diff --git a/HEIF_IMPLEMENTATION_PLAN.md b/HEIF_IMPLEMENTATION_PLAN.md
index 7ceea809e0..ff0659553e 100644
--- a/HEIF_IMPLEMENTATION_PLAN.md
+++ b/HEIF_IMPLEMENTATION_PLAN.md
@@ -826,7 +826,7 @@ Encoder verification contract:
 - [~] Finalized transform coefficients and packed EOB/type state now use raster-ordered, per-superblock plane segments matching current libaom's coefficient-pool geometry. One ImageSharp allocator owner replaces libaom's separate coefficient, EOB, and entropy-context allocations while preserving the full 1024 luma and 256-per-chroma 4x4 state capacity of a 128x128 4:2:0 superblock; the forward transform and mode-decision stages still need to populate this owner.
 - [~] Tile partition writing now follows current libaom's recursive `write_modes_sb` preorder traversal and `update_ext_partition_context` edge updates directly. The obsolete SVT-derived global geometry catalog and its unimplemented lookup are removed; transform geometry is derived in libaom's bounded 64x64 residual order, fixed intra transform-size symbols use the reference depth and neighbor contexts, frame-edge and segmentation syntax use mode-information units, and 128x128 CDEF units use libaom's 0-to-3 indexing and first-block strength ownership. Partition and mode analysis still need to populate these retained decisions; variable inter-transform syntax remains part of later inter-frame support.
 - [ ] Implement legal deblocking, CDEF, restoration, super-resolution, and film-grain signaling decisions.
-- [~] The coefficient symbol encoder now reuses tile-lifetime level and context workspaces instead of allocating per transform. Every remaining encoder fragment must be audited before it becomes active.
+- [~] The coefficient symbol encoder now reuses tile-lifetime level and context workspaces instead of allocating per transform. The reference-type symbol encoder is passed normally through tile traversal, and the operation boundary owns the allocator-backed item payload stream for exactly one synchronous encode. Every remaining encoder fragment must be audited before it becomes active.
 - [~] The planar conversion, forward transform, and forward quantizer use descending SIMD dispatch: Vector512, Vector256, Vector128, then scalar. Apply the same rule to every later hot-path family.
 - [~] Forward-quantizer FeatureTestRunner and zero-allocation tests compare every hardware tier with an independent scan-order scalar oracle shaped from current-main libaom. Both passed direct net11 VSTest in Release.
 - [~] The combined-frame writer now completes the byte-counted uncompressed frame header before starting the optional multi-tile tile-group flag, matching current libaom's separate frame-header and tile-group writers. A non-uniform two-tile round trip verifies the explicit boundaries, both tile payloads, and complete stream consumption through direct net11 VSTest in Release.
diff --git a/src/ImageSharp/Formats/Heif/Av1/Tiling/Av1TileWriter.cs b/src/ImageSharp/Formats/Heif/Av1/Tiling/Av1TileWriter.cs
index a1024cbfa6..1921f90b9d 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Tiling/Av1TileWriter.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Tiling/Av1TileWriter.cs
@@ -63,7 +63,7 @@ internal partial class Av1TileWriter
     public static void WriteSuperblock(
         Av1PictureControlSet pcs,
         Av1EntropyCodingContext ec_ctx,
-        ref Av1SymbolEncoder writer,
+        Av1SymbolEncoder writer,
         Av1Superblock superblock,
         Av1EncoderCoefficientBuffer coefficientBuffer,
         ushort tileIndex)
@@ -79,7 +79,7 @@ internal partial class Av1TileWriter
         WritePartitionTree(
             pcs,
             ec_ctx,
-            ref writer,
+            writer,
             superblock,
             coefficientBuffer,
             tileIndex,
@@ -95,7 +95,7 @@ internal partial class Av1TileWriter
     private static void WritePartitionTree(
         Av1PictureControlSet pcs,
         Av1EntropyCodingContext entropyCodingContext,
-        ref Av1SymbolEncoder writer,
+        Av1SymbolEncoder writer,
         Av1Superblock superblock,
         Av1EncoderCoefficientBuffer coefficientBuffer,
         ushort tileIndex,
@@ -119,7 +119,7 @@ internal partial class Av1TileWriter
 
         EncodePartition(
             pcs,
-            ref writer,
+            writer,
             blockSize,
             partition,
