PaperMC/paper-server/patches/sources/net/minecraft/world/entity/NeutralMob.java.patch

--- a/net/minecraft/world/entity/NeutralMob.java
+++ b/net/minecraft/world/entity/NeutralMob.java
@@ -8,6 +8,9 @@
 import net.minecraft.world.entity.player.Player;
 import net.minecraft.world.level.GameRules;
 import net.minecraft.world.level.Level;
+// CraftBukkit start
+import org.bukkit.event.entity.EntityTargetEvent;
+// CraftBukkit end
 
 public interface NeutralMob {
 
@@ -42,24 +45,11 @@
                 UUID uuid = nbt.getUUID("AngryAt");
 
                 this.setPersistentAngerTarget(uuid);
-                Entity entity = ((ServerLevel) world).getEntity(uuid);
-
-                if (entity != null) {
-                    if (entity instanceof Mob) {
-                        Mob entityinsentient = (Mob) entity;
-
-                        this.setTarget(entityinsentient);
-                        this.setLastHurtByMob(entityinsentient);
-                    }
-
-                    if (entity instanceof Player) {
-                        Player entityhuman = (Player) entity;
-
-                        this.setTarget(entityhuman);
-                        this.setLastHurtByPlayer(entityhuman);
-                    }
-
-                }
+                // Paper - Prevent entity loading causing async lookups; Moved diff to separate method
+                // If this entity already survived its first tick, e.g. is loaded and ticked in sync, actively
+                // tick the initial persistent anger.
+                // If not, let the first tick on the baseTick call the method later down the line.
+                if (this instanceof Entity entity && !entity.firstTick) this.tickInitialPersistentAnger(world);
             }
         }
     }
@@ -114,7 +104,7 @@
     default void stopBeingAngry() {
         this.setLastHurtByMob((LivingEntity) null);
         this.setPersistentAngerTarget((UUID) null);
-        this.setTarget((LivingEntity) null);
+        this.setTarget((LivingEntity) null, org.bukkit.event.entity.EntityTargetEvent.TargetReason.FORGOT_TARGET, true); // CraftBukkit
         this.setRemainingPersistentAngerTime(0);
     }
 
@@ -127,8 +117,34 @@
 
     void setTarget(@Nullable LivingEntity target);
 
+    boolean setTarget(@Nullable LivingEntity entityliving, org.bukkit.event.entity.EntityTargetEvent.TargetReason reason, boolean fireEvent); // CraftBukkit
+
     boolean canAttack(LivingEntity target);
 
     @Nullable
     LivingEntity getTarget();
+
+    // Paper start - Prevent entity loading causing async lookups
+    // Update last hurt when ticking
+    default void tickInitialPersistentAnger(Level level) {
+        UUID target = getPersistentAngerTarget();
+        if (target == null) {
+            return;
+        }
+
+        Entity entity = ((ServerLevel) level).getEntity(target);
+
+        if (entity != null) {
+            if (entity instanceof Mob mob) {
+                this.setTarget(mob, EntityTargetEvent.TargetReason.UNKNOWN, false); // CraftBukkit
+                this.setLastHurtByMob(mob);
+            }
+
+            if (entity instanceof Player player) {
+                this.setTarget(player, EntityTargetEvent.TargetReason.UNKNOWN, false); // CraftBukkit
+                this.setLastHurtByPlayer(player);
+            }
+        }
+    }
+    // Paper end - Prevent entity loading causing async lookups
 }