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NeoForge 1.21.9 incompatability #5670

Description

@Romaq

Operating System

Windows

Description of bug

On MultiMC V 0.7.0-4235 win32, I'm attempting to set up a NeoForge instance, but I get the following error:

Using onesix launcher.

Failed to start Minecraft:
java.lang.NoClassDefFoundError: cpw/mods/modlauncher/Launcher

Steps to reproduce

Create an instance named "1.21.9 w NeoForge"
Edit Instance on the Version panel
Note: "Minecraft version 1.21.9"

Install NeoForge v. 21.9.9-beta
Note: Version 21.9.0-beta through 21.9.9-beta do not appear to work

Launch

Suspected cause

I'm guessing NeoForge altered a class that causes cpw.mods.modlauncher.Launcher to freak out.

I'm happy to supply detailed log info if this can not be reproduced or the cause appears unknown.

This issue is unique

  • I have searched the issue tracker and did not find an issue describing my bug.

EDIT

I should note the above actions cause no issues with MC+NeoForge for 1.21.8, and the NeoForge change log https://neoforged.net/news/21.9release does suggest major changes that may be causing problems for the launcher.

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