First Test MV

core/src/main/java/art/arcane/iris/core/IrisDatapackCompiler.java

@@ -46,7 +46,6 @@ public final class IrisDatapackCompiler {
             List<File> packRoots,
             KList<File> datapackRoots,
             IDataFixer fixer,
-            int packFormat,
             boolean adjustVanillaHeight
     ) throws IOException {
         Objects.requireNonNull(packRoots, "packRoots");
@@ -98,7 +97,7 @@ public final class IrisDatapackCompiler {
             }
         }
 
-        IrisDimension.writeShared(datapackRoots, height, packFormat, adjustVanillaHeight);
+        IrisDimension.writeShared(datapackRoots, height, adjustVanillaHeight);
         validateOutputs(datapackRoots, dimensionCount);
         return new CompilationResult(packCount, dimensionCount, countBiomes(biomes));
     }

core/src/main/java/art/arcane/iris/core/ServerConfigurator.java

@@ -200,7 +200,6 @@ public class ServerConfigurator {
                     packRoots,
                     stagedRoots,
                     fixer,
-                    BukkitPlatform.dataPackFormat(),
                     IrisSettings.get().getGeneral().adjustVanillaHeight
             );
             for (int i = 0; i < liveRoots.size(); i++) {

core/src/main/java/art/arcane/iris/core/nms/INMSBinding.java

@@ -257,7 +257,7 @@ public interface INMSBinding {
         if (!supportsIrisWorldGeneration()) {
             throw new IllegalStateException("Iris world '" + c.name() + "' cannot be created with limited NMS binding "
                     + getClass().getSimpleName()
-                    + "; set general.disableNMS=false and use the supported Minecraft 26.2 server runtime");
+                    + "; set general.disableNMS=false and use a supported Minecraft server runtime (26.1.2 or 26.2)");
         }
         if (missingDimensionTypes(generator.getTarget().getDimension().getDimensionTypeKey())) {
             throw new IllegalStateException("Missing dimension types to create world");

core/src/main/java/art/arcane/iris/core/nms/NmsBindingSelector.java

@@ -1,7 +1,7 @@
 package art.arcane.iris.core.nms;
 
 final class NmsBindingSelector {
-    private static final String SUPPORTED_VERSION = "26.2";
+    private static final String SUPPORTED_VERSIONS = "26.1.2 or 26.2";
     private static final String SUPPORTED_TAG = "v26_2_R1";
 
     private NmsBindingSelector() {
@@ -11,8 +11,8 @@ final class NmsBindingSelector {
         if (version == null) {
             throw new IllegalStateException("Iris requires an exact Minecraft version before selecting NMS");
         }
-        if (!version.isSameRelease(26, 2, 0)) {
-            throw new IllegalStateException("Iris requires Minecraft " + SUPPORTED_VERSION
+        if (!version.isSameRelease(26, 2, 0) && !version.isSameRelease(26, 1, 2)) {
+            throw new IllegalStateException("Iris requires Minecraft " + SUPPORTED_VERSIONS
                     + ". Detected server version: " + version.value());
         }
         return SUPPORTED_TAG;

core/src/main/java/art/arcane/iris/core/nms/datapack/DataVersion.java

@@ -13,6 +13,7 @@ import java.util.function.Supplier;
 @Getter
 public enum DataVersion {
     UNSUPPORTED("0.0.0", 0, () -> null),
+    V26_1_2("26.1.2", 101, DataFixerV1217::new),
     V26_2("26.2", 107, DataFixerV1217::new);
     private static final KMap<DataVersion, IDataFixer> cache = new KMap<>();
     @Getter(AccessLevel.NONE)
@@ -51,4 +52,15 @@ public enum DataVersion {
     public static DataVersion getLatest() {
         return values()[values().length - 1];
     }
+
+    public static int minSupportedPackFormat() {
+        int minimum = Integer.MAX_VALUE;
+        for (DataVersion version : values()) {
+            if (version == UNSUPPORTED) {
+                continue;
+            }
+            minimum = Math.min(minimum, version.packFormat);
+        }
+        return minimum;
+    }
 }

core/src/main/java/art/arcane/iris/core/nms/v1X/NMSBinding1X.java

@@ -293,6 +293,6 @@ public class NMSBinding1X implements INMSBinding {
     private IllegalStateException unsupportedStructureHook(String operation) {
         return new IllegalStateException("Iris cannot " + operation + " with limited NMS binding "
                 + getClass().getSimpleName()
-                + "; set general.disableNMS=false and use the supported Minecraft 26.2 server runtime");
+                + "; set general.disableNMS=false and use a supported Minecraft server runtime (26.1.2 or 26.2)");
     }
 }

core/src/main/java/art/arcane/iris/core/pack/DefaultPackBootstrapProvisioner.java

