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Don't conflate request and response IDs in Streamable HTTP transports (#475)

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Stephen Halter 2025-06-03 12:17:11 -07:00 • committed by GitHub
commit 046903c27b
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2 changed files with 147 additions and 26 deletions
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27
src/ModelContextProtocol.Core/Client/StreamableHttpClientSessionTransport.cs
View file

@ -96,17 +96,17 @@ internal sealed partial class StreamableHttpClientSessionTransport : TransportBa
}
var rpcRequest = message as JsonRpcRequest;
JsonRpcMessage? rpcResponseCandidate = null;
JsonRpcMessageWithId? rpcResponseOrError = null;
if (response.Content.Headers.ContentType?.MediaType == "application/json")
{
var responseContent = await response.Content.ReadAsStringAsync(cancellationToken).ConfigureAwait(false);
rpcResponseCandidate = await ProcessMessageAsync(responseContent, cancellationToken).ConfigureAwait(false);
rpcResponseOrError = await ProcessMessageAsync(responseContent, rpcRequest, cancellationToken).ConfigureAwait(false);
}
else if (response.Content.Headers.ContentType?.MediaType == "text/event-stream")
{
using var responseBodyStream = await response.Content.ReadAsStreamAsync(cancellationToken);
rpcResponseCandidate = await ProcessSseResponseAsync(responseBodyStream, rpcRequest, cancellationToken).ConfigureAwait(false);
rpcResponseOrError = await ProcessSseResponseAsync(responseBodyStream, rpcRequest, cancellationToken).ConfigureAwait(false);
}
if (rpcRequest is null)
@ -114,12 +114,12 @@ internal sealed partial class StreamableHttpClientSessionTransport : TransportBa
return response;
}
if (rpcResponseCandidate is not JsonRpcMessageWithId messageWithId || messageWithId.Id != rpcRequest.Id)
if (rpcResponseOrError is null)
{
throw new McpException($"Streamable HTTP POST response completed without a reply to request with ID: {rpcRequest.Id}");
}
if (rpcRequest.Method == RequestMethods.Initialize && rpcResponseCandidate is JsonRpcResponse)
if (rpcRequest.Method == RequestMethods.Initialize && rpcResponseOrError is JsonRpcResponse)
{
// We've successfully initialized! Copy session-id and start GET request if any.
if (response.Headers.TryGetValues("mcp-session-id", out var sessionIdValues))
@ -193,20 +193,20 @@ internal sealed partial class StreamableHttpClientSessionTransport : TransportBa
continue;
}
var message = await ProcessMessageAsync(sseEvent.Data, cancellationToken).ConfigureAwait(false);
var rpcResponseOrError = await ProcessMessageAsync(sseEvent.Data, relatedRpcRequest, cancellationToken).ConfigureAwait(false);
// The server SHOULD end the response here anyway, but we won't leave it to chance. This transport makes
// The server SHOULD end the HTTP response body here anyway, but we won't leave it to chance. This transport makes
// a GET request for any notifications that might need to be sent after the completion of each POST.
if (message is JsonRpcMessageWithId messageWithId && relatedRpcRequest?.Id == messageWithId.Id)
if (rpcResponseOrError is not null)
{
return messageWithId;
return rpcResponseOrError;
}
}
return null;
}
private async Task<JsonRpcMessage?> ProcessMessageAsync(string data, CancellationToken cancellationToken)
private async Task<JsonRpcMessageWithId?> ProcessMessageAsync(string data, JsonRpcRequest? relatedRpcRequest, CancellationToken cancellationToken)
{
try
{
@ -218,7 +218,12 @@ internal sealed partial class StreamableHttpClientSessionTransport : TransportBa
}
await WriteMessageAsync(message, cancellationToken).ConfigureAwait(false);
return message;
if (message is JsonRpcResponse or JsonRpcError &&
message is JsonRpcMessageWithId rpcResponseOrError &&
rpcResponseOrError.Id == relatedRpcRequest?.Id)
{
return rpcResponseOrError;
}
}
catch (JsonException ex)
{

2
src/ModelContextProtocol.Core/Server/StreamableHttpPostTransport.cs
View file

@ -60,7 +60,7 @@ internal sealed class StreamableHttpPostTransport(StreamableHttpServerTransport
{
yield return message;
if (message.Data is JsonRpcMessageWithId response && response.Id == _pendingRequest)
if (message.Data is JsonRpcResponse or JsonRpcError && ((JsonRpcMessageWithId)message.Data).Id == _pendingRequest)
{
// Complete the SSE response stream now that all pending requests have been processed.
break;