Add QuicTransportOptions configuration documentation to HTTP/3 guide (#36341)

Co-authored-by: JamesNK <303201+JamesNK@users.noreply.github.com>
Co-authored-by: guardrex <1622880+guardrex@users.noreply.github.com>
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Co-authored-by: James Newton-King <james@newtonking.com>

Author: 3 people

aspnetcore/fundamentals/servers/kestrel/http3.md

@@ -1,11 +1,12 @@
 ---
 title: Use HTTP/3 with the ASP.NET Core Kestrel web server
+ai-usage: ai-assisted
 author: wtgodbe
 description: Learn about using HTTP/3 with Kestrel, the cross-platform web server for ASP.NET Core.
 monikerRange: '>= aspnetcore-6.0'
 ms.author: wigodbe
 ms.custom: mvc, linux-related-content
-ms.date: 06/08/2025
+ms.date: 11/13/2025
 uid: fundamentals/servers/kestrel/http3
 ---
 
@@ -64,6 +65,25 @@ Because not all routers, firewalls, and proxies properly support HTTP/3, HTTP/3
 
 For more information, see <xref:fundamentals/servers/kestrel/endpoints>.
 
+## Configure QuicTransportOptions
+
+QUIC transport options can be configured by calling the <xref:Microsoft.AspNetCore.Hosting.WebHostBuilderQuicExtensions.UseQuic%2A> extension method on <xref:Microsoft.AspNetCore.Hosting.IWebHostBuilder>.
+
+:::code language="csharp" source="samples/6.x/KestrelSample/Snippets/Program.cs" id="snippet_UseQuicWithOptions" highlight="3-8":::
+
+The following table describes the available <xref:Microsoft.AspNetCore.Server.Kestrel.Transport.Quic.QuicTransportOptions>.
+
+| Option | Default | Description |
+| ------ | ------- | ----------- |
+| <xref:Microsoft.AspNetCore.Server.Kestrel.Transport.Quic.QuicTransportOptions.MaxBidirectionalStreamCount> | `100` | The maximum number of concurrent bidirectional streams per connection. |
+| <xref:Microsoft.AspNetCore.Server.Kestrel.Transport.Quic.QuicTransportOptions.MaxUnidirectionalStreamCount> | `10` | The maximum number of concurrent inbound unidirectional streams per connection. |
+| <xref:Microsoft.AspNetCore.Server.Kestrel.Transport.Quic.QuicTransportOptions.MaxReadBufferSize> | `1024 * 1024` (1 MB) | The maximum read buffer size in bytes. |
+| <xref:Microsoft.AspNetCore.Server.Kestrel.Transport.Quic.QuicTransportOptions.MaxWriteBufferSize> | `64 * 1024` (64 KB) | The maximum write buffer size in bytes. |
+| <xref:Microsoft.AspNetCore.Server.Kestrel.Transport.Quic.QuicTransportOptions.Backlog> | `512` | The maximum length of the pending connection queue. |
+| <xref:Microsoft.AspNetCore.Server.Kestrel.Transport.Quic.QuicTransportOptions.DefaultStreamErrorCode> | `0x010c` (H3_REQUEST_CANCELLED) | Error code used when the stream should abort the read or write side of the stream internally. |
+| <xref:Microsoft.AspNetCore.Server.Kestrel.Transport.Quic.QuicTransportOptions.DefaultCloseErrorCode> | `0x100` (H3_NO_ERROR) | Error code used when an open connection is disposed. |
+
+
 ## Alt-svc
 
 HTTP/3 is discovered as an upgrade from HTTP/1.1 or HTTP/2 via the [`alt-svc`](https://developer.mozilla.org/docs/Web/HTTP/Headers/Alt-Svc) header. That means the first request will normally use HTTP/1.1 or HTTP/2 before switching to HTTP/3. Kestrel automatically adds the `alt-svc` header if HTTP/3 is enabled.

aspnetcore/fundamentals/servers/kestrel/samples/6.x/KestrelSample/Snippets/Program.cs

@@ -9,6 +9,7 @@
 using Microsoft.AspNetCore.Server.Kestrel.Core;
 using Microsoft.AspNetCore.Server.Kestrel.Core.Features;
 using Microsoft.AspNetCore.Server.Kestrel.Https;
+using Microsoft.AspNetCore.Server.Kestrel.Transport.Quic;
 
 namespace KestrelSample.Snippets;
 
@@ -595,4 +596,27 @@ public static void Http3(string[] args)
         });
         // </snippet_Http3>
     }
+
+    public static void UseQuicWithOptions(string[] args)
+    {
+        // <snippet_UseQuicWithOptions>
+        var builder = WebApplication.CreateBuilder(args);
+
+        builder.WebHost.UseQuic(options =>
+        {
+#pragma warning disable CA2252 // Using preview features
+            options.MaxBidirectionalStreamCount = 200;
+#pragma warning restore CA2252
+        });
+
+        builder.WebHost.ConfigureKestrel((context, serverOptions) =>
+        {
+            serverOptions.ListenAnyIP(5001, listenOptions =>
+            {
+                listenOptions.Protocols = HttpProtocols.Http1AndHttp2AndHttp3;
+                listenOptions.UseHttps();
+            });
+        });
+        // </snippet_UseQuicWithOptions>
+    }
 }