NoSuchMethodError: CraftAttribute.minecraftToBukkit - Paper 1.21.11 Remapping Removal

[xKlezee]

• This issue is not solved in a development build

Describe the bug
Recent Paper/ASP updates (1.21.11, Build 17060) have removed the runtime reflection remapping. This causes ProtocolLib to fail when attempting to access legacy NMS methods. Specifically, it throws a java.lang.NoSuchMethodError for org.bukkit.craftbukkit.attribute.CraftAttribute.minecraftToBukkit. Additionally, a RuntimeException occurs because the WorldType NMS class cannot be found.

To Reproduce
Steps to reproduce the behavior:
Use AdvancedSlimePaper (or Upstream Paper) build 1.21.11-17060 or newer.
Install ProtocolLib (Build f606cc9 or similar).
Start the server and attempt to join with a player.

See the Internal Exception kick and the NoSuchMethodError in the console logs during the PlayerLoginEvent (specifically the HorriblePlayerLoginEventHack).

Expected behavior
ProtocolLib should be able to handle the new R7/Mojang Mappings for Attributes and World classes without depending on the now-removed Paper runtime remapper.

ProtocolLib Dump
Timestamp: 03/26/26 08:37:27

ProtocolLib Version: ProtocolLib v5.4.1-SNAPSHOT-19cb81b
Bukkit Version: 1.21.11-R0.1-SNAPSHOT
Server Version: 1.21.11-17059-496f794 (MC: 1.21.11)
Java Version: 21.0.10

