken).ConfigureAwait(false);
-            }
-        }
-    }
-
     private async ValueTask OnMessageReceivedAsync(JsonRpcMessage? message, CancellationToken cancellationToken)
     {
         if (message is null)
@@ -108,27 +92,4 @@ internal sealed class StreamableHttpPostTransport(ChannelWriter<JsonRpcMessage>?
         Throw.IfNull(incomingChannel);
         await incomingChannel.WriteAsync(message, cancellationToken).ConfigureAwait(false);
     }
-
-    private async ValueTask<bool> IsJsonArrayAsync(PipeReader requestBody, CancellationToken cancellationToken)
-    {
-        // REVIEW: Should we bother trimming whitespace before checking for '['?
-        var firstCharacterResult = await requestBody.ReadAtLeastAsync(1, cancellationToken).ConfigureAwait(false);
-
-        try
-        {
-            if (firstCharacterResult.Buffer.Length == 0)
-            {
-                return false;
-            }
-
-            Span<byte> firstCharBuffer = stackalloc byte[1];
-            firstCharacterResult.Buffer.Slice(0, 1).CopyTo(firstCharBuffer);
-            return firstCharBuffer[0] == (byte)'[';
-        }
-        finally
-        {
-            // Never consume data when checking for '['. System.Text.Json still needs to consume it.
-            requestBody.AdvanceTo(firstCharacterResult.Buffer.Start);
-        }
-    }
 }

src/ModelContextProtocol/Shared/McpSession.cs

@@ -75,7 +75,7 @@ internal sealed partial class McpSession : IDisposable
             StdioClientSessionTransport or StdioServerTransport => "stdio",
             StreamClientSessionTransport or StreamServerTransport => "stream",
             SseClientSessionTransport or SseResponseStreamTransport => "sse",
-            StreamableHttpServerTransport or StreamableHttpPostTransport => "http",
+            StreamableHttpClientSessionTransport or StreamableHttpServerTransport or StreamableHttpPostTransport => "http",
             _ => "unknownTransport"
         };
 

tests/ModelContextProtocol.AspNetCore.Tests/StreamableHttpServerConformanceTests.cs

@@ -182,39 +182,6 @@ public class StreamableHttpServerConformanceTests(ITestOutputHelper outputHelper
         await CallInitializeAndValidateAsync();
     }
 
-    [Fact]
-    public async Task BatchedJsonRpcRequests_IsHandled_WithCompleteSseResponse()
-    {
-        await StartAsync();
-
-        using var response = await HttpClient.PostAsync("", JsonContent($"[{InitializeRequest},{EchoRequest}]"), TestContext.Current.CancellationToken);
-        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
-
-        var eventCount = 0;
-        await foreach (var sseEvent in ReadSseAsync(response.Content))
-        {
-            var jsonRpcResponse = JsonSerializer.Deserialize(sseEvent, GetJsonTypeInfo<JsonRpcResponse>());
-            Assert.NotNull(jsonRpcResponse);
-            var responseId = Assert.IsType<long>(jsonRpcResponse.Id.Id);
-
-            switch (responseId)
-            {
-                case 1:
-                    AssertServerInfo(jsonRpcResponse);
-                    break;
-                case 2:
-                    AssertEchoResponse(jsonRpcResponse);
-                    break;
-                default:
-                    throw new Exception($"Unexpected response ID: {jsonRpcResponse.Id}");
-            }
-
-            eventCount++;
-        }
-
-        Assert.Equal(2, eventCount);
-    }
-
     [Fact]
     public async Task SingleJsonRpcRequest_ThatThrowsIsHandled_WithCompleteSseResponse()
     {