Fix Strawberry Shake SSE subscriptions not streaming on Blazor WebAss…

src/StrawberryShake/Client/src/Transport.Http/HttpConnection.cs

@@ -12,6 +12,16 @@ public class HttpConnection : IHttpConnection
     public const string RequestUri = "StrawberryShake.Transport.Http.HttpConnection.RequestUri";
     public const string HttpClient = "StrawberryShake.Transport.Http.HttpConnection.HttpClient";
 
+    // Blazor WASM buffers the entire response body by default, so SSE subscription events only
+    // surface once the connection closes. Setting this per-request option opts into response
+    // streaming so events surface as they arrive. The option is ignored on non-WASM handlers
+    // and is the default on .NET 10+.
+    private static readonly HttpRequestOptionsKey<bool> s_enableWasmResponseStreaming =
+        new("WebAssemblyEnableStreamingResponse");
+
+    private static readonly OnHttpRequestMessageCreated s_enableResponseStreaming =
+        static (_, message, _) => message.Options.Set(s_enableWasmResponseStreaming, true);
+
     private readonly Func<OperationRequest, object?, HttpClient> _createClient;
     private readonly object? _clientFactoryState;
 
@@ -103,7 +113,14 @@ protected virtual GraphQLHttpRequest CreateHttpRequest(OperationRequest request)
             operation = new HotChocolate.Transport.OperationRequest(body, null, name, onError: null, variables, extensions);
         }
 
-        return new GraphQLHttpRequest(operation) { EnableFileUploads = hasFiles };
+        var httpRequest = new GraphQLHttpRequest(operation) { EnableFileUploads = hasFiles };
+
+        if (document.Kind == OperationKind.Subscription)
+        {
+            httpRequest.OnMessageCreated = s_enableResponseStreaming;
+        }
+
+        return httpRequest;
     }
 
     protected virtual Response<JsonDocument> CreateResponse(

src/StrawberryShake/Client/test/Transport.Http.Tests/HttpConnectionStreamingTests.cs

@@ -0,0 +1,105 @@
+using System.Diagnostics.CodeAnalysis;
+using System.Net;
+using System.Text;
+using System.Text.Json;
+
+namespace StrawberryShake.Transport.Http;
+
+public class HttpConnectionStreamingTests
+{
+    private static readonly HttpRequestOptionsKey<bool> s_streamingOption =
+        new("WebAssemblyEnableStreamingResponse");
+
+    [Fact]
+    public async Task CreateHttpRequest_Should_EnableResponseStreaming_When_OperationIsSubscription()
+    {
+        // arrange
+        var handler = new CapturingHandler(
+            "text/event-stream",
+            "event: next\ndata: {\"data\":{}}\n\nevent: complete\n\n");
+        var client = new HttpClient(handler) { BaseAddress = new Uri("http://localhost/graphql") };
+
+        var document = new TestDocument(OperationKind.Subscription, "subscription Test { __typename }");
+        var request = new OperationRequest("Test", document);
+
+        // act
+        var connection = new HttpConnection(() => client);
+        await foreach (var _ in connection.ExecuteAsync(request))
+        {
+        }
+
+        // assert
+        Assert.NotNull(handler.CapturedRequest);
+        var found = handler.CapturedRequest!.Options.TryGetValue(s_streamingOption, out var enabled);
+        Assert.True(found);
+        Assert.True(enabled);
+    }
+
+    [Fact]
+    public async Task CreateHttpRequest_Should_NotEnableResponseStreaming_When_OperationIsQuery()
+    {
+        // arrange
+        var handler = new CapturingHandler(
+            "application/graphql-response+json",
+            "{\"data\":{}}");
+        var client = new HttpClient(handler) { BaseAddress = new Uri("http://localhost/graphql") };
+
+        var document = new TestDocument(OperationKind.Query, "query Test { __typename }");
+        var request = new OperationRequest("Test", document);
+
+        // act
+        var connection = new HttpConnection(() => client);
+        await foreach (var _ in connection.ExecuteAsync(request))
+        {
+        }
+
+        // assert
+        Assert.NotNull(handler.CapturedRequest);
+        var found = handler.CapturedRequest!.Options.TryGetValue(s_streamingOption, out _);
+        Assert.False(found);
+    }
+
+    private sealed class CapturingHandler : HttpMessageHandler
+    {
+        private readonly string _contentType;
+        private readonly string _body;
+
+        public CapturingHandler(string contentType, string body)
+        {
+            _contentType = contentType;
+            _body = body;
+        }
+
+        public HttpRequestMessage? CapturedRequest { get; private set; }
+
+        protected override Task<HttpResponseMessage> SendAsync(
+            HttpRequestMessage request,
+            CancellationToken cancellationToken)
+        {
+            CapturedRequest = request;
+
+            var content = new ByteArrayContent(Encoding.UTF8.GetBytes(_body));
+            content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue(_contentType);
+
+            var response = new HttpResponseMessage(HttpStatusCode.OK) { Content = content };
+            return Task.FromResult(response);
+        }
+    }
+
+    private sealed class TestDocument : IDocument
+    {
+        private readonly byte[] _query;
+
+        public TestDocument(OperationKind kind, [StringSyntax("graphql")] string query)
+        {
+            Kind = kind;
+            _query = Encoding.UTF8.GetBytes(query);
+        }
+
+        public OperationKind Kind { get; }
+
+        public ReadOnlySpan<byte> Body => _query;
+
+        public DocumentHash Hash { get; } = new("MD5", "ABC");
+    }
+}

src/StrawberryShake/CodeGeneration/test/CodeGeneration.CSharp.Tests/Integration/StarWarsOnReviewSubGraphQLSSETest.cs

@@ -2,6 +2,8 @@
 using HotChocolate.StarWars.Models;
 using HotChocolate.Subscriptions;
 using Microsoft.Extensions.DependencyInjection;
+// TestServerHelper lives in the WebSocket test project's namespace; it only hosts the GraphQL
+// server here. This test runs subscriptions over SSE (HTTP), so no WebSocket client is registered.
 using StrawberryShake.Transport.WebSockets;
 using static HotChocolate.StarWars.Types.Subscriptions;
 
@@ -26,9 +28,6 @@ public async Task Execute_StarWarsOnReviewSubGraphQLSSE_Test()
         serviceCollection.AddHttpClient(
             StarWarsOnReviewSubGraphQLSSEClient.ClientName,
             c => c.BaseAddress = new Uri("http://localhost:" + port + "/graphql"));
-        serviceCollection.AddWebSocketClient(
-            StarWarsOnReviewSubGraphQLSSEClient.ClientName,
-            c => c.Uri = new Uri("ws://localhost:" + port + "/graphql"));
         serviceCollection.AddStarWarsOnReviewSubGraphQLSSEClient();
         IServiceProvider services = serviceCollection.BuildServiceProvider();
         var client = services.GetRequiredService<StarWarsOnReviewSubGraphQLSSEClient>();