ProtocolLib: com.comphenix.protocol.ProtocolLib@3fdd3072[
statistics=com.comphenix.protocol.metrics.Statistics@265d3f2e
packetTask=com.comphenix.protocol.scheduler.DefaultTask@64f46a1f
tickCounter=2
configExpectedMod=1
updater=com.comphenix.protocol.updater.SpigotUpdater@1835530f
redirectHandler=com.comphenix.protocol.ProtocolLib$2@1d64c7d
scheduler=com.comphenix.protocol.scheduler.DefaultScheduler@46357aca
commandProtocol=com.comphenix.protocol.CommandProtocol@742af428
commandPacket=com.comphenix.protocol.CommandPacket@57c2d700
commandFilter=com.comphenix.protocol.CommandFilter@64c4cc21
packetLogging=com.comphenix.protocol.PacketLogging@9ca1959
skipDisable=false
isEnabled=true
loader=io.papermc.paper.plugin.manager.DummyBukkitPluginLoader@2ae227fc
server=CraftServer{serverName=AdvancedSlimePaper,serverVersion=1.21.11-17059-496f794,minecraftVersion=1.21.11}
file=plugins\ProtocolLib.jar
description=org.bukkit.plugin.PluginDescriptionFile@29bee3e9
pluginMeta=org.bukkit.plugin.PluginDescriptionFile@29bee3e9
dataFolder=plugins\ProtocolLib
classLoader=PluginClassLoader{plugin=ProtocolLib v5.4.1-SNAPSHOT-19cb81b, pluginEnabled=true, url=plugins\ProtocolLib.jar}
naggable=true
newConfig=YamlConfiguration[path='', root='YamlConfiguration']
configFile=plugins\ProtocolLib\config.yml
logger=com.destroystokyo.paper.utils.PaperPluginLogger@4b812371
lifecycleEventManager=io.papermc.paper.plugin.lifecycle.event.PaperLifecycleEventManager@6c843f51
allowsLifecycleRegistration=false
isBeingEnabled=false
]
Manager: com.comphenix.protocol.injector.PacketFilterManager@32fb2883[
plugin=ProtocolLib v5.4.1-SNAPSHOT-19cb81b
server=CraftServer{serverName=AdvancedSlimePaper,serverVersion=1.21.11-17059-496f794,minecraftVersion=1.21.11}
reporter=com.comphenix.protocol.ProtocolLib$1@7beff40d
minecraftVersion=(MC: 1.21.11)
asyncFilterManager=com.comphenix.protocol.async.AsyncFilterManager@39b7caaa
pluginVerifier=com.comphenix.protocol.injector.PluginVerifier@7404147a
mainThreadPacketTypes=com.comphenix.protocol.concurrent.PacketTypeListenerSet@1f509549
inboundListeners=com.comphenix.protocol.injector.collection.InboundPacketListenerSet@1b1b5532
outboundListeners=com.comphenix.protocol.injector.collection.OutboundPacketListenerSet@1cfe3e61
registeredListeners=[PacketAdapter[plugin=ItemsAdder, sending=EMPTY_WHITELIST, receiving=ListeningWhitelist[priority=MONITOR, packets=[USE_ENTITY[class=ServerboundInteractPacket, id=25]], gamephase=PLAYING, options=[]]], PacketAdapter[plugin=ItemsAdder, sending=ListeningWhitelist[priority=NORMAL, packets=[CHAT[class=ClientboundPlayerChatPacket, id=63]], gamephase=PLAYING, options=[ASYNC]], receiving=EMPTY_WHITELIST], PacketAdapter[plugin=ItemsAdder, sending=EMPTY_WHITELIST, receiving=ListeningWhitelist[priority=NORMAL, packets=[BLOCK_DIG[class=ServerboundPlayerActionPacket, id=40]], gamephase=PLAYING, options=[]]], PacketAdapter[plugin=ItemsAdder, sending=EMPTY_WHITELIST, receiving=ListeningWhitelist[priority=NORMAL, packets=[UPDATE_SIGN[class=ServerboundSignUpdatePacket, id=59]], gamephase=PLAYING, options=[]]], PacketAdapter[plugin=ItemsAdder, sending=EMPTY_WHITELIST, receiving=ListeningWhitelist[priority=NORMAL, packets=[LOOK[class=Rot, id=31], POSITION_LOOK[class=PosRot, id=30], POSITION[class=Pos, id=29]], gamephase=PLAYING, options=[ASYNC]]], PacketAdapter[plugin=PlayerAuctions, sending=EMPTY_WHITELIST, receiving=ListeningWhitelist[priority=NORMAL, packets=[UPDATE_SIGN[class=ServerboundSignUpdatePacket, id=59]], gamephase=PLAYING, options=[]]], PacketAdapter[plugin=ItemsAdder, sending=ListeningWhitelist[priority=HIGHEST, packets=[ENTITY_EQUIPMENT[class=ClientboundSetEquipmentPacket, id=100], SET_SLOT[class=ClientboundContainerSetSlotPacket, id=20]], gamephase=PLAYING, options=[]], receiving=EMPTY_WHITELIST], PacketAdapter[plugin=ItemsAdder, sending=ListeningWhitelist[priority=HIGHEST, packets=[ADD_RESOURCE_PACK[class=ClientboundResourcePackPushPacket, id=79], ADD_RESOURCE_PACK[class=ClientboundResourcePackPushPacket, id=9]], gamephase=PLAYING, options=[]], receiving=EMPTY_WHITELIST], PacketAdapter[plugin=ItemsAdder, sending=EMPTY_WHITELIST, receiving=ListeningWhitelist[priority=NORMAL, packets=[PICK_ITEM_FROM_BLOCK[class=ServerboundPickItemFromBlockPacket, id=35]], gamephase=PLAYING, options=[]]], PacketAdapter[plugin=ItemsAdder, sending=ListeningWhitelist[priority=HIGHEST, packets=[MOUNT[class=ClientboundSetPassengersPacket, id=105]], gamephase=PLAYING, options=[]], receiving=EMPTY_WHITELIST], PacketAdapter[plugin=ItemsAdder, sending=ListeningWhitelist[priority=HIGHEST, packets=[RESPAWN[class=ClientboundRespawnPacket, id=80]], gamephase=PLAYING, options=[]], receiving=EMPTY_WHITELIST], PacketAdapter[plugin=ItemsAdder, sending=EMPTY_WHITELIST, receiving=ListeningWhitelist[priority=NORMAL, packets=[BLOCK_DIG[class=ServerboundPlayerActionPacket, id=40]], gamephase=PLAYING, options=[]]], PacketAdapter[plugin=ItemsAdder, sending=ListeningWhitelist[priority=NORMAL, packets=[SYSTEM_CHAT[class=ClientboundSystemChatPacket, id=119], SET_ACTION_BAR_TEXT[class=ClientboundSetActionBarTextPacket, id=85]], gamephase=PLAYING, options=[ASYNC]], receiving=EMPTY_WHITELIST], PacketAdapter[plugin=ItemsAdder, sending=ListeningWhitelist[priority=NORMAL, packets=[NAMED_SOUND_EFFECT[class=ClientboundSoundPacket, id=115]], gamephase=PLAYING, options=[]], receiving=EMPTY_WHITELIST], PacketAdapter[plugin=ItemsAdder, sending=ListeningWhitelist[priority=HIGH, packets=[OPEN_WINDOW[class=ClientboundOpenScreenPacket, id=57]], gamephase=PLAYING, options=[ASYNC]], receiving=EMPTY_WHITELIST], PacketAdapter[plugin=ItemsAdder, sending=ListeningWhitelist[priority=LOWEST, packets=[RECIPE_BOOK_ADD[class=ClientboundRecipeBookAddPacket, id=72]], gamephase=PLAYING, options=[]], receiving=EMPTY_WHITELIST], PacketAdapter[plugin=ItemsAdder, sending=EMPTY_WHITELIST, receiving=ListeningWhitelist[priority=NORMAL, packets=[STEER_VEHICLE[class=ServerboundPlayerInputPacket, id=42]], gamephase=PLAYING, options=[]]], PacketAdapter[plugin=ItemsAdder, sending=EMPTY_WHITELIST, receiving=ListeningWhitelist[priority=NORMAL, packets=[BLOCK_DIG[class=ServerboundPlayerActionPacket, id=40]], gamephase=PLAYING, options=[]]], PacketAdapter[plugin=ItemsAdder, sending=ListeningWhitelist[priority=NORMAL, packets=[SYSTEM_CHAT[class=ClientboundSystemChatPacket, id=119]], gamephase=PLAYING, options=[ASYNC]], receiving=EMPTY_WHITELIST], PacketAdapter[plugin=ItemsAdder, sending=ListeningWhitelist[priority=NORMAL, packets=[OPEN_WINDOW_MERCHANT[class=ClientboundMerchantOffersPacket, id=50]], gamephase=PLAYING, options=[]], receiving=EMPTY_WHITELIST], PacketAdapter[plugin=WorldGuardExtraFlagsPlus, sending=ListeningWhitelist[priority=NORMAL, packets=[REMOVE_ENTITY_EFFECT[class=ClientboundRemoveMobEffectPacket, id=76]], gamephase=PLAYING, options=[]], receiving=EMPTY_WHITELIST], PacketAdapter[plugin=ItemsAdder, sending=ListeningWhitelist[priority=NORMAL, packets=[CHAT[class=ClientboundPlayerChatPacket, id=63]], gamephase=PLAYING, options=[ASYNC]], receiving=EMPTY_WHITELIST], PacketAdapter[plugin=ItemsAdder, sending=EMPTY_WHITELIST, receiving=ListeningWhitelist[priority=NORMAL, packets=[TR_SEL[class=ServerboundSelectTradePacket, id=50]], gamephase=PLAYING, options=[]]], PacketAdapter[plugin=ItemsAdder, sending=ListeningWhitelist[priority=NORMAL, packets=[DISGUISED_CHAT[class=ClientboundDisguisedChatPacket, id=33]], gamephase=PLAYING, options=[ASYNC]], receiving=EMPTY_WHITELIST]]
networkManagerInjector=com.comphenix.protocol.injector.netty.manager.NetworkManagerInjector@480d4e40
debug=true
closed=false
injected=true
]

