diff --git a/.claude/settings.local.json b/.claude/settings.local.json
index 8866d3a..5ced01b 100644
--- a/.claude/settings.local.json
+++ b/.claude/settings.local.json
@@ -24,7 +24,8 @@
       "Bash(dir /B /O-D \"H:\\Applications\\Aycode\\Source\\AyCode.Core\\Test_Benchmark_Results\\Benchmark\\*.md\")",
       "Bash(cmd /c \"dir /B /O-D H:\\Applications\\Aycode\\Source\\AyCode.Core\\Test_Benchmark_Results\\Benchmark\\*.md\")",
       "Bash(cmd /c \"dir /B /O-D H:\\Applications\\Aycode\\Source\\AyCode.Core\\Test_Benchmark_Results\\Benchmark\\*.log 2>nul | head -3\")",
-      "Bash(cmd /c \"dir /B /O-D H:\\Applications\\Aycode\\Source\\AyCode.Core\\Test_Benchmark_Results\\Benchmark\\*.log 2>nul | head -1\")"
+      "Bash(cmd /c \"dir /B /O-D H:\\Applications\\Aycode\\Source\\AyCode.Core\\Test_Benchmark_Results\\Benchmark\\*.log 2>nul | head -1\")",
+      "Bash(timeout 30 dotnet run:*)"
     ]
   }
 }
diff --git a/AyCode.Core/Serializers/Toons/AcToonSerializer.MetaSection.cs b/AyCode.Core/Serializers/Toons/AcToonSerializer.MetaSection.cs
index 8ed59d2..ad5cdec 100644
--- a/AyCode.Core/Serializers/Toons/AcToonSerializer.MetaSection.cs
+++ b/AyCode.Core/Serializers/Toons/AcToonSerializer.MetaSection.cs
@@ -106,7 +106,8 @@ public static partial class AcToonSerializer
     }
 
     /// <summary>
-    /// Collect all types that need documentation (recursive).
+    /// Recursively collects all types that need metadata documentation.
+    /// Uses the same logic as AcBinarySerializer.RegisterMetadataForType.
     /// </summary>
     private static void CollectTypes(Type type, HashSet<Type> types)
     {
@@ -116,15 +117,7 @@ public static partial class AcToonSerializer
 
         if (!types.Add(underlyingType)) return; // Already processed
 
-        // Handle collections
-        var elementType = GetCollectionElementType(underlyingType);
-        if (elementType != null)
-        {
-            CollectTypes(elementType, types);
-            return;
-        }
-
-        // Handle dictionaries
+        // Handle dictionaries FIRST (before generic IEnumerable check)
         if (IsDictionaryType(underlyingType, out var keyType, out var valueType))
         {
             if (keyType != null) CollectTypes(keyType, types);
@@ -132,7 +125,18 @@ public static partial class AcToonSerializer
             return;
         }
 
-        // Handle object properties
+        // Handle collections/arrays (matches AcBinarySerializer logic)
+        if (typeof(IEnumerable).IsAssignableFrom(underlyingType) && !ReferenceEquals(underlyingType, StringType))
+        {
+            var elementType = GetCollectionElementType(underlyingType);
+            if (elementType != null)
+            {
+                CollectTypes(elementType, types);
+            }
+            return;
+        }
+
+        // Handle object properties (traverse type graph)
         var metadata = GetTypeMetadata(underlyingType);
         foreach (var prop in metadata.Properties)
         {
@@ -395,8 +399,11 @@ public static partial class AcToonSerializer
             return $"Enum type with values: {string.Join(", ", Enum.GetNames(type))}";
 
         var metadata = GetTypeMetadata(type);
-        if (metadata.IsCollection)
-            return $"Collection of {metadata.ElementType?.Name ?? "items"}";
+
+        // Only treat as collection if ElementType is not System.Object (fallback value from GetCollectionElementType)
+        if (metadata.IsCollection && metadata.ElementType != null && metadata.ElementType != typeof(object))
+            return $"Collection of {metadata.ElementType.Name}";
+
         if (metadata.IsDictionary)
             return "Dictionary mapping keys to values";
 
diff --git a/AyCode.Core/Serializers/Toons/AcToonSerializer.ToonSerializationContext.cs b/AyCode.Core/Serializers/Toons/AcToonSerializer.ToonSerializationContext.cs
index 8dd49b9..ae6420d 100644
--- a/AyCode.Core/Serializers/Toons/AcToonSerializer.ToonSerializationContext.cs
+++ b/AyCode.Core/Serializers/Toons/AcToonSerializer.ToonSerializationContext.cs
@@ -4,7 +4,7 @@ using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using System.Text;
-using ReferenceEqualityComparer = AyCode.Core.Serializers.Jsons.ReferenceEqualityComparer;
+using ReferenceEqualityComparer = AyCode.Core.Serializers.ReferenceEqualityComparer;
 
 namespace AyCode.Core.Serializers.Toons;
 
diff --git a/AyCode.Core/Serializers/Toons/AcToonSerializer.ToonTypeMetadata.cs b/AyCode.Core/Serializers/Toons/AcToonSerializer.ToonTypeMetadata.cs
index fcd2c07..c6f365a 100644
--- a/AyCode.Core/Serializers/Toons/AcToonSerializer.ToonTypeMetadata.cs
+++ b/AyCode.Core/Serializers/Toons/AcToonSerializer.ToonTypeMetadata.cs
@@ -1,3 +1,4 @@
+using System.Collections;
 using System.Linq.Expressions;
 using System.Reflection;
 using System.Runtime.CompilerServices;
@@ -28,12 +29,16 @@ public static partial class AcToonSerializer
             // Get custom attribute if present
             CustomDescription = type.GetCustomAttribute<ToonDescriptionAttribute>();
 
