`HttpClient.PostAsync` fails to reach controller endpoint during both Debug and Run sessions in integration tests.

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Describe the bug
`HttpClient.PostAync` does not reach controller endpoint at all. `GetAsync` and `DeleteAsync` are OK. The application web UI and swagger UI work perfectly. It seems that `HttpClient` doesn't manage to reach the controller endpoint somehow. Same behaviour observed in running a debug session of the application and sending a POST request from Postman. The POST request from Postman seems like taking forever and never hit the controller endpoint breakpoint. Debug console log:
```
[06/06/2025 10:57:19 +08:00] Debug { Id: 1, Name: "AuthenticationFailed" } IP: CorrelationId: Agent: ContentType: ContentLength: RequestBody: RequestQuery: MemoryUsage:/398065664 Failed to authenticate HTTPS connection. {SourceContext="Microsoft.AspNetCore.Server.Kestrel.Https.Internal.HttpsConnectionMiddleware", ConnectionId="0HND4KKA9F3V6", ThreadId=18, ExceptionDetail={["Type"]="System.IO.IOException", ["HResult"]=-2146232800, ["Message"]="Received an unexpected EOF or 0 bytes from the transport stream.", ["Source"]="System.Net.Security", ["TargetSite"]="Void MoveNext()"}}
System.IO.IOException: Received an unexpected EOF or 0 bytes from the transport stream.
at System.Net.Security.SslStream.ReceiveHandshakeFrameAsync[TIOAdapter](CancellationToken cancellationToken)
at System.Net.Security.SslStream.ForceAuthenticationAsync[TIOAdapter](Boolean receiveFirst, Byte[] reAuthenticationData, CancellationToken cancellationToken)
at Microsoft.AspNetCore.Server.Kestrel.Https.Internal.HttpsConnectionMiddleware.OnConnectionAsync(ConnectionContext context)

[06/06/2025 10:57:19 +08:00] Debug { Id: 2, Name: "ConnectionStop" } IP: CorrelationId: Agent: ContentType: ContentLength: RequestBody: RequestQuery: MemoryUsage:/398065664 Connection id ""0HND4KKA9F3V6"" stopped. {SourceContext="Microsoft.AspNetCore.Server.Kestrel.Connections", ThreadId=18}

[06/06/2025 10:57:19 +08:00] Debug { Id: 7, Name: "ConnectionWriteFin" } IP: CorrelationId: Agent: ContentType: ContentLength: RequestBody: RequestQuery: MemoryUsage:/398065664 Connection id ""0HND4KKA9F3V6"" sending FIN because: ""The Socket transport's send loop completed gracefully."" {SourceContext="Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets", ThreadId=18}

[06/06/2025 10:57:19 +08:00] Debug { Id: 3, Name: "HttpsConnectionEstablished" } IP: CorrelationId: Agent: ContentType: ContentLength: RequestBody: RequestQuery: MemoryUsage:/398065664 Connection "0HND4KKA9F3V7" established using the following protocol: "Tls13" {SourceContext="Microsoft.AspNetCore.Server.Kestrel.Https.Internal.HttpsConnectionMiddleware", ThreadId=8}

Exception thrown: 'System.InvalidOperationException' in Microsoft.AspNetCore.Server.Kestrel.Core.dll
4
Exception thrown: 'System.InvalidOperationException' in System.Private.CoreLib.dll
```
Irconically, once I cancel the request on the Postman side, it hits the contoller POST method/endpoint and the request completes successfully without seeing anything unusual at the Debug Console. Of course, the Postman won't show any response since the request was already cancelled.

`Program.cs`:
```
builder.Services.AddControllersWithViews();
app.MapControllers();
```
Controller:
```
[Route("api/[controller]")]
[ApiController]
public class AccountsController : ControllerBase {
[HttpPost("register")]
[Consumes("application/json")]
public async Task Register([FromBody] Models.Request.RegisterUserRequest request)
{
if (!ModelState.IsValid)
{
_logger.LogError($"{nameof(Register)} invalid model state!");
return BadRequest(ModelState);
}
_logger.LogDebug($"{nameof(Register)}");
RegisterUserResponse response = await _mediator.Send(new RegisterUserCommand(request.FirstName, request.LastName, request.Email, request.UserName, request.Password));
_logger.LogDebug($"{nameof(Register)} response: {JsonSerializer.Serialize(response)}");
return _mapper.Map(response);
}
}
```
Controller integration test code:
```
[Collection("Controller Test Collection")]
public class AccountsControllerIntegrationTests
{
private readonly HttpClient _client;
private readonly ITestOutputHelper _output;
public AccountsControllerIntegrationTests(ITestOutputHelper output, CustomWebApplicationFactory factory) => (_output, _client) = (output, factory.Client);
[Fact]
public async Task CanRegisterUserWithValidAccountDetails()
{
var httpResponse = await _client.PostAsync("/api/accounts/register", new StringContent(System.Text.Json.JsonSerializer.Serialize(new Models.Request.RegisterUserRequest("John", "Doe", "jdoe@gmail.com", "johndoe", "Pa$$word1")), Encoding.UTF8, "application/json"));
...
}
```
`CustomWebApplicationFactory`:
```
public class CustomWebApplicationFactory : WebApplicationFactory, IAsyncLifetime where TStartup : class
{
public HttpClient Client { get; set; }
protected override void ConfigureWebHost(IWebHostBuilder builder)
{
builder.UseEnvironment("IntegrationTests");
builder.ConfigureLogging((p) => p.SetMinimumLevel(LogLevel.Debug));
builder.ConfigureServices((context, services) =>
{
// Create a new service provider.
services.Configure(context.Configuration.GetSection(nameof(GrpcConfig)));
services.AddScoped>();
});
}
public async ValueTask InitializeAsync()
{
Client = CreateClient(new WebApplicationFactoryClientOptions
{
BaseAddress = new Uri("https://localhost:4433")
});
}
```
### Expected Behavior

What do you think?

