diff --git a/src/libraries/Common/tests/System/Net/Prerequisites/NetCoreServer/Handlers/EchoHandler.cs b/src/libraries/Common/tests/System/Net/Prerequisites/NetCoreServer/Handlers/EchoHandler.cs
index 6888c57e11285b..667e99c29dc398 100644
--- a/src/libraries/Common/tests/System/Net/Prerequisites/NetCoreServer/Handlers/EchoHandler.cs
+++ b/src/libraries/Common/tests/System/Net/Prerequisites/NetCoreServer/Handlers/EchoHandler.cs
@@ -7,6 +7,7 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Http.Features;
 
 namespace NetCoreServer
 {
@@ -30,6 +31,24 @@ public static async Task InvokeAsync(HttpContext context)
 
             byte[] bytes = Encoding.UTF8.GetBytes(echoJson);
 
+            var delay = 0;
+            if (context.Request.QueryString.HasValue)
+            {
+                if (context.Request.QueryString.Value.Contains("delay1sec"))
+                {
+                    delay = 1000;
+                }
+                else if (context.Request.QueryString.Value.Contains("delay10sec"))
+                {
+                    delay = 10000;
+                }
+            }
+
+            if (delay > 0)
+            {
+                context.Features.Get<IHttpResponseBodyFeature>().DisableBuffering();
+            }
+
             // Compute MD5 hash so that clients can verify the received data.
             using (MD5 md5 = MD5.Create())
             {
@@ -41,20 +60,19 @@ public static async Task InvokeAsync(HttpContext context)
                 context.Response.ContentLength = bytes.Length;
             }
 
-            if (context.Request.QueryString.HasValue && context.Request.QueryString.Value.Contains("delay10sec"))
+            if (delay > 0)
             {
                 await context.Response.StartAsync(CancellationToken.None);
+                await context.Response.Body.WriteAsync(bytes, 0, 10);
+                await context.Response.Body.FlushAsync();
+                await Task.Delay(delay);
+                await context.Response.Body.WriteAsync(bytes, 10, bytes.Length-10);
                 await context.Response.Body.FlushAsync();
-
-                await Task.Delay(10000);
             }
-            else if (context.Request.QueryString.HasValue && context.Request.QueryString.Value.Contains("delay1sec"))
+            else
             {
-                await context.Response.StartAsync(CancellationToken.None);
-                await Task.Delay(1000);
+                await context.Response.Body.WriteAsync(bytes, 0, bytes.Length);
             }
-            
-            await context.Response.Body.WriteAsync(bytes, 0, bytes.Length);
         }
     }
 }
diff --git a/src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Interop/JavaScriptImports.Generated.cs b/src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Interop/JavaScriptImports.Generated.cs
index 7d734d8babe780..10f737f5a9c9ce 100644
--- a/src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Interop/JavaScriptImports.Generated.cs
+++ b/src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Interop/JavaScriptImports.Generated.cs
@@ -43,7 +43,6 @@ internal static unsafe partial class JavaScriptImports
         [JSImport("INTERNAL.get_dotnet_instance")]
         public static partial JSObject GetDotnetInstance();
         [JSImport("INTERNAL.dynamic_import")]
-        // TODO: the continuation should be running on deputy or TP in MT
         public static partial Task<JSObject> DynamicImport(string moduleName, string moduleUrl);
 
         [JSImport("INTERNAL.mono_wasm_bind_cs_function")]
@@ -51,7 +50,6 @@ internal static unsafe partial class JavaScriptImports
 
 #if FEATURE_WASM_MANAGED_THREADS
         [JSImport("INTERNAL.thread_available")]
-        // TODO: the continuation should be running on deputy or TP in MT
         public static partial Task ThreadAvailable();
 #endif
 
