diff --git a/AyCode.Core.Serializers.Console/Program.cs b/AyCode.Core.Serializers.Console/Program.cs
index a645910..eeb06d6 100644
--- a/AyCode.Core.Serializers.Console/Program.cs
+++ b/AyCode.Core.Serializers.Console/Program.cs
@@ -50,7 +50,7 @@ public static class Program
     private static int TestIterations = 1;
     #else
     private static int WarmupIterations = 5000;
-    private static int TestIterations = 1000;
+    private static int TestIterations = 5000;
 
     //private static int WarmupIterations = 5000;
     //private static int TestIterations = 2000;
diff --git a/AyCode.Core.Serializers.SourceGenerator/AcBinarySourceGenerator.cs b/AyCode.Core.Serializers.SourceGenerator/AcBinarySourceGenerator.cs
index b401f03..407bd1d 100644
--- a/AyCode.Core.Serializers.SourceGenerator/AcBinarySourceGenerator.cs
+++ b/AyCode.Core.Serializers.SourceGenerator/AcBinarySourceGenerator.cs
@@ -193,8 +193,8 @@ public class AcBinarySourceGenerator : IIncrementalGenerator
                             collKind = origDef switch
                             {
                                 "System.Collections.Generic.List<T>" => "List",
-                                "System.Collections.Generic.IList<T>" => "List",           // has Count + indexer
-                                "System.Collections.Generic.IReadOnlyList<T>" => "List",    // has Count + indexer
+                                "System.Collections.Generic.IList<T>" => "IndexedCollection",
+                                "System.Collections.Generic.IReadOnlyList<T>" => "IndexedCollection",
                                 "System.Collections.Generic.HashSet<T>" => "Counted",       // has Count, no indexer
                                 "System.Collections.Generic.Queue<T>" => "Counted",
                                 "System.Collections.Generic.ICollection<T>" => "Counted",
@@ -304,6 +304,7 @@ public class AcBinarySourceGenerator : IIncrementalGenerator
         sb.AppendLine("// <auto-generated/>");
         sb.AppendLine("#nullable enable");
         sb.AppendLine("using System.Runtime.CompilerServices;");
+        sb.AppendLine("using System.Runtime.InteropServices;");
         sb.AppendLine("using AyCode.Core.Serializers.Binaries;");
         // ReferenceHandlingMode is needed for ScanObject self ref tracking and direct object write/scan
         sb.AppendLine("using AyCode.Core.Serializers;");
@@ -753,6 +754,13 @@ public class AcBinarySourceGenerator : IIncrementalGenerator
                 sb.AppendLine($"{i}        var se_{p.Name} = scol_{p.Name}[si_{p.Name}];");
             }
             else if (p.CollectionKind == "List")
+            {
+                sb.AppendLine($"{i}    var span_{p.Name} = CollectionsMarshal.AsSpan(scol_{p.Name});");
+                sb.AppendLine($"{i}    for (var si_{p.Name} = 0; si_{p.Name} < span_{p.Name}.Length; si_{p.Name}++)");
+                sb.AppendLine($"{i}    {{");
+                sb.AppendLine($"{i}        var se_{p.Name} = span_{p.Name}[si_{p.Name}];");
+            }
+            else if (p.CollectionKind == "IndexedCollection")
             {
                 sb.AppendLine($"{i}    for (var si_{p.Name} = 0; si_{p.Name} < scol_{p.Name}.Count; si_{p.Name}++)");
                 sb.AppendLine($"{i}    {{");
@@ -812,6 +820,13 @@ public class AcBinarySourceGenerator : IIncrementalGenerator
                 sb.AppendLine($"{i}        var se_{p.Name} = scol_{p.Name}[si_{p.Name}];");
             }
             else if (p.CollectionKind == "List")
+            {
+                sb.AppendLine($"{i}    var span_{p.Name} = CollectionsMarshal.AsSpan(scol_{p.Name});");
+                sb.AppendLine($"{i}    for (var si_{p.Name} = 0; si_{p.Name} < span_{p.Name}.Length; si_{p.Name}++)");
+                sb.AppendLine($"{i}    {{");
+                sb.AppendLine($"{i}        var se_{p.Name} = span_{p.Name}[si_{p.Name}];");
+            }
+            else if (p.CollectionKind == "IndexedCollection")
             {
                 sb.AppendLine($"{i}    for (var si_{p.Name} = 0; si_{p.Name} < scol_{p.Name}.Count; si_{p.Name}++)");
                 sb.AppendLine($"{i}    {{");
@@ -1025,14 +1040,23 @@ public class AcBinarySourceGenerator : IIncrementalGenerator
             sb.AppendLine($"{i}    foreach (var elem_{p.Name} in col_{p.Name})");
             sb.AppendLine($"{i}    {{");
         }