Listeners:
itemsadder.m.ef@322cbb48[
plugin=ItemsAdder v4.0.16
connectionSide=CLIENT_SIDE
receivingWhitelist=ListeningWhitelist[priority=MONITOR, packets=[USE_ENTITY[class=ServerboundInteractPacket, id=25]], gamephase=PLAYING, options=[]]
sendingWhitelist=EMPTY_WHITELIST
]
itemsadder.m.hv@27971bb0[
tc=itemsadder.m.hu@6d78a313
plugin=ItemsAdder v4.0.16
connectionSide=SERVER_SIDE
receivingWhitelist=EMPTY_WHITELIST
sendingWhitelist=ListeningWhitelist[priority=NORMAL, packets=[CHAT[class=ClientboundPlayerChatPacket, id=63]], gamephase=PLAYING, options=[ASYNC]]
]
itemsadder.m.xf@75052f4d[
plugin=ItemsAdder v4.0.16
connectionSide=CLIENT_SIDE
receivingWhitelist=ListeningWhitelist[priority=NORMAL, packets=[BLOCK_DIG[class=ServerboundPlayerActionPacket, id=40]], gamephase=PLAYING, options=[]]
sendingWhitelist=EMPTY_WHITELIST
]
itemsadder.m.xp@5d281540[
Pj=itemsadder.m.xo@4c06221a
plugin=ItemsAdder v4.0.16
connectionSide=CLIENT_SIDE
receivingWhitelist=ListeningWhitelist[priority=NORMAL, packets=[UPDATE_SIGN[class=ServerboundSignUpdatePacket, id=59]], gamephase=PLAYING, options=[]]
sendingWhitelist=EMPTY_WHITELIST
]
itemsadder.m.ais@70a7f3ef[
abx=itemsadder.m.air@644e60b2
plugin=ItemsAdder v4.0.16
connectionSide=CLIENT_SIDE
receivingWhitelist=ListeningWhitelist[priority=NORMAL, packets=[LOOK[class=Rot, id=31], POSITION_LOOK[class=PosRot, id=30], POSITION[class=Pos, id=29]], gamephase=PLAYING, options=[ASYNC]]
sendingWhitelist=EMPTY_WHITELIST
]
com.olziedev.playerauctions.j.b.b$1@1b6f6947[
plugin=PlayerAuctions v1.33.0
connectionSide=CLIENT_SIDE
receivingWhitelist=ListeningWhitelist[priority=NORMAL, packets=[UPDATE_SIGN[class=ServerboundSignUpdatePacket, id=59]], gamephase=PLAYING, options=[]]
sendingWhitelist=EMPTY_WHITELIST
]
itemsadder.m.ee@241c4774[
plugin=ItemsAdder v4.0.16
connectionSide=SERVER_SIDE
receivingWhitelist=EMPTY_WHITELIST
sendingWhitelist=ListeningWhitelist[priority=HIGHEST, packets=[ENTITY_EQUIPMENT[class=ClientboundSetEquipmentPacket, id=100], SET_SLOT[class=ClientboundContainerSetSlotPacket, id=20]], gamephase=PLAYING, options=[]]
]
itemsadder.m.arr@c1d848[
ahp=itemsadder.m.arv@3f40db55
plugin=ItemsAdder v4.0.16
connectionSide=SERVER_SIDE
receivingWhitelist=EMPTY_WHITELIST
sendingWhitelist=ListeningWhitelist[priority=HIGHEST, packets=[ADD_RESOURCE_PACK[class=ClientboundResourcePackPushPacket, id=79], ADD_RESOURCE_PACK[class=ClientboundResourcePackPushPacket, id=9]], gamephase=PLAYING, options=[]]
