PaperMC/paper-server/nms-patches/net/minecraft/world/level/block/BlockCauldron.patch

--- a/net/minecraft/world/level/block/BlockCauldron.java
+++ b/net/minecraft/world/level/block/BlockCauldron.java
@@ -12,6 +12,10 @@
 import net.minecraft.world.level.material.FluidType;
 import net.minecraft.world.level.material.FluidTypes;
 
+// CraftBukkit start
+import org.bukkit.event.block.CauldronLevelChangeEvent;
+// CraftBukkit end
+
 public class BlockCauldron extends AbstractCauldronBlock {
 
     public static final MapCodec<BlockCauldron> CODEC = simpleCodec(BlockCauldron::new);
@@ -61,13 +65,11 @@
 
         if (fluidtype == FluidTypes.WATER) {
             iblockdata1 = Blocks.WATER_CAULDRON.defaultBlockState();
-            world.setBlockAndUpdate(blockposition, iblockdata1);
-            world.gameEvent(GameEvent.BLOCK_CHANGE, blockposition, GameEvent.a.of(iblockdata1));
+            LayeredCauldronBlock.changeLevel(iblockdata, world, blockposition, iblockdata1, null, CauldronLevelChangeEvent.ChangeReason.NATURAL_FILL); // CraftBukkit
             world.levelEvent(1047, blockposition, 0);
         } else if (fluidtype == FluidTypes.LAVA) {
             iblockdata1 = Blocks.LAVA_CAULDRON.defaultBlockState();
-            world.setBlockAndUpdate(blockposition, iblockdata1);
-            world.gameEvent(GameEvent.BLOCK_CHANGE, blockposition, GameEvent.a.of(iblockdata1));
+            LayeredCauldronBlock.changeLevel(iblockdata, world, blockposition, iblockdata1, null, CauldronLevelChangeEvent.ChangeReason.NATURAL_FILL); // CraftBukkit
             world.levelEvent(1046, blockposition, 0);
         }