2

Uncaught exception in thread "main"

hahaiamdr3w 12/25/25 7:11 pm
366
1/2/2026 10:40 am
Hi, I'm trying to launch minecraft with the normal launcher (i normally use feather), so I can hack on 2b2t.

When i try to launch it, it says this:




Uncaught exception in thread "main"
java.lang.RuntimeException: Mixin transformation of net.minecraft.client.main.Main failed
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.getPostMixinClassByteArray(KnotClassDelegate.java:440)
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.tryLoadClass(KnotClassDelegate.java:336)
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.loadClass(KnotClassDelegate.java:231)
at net.fabricmc.loader.impl.launch.knot.KnotClassLoader.loadClass(KnotClassLoader.java:119)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:526)
at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.launch(MinecraftGameProvider.java:507)
at net.fabricmc.loader.impl.launch.knot.Knot.launch(Knot.java:72)
at net.fabricmc.loader.impl.launch.knot.KnotClient.main(KnotClient.java:23)
Caused by: java.lang.NoClassDefFoundError: feather/lib/sentry/Sentry
at knot//net.digitalingot.feather.zb.sa(FeatherSourceFile:84)
at knot//net.digitalingot.feather.mixin.FeatherMixinPlugin.onLoad(FeatherSourceFile:69)
at org.spongepowered.asm.mixin.transformer.PluginHandle.onLoad(PluginHandle.java:119)
at org.spongepowered.asm.mixin.transformer.MixinConfig.onSelect(MixinConfig.java:790)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.selectConfigs(MixinProcessor.java:546)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.select(MixinProcessor.java:508)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.checkSelect(MixinProcessor.java:486)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.lockAndSelect(MixinProcessor.java:438)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.couldTransformClass(MixinProcessor.java:398)
at org.spongepowered.asm.mixin.transformer.MixinTransformer.couldTransformClass(MixinTransformer.java:265)
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClass(MixinTransformer.java:233)
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClassBytes(MixinTransformer.java:202)
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.getPostMixinClassByteArray(KnotClassDelegate.java:435)
... 7 more
Caused by: java.lang.ClassNotFoundException: feather.lib.sentry.Sentry
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:526)
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.loadClass(KnotClassDelegate.java:239)
at net.fabricmc.loader.impl.launch.knot.KnotClassLoader.loadClass(KnotClassLoader.java:119)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:526)
... 20 more

Can someone please fix this
Note: i found the problem, it was that i had featherfabric in there
Posted by
hahaiamdr3w
Level 14 : Journeyman Warrior
0

  Have something to say?

JoinSign in

2

Morabon
12/28/2025 9:21 pm
Level 1 : New Crafter
мне нужен ответ на ето пиши как человек ето для форума

Ah, yep, that makes sense!

The error is because the normal launcher is trying to load Feather mods (like featherfabric), which rely on their own libraries and mixins. When you remove featherfabric, the game launches fine because the vanilla launcher doesn’t need Feather’s classes.


Basically: don’t keep Feather mods in your .minecraft/mods folder if you’re launching with the normal launcher. Those mods are specifically for Feather clients, so they’ll always cause mixin/class errors outside of Feather.


If you want to hack on 2b2t using the normal launcher, just keep it clean with only vanilla or Fabric/Forge mods that are compatible with vanilla. Anything Feather-specific needs to stay out.
2
hahaiamdr3w
01/02/2026 10:40 am
Level 14 : Journeyman Warrior
Oh ty
2

Welcome