]
itemsadder.m.ku@d81c9ac[
plugin=ItemsAdder v4.0.16
connectionSide=CLIENT_SIDE
receivingWhitelist=ListeningWhitelist[priority=NORMAL, packets=[PICK_ITEM_FROM_BLOCK[class=ServerboundPickItemFromBlockPacket, id=35]], gamephase=PLAYING, options=[]]
sendingWhitelist=EMPTY_WHITELIST
]
itemsadder.m.eg@334ee300[
plugin=ItemsAdder v4.0.16
connectionSide=SERVER_SIDE
receivingWhitelist=EMPTY_WHITELIST
sendingWhitelist=ListeningWhitelist[priority=HIGHEST, packets=[MOUNT[class=ClientboundSetPassengersPacket, id=105]], gamephase=PLAYING, options=[]]
]
itemsadder.m.ei@6fa6b9c8[
plugin=ItemsAdder v4.0.16
connectionSide=SERVER_SIDE
receivingWhitelist=EMPTY_WHITELIST
sendingWhitelist=ListeningWhitelist[priority=HIGHEST, packets=[RESPAWN[class=ClientboundRespawnPacket, id=80]], gamephase=PLAYING, options=[]]
]
itemsadder.m.ko@51d35a9c[
wY=itemsadder.m.kn@42ab3855
plugin=ItemsAdder v4.0.16
connectionSide=CLIENT_SIDE
receivingWhitelist=ListeningWhitelist[priority=NORMAL, packets=[BLOCK_DIG[class=ServerboundPlayerActionPacket, id=40]], gamephase=PLAYING, options=[]]
sendingWhitelist=EMPTY_WHITELIST
]
itemsadder.m.hw@3db9694[
td=itemsadder.m.hu@6d78a313
plugin=ItemsAdder v4.0.16
connectionSide=SERVER_SIDE
receivingWhitelist=EMPTY_WHITELIST
sendingWhitelist=ListeningWhitelist[priority=NORMAL, packets=[SYSTEM_CHAT[class=ClientboundSystemChatPacket, id=119], SET_ACTION_BAR_TEXT[class=ClientboundSetActionBarTextPacket, id=85]], gamephase=PLAYING, options=[ASYNC]]
]
itemsadder.m.kb@a8d7cf8[
wp=itemsadder.m.ka@55779b42
plugin=ItemsAdder v4.0.16
connectionSide=SERVER_SIDE
receivingWhitelist=EMPTY_WHITELIST
sendingWhitelist=ListeningWhitelist[priority=NORMAL, packets=[NAMED_SOUND_EFFECT[class=ClientboundSoundPacket, id=115]], gamephase=PLAYING, options=[]]
]
itemsadder.m.vi@43825994[
plugin=ItemsAdder v4.0.16
connectionSide=SERVER_SIDE
receivingWhitelist=EMPTY_WHITELIST
sendingWhitelist=ListeningWhitelist[priority=HIGH, packets=[OPEN_WINDOW[class=ClientboundOpenScreenPacket, id=57]], gamephase=PLAYING, options=[ASYNC]]
]
itemsadder.m.and@55d38144[
plugin=ItemsAdder v4.0.16
connectionSide=SERVER_SIDE
receivingWhitelist=EMPTY_WHITELIST
sendingWhitelist=ListeningWhitelist[priority=LOWEST, packets=[RECIPE_BOOK_ADD[class=ClientboundRecipeBookAddPacket, id=72]], gamephase=PLAYING, options=[]]