             blockOrigin,
@@ -131,7 +131,7 @@ internal partial class Av1TileWriter
                 WriteFinalBlock(
                     pcs,
                     entropyCodingContext,
-                    ref writer,
+                    writer,
                     superblock,
                     coefficientBuffer,
                     tileIndex,
@@ -143,7 +143,7 @@ internal partial class Av1TileWriter
                 WriteFinalBlock(
                     pcs,
                     entropyCodingContext,
-                    ref writer,
+                    writer,
                     superblock,
                     coefficientBuffer,
                     tileIndex,
@@ -155,7 +155,7 @@ internal partial class Av1TileWriter
                     WriteFinalBlock(
                         pcs,
                         entropyCodingContext,
-                        ref writer,
+                        writer,
                         superblock,
                         coefficientBuffer,
                         tileIndex,
@@ -168,7 +168,7 @@ internal partial class Av1TileWriter
                 WriteFinalBlock(
                     pcs,
                     entropyCodingContext,
-                    ref writer,
+                    writer,
                     superblock,
                     coefficientBuffer,
                     tileIndex,
@@ -180,7 +180,7 @@ internal partial class Av1TileWriter
                     WriteFinalBlock(
                         pcs,
                         entropyCodingContext,
-                        ref writer,
+                        writer,
                         superblock,
                         coefficientBuffer,
                         tileIndex,
@@ -193,7 +193,7 @@ internal partial class Av1TileWriter
                 WritePartitionTree(
                     pcs,
                     entropyCodingContext,
-                    ref writer,
+                    writer,
                     superblock,
                     coefficientBuffer,
                     tileIndex,
@@ -204,7 +204,7 @@ internal partial class Av1TileWriter
                 WritePartitionTree(
                     pcs,
                     entropyCodingContext,
-                    ref writer,
+                    writer,
                     superblock,
                     coefficientBuffer,
                     tileIndex,
@@ -215,7 +215,7 @@ internal partial class Av1TileWriter
                 WritePartitionTree(
                     pcs,
                     entropyCodingContext,
-                    ref writer,
+                    writer,
                     superblock,
                     coefficientBuffer,
                     tileIndex,
@@ -226,7 +226,7 @@ internal partial class Av1TileWriter
                 WritePartitionTree(
                     pcs,
                     entropyCodingContext,
-                    ref writer,
+                    writer,
                     superblock,
                     coefficientBuffer,
                     tileIndex,
@@ -240,7 +240,7 @@ internal partial class Av1TileWriter
                 WriteFinalBlock(
                     pcs,
                     entropyCodingContext,
-                    ref writer,
+                    writer,
                     superblock,
                     coefficientBuffer,
                     tileIndex,
@@ -249,7 +249,7 @@ internal partial class Av1TileWriter
                 WriteFinalBlock(
                     pcs,
                     entropyCodingContext,
-                    ref writer,
+                    writer,
                     superblock,
                     coefficientBuffer,
                     tileIndex,
@@ -258,7 +258,7 @@ internal partial class Av1TileWriter
                 WriteFinalBlock(
                     pcs,
                     entropyCodingContext,
-                    ref writer,
+                    writer,
                     superblock,
                     coefficientBuffer,
                     tileIndex,
@@ -270,7 +270,7 @@ internal partial class Av1TileWriter
                 WriteFinalBlock(
                     pcs,
                     entropyCodingContext,
-                    ref writer,
+                    writer,
                     superblock,
                     coefficientBuffer,
                     tileIndex,
@@ -279,7 +279,7 @@ internal partial class Av1TileWriter
