This is an extremely lightweight mod modifies the default Minecraft kick message for having an invalid session to better explain how to resolve the issue if using a game launcher.
As a modpack maintainer, this somehow remains one of the most common issues I have to explain to people so I hope improving the message will save everyone a lot of time.
Everything in the mod is configurable and it supports an alternate message if the player is using ReAuth.
By default it changes the normal message from
to
or with ReAuth installed...
This mod was created for the Voltz Community Modpack but anyone is free to use it in their modpack provided that credit is given by linking back to this page.