]
itemsadder.m.jt@3197d3ef[
plugin=ItemsAdder v4.0.16
connectionSide=CLIENT_SIDE
receivingWhitelist=ListeningWhitelist[priority=NORMAL, packets=[STEER_VEHICLE[class=ServerboundPlayerInputPacket, id=42]], gamephase=PLAYING, options=[]]
sendingWhitelist=EMPTY_WHITELIST
]
itemsadder.m.kc@6b38cf01[
wq=itemsadder.m.ka@55779b42
plugin=ItemsAdder v4.0.16
connectionSide=CLIENT_SIDE
receivingWhitelist=ListeningWhitelist[priority=NORMAL, packets=[BLOCK_DIG[class=ServerboundPlayerActionPacket, id=40]], gamephase=PLAYING, options=[]]
sendingWhitelist=EMPTY_WHITELIST
]
itemsadder.m.vg@53dac863[
Nc=itemsadder.m.ve@32ad25f5
plugin=ItemsAdder v4.0.16
connectionSide=SERVER_SIDE
receivingWhitelist=EMPTY_WHITELIST
sendingWhitelist=ListeningWhitelist[priority=NORMAL, packets=[SYSTEM_CHAT[class=ClientboundSystemChatPacket, id=119]], gamephase=PLAYING, options=[ASYNC]]
]
itemsadder.m.ad@2456d9f[
plugin=ItemsAdder v4.0.16
connectionSide=SERVER_SIDE
receivingWhitelist=EMPTY_WHITELIST
sendingWhitelist=ListeningWhitelist[priority=NORMAL, packets=[OPEN_WINDOW_MERCHANT[class=ClientboundMerchantOffersPacket, id=50]], gamephase=PLAYING, options=[]]
]
dev.tins.worldguardextraflagsplus.protocollib.RemoveEffectPacketListener@3b47529[
plugin=WorldGuardExtraFlagsPlus v4.3.11
connectionSide=SERVER_SIDE
receivingWhitelist=EMPTY_WHITELIST
sendingWhitelist=ListeningWhitelist[priority=NORMAL, packets=[REMOVE_ENTITY_EFFECT[class=ClientboundRemoveMobEffectPacket, id=76]], gamephase=PLAYING, options=[]]
]
itemsadder.m.vh@4621f95c[
plugin=ItemsAdder v4.0.16
connectionSide=SERVER_SIDE
receivingWhitelist=EMPTY_WHITELIST
sendingWhitelist=ListeningWhitelist[priority=NORMAL, packets=[CHAT[class=ClientboundPlayerChatPacket, id=63]], gamephase=PLAYING, options=[ASYNC]]
]
itemsadder.m.ae@145867a6[
fD=itemsadder.m.ac@5be91569
plugin=ItemsAdder v4.0.16
connectionSide=CLIENT_SIDE
receivingWhitelist=ListeningWhitelist[priority=NORMAL, packets=[TR_SEL[class=ServerboundSelectTradePacket, id=50]], gamephase=PLAYING, options=[]]
sendingWhitelist=EMPTY_WHITELIST
]
itemsadder.m.vf@19869698[
Nb=itemsadder.m.ve@32ad25f5
plugin=ItemsAdder v4.0.16
connectionSide=SERVER_SIDE
receivingWhitelist=EMPTY_WHITELIST
sendingWhitelist=ListeningWhitelist[priority=NORMAL, packets=[DISGUISED_CHAT[class=ClientboundDisguisedChatPacket, id=33]], gamephase=PLAYING, options=[ASYNC]]
]