                 WriteFinalBlock(
                     pcs,
                     entropyCodingContext,
-                    ref writer,
+                    writer,
                     superblock,
                     coefficientBuffer,
                     tileIndex,
@@ -288,7 +288,7 @@ internal partial class Av1TileWriter
                 WriteFinalBlock(
                     pcs,
                     entropyCodingContext,
-                    ref writer,
+                    writer,
                     superblock,
                     coefficientBuffer,
                     tileIndex,
@@ -300,7 +300,7 @@ internal partial class Av1TileWriter
                 WriteFinalBlock(
                     pcs,
                     entropyCodingContext,
-                    ref writer,
+                    writer,
                     superblock,
                     coefficientBuffer,
                     tileIndex,
@@ -309,7 +309,7 @@ internal partial class Av1TileWriter
                 WriteFinalBlock(
                     pcs,
                     entropyCodingContext,
-                    ref writer,
+                    writer,
                     superblock,
                     coefficientBuffer,
                     tileIndex,
@@ -318,7 +318,7 @@ internal partial class Av1TileWriter
                 WriteFinalBlock(
                     pcs,
                     entropyCodingContext,
-                    ref writer,
+                    writer,
                     superblock,
                     coefficientBuffer,
                     tileIndex,
@@ -330,7 +330,7 @@ internal partial class Av1TileWriter
                 WriteFinalBlock(
                     pcs,
                     entropyCodingContext,
-                    ref writer,
+                    writer,
                     superblock,
                     coefficientBuffer,
                     tileIndex,
@@ -339,7 +339,7 @@ internal partial class Av1TileWriter
                 WriteFinalBlock(
                     pcs,
                     entropyCodingContext,
-                    ref writer,
+                    writer,
                     superblock,
                     coefficientBuffer,
                     tileIndex,
@@ -348,7 +348,7 @@ internal partial class Av1TileWriter
                 WriteFinalBlock(
                     pcs,
                     entropyCodingContext,
-                    ref writer,
+                    writer,
                     superblock,
                     coefficientBuffer,
                     tileIndex,
@@ -369,7 +369,7 @@ internal partial class Av1TileWriter
                     WriteFinalBlock(
                         pcs,
                         entropyCodingContext,
-                        ref writer,
+                        writer,
                         superblock,
                         coefficientBuffer,
                         tileIndex,
@@ -391,7 +391,7 @@ internal partial class Av1TileWriter
                     WriteFinalBlock(
                         pcs,
                         entropyCodingContext,
-                        ref writer,
+                        writer,
                         superblock,
                         coefficientBuffer,
                         tileIndex,
@@ -416,7 +416,7 @@ internal partial class Av1TileWriter
     private static void WriteFinalBlock(
         Av1PictureControlSet pcs,
         Av1EntropyCodingContext entropyCodingContext,
-        ref Av1SymbolEncoder writer,
+        Av1SymbolEncoder writer,
         Av1Superblock superblock,
         Av1EncoderCoefficientBuffer coefficientBuffer,
         ushort tileIndex,
@@ -427,7 +427,7 @@ internal partial class Av1TileWriter
         WriteModesBlock(
             pcs,
             entropyCodingContext,
-            ref writer,
+            writer,
             superblock,
             ref block,
             tileIndex,
@@ -540,7 +540,7 @@ internal partial class Av1TileWriter
     /// <param name="partition_context_na">The partition neighbor arrays for the tile.</param>
     private static void EncodePartition(
         Av1PictureControlSet pcs,
-        ref Av1SymbolEncoder writer,
+        Av1SymbolEncoder writer,
         Av1BlockSize blockSize,
         Av1PartitionType partitionType,
         Point blockOrigin,
@@ -617,7 +617,7 @@ internal partial class Av1TileWriter
     private static void WriteModesBlock(