-        else // List, IList<T>, IReadOnlyList<T> — Count + indexer
+        else if (p.CollectionKind == "IndexedCollection")
         {
-            sb.AppendLine($"{i}    var list_{p.Name} = {a};");
-            sb.AppendLine($"{i}    context.WriteVarUInt((uint)list_{p.Name}.Count);");
+            sb.AppendLine($"{i}    var col_{p.Name} = {a};");
+            sb.AppendLine($"{i}    context.WriteVarUInt((uint)col_{p.Name}.Count);");
             sb.AppendLine($"{i}    var nextDepth_{p.Name} = depth + 1;");
-            sb.AppendLine($"{i}    for (var i_{p.Name} = 0; i_{p.Name} < list_{p.Name}.Count; i_{p.Name}++)");
+            sb.AppendLine($"{i}    for (var i_{p.Name} = 0; i_{p.Name} < col_{p.Name}.Count; i_{p.Name}++)");
             sb.AppendLine($"{i}    {{");
-            sb.AppendLine($"{i}        var elem_{p.Name} = list_{p.Name}[i_{p.Name}];");
+            sb.AppendLine($"{i}        var elem_{p.Name} = col_{p.Name}[i_{p.Name}];");
+        }
+        else // List — CollectionsMarshal.AsSpan for zero-overhead iteration
+        {
+            sb.AppendLine($"{i}    var span_{p.Name} = CollectionsMarshal.AsSpan({a});");
+            sb.AppendLine($"{i}    context.WriteVarUInt((uint)span_{p.Name}.Length);");
+            sb.AppendLine($"{i}    var nextDepth_{p.Name} = depth + 1;");
+            sb.AppendLine($"{i}    for (var i_{p.Name} = 0; i_{p.Name} < span_{p.Name}.Length; i_{p.Name}++)");
+            sb.AppendLine($"{i}    {{");
+            sb.AppendLine($"{i}        var elem_{p.Name} = span_{p.Name}[i_{p.Name}];");
         }
 
         // Per-element write
@@ -1542,7 +1566,7 @@ public class AcBinarySourceGenerator : IIncrementalGenerator
             EmitReadCollectionElement(sb, reader, elemCast, $"ri_{s}", s, i + "        ", isArray: true, p.ElementNeedsRefScan);
             sb.AppendLine($"{i}    }}");
         }
-        else // List, Counted — all use List<T> with Add
+        else // List, IndexedCollection, Counted — all use List<T> with Add
         {
             sb.AppendLine($"{i}    var col_{s} = new System.Collections.Generic.List<{elemType}>(cnt_{s});");
             sb.AppendLine($"{i}    for (var ri_{s} = 0; ri_{s} < cnt_{s}; ri_{s}++)");
@@ -2042,7 +2066,7 @@ internal sealed class PropInfo
     public string? ElementWriterClassName { get; }
     /// <summary>Id type name for collection element IId types. Null if not IId.</summary>
     public string? ElementIdTypeName { get; }
-    /// <summary>Collection type: "List", "Array", or null (unknown — fallback to runtime).</summary>
+    /// <summary>Collection type: "List", "Array", "IndexedCollection", "Counted", or null (unknown — fallback to runtime).</summary>
     public string? CollectionKind { get; }
     /// <summary>Full element type name for generated code (e.g. "SharedTag").</summary>
     public string? ElementFullTypeName { get; }
diff --git a/AyCode.Core.Tests/TestModels/SharedTestModels.cs b/AyCode.Core.Tests/TestModels/SharedTestModels.cs
index 0d4f97e..11129a1 100644
--- a/AyCode.Core.Tests/TestModels/SharedTestModels.cs
+++ b/AyCode.Core.Tests/TestModels/SharedTestModels.cs
@@ -55,7 +55,7 @@ public enum TestUserRole
 /// Implements IId&lt;int&gt; for semantic $id/$ref serialization.
 /// </summary>
 [MemoryPackable]
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 [MessagePackObject]
 public partial class SharedTag : IId<int>
 {
@@ -80,7 +80,7 @@ public partial class SharedTag : IId<int>
 /// Shared category - for hierarchical cross-reference testing.
 /// </summary>
 [MemoryPackable]
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 [MessagePackObject]
 public partial class SharedCategory : IId<int>
 {
@@ -106,7 +106,7 @@ public partial class SharedCategory : IId<int>
 /// Shared user reference - appears in many places to test $ref deduplication.
 /// </summary>
 [MemoryPackable]
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 [MessagePackObject]
 public partial class SharedUser : IId<int>
 {
@@ -136,7 +136,7 @@ public partial class SharedUser : IId<int>
 /// User preferences - non-IId nested object
 /// </summary>
 [MemoryPackable]
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 [MessagePackObject]
 public partial class UserPreferences
 {
@@ -162,7 +162,7 @@ public partial class UserPreferences
 /// Does NOT implement IId, so uses standard Newtonsoft reference tracking.
