Enhance CodexClient for deferred completion handling

Updated the CodexClient class to manage deferred completion of turn notifications. Added fields for tracking status and errors, and implemented logic to defer completion until necessary data is available. Introduced a background task for scheduling deferred completions and modified the completion method to accommodate these changes.

Author: matthewfurnari

Buffaly.CodexEmbedded.Core/CodexClient.cs

@@ -482,11 +482,16 @@ public static TurnNotification ForCompleted(string? threadId, string status, str
 
 	private sealed class TurnTracker
 	{
+		private static readonly TimeSpan DeferredCompletionDelay = TimeSpan.FromMilliseconds(50);
 		private readonly StringBuilder _text = new();
 		private readonly object _lock = new();
 		private readonly List<TurnNotification> _queuedNotifications = new();
 		private string? _lastError;
 		private bool _isPrimed;
+		private bool _hasDeferredCompletion;
+		private string _deferredCompletionStatus = "unknown";
+		private string? _deferredCompletionErrorMessage;
+		private bool _deferredCompletionScheduled;
 
 		public string ThreadId { get; }
 		public string TurnId { get; }
@@ -565,19 +570,82 @@ private void ApplyNotificationLocked(TurnNotification notification)
 
 					_text.Append(notification.Delta);
 					Progress?.Report(new CodexDelta(notification.ThreadId ?? ThreadId, TurnId, notification.Delta));
+
+					// Guard against out-of-order notification timing where completion is observed before
+					// the first delta for a turn. Finalize once delta text is available.
+					if (_hasDeferredCompletion)
+					{
+						CompleteTurnLocked(_deferredCompletionStatus, _deferredCompletionErrorMessage);
+					}
 					return;
 				}
 				case TurnNotificationKind.Completed:
 				{
-					var aggregated = _text.ToString();
 					var finalError = notification.ErrorMessage ?? _lastError;
-					Completion.TrySetResult(new CodexTurnResult(ThreadId, TurnId, notification.Status, finalError, aggregated));
+					if (_text.Length == 0 &&
+						string.IsNullOrWhiteSpace(finalError) &&
+						string.Equals(notification.Status, "completed", StringComparison.OrdinalIgnoreCase))
+					{
+						_hasDeferredCompletion = true;
+						_deferredCompletionStatus = notification.Status;
+						_deferredCompletionErrorMessage = finalError;
+						ScheduleDeferredCompletion();
+						return;
+					}
+
+					CompleteTurnLocked(notification.Status, finalError);
 					return;
 				}
 				default:
 					return;
 			}
 		}
+
+		private void CompleteTurnLocked(string status, string? errorMessage)
+		{
+			if (Completion.Task.IsCompleted)
+			{
+				return;
+			}
+
+			_hasDeferredCompletion = false;
+			var aggregated = _text.ToString();
+			Completion.TrySetResult(new CodexTurnResult(ThreadId, TurnId, status, errorMessage, aggregated));
+		}
+
+		private void ScheduleDeferredCompletion()
+		{
+			if (_deferredCompletionScheduled)
+			{
+				return;
+			}
+
+			_deferredCompletionScheduled = true;
+			_ = Task.Run(async () =>
+			{
+				try
+				{
+					await Task.Delay(DeferredCompletionDelay);
+					lock (_lock)
+					{
+						if (_hasDeferredCompletion)
+						{
+							CompleteTurnLocked(_deferredCompletionStatus, _deferredCompletionErrorMessage);
+						}
+					}
+				}
+				catch
+				{
+				}
+				finally
+				{
+					lock (_lock)
+					{
+						_deferredCompletionScheduled = false;
+					}
+				}
+			});
+		}
 	}
 }