         Av1PictureControlSet pcs,
         Av1EntropyCodingContext entropyCodingContext,
-        ref Av1SymbolEncoder writer,
+        Av1SymbolEncoder writer,
         Av1Superblock tb_ptr,
         ref Av1EncoderBlockStruct blk_ptr,
         ushort tile_idx,
@@ -655,14 +655,14 @@ internal partial class Av1TileWriter
         {
             if (pcs.Parent.FrameHeader.SegmentationParameters.Enabled && pcs.Parent.FrameHeader.SegmentationParameters.SegmentIdPrecedesSkip)
             {
-                WriteSegmentId(pcs, ref writer, blockSize, blockOrigin, macroBlock, ref blk_ptr, skipWritingCoefficients);
+                WriteSegmentId(pcs, writer, blockSize, blockOrigin, macroBlock, ref blk_ptr, skipWritingCoefficients);
             }
 
-            EncodeSkipCoefficients(ref writer, macroBlock, skipWritingCoefficients);
+            EncodeSkipCoefficients(writer, macroBlock, skipWritingCoefficients);
 
             if (pcs.Parent.FrameHeader.SegmentationParameters.Enabled && !pcs.Parent.FrameHeader.SegmentationParameters.SegmentIdPrecedesSkip)
             {
-                WriteSegmentId(pcs, ref writer, blockSize, blockOrigin, macroBlock, ref blk_ptr, skipWritingCoefficients);
+                WriteSegmentId(pcs, writer, blockSize, blockOrigin, macroBlock, ref blk_ptr, skipWritingCoefficients);
             }
 
             WriteCdef(
@@ -693,12 +693,12 @@ internal partial class Av1TileWriter
             Av1ChromaPredictionMode intra_chroma_mode = macroBlockModeInfo.Block.UvMode;
             if (IsIntraBlockCopyAllowed(pcs.Parent.FrameHeader/*, pcs.Parent.SliceType*/))
             {
-                WriteIntraBlockCopyInfo(ref writer, macroBlockModeInfo);
+                WriteIntraBlockCopyInfo(writer, macroBlockModeInfo);
             }
 
             if (!macroBlockModeInfo.Block.UseIntraBlockCopy)
             {
-                EncodeIntraLumaMode(ref writer, macroBlockModeInfo, macroBlock, ref blk_ptr, blockSize, intra_luma_mode);
+                EncodeIntraLumaMode(writer, macroBlockModeInfo, macroBlock, ref blk_ptr, blockSize, intra_luma_mode);
             }
 
             if (!macroBlockModeInfo.Block.UseIntraBlockCopy)
@@ -706,7 +706,7 @@ internal partial class Av1TileWriter
                 if (blk_ptr.HasChroma)
                 {
                     EncodeIntraChromaMode(
-                        ref writer,
+                        writer,
                         macroBlockModeInfo,
                         ref blk_ptr,
                         blockSize,
@@ -720,7 +720,7 @@ internal partial class Av1TileWriter
             {
                 WritePaletteModeInfo(
                     scs,
-                    ref writer,
+                    writer,
                     macroBlockModeInfo,
                     ref blk_ptr,
                     blockSize,
@@ -762,7 +762,7 @@ internal partial class Av1TileWriter
                 EncodeCoefficients1d(
                     pcs,
                     entropyCodingContext,
-                    ref writer,
+                    writer,
                     ref blk_ptr,
                     blockOrigin,
                     intra_luma_mode,
@@ -850,7 +850,7 @@ internal partial class Av1TileWriter
     /// <param name="chromaMode">The selected chroma prediction mode.</param>
     /// <param name="isChromaFromLumaAllowed">A value indicating whether chroma-from-luma mode is available.</param>
     private static void EncodeIntraChromaMode(
-        ref Av1SymbolEncoder writer,
+        Av1SymbolEncoder writer,
         Av1MacroBlockModeInfo macroBlockModeInfo,
         ref Av1EncoderBlockStruct blk_ptr,
         Av1BlockSize blockSize,
@@ -910,7 +910,7 @@ internal partial class Av1TileWriter
     /// <param name="blockSize">The block size.</param>
     /// <param name="lumaMode">The selected luma prediction mode.</param>
     private static void EncodeIntraLumaMode(
-        ref Av1SymbolEncoder writer,
+        Av1SymbolEncoder writer,
         Av1MacroBlockModeInfo macroBlockModeInfo,
         Av1MacroBlockD macroBlock,
         ref Av1EncoderBlockStruct blk_ptr,
@@ -938,7 +938,7 @@ internal partial class Av1TileWriter
     /// <exception cref="NotImplementedException">Palette-mode encoding is not implemented.</exception>
     private static void WritePaletteModeInfo(
         Av1SequenceControlSet scs,
-        ref Av1SymbolEncoder writer,