Plugins Using ProtocolLib:
WorldGuardExtraFlagsPlus by [tins, isokissa3]
PlayerAuctions by [Olzie]
ItemsAdder by [LoneDev]

Additional context
The server is running on Java 21. The issue seems to be a mismatch between the current NMS signatures in the server's JAR and the hardcoded reflection paths in ProtocolLib. Other plugins like ItemsAdder and ModelEngine are also being affected as a result of this network layer failure.

@dmulloy2

[xKlezee]

protocol debug:
[08:49:30 WARN]: [ProtocolLib] [Debug] Exception registering converter
java.lang.RuntimeException: Failed to find NMS class: WorldType
at ProtocolLib.jar//com.comphenix.protocol.utility.MinecraftReflection.lambda$getMinecraftClass$4(MinecraftReflection.java:1512) ~[?:?]
at java.base/java.util.Optional.orElseThrow(Optional.java:403) ~[?:?]
at ProtocolLib.jar//com.comphenix.protocol.utility.MinecraftReflection.getMinecraftClass(MinecraftReflection.java:1512) ~[?:?]
at ProtocolLib.jar//com.comphenix.protocol.utility.MinecraftReflection.getWorldTypeClass(MinecraftReflection.java:855) ~[?:?]
at ProtocolLib.jar//com.comphenix.protocol.wrappers.BukkitConverters.addConverter(BukkitConverters.java:1330) ~[?:?]
at ProtocolLib.jar//com.comphenix.protocol.wrappers.BukkitConverters.getConvertersForGeneric(BukkitConverters.java:1309) ~[?:?]
at ProtocolLib.jar//com.comphenix.protocol.wrappers.BukkitConverters.getUnwrappers(BukkitConverters.java:1350) ~[?:?]
at ProtocolLib.jar//com.comphenix.protocol.injector.PacketConstructor.(PacketConstructor.java:61) ~[?:?]
at ProtocolLib.jar//com.comphenix.protocol.injector.PacketConstructor.(PacketConstructor.java:46) ~[?:?]
at ProtocolLib.jar//com.comphenix.protocol.injector.BukkitUnwrapper.unwrapItem(BukkitUnwrapper.java:107) ~[?:?]
at ProtocolLib.jar//com.comphenix.protocol.utility.MinecraftFields.getNetworkManager(MinecraftFields.java:32) ~[?:?]
at ProtocolLib.jar//com.comphenix.protocol.injector.netty.channel.InjectionFactory.fromPlayer(InjectionFactory.java:98) ~[?:?]
at ProtocolLib.jar//com.comphenix.protocol.injector.netty.manager.NetworkManagerInjector.getInjector(NetworkManagerInjector.java:57) ~[?:?]
at ProtocolLib.jar//com.comphenix.protocol.injector.PacketFilterManager$1.handleLogin(PacketFilterManager.java:436) ~[?:?]
at co.aikar.timings.TimedEventExecutor.execute(TimedEventExecutor.java:80) ~[aspaper-api-1.21.11-R0.1-SNAPSHOT.jar:?]
at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:71) ~[aspaper-api-1.21.11-R0.1-SNAPSHOT.jar:?]
at io.papermc.paper.plugin.manager.PaperEventManager.callEvent(PaperEventManager.java:54) ~[aspaper-1.21.11.jar:1.21.11-17059-496f794]
at io.papermc.paper.plugin.manager.PaperPluginManagerImpl.callEvent(PaperPluginManagerImpl.java:131) ~[aspaper-1.21.11.jar:1.21.11-17059-496f794]
at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:628) ~[aspaper-api-1.21.11-R0.1-SNAPSHOT.jar:?]
at org.bukkit.event.Event.callEvent(Event.java:46) ~[aspaper-api-1.21.11-R0.1-SNAPSHOT.jar:?]
at io.papermc.paper.connection.HorriblePlayerLoginEventHack.execute(HorriblePlayerLoginEventHack.java:89) ~[aspaper-1.21.11.jar:1.21.11-17059-496f794]
at org.bukkit.craftbukkit.event.CraftEventFactory.handleLoginResult(CraftEventFactory.java:2302) ~[aspaper-1.21.11.jar:1.21.11-17059-496f794]
at net.minecraft.server.network.ServerLoginPacketListenerImpl.verifyLoginAndFinishConnectionSetup(ServerLoginPacketListenerImpl.java:209) ~[aspaper-1.21.11.jar:1.21.11-17059-496f794]
at net.minecraft.server.network.ServerLoginPacketListenerImpl.tick(ServerLoginPacketListenerImpl.java:97) ~[aspaper-1.21.11.jar:1.21.11-17059-496f794]
at net.minecraft.network.Connection.tick(Connection.java:573) ~[aspaper-1.21.11.jar:1.21.11-17059-496f794]
at net.minecraft.server.network.ServerConnectionListener.tick(ServerConnectionListener.java:230) ~[aspaper-1.21.11.jar:1.21.11-17059-496f794]
at net.minecraft.server.MinecraftServer.tickConnection(MinecraftServer.java:1870) ~[aspaper-1.21.11.jar:1.21.11-17059-496f794]
at net.minecraft.server.dedicated.DedicatedServer.tickConnection(DedicatedServer.java:549) ~[aspaper-1.21.11.jar:1.21.11-17059-496f794]
at net.minecraft.server.MinecraftServer.tickChildren(MinecraftServer.java:1833) ~[aspaper-1.21.11.jar:1.21.11-17059-496f794]
at net.minecraft.server.MinecraftServer.tickServer(MinecraftServer.java:1611) ~[aspaper-1.21.11.jar:1.21.11-17059-496f794]
at net.minecraft.server.dedicated.DedicatedServer.tickServer(DedicatedServer.java:427) ~[aspaper-1.21.11.jar:1.21.11-17059-496f794]
at net.minecraft.server.MinecraftServer.processPacketsAndTick(MinecraftServer.java:1667) ~[aspaper-1.21.11.jar:1.21.11-17059-496f794]
at net.minecraft.server.MinecraftServer.runServer(MinecraftServer.java:1335) ~[aspaper-1.21.11.jar:1.21.11-17059-496f794]
at net.minecraft.server.MinecraftServer.lambda$spin$2(MinecraftServer.java:388) ~[aspaper-1.21.11.jar:1.21.11-17059-496f794]
at java.base/java.lang.Thread.run(Thread.java:1583) ~[?:?]

[xKlezee]

The new Attribute is "minecraftholdertobukkit"