Unity-Technologies · SkowronskiAndrew · Aug 18, 2026
diff --git a/Archive/ArchiveTool.cs b/Archive/ArchiveTool.cs
@@ -163,6 +163,16 @@ public static int PrintSummary(FileInfo filename, OutputFormat format)
             uncompressedDataSize += block.UncompressedSize;
         }
 
+        // The data section can be larger than the sum of the blocks, because of the alignment
+        // padding that separates chunk-based blocks (the BlockPaddingBetweenChunks flag).
+        long paddingSize = 0;
+        if (blocks.Length > 0)
+        {
+            var lastBlock = blocks[blocks.Length - 1];
+            long dataSectionSize = lastBlock.FileOffset + lastBlock.CompressedSize - ArchiveDetector.GetDataOffset(header);
+            paddingSize = dataSectionSize - dataSize;
+        }
+
         // Determine the compression algorithm by finding the first block that uses compression.
         // Individual blocks may be stored uncompressed even when compression is enabled, because
         // compression is skipped when it provides no size reduction. So the first compressed block
@@ -193,6 +203,7 @@ public static int PrintSummary(FileInfo filename, OutputFormat format)
                 unityVersion = header.UnityVersion,
                 fileSize = header.Size,
                 dataSize = dataSize,
+                blockPaddingSize = paddingSize,
                 uncompressedDataSize = uncompressedDataSize,
                 compressionRatio = Math.Round(compressionRatio, 2),
                 compression = compression,
@@ -208,6 +219,8 @@ public static int PrintSummary(FileInfo filename, OutputFormat format)
             Console.WriteLine($"{"Unity Version",-30} {header.UnityVersion}");
             Console.WriteLine($"{"File Size",-30} {header.Size:N0} bytes");
             Console.WriteLine($"{"Data Size",-30} {dataSize:N0} bytes");
+            if (paddingSize > 0)
+                Console.WriteLine($"{"Block Padding Size",-30} {paddingSize:N0} bytes");
             Console.WriteLine($"{"Uncompressed Data Size",-30} {uncompressedDataSize:N0} bytes");
             Console.WriteLine($"{"Compression Ratio",-30} {compressionRatio:F2}x");
             Console.WriteLine($"{"Compression",-30} {compression}");
@@ -263,10 +276,11 @@ static string FormatCompressionType(int compressionType)
 
     static readonly (uint bit, string name)[] KnownArchiveFlags =
     {
-        (0x40,  "BlocksAndDirectoryInfoCombined"),
-        (0x80,  "BlocksInfoAtTheEnd"),
-        (0x100, "OldWebPluginCompatibility"),
-        (0x200, "BlockInfoNeedPaddingAtStart"),
+        (ArchiveFlags.BlocksAndDirectoryInfoCombined, "BlocksAndDirectoryInfoCombined"),
+        (ArchiveFlags.BlocksInfoAtTheEnd,             "BlocksInfoAtTheEnd"),
+        (ArchiveFlags.OldWebPluginCompatibility,      "OldWebPluginCompatibility"),
+        (ArchiveFlags.BlockInfoNeedPaddingAtStart,    "BlockInfoNeedPaddingAtStart"),
+        (ArchiveFlags.BlockPaddingBetweenChunks,      "BlockPaddingBetweenChunks"),
     };
 
     static string[] GetArchiveFlagNames(uint flagBits)

diff --git a/TestCommon/Data/LeadingEdgeBuilds/AGENTS.md b/TestCommon/Data/LeadingEdgeBuilds/AGENTS.md
@@ -6,7 +6,8 @@ The LeadingEdge build scripts regenerate this folder directly, so to update it,
 
