Audited datapack priority mixin

- The modded mixin audit checks that the pack selection mixin keeping the Iris forced datapack last is applied
- Ordering tests cover a world datapack saved after the Iris pack and already-ordered selections

adapters/modded-common/src/main/java/art/arcane/iris/modded/ModdedMixinAudit.java

@@ -61,6 +61,10 @@ public final class ModdedMixinAudit {
                     NativeMixinTarget.STRUCTURE_PALETTE,
                     "iris$installConcurrentBlockCache",
                     false, NativeMixinFlags::structureTemplatePaletteRan),
+            new ExpectedMixin(ENTITY_CONFIG, "PackRepositorySelectionMixin",
+                    NativeMixinTarget.PACK_REPOSITORY,
+                    "volmlib$keepNativeDatapacksLast",
+                    false, NativeMixinFlags::packSelectionRan),
             new ExpectedMixin(CLIENT_CONFIG, "NativeWorldOpenFlowsMixin",
                     NativeMixinTarget.WORLD_OPEN_FLOWS,
                     "volmlib$openWorldCheckWorldStemCompatibility",
@@ -111,7 +115,7 @@ public final class ModdedMixinAudit {
             ModdedIrisLog.error("  missing: {}", entry);
         }
         ModdedIrisLog.error("The mixin config was not registered for this loader (fabric.mod.json mixins, neoforge.mods.toml [[mixins]], forge MixinConfigs manifest attribute).");
-        ModdedIrisLog.error("Entity persistence, custom mob loot, parallel structure safety, readable biome identifiers, or Iris world-type labels are disabled until this is fixed.");
+        ModdedIrisLog.error("Entity persistence, custom mob loot, parallel structure safety, Iris datapack priority, readable biome identifiers, or Iris world-type labels are disabled until this is fixed.");
         ModdedIrisLog.error("===============================================================");
     }
 

adapters/modded-common/src/test/java/art/arcane/iris/modded/ModdedDatapackOrderTest.java

@@ -0,0 +1,51 @@
+/*
+ * Iris is a World Generator for Minecraft Servers
+ * Copyright (c) 2026 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package art.arcane.iris.modded;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeDatapackSource;
+import org.junit.Test;
+
+import java.util.List;
+import java.util.Set;
+import java.util.function.Function;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertSame;
+
+public class ModdedDatapackOrderTest {
+    private static final Set<String> PINNED = Set.of("iris_worldgen");
+
+    @Test
+    public void worldDatapacksSavedAfterTheIrisPackNoLongerOverrideIt() {
+        List<String> saved = List.of("vanilla", "mod_data", "iris_worldgen", "file/iristest");
+
+        assertEquals(List.of("vanilla", "mod_data", "file/iristest", "iris_worldgen"),
+                NativeDatapackSource.orderPinnedLast(saved, Function.identity(), PINNED));
+    }
+
+    @Test
+    public void alreadyLastOrUnpinnedSelectionsAreReturnedUnchanged() {
+        List<String> ordered = List.of("vanilla", "file/iristest", "iris_worldgen");
+        List<String> withoutIris = List.of("vanilla", "file/iristest");
+
+        assertSame(ordered, NativeDatapackSource.orderPinnedLast(ordered, Function.identity(), PINNED));
+        assertSame(withoutIris, NativeDatapackSource.orderPinnedLast(withoutIris, Function.identity(), PINNED));
+        assertSame(withoutIris, NativeDatapackSource.orderPinnedLast(withoutIris, Function.identity(), Set.of()));
+    }
+}