diff --git a/AyCode.Core.Serializers.Console/Program.cs b/AyCode.Core.Serializers.Console/Program.cs
index 04309a4..77ef1df 100644
--- a/AyCode.Core.Serializers.Console/Program.cs
+++ b/AyCode.Core.Serializers.Console/Program.cs
@@ -212,15 +212,15 @@ public static class Program
         {
             
             // AcBinary variants
-            //new AcBinaryBenchmark(testData.Order, AcBinarySerializerOptions.Default, SerializerAcBinaryDefault),
-            //new AcBinaryBenchmark(testData.Order, AcBinarySerializerOptions.WithoutReferenceHandling, SerializerAcBinaryNoRef),
-            //new AcBinaryBenchmark(testData.Order, AcBinarySerializerOptions.FastMode, SerializerAcBinaryFastMode),
-            //new AcBinaryBenchmark(testData.Order, new AcBinarySerializerOptions { UseStringInterning = StringInterningMode.None }, SerializerAcBinaryNoIntern),
-
-            new AcBinaryBenchmark(testData.Order, AcBinarySerializerOptions.FastMode, SerializerAcBinaryDefault),
-            new AcBinaryBenchmark(testData.Order, AcBinarySerializerOptions.FastMode, SerializerAcBinaryNoRef),
+            new AcBinaryBenchmark(testData.Order, AcBinarySerializerOptions.Default, SerializerAcBinaryDefault),
+            new AcBinaryBenchmark(testData.Order, AcBinarySerializerOptions.WithoutReferenceHandling, SerializerAcBinaryNoRef),
             new AcBinaryBenchmark(testData.Order, AcBinarySerializerOptions.FastMode, SerializerAcBinaryFastMode),
-            new AcBinaryBenchmark(testData.Order, AcBinarySerializerOptions.FastMode, SerializerAcBinaryNoIntern),
+            new AcBinaryBenchmark(testData.Order, new AcBinarySerializerOptions { UseStringInterning = StringInterningMode.None }, SerializerAcBinaryNoIntern),
+
+            //new AcBinaryBenchmark(testData.Order, AcBinarySerializerOptions.FastMode, SerializerAcBinaryDefault),
+            //new AcBinaryBenchmark(testData.Order, AcBinarySerializerOptions.FastMode, SerializerAcBinaryNoRef),
+            //new AcBinaryBenchmark(testData.Order, AcBinarySerializerOptions.FastMode, SerializerAcBinaryFastMode),
+            //new AcBinaryBenchmark(testData.Order, AcBinarySerializerOptions.FastMode, SerializerAcBinaryNoIntern),
 
             // AcJson
             new AcJsonBenchmark(testData.Order, AcJsonSerializerOptions.Default, SerializerAcJsonDefault),
diff --git a/AyCode.Core/Serializers/Binaries/AcBinaryDeserializer.BinaryDeserializationContext.Read.cs b/AyCode.Core/Serializers/Binaries/AcBinaryDeserializer.BinaryDeserializationContext.Read.cs
index b1c7e00..69313b9 100644
--- a/AyCode.Core/Serializers/Binaries/AcBinaryDeserializer.BinaryDeserializationContext.Read.cs
+++ b/AyCode.Core/Serializers/Binaries/AcBinaryDeserializer.BinaryDeserializationContext.Read.cs
@@ -276,6 +276,16 @@ public static partial class AcBinaryDeserializer
 