### Steps To Reproduce

_No response_

### Exceptions (if any)

```
Message: 
System.Threading.Tasks.TaskCanceledException : The request was canceled due to the configured HttpClient.Timeout of 100 seconds elapsing.
---- System.TimeoutException : Flush was canceled on underlying PipeWriter.
-------- System.OperationCanceledException : Flush was canceled on underlying PipeWriter.

Stack Trace: 
HttpClient.HandleFailure(Exception e, Boolean telemetryStarted, HttpResponseMessage response, CancellationTokenSource cts, CancellationToken cancellationToken, CancellationTokenSource pendingRequestsCts)
HttpClient.g__Core|83_0(HttpRequestMessage request, HttpCompletionOption completionOption, CancellationTokenSource cts, Boolean disposeCts, CancellationTokenSource pendingRequestsCts, CancellationToken originalCancellationToken)
AccountsControllerIntegrationTests.CanChangePasswordWithValidAccountDetails() line 133
--- End of stack trace from previous location ---
----- Inner Stack Trace -----
----- Inner Stack Trace -----
ThrowHelper.ThrowOperationCanceledException_FlushCanceled()
PipeWriter.CopyFromAsync(Stream source, CancellationToken cancellationToken)
<b__0>d.MoveNext()
--- End of stack trace from previous location ---
<g__RunRequestAsync|0>d.MoveNext()
--- End of stack trace from previous location ---
ClientHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
CookieContainerHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
RedirectHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
HttpClient.g__Core|83_0(HttpRequestMessage request, HttpCompletionOption completionOption, CancellationTokenSource cts, Boolean disposeCts, CancellationTokenSource pendingRequestsCts, CancellationToken originalCancellationToken)
```

### .NET Version

10.0.0

### Anything else?

```
.NET SDK:
Version: 10.0.100
Commit: b0f34d51fc
Workload version: 10.0.100-manifests.5fb86115
MSBuild version: 18.0.2+b0f34d51f

Runtime Environment:
OS Name: Windows
OS Version: 10.0.26200
OS Platform: Windows
RID: win-x64
Base Path: C:\Program Files\dotnet\sdk\10.0.100\

.NET workloads installed:
[maui-windows]
Installation Source: VS 18.3.11218.70, VS 17.14.36717.8
Manifest Version: 10.0.0/10.0.100
Manifest Path: C:\Program Files\dotnet\sdk-manifests\10.0.100\microsoft.net.sdk.maui\10.0.0\WorkloadManifest.json
Install Type: Msi

[maccatalyst]
Installation Source: VS 18.3.11218.70, VS 17.14.36717.8
Manifest Version: 26.1.10494/10.0.100
Manifest Path: C:\Program Files\dotnet\sdk-manifests\10.0.100\microsoft.net.sdk.maccatalyst\26.1.10494\WorkloadManifest.json
Install Type: Msi

[android]
Installation Source: VS 18.3.11218.70, VS 17.14.36717.8
Manifest Version: 36.1.2/10.0.100
Manifest Path: C:\Program Files\dotnet\sdk-manifests\10.0.100\microsoft.net.sdk.android\36.1.2\WorkloadManifest.json
Install Type: Msi

[ios]
Installation Source: VS 18.3.11218.70, VS 17.14.36717.8
Manifest Version: 26.1.10494/10.0.100
Manifest Path: C:\Program Files\dotnet\sdk-manifests\10.0.100\microsoft.net.sdk.ios\26.1.10494\WorkloadManifest.json
Install Type: Msi

Configured to use workload sets when installing new manifests.
No workload sets are installed. Run "dotnet workload restore" to install a workload set.

Host:
Version: 10.0.0
Architecture: x64
Commit: b0f34d51fc

.NET SDKs installed:
6.0.202 [C:\Program Files\dotnet\sdk]
6.0.401 [C:\Program Files\dotnet\sdk]
6.0.428 [C:\Program Files\dotnet\sdk]
7.0.120 [C:\Program Files\dotnet\sdk]
9.0.112 [C:\Program Files\dotnet\sdk]
9.0.308 [C:\Program Files\dotnet\sdk]
10.0.100 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 6.0.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.9 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 8.0.22 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 9.0.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 9.0.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 10.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 6.0.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.22 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 9.0.8 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 9.0.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 10.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 6.0.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.4 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.9 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 8.0.22 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 9.0.8 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 9.0.11 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 10.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
x86 [C:\Program Files (x86)\dotnet]
registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables:
Not set

global.json file:
Not found

Learn more:
https://aka.ms/dotnet/info

Download .NET:
https://aka.ms/dotnet/download
```

Start with CustomWebApplicationFactory.InitializeAsync and the AccountsControllerIntegrationTests POST test, then review Program.cs and AccountsController alongside the Kestrel TLS and timeout logs. Reproduce the 100-second cancellation and determine why the POST does not complete; done should include a verified explanation and regression coverage or a documented resolution.

Written by the indexing model from the issue text.