Add application_type to the Dynamic Client Registration request (#1613)

tests/ModelContextProtocol.Tests/Authentication/ClientOAuthProviderApplicationTypeTests.cs

@@ -0,0 +1,41 @@
+using ModelContextProtocol.Authentication;
+using ModelContextProtocol.Client;
+
+namespace ModelContextProtocol.Tests.Authentication;
+
+// ClientOAuthProvider is internal; construct it indirectly via HttpClientTransport
+// to verify DCR application_type validation is deferred until DCR is selected.
+public class ClientOAuthProviderApplicationTypeTests
+{
+    private static readonly Uri ServerEndpoint = new("https://server.example.com/mcp");
+
+    private static HttpClientTransportOptions BuildOptions(string redirectUri, string? explicitApplicationType = null)
+    {
+        return new HttpClientTransportOptions
+        {
+            Endpoint = ServerEndpoint,
+            OAuth = new ClientOAuthOptions
+            {
+                RedirectUri = new Uri(redirectUri),
+                DynamicClientRegistration = new DynamicClientRegistrationOptions
+                {
+                    ApplicationType = explicitApplicationType,
+                },
+            },
+        };
+    }
+
+    [Theory]
+    [InlineData("http://localhost:8080/callback", "web")]
+    [InlineData("https://example.com/callback", "native")]
+    public void Constructor_Defers_ApplicationTypeValidation_UntilDynamicRegistration(
+        string redirectUri, string explicitType)
+    {
+        var options = BuildOptions(redirectUri, explicitType);
+
+        using var httpClient = new HttpClient();
+        _ = new HttpClientTransport(options, httpClient);
+
+        Assert.Equal(explicitType, options.OAuth!.DynamicClientRegistration!.ApplicationType);
+    }
+}