diff --git a/src/AcDream.Core.Net/Messages/VectorUpdate.cs b/src/AcDream.Core.Net/Messages/VectorUpdate.cs
index f9dfcff..d695022 100644
--- a/src/AcDream.Core.Net/Messages/VectorUpdate.cs
+++ b/src/AcDream.Core.Net/Messages/VectorUpdate.cs
@@ -39,27 +39,38 @@ public static class VectorUpdate
         ushort VectorSequence);
 
     /// <summary>
-    /// Parse a 0xF74E body. Returns null if the buffer is truncated or
-    /// malformed (sequence-number mismatch is not checked here — the
-    /// session-level handler decides what to do).
+    /// Parse a 0xF74E body. <paramref name="body"/> must start with the
+    /// 4-byte opcode (matches the convention used by UpdateMotion /
+    /// UpdatePosition / etc.). Returns null on truncation or opcode
+    /// mismatch.
     /// </summary>
     public static Parsed? TryParse(ReadOnlySpan<byte> body)
     {
-        if (body.Length < 32) return null;
+        // K-fix16 (2026-04-26): body convention includes the opcode at
+        // offset 0 — every other parser in this folder verifies the
+        // opcode word before reading payload fields. The previous
+        // version of this method skipped that, reading guid from the
+        // opcode bytes (and shifting every subsequent field by 4),
+        // which is why VU.recv lines showed guid=0xF74E and gigantic
+        // garbage velocity values.
+        if (body.Length < 4 + 32) return null;
         try
         {
-            uint guid = BinaryPrimitives.ReadUInt32LittleEndian(body[..4]);
+            uint opcode = BinaryPrimitives.ReadUInt32LittleEndian(body.Slice(0, 4));
+            if (opcode != Opcode) return null;
 
-            float vx = BitConverter.Int32BitsToSingle(BinaryPrimitives.ReadInt32LittleEndian(body.Slice(4, 4)));
-            float vy = BitConverter.Int32BitsToSingle(BinaryPrimitives.ReadInt32LittleEndian(body.Slice(8, 4)));
-            float vz = BitConverter.Int32BitsToSingle(BinaryPrimitives.ReadInt32LittleEndian(body.Slice(12, 4)));
+            uint guid = BinaryPrimitives.ReadUInt32LittleEndian(body.Slice(4, 4));
 
-            float ox = BitConverter.Int32BitsToSingle(BinaryPrimitives.ReadInt32LittleEndian(body.Slice(16, 4)));
-            float oy = BitConverter.Int32BitsToSingle(BinaryPrimitives.ReadInt32LittleEndian(body.Slice(20, 4)));
-            float oz = BitConverter.Int32BitsToSingle(BinaryPrimitives.ReadInt32LittleEndian(body.Slice(24, 4)));
+            float vx = BitConverter.Int32BitsToSingle(BinaryPrimitives.ReadInt32LittleEndian(body.Slice(8, 4)));
+            float vy = BitConverter.Int32BitsToSingle(BinaryPrimitives.ReadInt32LittleEndian(body.Slice(12, 4)));
+            float vz = BitConverter.Int32BitsToSingle(BinaryPrimitives.ReadInt32LittleEndian(body.Slice(16, 4)));
 
-            ushort instSeq = BinaryPrimitives.ReadUInt16LittleEndian(body.Slice(28, 2));
-            ushort vecSeq = BinaryPrimitives.ReadUInt16LittleEndian(body.Slice(30, 2));
+            float ox = BitConverter.Int32BitsToSingle(BinaryPrimitives.ReadInt32LittleEndian(body.Slice(20, 4)));
+            float oy = BitConverter.Int32BitsToSingle(BinaryPrimitives.ReadInt32LittleEndian(body.Slice(24, 4)));
+            float oz = BitConverter.Int32BitsToSingle(BinaryPrimitives.ReadInt32LittleEndian(body.Slice(28, 4)));
+
+            ushort instSeq = BinaryPrimitives.ReadUInt16LittleEndian(body.Slice(32, 2));
+            ushort vecSeq = BinaryPrimitives.ReadUInt16LittleEndian(body.Slice(34, 2));
 
             return new Parsed(guid, new Vector3(vx, vy, vz), new Vector3(ox, oy, oz), instSeq, vecSeq);
         }