Description:
When a player joins the server, the Configurable mod tries to sync its configuration from the server to the client. On NeoForge 21.1.x this causes an error, since sending arbitrary payloads during the configuration phase is no longer allowed.

As a result, the login fails and the player is disconnected with "Invalid player data".

Steps to Reproduce:

Install configurable-3.2.3+1.21.1-neoforge.jar on server & client

Start a NeoForge 21.1.x server (tested on 21.1.203)

Try to join with a client

Observe disconnect

Expected Behavior:
The player should be able to join normally, or the config sync should be skipped if not supported.

Actual Behavior:
The player is disconnected during the configuration phase with this error:

java.lang.UnsupportedOperationException: Payload configurable:sync_config_payload may not be sent to the client!
at net.neoforged.neoforge.network.registration.NetworkRegistry.checkPacket(NetworkRegistry.java:446) ~[neoforge-21.1.203-universal.jar:?]
at net.minecraft.server.network.ServerCommonPacketListenerImpl.send(ServerCommonPacketListenerImpl.java:178) ~[server-1.21.1-20240808.144430-srg.jar:?]
...
[Server thread/INFO]: lost connection: Invalid player data

i hope this helps

Fixed in Configurable 3.2.4, you can update neruina too if you like as that just enforces the dep

It was caused by sending packets to clients that didn't have configurable's payload receiver registered - unrelated to configuration phase.

Now why would neo decide that's a good idea. I'll look into it shortly

Version 2.2.11 works fine, and only the new beta with Configurable is not working. Maybe there is a workaround, but I never tried one because the stable version works as intended.