[Bug] Vanilla client can't join a LAN server installed ViaFabricPlus

[Dainsleif233]

General Information

https://dump.viaversion.com/90b8bd3b6f3d19ccc14afae422524ed4059edfe77cda6dd46e079b4ac44511a4

Bug Description

The vanilla client log:

Client disconnected with reason: This server requires Fabric Loader and Fabric API installed on your client!
The following registry entry namespaces may be related:



Contact the server's administrator for more information!

Steps to Reproduce

1. Start a fabric client installed ViaFabricPlus, then host a lan world
2. Start a vanilla client, join the lan world

Expected Behavior

joined successfully

[Exterminate5573]

This is odd, something is sending Fabric and FAPI as client side mods that are required to join. I doubt this is a VFP issue have you tried this on normal Fabric?

[Dainsleif233]

This is odd, something is sending Fabric and FAPI as client side mods that are required to join. I doubt this is a VFP issue have you tried this on normal Fabric?

joined successfully on normal Fabric with only FAPI.
been blocked after adding VFP.
I tested on 1.21.5 & 1.21.8

[florianreuth]

I confirmed it's a VFP issue, see the label "S-confirmed". It's probably because of the footstep 1.12.2 particle we add Dainsleif ***@***.***> schrieb am Di., 19. Aug. 2025, 06:52:

…

*Dainsleif233* left a comment (ViaVersion/ViaFabricPlus#861) <#861 (comment)> This is odd, something is sending Fabric and FAPI as client side mods that are required to join. I doubt this is a VFP issue have you tried this on normal Fabric? joined successfully on normal Fabric — Reply to this email directly, view it on GitHub <#861 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AOKAS77KRJRIQ4UBA4WURGT3OKUPXAVCNFSM6AAAAACEBZG63GVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTCOJZGE4TONRTGM> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[Exterminate5573]

Its a bit odd that it shows Fabric Loader and FAPI as the issue not VFP but I don't know much about the LAN protocol