         #endregion
 
+        /// <summary>
+        /// Called on first StringInternFirst marker — disables _stringCache because
+        /// interned strings are resolved via _internCache and plain strings appear only once.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal void DisableStringCaching()
+        {
+            _useStringCaching = false;
+        }
+
         #region Bytes & String Reading
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
diff --git a/AyCode.Core/Serializers/Binaries/AcBinaryDeserializer.cs b/AyCode.Core/Serializers/Binaries/AcBinaryDeserializer.cs
index 8e8645b..75f68d8 100644
--- a/AyCode.Core/Serializers/Binaries/AcBinaryDeserializer.cs
+++ b/AyCode.Core/Serializers/Binaries/AcBinaryDeserializer.cs
@@ -912,6 +912,9 @@ public static partial class AcBinaryDeserializer
     private static string ReadAndRegisterInternedString<TInput>(BinaryDeserializationContext<TInput> context)
     where TInput : struct, IBinaryInputBase
     {
+        // First StringInternFirst marker proves payload uses string interning →
+        // plain String entries appear only once, so _stringCache would never hit
+        context.DisableStringCaching();
         var cacheIndex = (int)context.ReadVarUInt();
         var length = (int)context.ReadVarUInt();
         if (length == 0) return string.Empty;
diff --git a/AyCode.Core/Serializers/Binaries/AcBinarySerializer.ScanPass.cs b/AyCode.Core/Serializers/Binaries/AcBinarySerializer.ScanPass.cs
index b12b69c..394d10c 100644
--- a/AyCode.Core/Serializers/Binaries/AcBinarySerializer.ScanPass.cs
+++ b/AyCode.Core/Serializers/Binaries/AcBinarySerializer.ScanPass.cs
@@ -40,16 +40,22 @@ public static partial class AcBinarySerializer
         // Collection → iterate elements using IList fast path (no IEnumerator alloc)
         if (metadata.IsCollection)
         {
-            if (metadata.ElementNeedsScan)
+            var isStringCollectionElementType = false;
+
+            if (metadata.ElementNeedsScan && 
+                !((isStringCollectionElementType = ReferenceEquals(metadata.CollectionElementType, StringType)) && !context.UseStringInterning))
             {
                 var nextDepth = depth + 1;
+                // Pre-cache element wrapper for non-string collections (string fast path in ScanItem doesn't need it)
+                var elementWrapper = isStringCollectionElementType ? null : context.GetWrapper(metadata.CollectionElementType!);
+
                 if (value is IList list)
                 {
                     for (var i = 0; i < list.Count; i++)
                     {
                         var item = list[i];
                         if (item != null)
-                            ScanItem(item, context, nextDepth);
+                            ScanItem(item, elementWrapper, context, nextDepth);
                     }
                 }
                 else if (value is IEnumerable enumerable)
@@ -57,7 +63,7 @@ public static partial class AcBinarySerializer
                     foreach (var item in enumerable)
                     {
                         if (item != null)
-                            ScanItem(item, context, nextDepth);
+                            ScanItem(item, elementWrapper, context, nextDepth);
                     }
                 }
             }
@@ -102,10 +108,16 @@ public static partial class AcBinarySerializer
         // Recursive scan on reference properties only
         // Use typed getter for strings (much faster than reflection GetValue)
         var refProperties = metadata.ReferenceProperties;
+        var hasPropertyFilter = context.HasPropertyFilter;
         var nextDepth2 = depth + 1;
         for (var i = 0; i < refProperties.Length; i++)
         {
             var prop = refProperties[i];
+            // Must match write pass: filtered properties write PropertySkip (no value) →
+            // scanning them would assign CacheIndex for strings/objects never in output
+            if (hasPropertyFilter && !context.ShouldSerializeProperty(value, prop))
+                continue;
+
             if (prop.AccessorType == PropertyAccessorType.String)
             {
                 // Fast path: typed getter for string
@@ -127,10 +139,11 @@ public static partial class AcBinarySerializer
     }
 
     /// <summary>
-    /// Scans a collection item. Handles string fast path and gets wrapper for the runtime type.
+    /// Scans a collection item. Uses pre-cached element wrapper when runtime type matches,
+    /// falls back to GetWrapper for polymorphic items.
     /// </summary>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    private static void ScanItem<TOutput>(object item, BinarySerializationContext<TOutput> context, int depth)
+    private static void ScanItem<TOutput>(object item, TypeMetadataWrapper<BinarySerializeTypeMetadata>? elementWrapper, BinarySerializationContext<TOutput> context, int depth)
         where TOutput : struct, IBinaryOutputBase
     {
         // String fast path — avoid GetWrapper entirely
@@ -141,7 +154,7 @@ public static partial class AcBinarySerializer
             return;
         }
 
-        var itemWrapper = context.GetWrapper(item.GetType());
+        var itemWrapper = item.GetType() == elementWrapper!.Metadata.SourceType ? elementWrapper : context.GetWrapper(item.GetType());
         ScanValue(item, itemWrapper, context, depth);
     }
 }