Archive version is now loaded from the version of block 2 in the existing archive, or "defaultArchiveVersion" in settings if not available (default: 1).

src/main/java/org/qortal/api/resource/AdminResource.java

@@ -738,8 +738,17 @@ public class AdminResource {
 	@POST
 	@Path("/repository/archive/rebuild")
 	@Operation(
-			summary = "Rebuild archive.",
-			description = "Rebuilds archive files, using the serialization version specified via the archiveVersion setting.",
+			summary = "Rebuild archive",
+			description = "Rebuilds archive files, using the specified serialization version",
+			requestBody = @RequestBody(
+					required = true,
+					content = @Content(
+							mediaType = MediaType.TEXT_PLAIN,
+							schema = @Schema(
+									type = "number", example = "2"
+							)
+					)
+			),
 			responses = {
 					@ApiResponse(
 							description = "\"true\"",
@@ -749,9 +758,14 @@ public class AdminResource {
 	)
 	@ApiErrors({ApiError.REPOSITORY_ISSUE})
 	@SecurityRequirement(name = "apiKey")
-	public String rebuildArchive(@HeaderParam(Security.API_KEY_HEADER) String apiKey) {
+	public String rebuildArchive(@HeaderParam(Security.API_KEY_HEADER) String apiKey, Integer serializationVersion) {
 		Security.checkApiCallAllowed(request);
 
+		// Default serialization version to value specified in settings
+		if (serializationVersion == null) {
+			serializationVersion = Settings.getInstance().getDefaultArchiveVersion();
+		}
+
 		try {
 			// We don't actually need to lock the blockchain here, but we'll do it anyway so that
 			// the node can focus on rebuilding rather than synchronizing / minting.
@@ -760,9 +774,7 @@ public class AdminResource {
 			blockchainLock.lockInterruptibly();
 
 			try {
-				int archiveVersion = Settings.getInstance().getArchiveVersion();
-
-				BlockArchiveRebuilder blockArchiveRebuilder = new BlockArchiveRebuilder(archiveVersion);
+				BlockArchiveRebuilder blockArchiveRebuilder = new BlockArchiveRebuilder(serializationVersion);
 				blockArchiveRebuilder.start();
 
 				return "true";

src/main/java/org/qortal/repository/BlockArchiveReader.java

@@ -64,6 +64,19 @@ public class BlockArchiveReader {
         this.fileListCache = Map.copyOf(map);
     }
 
+    public Integer fetchSerializationVersionForHeight(int height) {
+        if (this.fileListCache == null) {
+            this.fetchFileList();
+        }
+
+        Triple<byte[], Integer, Integer> serializedBlock = this.fetchSerializedBlockBytesForHeight(height);
+        if (serializedBlock == null) {
+            return null;
+        }
+        Integer serializationVersion = serializedBlock.getB();
+        return serializationVersion;
+    }
+
     public BlockTransformation fetchBlockAtHeight(int height) {
         if (this.fileListCache == null) {
             this.fetchFileList();

src/main/java/org/qortal/repository/BlockArchiveWriter.java

@@ -43,7 +43,7 @@ public class BlockArchiveWriter {
 
     private int startHeight;
     private final int endHeight;
-    private final int serializationVersion;
+    private final Integer serializationVersion;
     private final Path archivePath;
     private final Repository repository;
 
@@ -65,12 +65,17 @@ public class BlockArchiveWriter {
      * @param endHeight
      * @param repository
      */
-    public BlockArchiveWriter(int startHeight, int endHeight, int serializationVersion, Path archivePath, Repository repository) {
+    public BlockArchiveWriter(int startHeight, int endHeight, Integer serializationVersion, Path archivePath, Repository repository) {
         this.startHeight = startHeight;
         this.endHeight = endHeight;
-        this.serializationVersion = serializationVersion;
         this.archivePath = archivePath.toAbsolutePath();
         this.repository = repository;
+
+        if (serializationVersion == null) {
+            // When serialization version isn't specified, fetch it from the existing archive
+            serializationVersion = this.findSerializationVersion();
+        }
+        this.serializationVersion = serializationVersion;
     }
 
     /**
@@ -80,7 +85,18 @@ public class BlockArchiveWriter {
      * @param repository
      */
     public BlockArchiveWriter(int startHeight, int endHeight, Repository repository) {
-        this(startHeight, endHeight, Settings.getInstance().getArchiveVersion(), Paths.get(Settings.getInstance().getRepositoryPath(), "archive"), repository);
+        this(startHeight, endHeight, null, Paths.get(Settings.getInstance().getRepositoryPath(), "archive"), repository);
+    }
+
+    private int findSerializationVersion() {
+        // Attempt to fetch the serialization version from the existing archive
+        Integer block2SerializationVersion = BlockArchiveReader.getInstance().fetchSerializationVersionForHeight(2);
+        if (block2SerializationVersion != null) {
+            return block2SerializationVersion;
+        }
+
+        // Default to version specified in settings
+        return Settings.getInstance().getDefaultArchiveVersion();
     }
 
     public static int getMaxArchiveHeight(Repository repository) throws DataException {

src/main/java/org/qortal/settings/Settings.java

@@ -179,7 +179,7 @@ public class Settings {
 	/** How often to attempt archiving (ms). */
 	private long archiveInterval = 7171L; // milliseconds
 	/** Serialization version to use when building an archive */
-	private int archiveVersion = 1;
+	private int defaultArchiveVersion = 1;
 
 
 	/** Whether to automatically bootstrap instead of syncing from genesis */
@@ -928,8 +928,8 @@ public class Settings {
 		return this.archiveInterval;
 	}
 
-	public int getArchiveVersion() {
-		return this.archiveVersion;
+	public int getDefaultArchiveVersion() {
+		return this.defaultArchiveVersion;
 	}