PaperMC/paper-server/nms-patches/net/minecraft/server/commands/CommandSummon.patch

--- a/net/minecraft/server/commands/CommandSummon.java
+++ b/net/minecraft/server/commands/CommandSummon.java
@@ -66,7 +66,7 @@
                     ((EntityInsentient) entity).prepare(commandlistenerwrapper.getWorld(), commandlistenerwrapper.getWorld().getDamageScaler(entity.getChunkCoordinates()), EnumMobSpawn.COMMAND, (GroupDataEntity) null, (NBTTagCompound) null);
                 }
 
-                if (!worldserver.addAllEntitiesSafely(entity)) {
+                if (!worldserver.addAllEntitiesSafely(entity, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.COMMAND)) { // CraftBukkit - pass a spawn reason of "COMMAND"
                     throw CommandSummon.ERROR_DUPLICATE_UUID.create();
                 } else {
                     commandlistenerwrapper.sendMessage(new ChatMessage("commands.summon.success", new Object[]{entity.getScoreboardDisplayName()}), true);