@@ -41,7 +41,6 @@ import java.util.zip.ZipInputStream;
 public final class DefaultPackBootstrapProvisioner {
     private static final URI DEFAULT_SOURCE = URI.create("https://github.com/IrisDimensions/overworld/releases/download/beta/overworld.zip");
     private static final String WORLD_DATAPACK_DIRECTORY = "iris";
-    private static final int PACK_FORMAT = 107;
     private static final int MARKER_SCHEMA = 2;
     private static final int MAX_ARCHIVE_ENTRIES = 100_000;
     private static final long MAX_ARCHIVE_BYTES = 512L * 1024L * 1024L;
@@ -189,7 +188,7 @@ public final class DefaultPackBootstrapProvisioner {
                 if (fixer == null) {
                     throw new IOException("Latest Iris datapack fixer is unavailable during bootstrap");
                 }
-                IrisDatapackCompiler.compile(packRoots, outputFolders, fixer, PACK_FORMAT, false);
+                IrisDatapackCompiler.compile(packRoots, outputFolders, fixer, false);
                 if (!isDatapackRoot(compileContainer)) {
                     throw new IOException("Canonical Iris datapack compiler produced incomplete output at " + compileContainer);
                 }

core/src/main/java/art/arcane/iris/engine/object/IrisDimension.java

@@ -23,6 +23,7 @@ import art.arcane.iris.core.loader.IrisData;
 import art.arcane.iris.spi.IrisLogging;
 import art.arcane.iris.spi.PlatformBlockState;
 import art.arcane.iris.core.loader.IrisRegistrant;
+import art.arcane.iris.core.nms.datapack.DataVersion;
 import art.arcane.iris.core.nms.datapack.IDataFixer;
 import art.arcane.iris.core.nms.datapack.IDataFixer.Dimension;
 import art.arcane.iris.engine.data.cache.AtomicCache;
@@ -763,7 +764,6 @@ public class IrisDimension extends IrisRegistrant {
     public static void writeShared(
             KList<File> datapackRoots,
             DimensionHeight height,
-            int packFormat,
             boolean adjustVanillaHeight
     ) throws IOException {
         IrisLogging.debug("    Installing Data Pack Vanilla Dimension Types");
@@ -774,16 +774,22 @@ public class IrisDimension extends IrisRegistrant {
             write(datapackRoot, "the_end", jsonStrings[2], adjustVanillaHeight);
         }
 
+        // Ranged formats spanning every supported runtime (26.1.2 = 101, 26.2 = 107). The bootstrap
+        // provisioner stages this datapack before the server (and INMS) exists, so the runtime
+        // version cannot be resolved there; a range keeps the emitted bytes identical on both
+        // install paths and both Paper versions parse ranged min_format/max_format.
+        int minFormat = DataVersion.minSupportedPackFormat();
+        int maxFormat = DataVersion.getLatest().getPackFormat();
         String raw = """
                         {
                             "pack": {
                                 "description": "Iris Data Pack. This pack contains all installed Iris Packs' resources.",
-                                "pack_format": {},
-                                "min_format": {},
-                                "max_format": {}
+                                "pack_format": %d,
+                                "min_format": %d,
+                                "max_format": %d
                             }
                         }
-                        """.replace("{}", Integer.toString(packFormat));
+                        """.formatted(maxFormat, minFormat, maxFormat);
 
         for (File datapackRoot : datapackRoots) {
             File mcm = new File(datapackRoot, "pack.mcmeta");

core/src/main/java/art/arcane/iris/platform/bukkit/BukkitPlatform.java

@@ -242,10 +242,6 @@ public final class BukkitPlatform implements IrisPlatform {
         return INMS.get().applyCustomNbt(itemStack, customNbt);
     }
 
-    public static int dataPackFormat() {
-        return INMS.get().getDataVersion().getPackFormat();
-    }
-
     public static java.util.concurrent.CompletableFuture<Boolean> teleportAsync(Entity entity, Location destination) {
         return io.papermc.lib.PaperLib.teleportAsync(entity, destination);
     }

core/src/main/java/art/arcane/iris/util/common/director/DirectorExecutor.java

@@ -36,6 +36,11 @@ public interface DirectorExecutor extends DirectorExecutorBase {
         return sender == null ? null : sender.player();
     }
 
+    default boolean playerWorldGeneratesStructures() {
+        Player activePlayer = player();
+        return activePlayer != null && activePlayer.getWorld().canGenerateStructures();
+    }
+
     default IrisData data() {
         var access = access();
         if (access != null) {

core/src/main/java/art/arcane/iris/util/common/director/specialhandlers/StructureHandler.java

@@ -29,7 +29,6 @@ import art.arcane.iris.spi.PlatformStructureHooks;
 import art.arcane.iris.util.common.director.DirectorParameterHandler;
 import art.arcane.volmlib.util.collection.KList;
 import art.arcane.volmlib.util.director.exceptions.DirectorParsingException;
-import org.bukkit.entity.Player;
 
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -100,8 +99,7 @@ public class StructureHandler implements DirectorParameterHandler<String> {
     }
 
     protected boolean nativeStructureGenerationEnabled() {
-        Player activePlayer = player();
-        return activePlayer != null && activePlayer.getWorld().canGenerateStructures();
+        return playerWorldGeneratesStructures();
     }
 
     private static Map<String, String> distinctKeys(List<String> keys) {