Add C# MCP OAuth config parity

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: stephentoub

dotnet/src/Types.cs

@@ -1526,6 +1526,21 @@ public class AzureOptions
 // MCP Server Configuration Types
 // ============================================================================
 
+/// <summary>
+/// OAuth grant type for a remote MCP server.
+/// </summary>
+[JsonConverter(typeof(JsonStringEnumConverter<McpHttpServerConfigOauthGrantType>))]
+public enum McpHttpServerConfigOauthGrantType
+{
+    /// <summary>Use the authorization code OAuth flow.</summary>
+    [JsonStringEnumMemberName("authorization_code")]
+    AuthorizationCode,
+
+    /// <summary>Use the client credentials OAuth flow.</summary>
+    [JsonStringEnumMemberName("client_credentials")]
+    ClientCredentials
+}
+
 /// <summary>
 /// Abstract base class for MCP server configurations.
 /// </summary>
@@ -1611,6 +1626,24 @@ public sealed class McpHttpServerConfig : McpServerConfig
     /// </summary>
     [JsonPropertyName("headers")]
     public IDictionary<string, string>? Headers { get; set; }
+
+    /// <summary>
+    /// Optional OAuth client ID for the remote server.
+    /// </summary>
+    [JsonPropertyName("oauthClientId")]
+    public string? OauthClientId { get; set; }
+
+    /// <summary>
+    /// Whether this is a public OAuth client.
+    /// </summary>
+    [JsonPropertyName("oauthPublicClient")]
+    public bool? OauthPublicClient { get; set; }
+
+    /// <summary>
+    /// Optional OAuth grant type for the remote server.
+    /// </summary>
+    [JsonPropertyName("oauthGrantType")]
+    public McpHttpServerConfigOauthGrantType? OauthGrantType { get; set; }
 }
 
 // ============================================================================

dotnet/test/SerializationTests.cs

@@ -81,6 +81,44 @@ public void SendMessageRequest_CanSerializeRequestHeaders_WithSdkOptions()
         Assert.Equal("trace-value", root.GetProperty("requestHeaders").GetProperty("X-Trace").GetString());
     }
 
+    [Fact]
+    public void McpHttpServerConfig_CanSerializeOauthOptions_WithSdkOptions()
+    {
+        var options = GetSerializerOptions();
+        McpServerConfig original = new McpHttpServerConfig
+        {
+            Url = "https://example.com/mcp",
+            Headers = new Dictionary<string, string> { ["Authorization"] = "Bearer token" },
+            OauthClientId = "client-id",
+            OauthPublicClient = false,
+            OauthGrantType = McpHttpServerConfigOauthGrantType.ClientCredentials,
+            Tools = ["*"],
+            Timeout = 3000
+        };
+
+        var json = JsonSerializer.Serialize(original, options);
+        using var document = JsonDocument.Parse(json);
+        var root = document.RootElement;
+        Assert.Equal("http", root.GetProperty("type").GetString());
+        Assert.Equal("https://example.com/mcp", root.GetProperty("url").GetString());
+        Assert.Equal("Bearer token", root.GetProperty("headers").GetProperty("Authorization").GetString());
+        Assert.Equal("client-id", root.GetProperty("oauthClientId").GetString());
+        Assert.False(root.GetProperty("oauthPublicClient").GetBoolean());
+        Assert.Equal("client_credentials", root.GetProperty("oauthGrantType").GetString());
+        Assert.Equal("*", root.GetProperty("tools")[0].GetString());
+        Assert.Equal(3000, root.GetProperty("timeout").GetInt32());
+
+        var deserialized = JsonSerializer.Deserialize<McpServerConfig>(json, options);
+        var httpConfig = Assert.IsType<McpHttpServerConfig>(deserialized);
+        Assert.Equal("https://example.com/mcp", httpConfig.Url);
+        Assert.Equal("Bearer token", httpConfig.Headers!["Authorization"]);
+        Assert.Equal("client-id", httpConfig.OauthClientId);
+        Assert.False(httpConfig.OauthPublicClient);
+        Assert.Equal(McpHttpServerConfigOauthGrantType.ClientCredentials, httpConfig.OauthGrantType);
+        Assert.Equal("*", Assert.Single(httpConfig.Tools));
+        Assert.Equal(3000, httpConfig.Timeout);
+    }
+
     private static JsonSerializerOptions GetSerializerOptions()
     {
         var prop = typeof(CopilotClient)