From 0cb3978a8f26caf294673440cfc412516754cecf Mon Sep 17 00:00:00 2001
From: JustAHuman-xD <imjustahuman.xd@gmail.com>
Date: Thu, 11 Jun 2026 16:29:14 -0500
Subject: [PATCH 1/3] Add Block#isFluidReplaceable

---
 paper-api/src/main/java/org/bukkit/block/Block.java    | 10 ++++++++++
 .../java/org/bukkit/craftbukkit/block/CraftBlock.java  |  7 +++++++
 2 files changed, 17 insertions(+)

diff --git a/paper-api/src/main/java/org/bukkit/block/Block.java b/paper-api/src/main/java/org/bukkit/block/Block.java
index 5c75b3d049f2..b7bf537fc97e 100644
--- a/paper-api/src/main/java/org/bukkit/block/Block.java
+++ b/paper-api/src/main/java/org/bukkit/block/Block.java
@@ -2,6 +2,7 @@
 
 import java.util.Collection;
 import org.bukkit.Chunk;
+import org.bukkit.Fluid;
 import org.bukkit.FluidCollisionMode;
 import org.bukkit.Location;
 import org.bukkit.Material;
@@ -492,6 +493,15 @@ default int getBlockPower() {
      * @return true if block is replaceable
      */
     boolean isReplaceable();
+
+    /**
+     * Checks if this block can be immediately replaced by a specific fluid
+     *
+     * @param fluid the fluid to be replaceable with
+     * @return true if the block can be replaced
+     */
+    boolean isFluidReplaceable(Fluid fluid);
+
     /**
      * Check if this block is solid
      * <p>
diff --git a/paper-server/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java b/paper-server/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
index 5d6116c55072..ca1c4e75a641 100644
--- a/paper-server/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
+++ b/paper-server/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
@@ -32,6 +32,7 @@
 import net.minecraft.world.phys.shapes.VoxelShape;
 import org.bukkit.Bukkit;
 import org.bukkit.Chunk;
+import org.bukkit.Fluid;
 import org.bukkit.FluidCollisionMode;
 import org.bukkit.Location;
 import org.bukkit.Material;
@@ -42,6 +43,7 @@
 import org.bukkit.block.BlockFace;
 import org.bukkit.block.PistonMoveReaction;
 import org.bukkit.block.data.BlockData;
+import org.bukkit.craftbukkit.CraftFluid;
 import org.bukkit.craftbukkit.CraftFluidCollisionMode;
 import org.bukkit.craftbukkit.CraftWorld;
 import org.bukkit.craftbukkit.block.data.CraftBlockData;
@@ -443,6 +445,11 @@ public boolean isReplaceable() {
         return this.getBlockState().canBeReplaced();
     }
 
+    @Override
+    public boolean isFluidReplaceable(final Fluid fluid) {
+        return this.getBlockState().canBeReplaced(CraftFluid.bukkitToMinecraft(fluid));
+    }
+
     @Override
     public boolean isSolid() {
         return this.getBlockState().blocksMotion();

From 35dbfbae03c0f891bfc53477c4f6e7f6c5eb792c Mon Sep 17 00:00:00 2001
From: JustAHuman-xD <imjustahuman.xd@gmail.com>
Date: Thu, 11 Jun 2026 16:35:58 -0500
Subject: [PATCH 2/3] add annotation

---
 paper-api/src/main/java/org/bukkit/block/Block.java | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/paper-api/src/main/java/org/bukkit/block/Block.java b/paper-api/src/main/java/org/bukkit/block/Block.java
index b7bf537fc97e..18854b201bc9 100644
--- a/paper-api/src/main/java/org/bukkit/block/Block.java
+++ b/paper-api/src/main/java/org/bukkit/block/Block.java
@@ -500,7 +500,7 @@ default int getBlockPower() {
      * @param fluid the fluid to be replaceable with
      * @return true if the block can be replaced
      */
-    boolean isFluidReplaceable(Fluid fluid);
+    boolean isFluidReplaceable(@NotNull Fluid fluid);
 
     /**
      * Check if this block is solid

From f43bc53a171db743a453da7fd37326bed8187673 Mon Sep 17 00:00:00 2001
From: JustAHuman-xD <imjustahuman.xd@gmail.com>
Date: Sat, 13 Jun 2026 14:05:37 -0500
Subject: [PATCH 3/3] add precondition check

---
 .../src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java   | 1 +
 1 file changed, 1 insertion(+)

diff --git a/paper-server/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java b/paper-server/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
index ca1c4e75a641..f063d425d863 100644
--- a/paper-server/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
+++ b/paper-server/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
@@ -447,6 +447,7 @@ public boolean isReplaceable() {
 
     @Override
     public boolean isFluidReplaceable(final Fluid fluid) {
+        Preconditions.checkArgument(fluid != null, "Fluid cannot be null");
         return this.getBlockState().canBeReplaced(CraftFluid.bukkitToMinecraft(fluid));
     }