Client disconnect when executing commands with lots of macros

Expected behavior

When executing a command with a high amount of macro inputs, the command should work fine and be executed.

Observed/Actual behavior

The client gets disconnected from the server with the following exception when executing the command:

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

Unfortunately, I was not able to get a proper stacktrace.

Steps/models to reproduce

Run a function that requires a large amount of macro inputs. The command used in my case belongs to my datapack and looks like this:

/function randomitemgiver:settings/save_item_settings {same_item: $(same_item), amount: $(amount), random_amount: $(random_amount), spawn_eggs: $(spawn_eggs), command_blocks: $(command_blocks), other_creatives: $(other_creatives), enchanted_books: $(enchanted_books), potions: $(potions), lingering_potions: $(lingering_potions), splash_potions: $(splash_potions), tipped_arrows: $(tipped_arrows), suspicious_stews: $(suspicious_stews), goat_horns: $(goat_horns), paintings: $(paintings), pottery_sherds: $(pottery_sherds), smithing_templates: $(smithing_templates)}

Plugin and Datapack List

The datapack used in my case was the "Random Item Giver Datapack" (https://github.com/Seeloewen/Random-Item-Giver-Datapack). The issue occurs when trying to save the item settings.

Paper version

This server is running Paper version 1.21.11-92-main@e7445e1 (2026-01-11T23:38:04Z) (Implementing API version 1.21.11-R0.1-SNAPSHOT)
You are running the latest version
Previous version: 1.21.11-85-ede8d0d (MC: 1.21.11)

Other

No response

Start by reproducing the issue with the Random Item Giver Datapack and the /function randomitemgiver:settings/save_item_settings command containing many macro inputs. Investigate the serverbound minecraft:chat_command decoding failure; done means the client stays connected and the command executes successfully with a large macro input set.