-            // Check if collection or dictionary
+            // Check if collection or dictionary (matches AcBinarySerializer logic)
             IsDictionary = IsDictionaryType(type, out _, out _);
             if (!IsDictionary)
             {
-                ElementType = GetCollectionElementType(type);
-                IsCollection = ElementType != null;
+                // Only treat as collection if it implements IEnumerable (excluding string)
+                if (typeof(IEnumerable).IsAssignableFrom(type) && !ReferenceEquals(type, StringType))
+                {
+                    ElementType = GetCollectionElementType(type);
+                    IsCollection = true;
+                }
             }
 
             // Build property accessors
@@ -137,8 +142,13 @@ public static partial class AcToonSerializer
             return false;
         }
 
+        // Thread-local visited set to prevent circular reference stack overflow
+        [ThreadStatic]
+        private static HashSet<Type>? t_visitedTypes;
+
         /// <summary>
         /// Build human-readable type name for meta section.
+        /// Uses thread-local visited set to prevent stack overflow on circular references.
         /// </summary>
         private static string BuildTypeDisplayName(Type type)
         {
@@ -169,30 +179,60 @@ public static partial class AcToonSerializer
             return isNullable ? baseName + "?" : baseName;
         }
 
+        /// <summary>
+        /// Get complex type name WITH circular reference protection using thread-local visited set.
+        /// </summary>
         private static string GetComplexTypeName(Type type)
         {
-            if (ReferenceEquals(type, GuidType)) return "guid";
-            if (ReferenceEquals(type, DateTimeOffsetType)) return "datetimeoffset";
-            if (ReferenceEquals(type, TimeSpanType)) return "timespan";
-            if (type.IsEnum) return "enum";
+            // Initialize thread-local visited set if needed
+            t_visitedTypes ??= new HashSet<Type>();
 
-            // Check for collections
-            var elementType = GetCollectionElementType(type);
-            if (elementType != null)
+            // Check for circular reference - if already visiting, return simple name
+            if (!t_visitedTypes.Add(type))
             {
-                var elementTypeName = BuildTypeDisplayName(elementType);
-                return $"{elementTypeName}[]";
+                return type.Name; // Break circular reference
             }
 
-            // Check for dictionaries
-            if (IsDictionaryType(type, out var keyType, out var valueType))
+            try
             {
-                var keyTypeName = keyType != null ? BuildTypeDisplayName(keyType) : "object";
-                var valueTypeName = valueType != null ? BuildTypeDisplayName(valueType) : "object";
-                return $"dict<{keyTypeName}, {valueTypeName}>";
-            }
+                if (ReferenceEquals(type, GuidType)) return "guid";
+                if (ReferenceEquals(type, DateTimeOffsetType)) return "datetimeoffset";
+                if (ReferenceEquals(type, TimeSpanType)) return "timespan";
+                if (type.IsEnum) return "enum";
 
-            return type.Name;
+                // For collections: recursively build element type name (safe with visited tracking)
+                if (typeof(IEnumerable).IsAssignableFrom(type) && !ReferenceEquals(type, StringType))
+                {
+                    var elementType = GetCollectionElementType(type);
+                    if (elementType != null && elementType != typeof(object))
+                    {
+                        var elementTypeName = BuildTypeDisplayName(elementType);
+                        return $"{elementTypeName}[]";
+                    }
+                }
+
+                // For dictionaries: recursively build key/value type names (safe with visited tracking)
+                if (IsDictionaryType(type, out var keyType, out var valueType))
+                {
+                    var keyTypeName = keyType != null ? BuildTypeDisplayName(keyType) : "object";
+                    var valueTypeName = valueType != null ? BuildTypeDisplayName(valueType) : "object";
+                    return $"dict<{keyTypeName}, {valueTypeName}>";
+                }
+
+                // Simple type name for complex objects
+                return type.Name;
+            }
+            finally
+            {
+                // Remove from visited set when done (allows reuse in different branches)
+                t_visitedTypes.Remove(type);
+
+                // Clear the set if empty to avoid memory leaks
+                if (t_visitedTypes.Count == 0)
+                {
+                    t_visitedTypes = null;
+                }
+            }
         }
     }
 }
diff --git a/AyCode.Core/Serializers/Toons/AcToonSerializerOptions.cs b/AyCode.Core/Serializers/Toons/AcToonSerializerOptions.cs
index 23f0567..0f75579 100644
--- a/AyCode.Core/Serializers/Toons/AcToonSerializerOptions.cs
+++ b/AyCode.Core/Serializers/Toons/AcToonSerializerOptions.cs
@@ -181,7 +181,7 @@ public sealed class AcToonSerializerOptions : AcSerializerOptions
     {
         Mode = ToonSerializationMode.DataOnly,
         UseMeta = false,
-        UseIndentation = false,
+        UseIndentation = true,
         OmitDefaultValues = true,
         WriteTypeNames = false,
         UseReferenceHandling = false