 ## Layout
 
-* `AssetBundles/` - the AssetBundle build: one bundle per asset (named after the asset) plus the `AssetBundles` manifest bundle.
+* `AssetBundles/` - the AssetBundle build: one bundle per asset (named after the asset) plus the `AssetBundles` manifest bundle. LZMA compressed, so each archive has a single data block.
+* `AssetBundlesLz4/` - the same bundle layout built with chunk-based (LZ4) compression, giving archives with multiple data blocks separated by alignment padding (archive format version 9).
 * `ContentDirectory/` - the Content Directory build: content (`.cf`) files, `.resource` files and the build manifest.
 * `BuildReport-AssetBundles/LastBuild.buildreport` - the AssetBundle build report.
 * `BuildReport-ContentDirectory/` - the Content Directory build report folder, including `ContentLayout.json`.
diff --git a/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/6 b/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/6
diff --git a/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/6.manifest b/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/6.manifest
@@ -0,0 +1,21 @@
+ManifestFileVersion: 0
+UnityVersion: 6000.7.0a6
+CRC: 1054287113
+Hashes:
+  AssetFileHash:
+    serializedVersion: 2
+    Hash: ef4548464eae98b6ab651c92a869edc9
+  TypeTreeHash:
+    serializedVersion: 2
+    Hash: 9a2ca7bdbd1871f7131daf57de908e0c
+  IncrementalBuildHash:
+    serializedVersion: 2
+    Hash: 818e83165880f042a3252a52b336d06a
+HashAppended: 0
+ClassTypes:
+- Class: 83
+  Script: {instanceID: 0}
+SerializeReferenceClassIdentifiers: []
+Assets:
+- Assets/Audio/6.mp3
+Dependencies: []
diff --git a/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/AssetBundlesLz4 b/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/AssetBundlesLz4
diff --git a/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/AssetBundlesLz4.manifest b/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/AssetBundlesLz4.manifest
@@ -0,0 +1,33 @@
+ManifestFileVersion: 0
+UnityVersion: 6000.7.0a6
+CRC: 2935431312
+HashAppended: 0
+AssetBundleManifest:
+  AssetBundleInfos:
+    Info_0:
+      Name: assetbundleroot
+      Dependencies:
+        Dependency_0: directaudioclipreference
+        Dependency_1: singleaudioclipdirectreference
+        Dependency_2: serializationdemo
+    Info_1:
+      Name: directaudioclipreference
+      Dependencies:
+        Dependency_0: 6
+        Dependency_1: a
+    Info_2:
+      Name: singleaudioclipdirectreference
+      Dependencies:
+        Dependency_0: a
+    Info_3:
+      Name: serializationdemo
+      Dependencies: {}
+    Info_4:
+      Name: 6
+      Dependencies: {}
+    Info_5:
+      Name: a
+      Dependencies: {}
+    Info_6:
+      Name: scenes
+      Dependencies: {}
diff --git a/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/a b/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/a
diff --git a/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/a.manifest b/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/a.manifest
@@ -0,0 +1,21 @@
+ManifestFileVersion: 0
+UnityVersion: 6000.7.0a6
+CRC: 1988020392
+Hashes:
+  AssetFileHash:
+    serializedVersion: 2
+    Hash: 6175fa89f0b4cfd7cc433b0b143ab713
+  TypeTreeHash:
+    serializedVersion: 2
+    Hash: 9a2ca7bdbd1871f7131daf57de908e0c
+  IncrementalBuildHash:
+    serializedVersion: 2
+    Hash: ac9603f3b25ca1814eb4841392a9ff7e
+HashAppended: 0
+ClassTypes:
+- Class: 83
+  Script: {instanceID: 0}
+SerializeReferenceClassIdentifiers: []
+Assets:
+- Assets/Audio/a.mp3
+Dependencies: []
diff --git a/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/assetbundleroot b/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/assetbundleroot
diff --git a/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/assetbundleroot.manifest b/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/assetbundleroot.manifest
@@ -0,0 +1,34 @@
+ManifestFileVersion: 0
+UnityVersion: 6000.7.0a6
+CRC: 4203871746
+Hashes:
+  AssetFileHash:
+    serializedVersion: 2
+    Hash: 8ae6ceb771f9c15f2dde5117d3f67798
+  TypeTreeHash:
+    serializedVersion: 2
+    Hash: e4c92e7ce30487f41e62ec475c399971
+  IncrementalBuildHash:
+    serializedVersion: 2
+    Hash: 00f65fc945d785da9075745396600fe2
+HashAppended: 0
+ClassTypes:
+- Class: 114
+  Script: {fileID: 11500000, guid: d6330d3e9b8e5a0439e4dd147cec19dd, type: 3}
+- Class: 114
+  Script: {fileID: 11500000, guid: 8623c5efbb626994da80931050f0aba0, type: 3}
+- Class: 114
+  Script: {fileID: 11500000, guid: f44aeb02ae06dd84bb3ef76e1df8d525, type: 3}
+- Class: 115
+  Script: {instanceID: 0}
+SerializeReferenceClassIdentifiers:
+- AssemblyName: Assembly-CSharp
+  ClassName: SerializationDemo/SerializedData
+- AssemblyName: UnityEngine.CoreModule
+  ClassName: UnityEngine.DictionarySerialization/SerializedKeyValue`2
+Assets:
+- Assets/ScriptableObjects/AssetBundleRoot.asset
+Dependencies:
+- C:/UnitySrc/UnityDataTools/UnityProjects/LeadingEdge/../../TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/directaudioclipreference
+- C:/UnitySrc/UnityDataTools/UnityProjects/LeadingEdge/../../TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/serializationdemo