 /// </summary>
 [MemoryPackable]
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 [MessagePackObject]
 public partial class MetadataInfo
 {
@@ -190,7 +190,7 @@ public partial class MetadataInfo
 /// Level 1: Main order - root of the hierarchy
 /// </summary>
 [MemoryPackable]
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 [MessagePackObject]
 public partial class TestOrder : IId<int>
 {
@@ -250,7 +250,7 @@ public partial class TestOrder : IId<int>
 /// Level 2: Order item with pallets
 /// </summary>
 [MemoryPackable]
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 [MessagePackObject]
 public partial class TestOrderItem : IId<int>
 {
@@ -290,7 +290,7 @@ public partial class TestOrderItem : IId<int>
 /// Level 3: Pallet containing measurements
 /// </summary>
 [MemoryPackable]
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 [MessagePackObject]
 public partial class TestPallet : IId<int>
 {
@@ -333,7 +333,7 @@ public partial class TestPallet : IId<int>
 /// Level 4: Measurement with multiple points
 /// </summary>
 [MemoryPackable]
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 [MessagePackObject]
 public partial class TestMeasurement : IId<int>
 {
@@ -368,7 +368,7 @@ public partial class TestMeasurement : IId<int>
 /// Level 5: Deepest level - measurement point
 /// </summary>
 [MemoryPackable]
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 [MessagePackObject]
 public partial class TestMeasurementPoint : IId<int>
 {
@@ -402,7 +402,7 @@ public partial class TestMeasurementPoint : IId<int>
 /// <summary>
 /// Order with Guid Id - for testing Guid-based IId
 /// </summary>
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 public class TestGuidOrder : IId<Guid>
 {
     public Guid Id { get; set; }
@@ -414,7 +414,7 @@ public class TestGuidOrder : IId<Guid>
 /// <summary>
 /// Item with Guid Id
 /// </summary>
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 public class TestGuidItem : IId<Guid>
 {
     public Guid Id { get; set; }
@@ -430,7 +430,7 @@ public class TestGuidItem : IId<Guid>
 /// Simulates NopCommerce GenericAttribute - stores key-value pairs where DateTime values
 /// are stored as strings in the database.
 /// </summary>
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 public class TestGenericAttribute
 {
     public int Id { get; set; }
@@ -442,7 +442,7 @@ public class TestGenericAttribute
 /// DTO with GenericAttributes collection - simulates OrderDto with string-stored DateTime values.
 /// This reproduces the production bug where Binary serialization was thought to corrupt DateTime strings.
 /// </summary>
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 public class TestDtoWithGenericAttributes : IId<int>
 {
     public int Id { get; set; }
@@ -453,7 +453,7 @@ public class TestDtoWithGenericAttributes : IId<int>
 /// <summary>
 /// Order with nullable collections for null vs empty testing
 /// </summary>
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 public class TestOrderWithNullableCollections
 {
     public int Id { get; set; }
@@ -466,7 +466,7 @@ public class TestOrderWithNullableCollections
 /// Class with all primitive types for WASM/serialization testing
 /// </summary>
 [MemoryPackable]
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 public partial class PrimitiveTestClass
 {
     public int IntValue { get; set; }
@@ -489,7 +489,7 @@ public partial class PrimitiveTestClass
 /// Class with extended primitive types for full serializer coverage.
 /// Includes DateTimeOffset, TimeSpan, Dictionary, null properties.
 /// </summary>
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 public class ExtendedPrimitiveTestClass
 {
     public int Id { get; set; }
@@ -519,7 +519,7 @@ public class ExtendedPrimitiveTestClass
 /// <summary>
 /// Class with array of objects containing null items for WriteNull coverage
 /// </summary>
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 public class ObjectWithNullItems
 {
     public int Id { get; set; }
@@ -534,7 +534,7 @@ public class ObjectWithNullItems
 /// "Server-side" DTO with extra properties that the "client" doesn't know about.
 /// Used to test SkipValue functionality when deserializing unknown properties.
 /// </summary>
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 public class ServerCustomerDto : IId<int>
 {
     public int Id { get; set; }
@@ -567,7 +567,7 @@ public class ServerCustomerDto : IId<int>
 /// the deserializer must skip unknown properties correctly 
 /// while still maintaining string intern table consistency.
 /// </summary>
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 public class ClientCustomerDto : IId<int>
 {
     public int Id { get; set; }
@@ -581,7 +581,7 @@ public class ClientCustomerDto : IId<int>
 /// Server DTO with nested objects that client doesn't know about.
 /// Tests skipping complex nested structures.
 /// </summary>
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 public class ServerOrderWithExtras : IId<int>
 {
     public int Id { get; set; }
@@ -602,7 +602,7 @@ public class ServerOrderWithExtras : IId<int>
 /// <summary>
 /// Client version of the order - doesn't have Customer/RelatedCustomers properties.
 /// </summary>
-[AcBinarySerializable(false)]
+[AcBinarySerializable(true)]
 public class ClientOrderSimple : IId<int>
 {
     public int Id { get; set; }