craftbukkit/nms-patches/net/minecraft/world/item/ItemMonsterEgg.patch

--- a/net/minecraft/world/item/ItemMonsterEgg.java
+++ b/net/minecraft/world/item/ItemMonsterEgg.java
@@ -176,7 +176,7 @@
                 } else {
                     entityinsentient1.snapTo(vec3d.x(), vec3d.y(), vec3d.z(), 0.0F, 0.0F);
                     entityinsentient1.applyComponentsFromItemStack(itemstack);
-                    worldserver.addFreshEntityWithPassengers(entityinsentient1);
+                    worldserver.addFreshEntityWithPassengers(entityinsentient1, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.SPAWNER_EGG); // CraftBukkit
                     itemstack.consume(1, entityhuman);
                     return Optional.of(entityinsentient1);
                 }