+        Av1SymbolEncoder writer,
         Av1MacroBlockModeInfo macroBlockModeInfo,
         ref Av1EncoderBlockStruct blk_ptr,
         Av1BlockSize blockSize,
@@ -985,7 +985,7 @@ internal partial class Av1TileWriter
     /// <param name="macroBlockModeInfo">The selected block modes.</param>
     /// <exception cref="NotImplementedException">The displacement-vector syntax is not implemented when intra block copy is selected.</exception>
     private static void WriteIntraBlockCopyInfo(
-        ref Av1SymbolEncoder writer,
+        Av1SymbolEncoder writer,
         Av1MacroBlockModeInfo macroBlockModeInfo)
     {
         bool use_intrabc = macroBlockModeInfo.Block.UseIntraBlockCopy;
@@ -1220,7 +1220,7 @@ internal partial class Av1TileWriter
     private static void EncodeCoefficients1d(
         Av1PictureControlSet pcs,
         Av1EntropyCodingContext ec_ctx,
-        ref Av1SymbolEncoder writer,
+        Av1SymbolEncoder writer,
         ref Av1EncoderBlockStruct blk_ptr,
         Point blockOrigin,
         Av1PredictionMode intraLumaDir,
@@ -1234,7 +1234,7 @@ internal partial class Av1TileWriter
         EncodeTransformCoefficientsY(
             pcs,
             ec_ctx,
-            ref writer,
+            writer,
             ref blk_ptr,
             blockOrigin,
             intraLumaDir,
@@ -1246,7 +1246,7 @@ internal partial class Av1TileWriter
         EncodeTransformCoefficientsUv(
             pcs,
             ec_ctx,
-            ref writer,
+            writer,
             ref blk_ptr,
             blockOrigin,
             intraLumaDir,
@@ -1273,7 +1273,7 @@ internal partial class Av1TileWriter
     public static void EncodeTransformCoefficientsY(
         Av1PictureControlSet pcs,
         Av1EntropyCodingContext entropyCodingContext,
-        ref Av1SymbolEncoder writer,
+        Av1SymbolEncoder writer,
         ref Av1EncoderBlockStruct blk_ptr,
         Point blockOrigin,
         Av1PredictionMode intraLumaDir,
@@ -1387,7 +1387,7 @@ internal partial class Av1TileWriter
     private static void EncodeTransformCoefficientsUv(
         Av1PictureControlSet pcs,
         Av1EntropyCodingContext entropyCodingContext,
-        ref Av1SymbolEncoder writer,
+        Av1SymbolEncoder writer,
         ref Av1EncoderBlockStruct blk_ptr,
         Point blockOrigin,
         Av1PredictionMode intraLumaDir,
@@ -1631,7 +1631,7 @@ internal partial class Av1TileWriter
     /// <param name="skip">A value indicating whether residual coefficients are omitted.</param>
     private static void WriteSegmentId(
         Av1PictureControlSet pcs,
-        ref Av1SymbolEncoder writer,
+        Av1SymbolEncoder writer,
         Av1BlockSize blockSize,
         Point blockOrigin,
         Av1MacroBlockD macroBlock,
@@ -1738,7 +1738,7 @@ internal partial class Av1TileWriter
     /// <param name="writer">The tile symbol encoder.</param>
     /// <param name="macroBlock">The reusable macroblock edge and neighbor state.</param>
     /// <param name="skip">The skip value to write.</param>
-    public static void EncodeSkipCoefficients(ref Av1SymbolEncoder writer, Av1MacroBlockD macroBlock, bool skip)
+    public static void EncodeSkipCoefficients(Av1SymbolEncoder writer, Av1MacroBlockD macroBlock, bool skip)
     {
         Av1MacroBlockModeInfo? above_mi = macroBlock.AboveMacroBlock;
         Av1MacroBlockModeInfo? left_mi = macroBlock.LeftMacroBlock;
diff --git a/src/ImageSharp/Formats/Heif/HeifEncoderCore.cs b/src/ImageSharp/Formats/Heif/HeifEncoderCore.cs
index 747a18f1c7..25704b2f57 100644
--- a/src/ImageSharp/Formats/Heif/HeifEncoderCore.cs
+++ b/src/ImageSharp/Formats/Heif/HeifEncoderCore.cs
@@ -48,12 +48,17 @@ internal sealed class HeifEncoderCore
         Guard.NotNull(image, nameof(image));
         Guard.NotNull(stream, nameof(stream));
 
-        using ChunkedMemoryStream compressedPixels = this.encoder.CompressionMethod switch
+        using ChunkedMemoryStream compressedPixels = new(this.configuration.MemoryAllocator);
+        switch (this.encoder.CompressionMethod)
         {
-            HeifCompressionMethod.LegacyJpeg => this.CompressPixels(image, cancellationToken),
-            HeifCompressionMethod.Av1 => throw new NotSupportedException("AV1 encoding is not implemented."),
-            _ => throw new NotSupportedException($"HEIF compression method '{this.encoder.CompressionMethod}' is not supported.")
