diff --git a/Lagrange.Core/Message/Entities/MultiMsgEntity.cs b/Lagrange.Core/Message/Entities/MultiMsgEntity.cs
index 44be011c..d7aca564 100644
--- a/Lagrange.Core/Message/Entities/MultiMsgEntity.cs
+++ b/Lagrange.Core/Message/Entities/MultiMsgEntity.cs
@@ -26,9 +26,34 @@ public async Task Preprocess(BotContext context, BotMessage message)
     {
         if (string.IsNullOrEmpty(ResId))
         {
+            // Recursively preprocess internal messages
+            Console.WriteLine($"[MultiMsgEntity] Preprocessing {Messages.Count} messages for forward chain...");
+            
+            foreach (var innerMsg in Messages)
+            {
+                foreach (var entity in innerMsg.Entities)
+                {
+                    try 
+                    {
+                        await entity.Preprocess(context, message);
+
+                        if (entity is ImageEntity img)
+                        {
+                            if (img.MsgInfo != null)
+                                Console.WriteLine($"[MultiMsgEntity] Image uploaded successfully. Size: {img.ImageSize}");
+                            else
+                                Console.WriteLine("[MultiMsgEntity] WARNING: Image MsgInfo is NULL after preprocess!");
+                        }
+                    }
+                    catch (Exception ex)
+                    {
+                        Console.WriteLine($"[MultiMsgEntity] Error preprocessing entity: {ex.Message}");
+                    }
+                }
+            }
+
             var result = await context.EventContext.SendEvent<LongMsgSendEventResp>(new LongMsgSendEventReq(message.Receiver, Messages));
             ResId = result.ResId;
-
         }
     }
     
diff --git a/Lagrange.Proto.Test/CrashTest.cs b/Lagrange.Proto.Test/CrashTest.cs
new file mode 100644
index 00000000..6b4c37f8
--- /dev/null
+++ b/Lagrange.Proto.Test/CrashTest.cs
@@ -0,0 +1,45 @@
+using NUnit.Framework;
+using Lagrange.Proto.Utility;
+
+namespace Lagrange.Proto.Test
+{
+    [TestFixture]
+    public class CrashTest
+    {
+        [Test]
+        public void TestNegativeInt32VarIntLength()
+        {
+            // This test is used to reproduce the IndexOutOfRangeException Bug
+            int value = -1;
+            
+            int length = ProtoHelper.GetVarIntLength(value);
+            
+            // Verify: For a 32-bit all-ones number (0xFFFF), VarInt encoding should be 5 bytes
+            Assert.That(length, Is.EqualTo(5));
+        }
+
+        [Test]
+        public void TestNegativeInt64VarIntLength()
+        {
+            long value = -1;
+            
+            // For 64-bit numbers with all 1s, VarInt encoding should be 10 bytes
+            int length = ProtoHelper.GetVarIntLength(value);
+            
+            Assert.That(length, Is.EqualTo(10));
+        }
+        
+        [Test]
+        public void TestOtherNegativeValues()
+        {
+             // Test other negative values to ensure stability
+             int val1 = -100;
+             int len1 = ProtoHelper.GetVarIntLength(val1);
+             Assert.That(len1, Is.GreaterThan(0));
+
+             long val2 = long.MinValue; // 0x8000000000000000
+             int len2 = ProtoHelper.GetVarIntLength(val2);
+             Assert.That(len2, Is.EqualTo(10));
+        }
+    }
+}
\ No newline at end of file
diff --git a/Lagrange.Proto/Primitives/ProtoWriter.cs b/Lagrange.Proto/Primitives/ProtoWriter.cs
index 55b5da29..a59946b2 100644
--- a/Lagrange.Proto/Primitives/ProtoWriter.cs
+++ b/Lagrange.Proto/Primitives/ProtoWriter.cs
@@ -96,7 +96,8 @@ public void EncodeVarInt<T>(T value) where T : unmanaged, INumber<T>
     {
         if (_memory.Length - BytesPending >= 10)
         {
-            if (value < T.CreateTruncating(0x80))
+            // For-1 (int), converting to ulong is 0xFF... FF, much greater than 0x80, will not mistakenly enter this branch.
+            if (ulong.CreateTruncating(value) < 0x80)
             {
                 Unsafe.Add(ref MemoryMarshal.GetReference(_memory.Span), BytesPending++) = byte.CreateTruncating(value);
                 return;
diff --git a/Lagrange.Proto/Utility/ProtoHelper.cs b/Lagrange.Proto/Utility/ProtoHelper.cs
index 01517c05..399db314 100644
--- a/Lagrange.Proto/Utility/ProtoHelper.cs
+++ b/Lagrange.Proto/Utility/ProtoHelper.cs
@@ -36,12 +36,12 @@ public static unsafe int GetVarIntLength<T>(T value) where T : unmanaged, INumbe
         
         if (sizeof(T) <= 4)
         {
-            int leadingZeros = BitOperations.LeadingZeroCount(uint.CreateSaturating(value));
+            int leadingZeros = BitOperations.LeadingZeroCount(uint.CreateTruncating(value));
             return VarIntLengths32[leadingZeros];
         }
         else
         {
-            int leadingZeros = BitOperations.LeadingZeroCount(ulong.CreateSaturating(value));
+            int leadingZeros = BitOperations.LeadingZeroCount(ulong.CreateTruncating(value));
             return VarIntLengths64[leadingZeros];
         }
     }
@@ -98,4 +98,4 @@ public static int CountBytes(ReadOnlySpan<byte> str)
     {
         return GetVarIntLength(str.Length) + str.Length;
     }
-}
\ No newline at end of file
+}