diff --git a/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/WebWorkerTest.Http.cs b/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/WebWorkerTest.Http.cs
index 53d45b99678e90..16ef9f72cf5573 100644
--- a/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/WebWorkerTest.Http.cs
+++ b/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/WebWorkerTest.Http.cs
@@ -81,23 +81,11 @@ await HttpClient_ActionInDifferentThread(url, executor1, executor2, async (HttpR
                 await Assert.ThrowsAsync<TaskCanceledException>(async () =>
                 {
                     CancellationTokenSource cts = new CancellationTokenSource();
-                    try
-                    {
-                        var promise = response.Content.ReadAsStringAsync(cts.Token);
-                        Console.WriteLine("HttpClient_CancelInDifferentThread: ManagedThreadId: " + Environment.CurrentManagedThreadId + " NativeThreadId: " + WebWorkerTestHelper.NativeThreadId);
-                        cts.Cancel();
-                        await promise;
-                    }
-                    catch (TaskCanceledException ex)
-                    {
-                        Console.WriteLine("HttpClient_CancelInDifferentThread: TaskCanceledException is thrown with message: " + ex.ToString());
-                        throw;
-                    }
-                    catch (OperationCanceledException ex)
-                    {
-                        Console.WriteLine("HttpClient_CancelInDifferentThread: OperationCanceledException is thrown with message: " + ex.ToString());
-                        throw;
-                    }
+                    var promise = response.Content.ReadAsStringAsync(cts.Token);
+                    Console.WriteLine("HttpClient_CancelInDifferentThread: ManagedThreadId: " + Environment.CurrentManagedThreadId + " NativeThreadId: " + WebWorkerTestHelper.NativeThreadId);
+                    cts.Cancel();
+                    var res = await promise;
+                    throw new Exception("This should be unreachable: " + res);
                 });
             });
         }
diff --git a/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/WebWorkerTestBase.cs b/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/WebWorkerTestBase.cs
index 3fb53d484def06..1df4c61e6bcbc6 100644
--- a/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/WebWorkerTestBase.cs
+++ b/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/WebWorkerTestBase.cs
@@ -135,12 +135,15 @@ async Task ActionsInDifferentThreads2()
                 {
                     throw;
                 }
-                Console.WriteLine("ActionsInDifferentThreads failed with: \n" + ex);
                 if (!e1Done || !e2Done)
                 {
-                    Console.WriteLine("ActionsInDifferentThreads canceling!");
+                    Console.WriteLine("ActionsInDifferentThreads canceling because of unexpected fail: \n" + ex);
                     cts.Cancel();
                 }
+                else
+                {
+                    Console.WriteLine("ActionsInDifferentThreads failed with: \n" + ex);
+                }
                 throw;
             }
         }
diff --git a/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/WebWorkerTestHelper.cs b/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/WebWorkerTestHelper.cs
index 1fc94b83adba99..9a1856780d5d5b 100644
--- a/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/WebWorkerTestHelper.cs
+++ b/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/WebWorkerTestHelper.cs
@@ -48,7 +48,7 @@ public partial class WebWorkerTestHelper
         public static NamedCall CurrentCallback;
         public static CancellationToken CurrentCancellationToken = CancellationToken.None;
         public static Exception? LastException = null;
-        
+
         [JSExport]
         public static void CallCurrentCallback()
         {
@@ -333,7 +333,7 @@ public static Task RunOnNewThread(Func<Task> job, CancellationToken cancellation
                 }
                 catch (Exception ex)
                 {
-                    if(ex is AggregateException agg)
+                    if (ex is AggregateException agg)
                     {
                         tcs.TrySetException(agg.InnerException);
                     }
diff --git a/src/mono/browser/runtime/cancelable-promise.ts b/src/mono/browser/runtime/cancelable-promise.ts
index cf0b048a2c60cd..362ad3c5de30f5 100644
--- a/src/mono/browser/runtime/cancelable-promise.ts
+++ b/src/mono/browser/runtime/cancelable-promise.ts
@@ -56,7 +56,7 @@ export class PromiseHolder extends ManagedObject {
     public isPosted = false;
     public isPostponed = false;
     public data: any = null;
-    public reason: any = null;
+    public reason: any = undefined;
     public constructor(public promise: Promise<any>,
         private gc_handle: GCHandle,
         private promiseHolderPtr: number, // could be null for GCV_handle 
diff --git a/src/mono/browser/runtime/http.ts b/src/mono/browser/runtime/http.ts
index 0e45e2ec819752..6e4f66d0e214a8 100644
--- a/src/mono/browser/runtime/http.ts
+++ b/src/mono/browser/runtime/http.ts
@@ -87,6 +87,7 @@ export function http_wasm_abort_request(controller: HttpController): void {
 export function http_wasm_abort_response(controller: HttpController): void {
     if (BuildConfiguration === "Debug") commonAsserts(controller);
     try {
+        controller.isAborted = true;
         if (controller.streamReader) {
             controller.streamReader.cancel().catch((err) => {
                 if (err && err.name !== "AbortError") {
@@ -251,6 +252,9 @@ export function http_wasm_get_streamed_response_bytes(controller: HttpController
             controller.currentBufferOffset = 0;
         }
         if (controller.currentStreamReaderChunk.done) {
+            if (controller.isAborted) {
+                throw new Error("OperationCanceledException");
+            }
             return 0;
         }
 
@@ -271,6 +275,7 @@ export function http_wasm_get_streamed_response_bytes(controller: HttpController
 
 interface HttpController {
     abortController: AbortController
+    isAborted?: boolean
 
     // streaming request
     streamReader?: ReadableStreamDefaultReader<Uint8Array>
diff --git a/src/mono/mono/utils/mono-threads-wasm.c b/src/mono/mono/utils/mono-threads-wasm.c
index cfd411c712c385..97ac4e1e2cea25 100644
--- a/src/mono/mono/utils/mono-threads-wasm.c
+++ b/src/mono/mono/utils/mono-threads-wasm.c
@@ -629,7 +629,6 @@ mono_wasm_register_ui_thread (void)
 	MONO_ENTER_GC_SAFE_UNBALANCED;
 }
 
-// TODO ideally we should not need to have UI thread registered as managed
 EMSCRIPTEN_KEEPALIVE void
 mono_wasm_register_io_thread (void)
 {