Merge pull request #473 from IvanMurzak/471-mcp-server-does-not-start-automatically-when-unity-project-is-opened-in-background

fix: MCP server does not start automatically when unity project is opened in background

Author: IvanMurzak

Unity-MCP-Plugin/Assets/root/Editor/Scripts/McpServerManager.cs

@@ -70,7 +70,22 @@ static McpServerManager()
             EditorApplication.quitting += OnEditorQuitting;
 
             // Check if server process is still running (e.g., after domain reload)
-            CheckExistingProcess();
+            EditorApplication.update += CheckExistingProcess;
+
+            DownloadServerBinaryIfNeeded()
+                .ContinueWith(task =>
+                {
+                    if (task.IsFaulted || !task.Result)
+                        return; // Failed to download binaries, skip auto-start
+
+                    if (!task.Result)
+                        return; // No binaries available (either in CI or failed to download), skip auto-start
+
+                    if (EnvironmentUtils.IsCi())
+                        return; // Skip auto-start in CI environment
+
+                    EditorApplication.update += StartServerIfNeeded;
+                });
         }
 
         #region Binary Metadata
@@ -467,6 +482,7 @@ public static string DockerRunCommand()
 
         static void CheckExistingProcess()
         {
+            EditorApplication.update -= CheckExistingProcess;
             // Try to find an existing server process by checking if our tracked PID is still running
             // This helps maintain state across domain reloads
             var savedPid = EditorPrefs.GetInt(ProcessIdKey, -1);
@@ -1055,21 +1071,15 @@ static void CleanupProcess()
             }
         }
 
-        public static void ToggleServer()
-        {
-            if (IsRunning)
-                StopServer();
-            else
-                StartServer();
-        }
-
         /// <summary>
         /// Starts the MCP server if KeepServerRunning is enabled and no external server is detected.
         /// This method is called during Unity Editor startup to auto-start the server based on user preference.
         /// The external server check is performed asynchronously to avoid blocking the main thread.
         /// </summary>
         public static void StartServerIfNeeded()
         {
+            EditorApplication.update -= StartServerIfNeeded;
+
             // Check if user wants the server to keep running
             if (!UnityMcpPlugin.KeepServerRunning)
             {
@@ -1126,10 +1136,9 @@ static void CheckExternalServerAsync(int port, Action<bool> onResult)
                 {
                     _logger.LogDebug("CheckExternalServerAsync: No server detected on port {port} ({message})", port, ex.Message);
                 }
-
-                // Marshal callback back to the main thread
-                EditorApplication.delayCall += () => onResult(result);
-            });
+                return result;
+            })
+            .ContinueWith(task => onResult(task.Result), TaskScheduler.FromCurrentSynchronizationContext());
         }
 
         #endregion // Process Lifecycle

Unity-MCP-Plugin/Assets/root/Editor/Scripts/Startup.cs

@@ -28,20 +28,6 @@ static Startup()
             UnityMcpPlugin.Instance.BuildMcpPluginIfNeeded();
             UnityMcpPlugin.Instance.AddUnityLogCollectorIfNeeded(() => new BufferedFileLogStorage());
 
-            // Defer connection to avoid blocking during domain reload.
-            // Starting async SignalR connections during [InitializeOnLoad] can cause
-            // Unity to freeze because async continuations may run on the main thread
-            // while it's still processing the domain reload.
-            if (!EnvironmentUtils.IsCi())
-                EditorApplication.delayCall += () => UnityMcpPlugin.ConnectIfNeeded();
-
-            McpServerManager.DownloadServerBinaryIfNeeded();
-
-            // Defer MCP server auto-start to avoid blocking during domain reload
-            // and to ensure configuration is fully loaded
-            if (!EnvironmentUtils.IsCi())
-                EditorApplication.delayCall += () => McpServerManager.StartServerIfNeeded();
-
             if (Application.dataPath.Contains(" "))
                 Debug.LogError("The project path contains spaces, which may cause issues during usage of AI Game Developer. Please consider the move the project to a folder without spaces.");