+- C:/UnitySrc/UnityDataTools/UnityProjects/LeadingEdge/../../TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/singleaudioclipdirectreference
diff --git a/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/directaudioclipreference b/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/directaudioclipreference
diff --git a/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/directaudioclipreference.manifest b/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/directaudioclipreference.manifest
@@ -0,0 +1,29 @@
+ManifestFileVersion: 0
+UnityVersion: 6000.7.0a6
+CRC: 3469506813
+Hashes:
+  AssetFileHash:
+    serializedVersion: 2
+    Hash: 5fd4865f81b71364e957dc7644afd47c
+  TypeTreeHash:
+    serializedVersion: 2
+    Hash: 4c88c857f41d6968a1090f557f31c5ed
+  IncrementalBuildHash:
+    serializedVersion: 2
+    Hash: 015f1d03897964d24d88747ea37642b1
+HashAppended: 0
+ClassTypes:
+- Class: 83
+  Script: {instanceID: 0}
+- Class: 114
+  Script: {fileID: 11500000, guid: d6330d3e9b8e5a0439e4dd147cec19dd, type: 3}
+- Class: 115
+  Script: {instanceID: 0}
+SerializeReferenceClassIdentifiers:
+- AssemblyName: UnityEngine.CoreModule
+  ClassName: UnityEngine.DictionarySerialization/SerializedKeyValue`2
+Assets:
+- Assets/ScriptableObjects/DirectAudioClipReference.asset
+Dependencies:
+- C:/UnitySrc/UnityDataTools/UnityProjects/LeadingEdge/../../TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/6
+- C:/UnitySrc/UnityDataTools/UnityProjects/LeadingEdge/../../TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/a
diff --git a/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/scenes b/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/scenes
diff --git a/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/scenes.manifest b/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/scenes.manifest
@@ -0,0 +1,42 @@
+ManifestFileVersion: 0
+UnityVersion: 6000.7.0a6
+CRC: 357273879
+Hashes:
+  AssetFileHash:
+    serializedVersion: 2
+    Hash: 531bc5793378ad5f958e829f6098afdf
+  TypeTreeHash:
+    serializedVersion: 2
+    Hash: 62ed4bb4a9e4f0abaa38cfea31ee7bca
+  IncrementalBuildHash:
+    serializedVersion: 2
+    Hash: 259ca50b232fd1006951e68b47ff4a66
+HashAppended: 0
+ClassTypes:
+- Class: 1
+  Script: {instanceID: 0}
+- Class: 4
+  Script: {instanceID: 0}
+- Class: 21
+  Script: {instanceID: 0}
+- Class: 28
+  Script: {instanceID: 0}
+- Class: 48
+  Script: {instanceID: 0}
+- Class: 89
+  Script: {instanceID: 0}
+- Class: 104
+  Script: {instanceID: 0}
+- Class: 157
+  Script: {instanceID: 0}
+- Class: 196
+  Script: {instanceID: 0}
+- Class: 212
+  Script: {instanceID: 0}
+- Class: 213
+  Script: {instanceID: 0}
+SerializeReferenceClassIdentifiers: []
+Assets:
+- Assets/Scenes/Scene1.unity
+- Assets/Scenes/Scene2.unity
+Dependencies: []
diff --git a/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/serializationdemo b/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/serializationdemo
diff --git a/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/serializationdemo.manifest b/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/serializationdemo.manifest
@@ -0,0 +1,25 @@
+ManifestFileVersion: 0
+UnityVersion: 6000.7.0a6
+CRC: 3418023709
+Hashes:
+  AssetFileHash:
+    serializedVersion: 2
+    Hash: 8787e29fd3c31264a27ae0c18c07b815
+  TypeTreeHash:
+    serializedVersion: 2
+    Hash: d0726b8e1199eb6125e2245ce15343f9
+  IncrementalBuildHash:
+    serializedVersion: 2
+    Hash: 1393a4a257b5b48e78eead885e48b68d
+HashAppended: 0
+ClassTypes:
+- Class: 114
+  Script: {fileID: 11500000, guid: f44aeb02ae06dd84bb3ef76e1df8d525, type: 3}
+- Class: 115
+  Script: {instanceID: 0}
+SerializeReferenceClassIdentifiers:
+- AssemblyName: Assembly-CSharp
+  ClassName: SerializationDemo/SerializedData
+Assets:
+- Assets/ScriptableObjects/SerializationDemo.asset
+Dependencies: []
diff --git a/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/singleaudioclipdirectreference b/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/singleaudioclipdirectreference
diff --git a/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/singleaudioclipdirectreference.manifest b/TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/singleaudioclipdirectreference.manifest
@@ -0,0 +1,28 @@
+ManifestFileVersion: 0
+UnityVersion: 6000.7.0a6
+CRC: 1388156890
+Hashes:
+  AssetFileHash:
+    serializedVersion: 2
+    Hash: f3732a953b4cba83b6943cfa13225c56
+  TypeTreeHash:
+    serializedVersion: 2
+    Hash: 4c88c857f41d6968a1090f557f31c5ed
+  IncrementalBuildHash:
+    serializedVersion: 2
+    Hash: 57215df3b8d2b5c11e9501a26ababda4
+HashAppended: 0
+ClassTypes:
+- Class: 83
+  Script: {instanceID: 0}
+- Class: 114
+  Script: {fileID: 11500000, guid: d6330d3e9b8e5a0439e4dd147cec19dd, type: 3}
+- Class: 115
+  Script: {instanceID: 0}
+SerializeReferenceClassIdentifiers:
+- AssemblyName: UnityEngine.CoreModule
+  ClassName: UnityEngine.DictionarySerialization/SerializedKeyValue`2
+Assets:
+- Assets/ScriptableObjects/SingleAudioClipDirectReference.asset
+Dependencies:
+- C:/UnitySrc/UnityDataTools/UnityProjects/LeadingEdge/../../TestCommon/Data/LeadingEdgeBuilds/AssetBundlesLz4/a