-        };
+            case HeifCompressionMethod.LegacyJpeg:
+                this.CompressPixels(image, compressedPixels, cancellationToken);
+                break;
+            case HeifCompressionMethod.Av1:
+                throw new NotSupportedException("AV1 encoding is not implemented.");
+            default:
+                throw new NotSupportedException($"HEIF compression method '{this.encoder.CompressionMethod}' is not supported.");
+        }
 
         List<HeifItem> items = new();
         List<HeifItemLink> links = new();
@@ -430,9 +435,12 @@ internal sealed class HeifEncoderCore
     /// </summary>
     /// <typeparam name="TPixel">The source pixel format.</typeparam>
     /// <param name="image">The source image.</param>
+    /// <param name="stream">The destination for the encoded JPEG item bytes.</param>
     /// <param name="cancellationToken">The token used to cancel payload encoding.</param>
-    /// <returns>The pooled stream containing the encoded JPEG item bytes.</returns>
-    private ChunkedMemoryStream CompressPixels<TPixel>(Image<TPixel> image, CancellationToken cancellationToken)
+    private void CompressPixels<TPixel>(
+        Image<TPixel> image,
+        ChunkedMemoryStream stream,
+        CancellationToken cancellationToken)
         where TPixel : unmanaged, IPixel<TPixel>
     {
         if (this.encoder.Lossless)
@@ -454,7 +462,6 @@ internal sealed class HeifEncoderCore
             _ => throw new NotSupportedException($"HEIF chroma sampling '{this.encoder.ChromaSubsampling}' is not supported.")
         };
 
-        ChunkedMemoryStream stream = new(this.configuration.MemoryAllocator);
         JpegEncoder encoder = new()
         {
             // The HEIF quality scale includes zero while the JPEG payload encoder starts at one.
@@ -463,18 +470,8 @@ internal sealed class HeifEncoderCore
             ColorType = colorType
         };
 
-        try
-        {
-            // ImageEncoder is a synchronous contract. Wait for the cancellable JPEG operation so HEIF encoding
-            // cannot return while its pooled item payload is still being produced.
-            image.SaveAsJpegAsync(stream, encoder, cancellationToken).GetAwaiter().GetResult();
-            return stream;
-        }
-        catch
-        {
-            // Ownership transfers to the caller only after encoding succeeds.
-            stream.Dispose();
-            throw;
-        }
+        // ImageEncoder is a synchronous contract. Wait for the cancellable JPEG operation so HEIF encoding
+        // cannot return while its pooled item payload is still being produced.
+        image.SaveAsJpegAsync(stream, encoder, cancellationToken).GetAwaiter().GetResult();
     }
 }
diff --git a/tests/ImageSharp.Tests/Formats/Heif/Av1/Av1CoefficientsEntropyTests.cs b/tests/ImageSharp.Tests/Formats/Heif/Av1/Av1CoefficientsEntropyTests.cs
index 89635e9f47..fa5411dcd2 100644
--- a/tests/ImageSharp.Tests/Formats/Heif/Av1/Av1CoefficientsEntropyTests.cs
+++ b/tests/ImageSharp.Tests/Formats/Heif/Av1/Av1CoefficientsEntropyTests.cs
@@ -299,7 +299,7 @@ public class Av1CoefficientsEntropyTests
         Av1TileWriter.EncodeTransformCoefficientsY(
             picture,
             context,
-            ref writer,
+            writer,
             ref block,
             Point.Empty,
             Av1PredictionMode.DC,
@@ -636,7 +636,7 @@ public class Av1CoefficientsEntropyTests
         Av1TileWriter.WriteSuperblock(
             picture,
             context,
-            ref writer,
+            writer,
             superblock,
             coefficients,
             tileIndex: 0);