Describe
On Minecraft 1.21.1 with Advanced Peripherals 0.8.0a, a placed Chat Box can crash a dedicated server when it processes a chat message whose ChatMessageRecord.senderId() is null.
The crash occurs inside ChatBoxPeripheral.update() when Advanced Peripherals executes:
message.senderId().toString()
If the message has no associated player UUID, senderId() returns null and the server crashes with a NullPointerException.
This appears to affect server/system-generated chat messages rather than normal player chat.
Error
java.lang.NullPointerException:
Cannot invoke "java.util.UUID.toString()"
because the return value of
"de.srendi.advancedperipherals.common.events.Events$ChatMessageRecord.senderId()"
is null
at de.srendi.advancedperipherals.common.addons.computercraft.peripheral.ChatBoxPeripheral.lambda$update$5(ChatBoxPeripheral.java:538)
The relevant source is effectively:
queueEvent(
CCEvents.CHAT,
message.senderId().toString(),
message.senderName(),
message.message(),
message.isHidden(),
StringUtil.utf8ToByteString(message.message())
);There is currently no null check before calling .toString().
Observed trigger
On my dedicated server this has reproduced multiple times around server/system-generated chat messages. One particularly clean reproduction occurred immediately after a scheduled restart warning was broadcast:
[26Aug2026 06:17:07.367] [Server thread/INFO] [MinecraftServer]:
[Not Secure] [Server] Server will be restarting in 30 minutes.
[26Aug2026 06:17:07.419] [Server thread/ERROR]:
Encountered an unexpected exception
The crash occurred about 50 ms after the server-generated message.
I have also reproduced the same null-UUID exception on August 28, 2026 at 06:32:09, again at the same Chat Box and same AP code path.
Normal player chat does not appear to trigger the issue.
Steps to reproduce
The exact senderless-message source may depend on the server environment, but the apparent failure condition is:
- Run a Minecraft 1.21.1 dedicated NeoForge server.
- Install Advanced Peripherals
0.8.0a and CC:Tweaked.
- Place an Advanced Peripherals Chat Box.
- Use it from a CC:Tweaked computer so chat events are being consumed.
- Generate or receive a server/system chat message that has no player UUID associated with it.
- Allow the Chat Box to process that message.
- The server crashes when
ChatBoxPeripheral evaluates message.senderId().toString().
A server-host restart-warning broadcast has reliably triggered this on my server.
Expected behavior
A senderless/server-generated message should not crash the server.
Possible acceptable behaviors would include:
- queueing the event with an empty/sentinel UUID,
- exposing the sender UUID as optional/null in an appropriate way,
- or ignoring chat records that do not contain a sender UUID.
Actual behavior
The Chat Box block entity throws a NullPointerException while ticking, which terminates the Minecraft server.
One affected block:
advancedperipherals:chat_box
Block position: 136, 64, -255
The physical block itself does not appear corrupted. The failure occurs while processing the queued chat record.
Environment
Minecraft: 1.21.1
NeoForge: 21.1.248
Advanced Peripherals: 0.8.0a
CC:Tweaked: 1.120.0
Java: 21.0.12.x Eclipse Adoptium
Server type: Dedicated server
Multiplayer: Yes
OS: Linux
Additional information
This does not appear to be a CC:Tweaked Lua error. The exception occurs inside the Advanced Peripherals server-side Chat Box update code before the event can be safely delivered to the computer.
The important failure condition appears to be:
message.senderId() == null
followed by:
message.senderId().toString()
A defensive null check around senderId() in ChatBoxPeripheral.update() should prevent the dedicated-server crash.
I have reproduced the same senderId() == null exception on multiple occasions. I also tested a local mitigation mixin separately; that is not part of Advanced Peripherals and is not required to reproduce the underlying bug. I can attach the full crash report in a follow-up comment/attachment.
Describe
On Minecraft 1.21.1 with Advanced Peripherals
0.8.0a, a placed Chat Box can crash a dedicated server when it processes a chat message whoseChatMessageRecord.senderId()isnull.The crash occurs inside
ChatBoxPeripheral.update()when Advanced Peripherals executes:If the message has no associated player UUID,
senderId()returnsnulland the server crashes with aNullPointerException.This appears to affect server/system-generated chat messages rather than normal player chat.
Error
The relevant source is effectively:
There is currently no null check before calling
.toString().Observed trigger
On my dedicated server this has reproduced multiple times around server/system-generated chat messages. One particularly clean reproduction occurred immediately after a scheduled restart warning was broadcast:
The crash occurred about 50 ms after the server-generated message.
I have also reproduced the same null-UUID exception on August 28, 2026 at 06:32:09, again at the same Chat Box and same AP code path.
Normal player chat does not appear to trigger the issue.
Steps to reproduce
The exact senderless-message source may depend on the server environment, but the apparent failure condition is:
0.8.0aand CC:Tweaked.ChatBoxPeripheralevaluatesmessage.senderId().toString().A server-host restart-warning broadcast has reliably triggered this on my server.
Expected behavior
A senderless/server-generated message should not crash the server.
Possible acceptable behaviors would include:
Actual behavior
The Chat Box block entity throws a
NullPointerExceptionwhile ticking, which terminates the Minecraft server.One affected block:
The physical block itself does not appear corrupted. The failure occurs while processing the queued chat record.
Environment
Additional information
This does not appear to be a CC:Tweaked Lua error. The exception occurs inside the Advanced Peripherals server-side Chat Box update code before the event can be safely delivered to the computer.
The important failure condition appears to be:
followed by:
A defensive null check around
senderId()inChatBoxPeripheral.update()should prevent the dedicated-server crash.I have reproduced the same
senderId() == nullexception on multiple occasions. I also tested a local mitigation mixin separately; that is not part of Advanced Peripherals and is not required to reproduce the underlying bug. I can attach the full crash report in a follow-up comment/attachment.