Fix array-backed generated slices

BitsKit.Generator/Models/BitFieldModel.cs

@@ -417,6 +417,8 @@ private bool TryGetByteStorageSource(bool writable, out string source)
         source = BackingFieldType switch
         {
             BackingFieldType.Memory => "{4}.Span",
+            BackingFieldType.Span when BackingField.TypeString == "byte[]" =>
+                writable ? "((Span<Byte>){4})" : "((ReadOnlySpan<Byte>){4})",
             BackingFieldType.Span => "{4}",
             BackingFieldType.InlineArray when BackingField.TypeString == "byte" =>
                 writable ? "((Span<Byte>)this)" : "((ReadOnlySpan<Byte>)this)",

BitsKit.Tests/GeneratorTests.Models.cs

@@ -328,6 +328,22 @@ public partial struct SpecializedMemoryAccessorStruct
     public Memory<byte> BigEndianBacking48;
 }
 
+[BitObject(BitOrder.LeastSignificant)]
+public partial struct OffsetArrayAccessorStruct
+{
+    [BitField(8)]
+    [BitField("AlignedValue", 32, BitFieldType.UInt32)]
+    public byte[] AlignedBacking;
+
+    [BitField(13)]
+    [BitField("Value11", 11, BitFieldType.UInt32)]
+    public byte[] Backing11;
+
+    [BitField(15)]
+    [BitField("BigEndianValue48", 48, BitFieldType.UInt64, ReverseBitOrder = true)]
+    public byte[] BigEndianBacking48;
+}
+
 [BitObject(BitOrder.LeastSignificant, AccessMode = BitObjectAccessMode.Unsafe)]
 public partial struct UnsafeMemoryAccessorStruct
 {

BitsKit.Tests/GeneratorTests.cs

@@ -575,6 +575,51 @@ public void SpecializedStorageAccessorsMatchReferenceBits()
         }
     }
 
+    [TestMethod]
+    public void OffsetArrayAccessorsMatchReferenceBits()
+    {
+        Random random = new(0xA22A7);
+
+        for (int i = 0; i < 1000; i++)
+        {
+            byte[] alignedBytes = new byte[5];
+            byte[] bytes11 = new byte[(i & 1) == 0 ? 3 : 5];
+            byte[] bigEndianBytes48 = new byte[(i & 1) == 0 ? 8 : 9];
+            random.NextBytes(alignedBytes);
+            random.NextBytes(bytes11);
+            random.NextBytes(bigEndianBytes48);
+
+            var actual = new OffsetArrayAccessorStruct
+            {
+                AlignedBacking = alignedBytes,
+                Backing11 = bytes11,
+                BigEndianBacking48 = bigEndianBytes48
+            };
+
+            Assert.AreEqual(BitPrimitives.ReadUInt32LSB(alignedBytes, 8, 32), actual.AlignedValue);
+            Assert.AreEqual((uint)Helpers.ReadBitsLSB(bytes11, 13, 11), actual.Value11);
+            Assert.AreEqual(Helpers.ReadBitsMSB(bigEndianBytes48, 15, 48), actual.BigEndianValue48);
+
+            uint nextAligned = unchecked((uint)random.NextInt64());
+            uint next11 = (uint)random.Next(1 << 11);
+            ulong next48 = unchecked((ulong)random.NextInt64()) & 0xFFFFFFFFFFFFUL;
+            byte[] expectedAligned = (byte[])alignedBytes.Clone();
+            byte[] expected11 = (byte[])bytes11.Clone();
+            byte[] expected48 = (byte[])bigEndianBytes48.Clone();
+            BitPrimitives.WriteUInt32LSB(expectedAligned, 8, nextAligned, 32);
+            Helpers.WriteBitsLSB(expected11, 13, next11, 11);
+            Helpers.WriteBitsMSB(expected48, 15, next48, 48);
+
+            actual.AlignedValue = nextAligned;
+            actual.Value11 = next11;
+            actual.BigEndianValue48 = next48;
+
+            CollectionAssert.AreEqual(expectedAligned, alignedBytes);
+            CollectionAssert.AreEqual(expected11, bytes11);
+            CollectionAssert.AreEqual(expected48, bigEndianBytes48);
+        }
+    }
+
     [TestMethod]
     public void ReadOnlyMemberTest()
     {

CHANGELOG.md

@@ -11,6 +11,10 @@ Notable changes to the community-maintained fork are documented here. This proje
 - `BitBatchPrimitives` provides allocation-free contiguous and record-strided reads and writes for every supported integral type, Boolean values, and both bit orders.
 - `BitObjectAttribute.GenerateBatchAccessors` generates strongly typed packed and strided helpers for integral, Boolean, and enum fields.
 
+### Fixed
+
+- Array-backed generated accessors compile when an optimized field begins at a nonzero byte offset.
+
 ## 1.5.0 - 2026-07-21
 
 ### Added