Internal Exception: io.netty.handler.codec.DecoderException: Failed to decode packet 'clientbound/minecraft:system_chat'

[asdassafas]

When a player shows an item and sends it to the chat box, only players in version 1.21.11 will be kicked out of the server and this message will be displayed.

I am currently using the latest version of viaproxy, and my server core is paper 1.12.2.

[RaphiMC]

Try reproducing the issue with the latest dev build: https://ci.viaversion.com/view/Platforms/job/ViaProxy/ and upload the ViaProxy and Minecraft log if it still happens

[asdassafas]

Try reproducing the issue with the latest dev build: https://ci.viaversion.com/view/Platforms/job/ViaProxy/ and upload the ViaProxy and Minecraft log if it still happens

Using plugins to display any pickaxes will result in the player being kicked out from version 1.21.11.
This is the client-side debugging.

disconnect-2026-07-23_19.30.34-client.txt

[asdassafas]

Try reproducing the issue with the latest dev build: https://ci.viaversion.com/view/Platforms/job/ViaProxy/ and upload the ViaProxy and Minecraft log if it still happens

I conducted another test. All I needed to do was to use the pickaxe to kill any player, display all the information of that pickaxe in the server chat box, and then I could kick out all the players in version 1.21.11.

[RaphiMC]

Should now be fixed in the latest dev build. Fix commit reference: ViaVersion/ViaVersion@2d78597