From cf65c442de6fbc733e7732b16bc10a8d708d8ea3 Mon Sep 17 00:00:00 2001
From: Wojtek Figat <wojtek@figat.pl>
Date: Fri, 17 Apr 2026 18:51:50 +0200
Subject: [PATCH] Add `AutoAttachDebugPreviewActor` for Behavior Tree editor

---
 .../Editor/Windows/Assets/BehaviorTreeWindow.cs | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/Source/Editor/Windows/Assets/BehaviorTreeWindow.cs b/Source/Editor/Windows/Assets/BehaviorTreeWindow.cs
index 03ba26fc8..1317300c3 100644
--- a/Source/Editor/Windows/Assets/BehaviorTreeWindow.cs
+++ b/Source/Editor/Windows/Assets/BehaviorTreeWindow.cs
@@ -509,10 +509,25 @@ namespace FlaxEditor.Windows.Assets
             // Check if don't have valid behavior picked
             if (!_behaviorPicker.Value)
             {
-                // Try to reassign the debug behavior
                 var id = _cachedBehaviorId;
+                if (id == Guid.Empty && Editor.IsPlayMode && Editor.Options.Options.General.AutoAttachDebugPreviewActor)
+                {
+                    // Auto-attach preview
+                    var behaviorTree = Asset;
+                    var behaviors = Level.GetScripts<Behavior>();
+                    foreach (var behavior in behaviors)
+                    {
+                        if (behavior.Tree == behaviorTree &&
+                            behavior.IsEnabledInHierarchy)
+                        {
+                            id = behavior.ID;
+                            break;
+                        }
+                    }
+                }
                 if (id != Guid.Empty)
                 {
+                    // Try to reassign the debug behavior
                     var obj = FlaxEngine.Object.TryFind<Behavior>(ref id);
                     if (obj && obj.Tree == Asset)
                         _behaviorPicker.Value = obj;