Mixin failures

MixinTargetAlreadyLoadedException: Required Class Loaded Prematurely

What the log looks like

org\.spongepowered\.asm\.mixin\.transformer\.throwables\.MixinTargetAlreadyLoadedException
Sponge could not apply one or more patches\. A required class was loaded prematurely!
An essential class was loaded before Sponge could patch it

How to fix it

  1. Rename your SpongeForge JAR file in the mods folder so it begins with an underscore or 'aaa' (for example, '_spongeforge-1.10.2-...jar') to force Forge to load Sponge's Mixin tweaker before other coremods.
  2. Update SpongeForge and any coremods listed above the crash banner in your log (such as Applied Energistics 2) to the latest builds available for your Minecraft version.
  3. If you are running Applied Energistics 2 rv4-alpha on a 1.10.2 SpongeForge server, replace it with a newer AE2 release or a SpongeForge-compatible patched build, as early alpha builds prematurely load DummyModContainer.
  4. Check that your installed Forge server version matches the recommended Forge build number indicated in your SpongeForge JAR filename.
  5. If the error continues, temporarily remove other early-loading coremods shown in the log (such as CodeChickenCore or IC2) one by one to isolate which mod is triggering premature class loading.
LoadersForge, Server
SeverityStops the game
CategoryMixin failures

Check your own log

Related errors

Mixin failuresCritical injection failure — a mixin could not find its targetTwo mods are usually fighting over the same game methodMixin failuresInvalidMixinException: Mod Mixin Failed to ApplyOpen your latest.log or crash report and look for 'Mixin apply for mod' or the 'Config :' line inside the 'InvMixin failuresInvalidMixinException: Unexpecteded ClassMetadataNotFoundExceptionFind the line saying 'Mixin apply for mod <modname> failed' or 'from mod <modname>' right above the error in yMixin failuresMixin Transformation of net.minecraft.client.main.Main FailedOpen latest.log or the launcher crash output and look at the Caused by lines below Mixin transformation of netMixin failuresMixin apply failed — one mod could not patch the gameThe line names the mixin config, and its prefix is the mod id that brokeMixin failuresMixinExtras is missing or too oldUpdate the mod that needs it — modern mods bundle MixinExtras themselves