fix: address human review feedback

.NET:
- Cache SessionUiApiImpl instance via Lazy<> instead of allocating on
  every .Ui access
- Await command/elicitation handler calls instead of redundant
  fire-and-forget (outer caller already fire-and-forgets)
- Use ElicitationRequestedDataMode enum for Mode instead of string

Go:
- Handle SessionEventTypeCapabilitiesChanged in handleBroadcastEvent
  to update session capabilities when other clients join/leave with
  elicitation handlers
- Add test verifying capabilities.changed event updates session

Author: MRayermannMSFT

dotnet/src/Session.cs

@@ -63,6 +63,7 @@ public sealed partial class CopilotSession : IAsyncDisposable
     private volatile PermissionRequestHandler? _permissionHandler;
     private volatile UserInputHandler? _userInputHandler;
     private volatile ElicitationHandler? _elicitationHandler;
+    private readonly Lazy<ISessionUiApi> _ui;
     private ImmutableArray<SessionEventHandler> _eventHandlers = ImmutableArray<SessionEventHandler>.Empty;
 
     private SessionHooks? _hooks;
@@ -122,7 +123,7 @@ public sealed partial class CopilotSession : IAsyncDisposable
     /// if the host does not report elicitation support via <see cref="Capabilities"/>.
     /// Check <c>session.Capabilities.Ui?.Elicitation == true</c> before calling.
     /// </remarks>
-    public ISessionUiApi Ui => new SessionUiApiImpl(this);
+    public ISessionUiApi Ui => _ui.Value;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="CopilotSession"/> class.
@@ -140,6 +141,7 @@ internal CopilotSession(string sessionId, JsonRpc rpc, ILogger logger, string? w
         _rpc = rpc;
         _logger = logger;
         WorkspacePath = workspacePath;
+        _ui = new Lazy<ISessionUiApi>(() => new SessionUiApiImpl(this));
 
         // Start the asynchronous processing loop.
         _ = ProcessEventsAsync();
@@ -469,7 +471,7 @@ private async Task HandleBroadcastEventAsync(SessionEvent sessionEvent)
                         if (string.IsNullOrEmpty(data.RequestId))
                             return;
 
-                        _ = ExecuteCommandAndRespondAsync(data.RequestId, data.CommandName, data.Command, data.Args);
+                        await ExecuteCommandAndRespondAsync(data.RequestId, data.CommandName, data.Command, data.Args);
                         break;
                     }
 
@@ -490,12 +492,12 @@ private async Task HandleBroadcastEventAsync(SessionEvent sessionEvent)
                                 }
                                 : null;
 
-                            _ = HandleElicitationRequestAsync(
+                            await HandleElicitationRequestAsync(
                                 new ElicitationRequest
                                 {
                                     Message = data.Message,
                                     RequestedSchema = schema,
-                                    Mode = data.Mode?.ToString().ToLowerInvariant(),
+                                    Mode = data.Mode,
                                     ElicitationSource = data.ElicitationSource,
                                     Url = data.Url
                                 },

dotnet/src/Types.cs

@@ -704,7 +704,7 @@ public class ElicitationRequest
     public ElicitationSchema? RequestedSchema { get; set; }
 
     /// <summary>Elicitation mode: <c>"form"</c> for structured input, <c>"url"</c> for browser redirect.</summary>
-    public string? Mode { get; set; }
+    public ElicitationRequestedDataMode? Mode { get; set; }
 
     /// <summary>The source that initiated the request (e.g., MCP server name).</summary>
     public string? ElicitationSource { get; set; }

dotnet/test/ElicitationTests.cs

@@ -243,14 +243,14 @@ public void ElicitationRequest_Has_All_Properties()
                     ["color"] = new Dictionary<string, object> { ["type"] = "string", ["enum"] = new[] { "red", "blue" } },
                 },
             },
-            Mode = "form",
+            Mode = ElicitationRequestedDataMode.Form,
             ElicitationSource = "mcp-server",
             Url = null,
         };
 
         Assert.Equal("Pick a color", request.Message);
         Assert.NotNull(request.RequestedSchema);
-        Assert.Equal("form", request.Mode);
+        Assert.Equal(ElicitationRequestedDataMode.Form, request.Mode);
         Assert.Equal("mcp-server", request.ElicitationSource);
         Assert.Null(request.Url);
     }

go/session.go

@@ -983,6 +983,13 @@ func (s *Session) handleBroadcastEvent(event SessionEvent) {
 			ElicitationSource: elicitationSource,
 			URL:               url,
 		}, *requestID)
+
+	case SessionEventTypeCapabilitiesChanged:
+		if event.Data.UI != nil && event.Data.UI.Elicitation != nil {
+			s.setCapabilities(&SessionCapabilities{
+				UI: &UICapabilities{Elicitation: *event.Data.UI.Elicitation},
+			})
+		}
 	}
 }
 

go/session_test.go

@@ -386,6 +386,50 @@ func TestSession_Capabilities(t *testing.T) {
 			t.Errorf("Expected UI to be nil after reset, got %+v", caps.UI)
 		}
 	})
+
+	t.Run("capabilities.changed event updates session capabilities", func(t *testing.T) {
+		session, cleanup := newTestSession()
+		defer cleanup()
+
+		// Initially no capabilities
+		caps := session.Capabilities()
+		if caps.UI != nil {
+			t.Fatal("Expected UI to be nil initially")
+		}
+
+		// Dispatch a capabilities.changed event with elicitation=true
+		elicitTrue := true
+		session.dispatchEvent(SessionEvent{
+			Type: SessionEventTypeCapabilitiesChanged,
+			Data: Data{
+				UI: &UI{Elicitation: &elicitTrue},
+			},
+		})
+
+		// Give the broadcast handler time to process
+		time.Sleep(50 * time.Millisecond)
+
+		caps = session.Capabilities()
+		if caps.UI == nil || !caps.UI.Elicitation {
+			t.Error("Expected UI.Elicitation to be true after capabilities.changed event")
+		}
+
+		// Dispatch with elicitation=false
+		elicitFalse := false
+		session.dispatchEvent(SessionEvent{
+			Type: SessionEventTypeCapabilitiesChanged,
+			Data: Data{
+				UI: &UI{Elicitation: &elicitFalse},
+			},
+		})
+
+		time.Sleep(50 * time.Millisecond)
+
+		caps = session.Capabilities()
+		if caps.UI == nil || caps.UI.Elicitation {
+			t.Error("Expected UI.Elicitation to be false after second capabilities.changed event")
+		}
+	})
 }
 
 func TestSession_ElicitationCapabilityGating(t *testing.T) {