Fix Unity 6000.6 InstanceIDToObjectCompat NotImplementedException

MCPForUnity/Runtime/Helpers/UnityObjectIdCompat.cs

@@ -1,8 +1,10 @@
 using UnityEngine;
 #if UNITY_EDITOR
-using System.Reflection;
 using UnityEditor;
 #endif
+#if UNITY_6000_6_OR_NEWER
+using System.Collections.Generic;
+#endif
 
 namespace MCPForUnity.Runtime.Helpers
 {
@@ -16,6 +18,18 @@ namespace MCPForUnity.Runtime.Helpers
     /// </summary>
     public static class UnityObjectIdCompat
     {
+#if UNITY_6000_6_OR_NEWER
+        // 6000.6 stubs out both EditorUtility.InstanceIDToObject(int) and EntityId's
+        // implicit int->EntityId conversion (both throw NotImplementedException at
+        // runtime despite existing in the API surface - verified against 6000.6.0f1).
+        // The only working reverse path is EntityIdToObject(EntityId) fed a value built
+        // via EntityId.FromULong(ulong), which needs the full 64-bit id, not the
+        // truncated int this class hands out. So we cache the full value behind the
+        // truncated int at mint time and look it up here instead of trying to
+        // reconstruct it from the int alone.
+        private static readonly Dictionary<int, ulong> _fullIdCache = new Dictionary<int, ulong>();
+#endif
+
         /// <summary>
         /// Returns a session-scoped int handle for the object. On 6.5+ truncates the
         /// EntityId's underlying ulong; lossy but stable within a session and preserves
@@ -30,40 +44,35 @@ public static int GetInstanceIDCompat(this Object obj)
             }
 
 #if UNITY_6000_5_OR_NEWER
-            return (int)EntityId.ToULong(obj.GetEntityId());
+            ulong full = EntityId.ToULong(obj.GetEntityId());
+            int truncated = (int)full;
+#if UNITY_6000_6_OR_NEWER
+            _fullIdCache[truncated] = full;
+#endif
+            return truncated;
 #else
             return obj.GetInstanceID();
 #endif
         }
 
 #if UNITY_EDITOR
-#if UNITY_6000_6_OR_NEWER
-        private static MethodInfo _instanceIdToObject;
-        private static bool _instanceIdToObjectInitialized;
-#endif
-
         /// <summary>
         /// Resolves an int instance ID handle back to a UnityEngine.Object.
         ///   Pre-6.0  : EditorUtility.InstanceIDToObject(int)
         ///   6.0–6.5  : EditorUtility.EntityIdToObject(int)  (implicit int→EntityId cast)
-        ///   6.6+     : reflection on InstanceIDToObject(int) — the API still exists at runtime
-        ///              but is obsolete-as-error; reflection bypasses CS0619 until the public
-        ///              EntityId(int) ctor stabilizes.
+        ///   6.6+     : EditorUtility.EntityIdToObject(EntityId.FromULong(full)) using the
+        ///              full 64-bit value cached in GetInstanceIDCompat, since the int-only
+        ///              paths (including the implicit int→EntityId cast) are unimplemented
+        ///              stubs on this Unity version. Only resolves ids minted this session.
         /// </summary>
         public static Object InstanceIDToObjectCompat(int instanceId)
         {
 #if UNITY_6000_6_OR_NEWER
-            if (!_instanceIdToObjectInitialized)
+            if (_fullIdCache.TryGetValue(instanceId, out ulong full))
             {
-                _instanceIdToObject = typeof(EditorUtility).GetMethod(
-                    "InstanceIDToObject",
-                    BindingFlags.Public | BindingFlags.Static,
-                    null,
-                    new[] { typeof(int) },
-                    null);
-                _instanceIdToObjectInitialized = true;
+                return EditorUtility.EntityIdToObject(EntityId.FromULong(full));
             }
-            return _instanceIdToObject?.Invoke(null, new object[] { instanceId }) as Object;
+            return null;
 #elif UNITY_6000_3_OR_NEWER
             return EditorUtility.EntityIdToObject(instanceId);
 #else