[dotnet] [bidi] Preserve configurable options pattern

dotnet/src/webdriver/BiDi/BiDi.cs

@@ -52,9 +52,12 @@ private BiDi() { }
 
     public Emulation.IEmulationModule Emulation => AsModule<Emulation.EmulationModule>();
 
-    public static async Task<IBiDi> ConnectAsync(string url, BiDiOptions? options = null, CancellationToken cancellationToken = default)
+    public static async Task<IBiDi> ConnectAsync(string url, Action<BiDiOptionsBuilder>? configure = null, CancellationToken cancellationToken = default)
     {
-        var transport = await WebSocketTransport.ConnectAsync(new Uri(url), cancellationToken).ConfigureAwait(false);
+        BiDiOptionsBuilder builder = new();
+        configure?.Invoke(builder);
+
+        var transport = await builder.TransportFactory(new Uri(url), cancellationToken).ConfigureAwait(false);
 
         BiDi bidi = new();
 

dotnet/src/webdriver/BiDi/BiDiOptionsBuilder.cs

@@ -0,0 +1,48 @@
+// <copyright file="BiDiOptionsBuilder.cs" company="Selenium Committers">
+// Licensed to the Software Freedom Conservancy (SFC) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The SFC licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+// </copyright>
+
+using System.Net.WebSockets;
+
+namespace OpenQA.Selenium.BiDi;
+
+/// <summary>
+/// Provides a fluent API for configuring BiDi connection options,
+/// such as the underlying transport mechanism.
+/// </summary>
+public sealed class BiDiOptionsBuilder
+{
+    internal Func<Uri, CancellationToken, Task<ITransport>> TransportFactory { get; private set; }
+        = (uri, ct) => WebSocketTransport.ConnectAsync(uri, null, ct);
+
+    /// <summary>
+    /// Configures the BiDi connection to use a WebSocket transport.
+    /// </summary>
+    /// <remarks>
+    /// WebSocket is the default transport; calling this method is only necessary
+    /// when you need to customize the underlying <see cref="ClientWebSocketOptions"/>
+    /// (e.g., to set headers, proxy, or certificates).
+    /// </remarks>
+    /// <param name="configure">An optional action to configure the <see cref="ClientWebSocketOptions"/> before connecting.</param>
+    /// <returns>The current <see cref="BiDiOptionsBuilder"/> instance for chaining.</returns>
+    public BiDiOptionsBuilder UseWebSocket(Action<ClientWebSocketOptions>? configure = null)
+    {
+        TransportFactory = (uri, ct) => WebSocketTransport.ConnectAsync(uri, configure, ct);
+        return this;
+    }
+}

dotnet/src/webdriver/BiDi/WebDriver.Extensions.cs

@@ -21,7 +21,7 @@ namespace OpenQA.Selenium.BiDi;
 
 public static class WebDriverExtensions
 {
-    public static async Task<IBiDi> AsBiDiAsync(this IWebDriver webDriver, BiDiOptions? options = null, CancellationToken cancellationToken = default)
+    public static async Task<IBiDi> AsBiDiAsync(this IWebDriver webDriver, Action<BiDiOptionsBuilder>? configure = null, CancellationToken cancellationToken = default)
     {
         if (webDriver is null) throw new ArgumentNullException(nameof(webDriver));
 
@@ -34,7 +34,7 @@ public static async Task<IBiDi> AsBiDiAsync(this IWebDriver webDriver, BiDiOptio
 
         if (webSocketUrl is null) throw new BiDiException("The driver is not compatible with bidirectional protocol or \"webSocketUrl\" not enabled in driver options.");
 
-        var bidi = await BiDi.ConnectAsync(webSocketUrl, options, cancellationToken).ConfigureAwait(false);
+        var bidi = await BiDi.ConnectAsync(webSocketUrl, configure, cancellationToken).ConfigureAwait(false);
 
         return bidi;
     }

dotnet/src/webdriver/BiDi/WebSocketTransport.cs

@@ -32,12 +32,14 @@ sealed class WebSocketTransport(ClientWebSocket webSocket) : ITransport
     private readonly SemaphoreSlim _socketSendSemaphoreSlim = new(1, 1);
     private readonly MemoryStream _sharedMemoryStream = new();
 
-    public static async Task<WebSocketTransport> ConnectAsync(Uri uri, CancellationToken cancellationToken)
+    public static async Task<ITransport> ConnectAsync(Uri uri, Action<ClientWebSocketOptions>? configure, CancellationToken cancellationToken)
     {
         ClientWebSocket webSocket = new();
 
         try
         {
+            configure?.Invoke(webSocket.Options);
+
             await webSocket.ConnectAsync(uri, cancellationToken).ConfigureAwait(false);
         }
         catch (Exception)