Performance and fixes

Mixin apply for mod failed: find the mod and the build that fits

Mixin apply for mod lootr failed means a mod could not apply one of its mixins, the small patches mods use to change a method in Minecraft or in another mod, and the server stopped. The line names three things: the mod, the class it tried to change and what went wrong. When it says No candidates were found or could not find any targets, the method the patch was written for does not exist in the version on your server, and the fix is the build of the mod that matches your versions. This guide shows how to read the line on Fabric and NeoForge, which mixin warnings you can leave alone, and how to swap the file on Lodehost.

6 min read

Configure your serverPick a plan and order your server.

A grass island with a server tower, a stone block with a square socket, and a mint mod crate whose copper hook reaches past the block and misses the socket — A mixin hooks into one exact method. When that method is not there, the hook finds nothing and the server stops.

What "Mixin apply for mod failed" means

Mixin apply for mod failed means a mod could not apply one of its mixins, the patches it makes to Minecraft or to another mod, and the loader stopped the server. In the crash below it was Lootr on Minecraft 26.3:

Fabric 26.3, in the console

[main/ERROR]: Mixin apply for mod lootr failed lootr-common.mixins.json:accessor.AccessorMixinBlock from mod lootr -> net.minecraft.world.level.block.Block: ...
org.spongepowered.asm.mixin.gen.throwables.InvalidAccessorException: No candidates were found matching spawnDestroyParticles(Lnet/minecraft/world/level/Level;Lnet/minecraft/world/entity/player/Player;Lnet/minecraft/core/BlockPos;Lnet/minecraft/world/level/block/state/BlockState;)V in net/minecraft/world/level/block/Block for lootr-common.mixins.json:accessor.AccessorMixinBlock ...

Part of the line	What it tells you
`for mod lootr`	The mod that failed, here Lootr. This is the file to look at.
`lootr-common.mixins.json:accessor.AccessorMixinBlock`	Which of the mod's patches failed. Useful for the mod's author, not needed for the fix.
`-> net.minecraft.world.level.block.Block`	What it tried to change. A name that starts with `net.minecraft` is Minecraft itself.
`No candidates were found matching spawnDestroyParticles(...)`	What went wrong: the `Block` class on this server has no method by that name with those four arguments.

A mixin finds the method it changes by its exact name and arguments. When a Minecraft update renames that method or gives it other arguments, or the other mod it patches does, the mixin has nothing to attach to.

On Fabric for 1.21.11 and older, Minecraft's own classes show up as code names: net.minecraft.class_ followed by a number. From 26.1 on, Minecraft comes with readable names, which is why the target above reads net.minecraft.world.level.block.Block.

Critical injection failure: when the target is another mod

Critical injection failure means an @Inject patch in a mod found no method with the name it was written for, so it could not add its code. On a Fabric 1.21.11 server, the mod polymer_patch_for_servux stopped the start this way:

Fabric 1.21.11, in the console

[main/ERROR]: Mixin apply for mod polymer_patch_for_servux failed polymer_patch_for_servux.mixins.json:MixinServuxStructuresHandler from mod polymer_patch_for_servux -> fi.dy.masa.servux.network.packet.ServuxStructuresHandler: ...
org.spongepowered.asm.mixin.injection.throwables.InvalidInjectionException: Critical injection failure: @Inject annotation on beforeEncode could not find any targets matching 'encodeStructuresPacket' in fi/dy/masa/servux/network/packet/ServuxStructuresHandler. No refMap loaded. ...

Here the target after -> does not start with net.minecraft. fi.dy.masa.servux is Servux, a separate mod. The patch was written for a Servux that has a method called encodeStructuresPacket, and the Servux on this server has none. Minecraft's version is not the problem: the two mods do not match each other.

Target after the arrow	What does not match	What to change
Starts with `net.minecraft`	The mod and your Minecraft version	Install the build of the mod for your exact Minecraft version and loader
Another name, such as `fi.dy.masa.servux`	The mod and the mod it patches	Update both, or install the version of the other mod that this mod's page asks for

MixinTransformerError: "An unexpected critical error was encountered"

An unexpected critical error was encountered shows up in Fabric crashes such as the Minecraft 26.3 one above, as a Caused by: line under the stack of at lines. It only says that Mixin stopped, not why.

Fabric 26.3, further down the same crash

Caused by: org.spongepowered.asm.mixin.transformer.throwables.MixinTransformerError: An unexpected critical error was encountered

The mod is in the Mixin apply for mod line above it. The reason is in the last Caused by: line of the crash, such as No candidates were found or Critical injection failure. The crash report guide shows where those lines sit.

On NeoForge the crash can start with MixinApplyError instead, with the mod after from mod. The stage at the end, PREPARE or APPLY, only says when Mixin gave up. The first step is still to find the mod.

NeoForge 1.21.1, in the console

java.lang.RuntimeException: org.spongepowered.asm.mixin.throwables.MixinApplyError: Mixin [lowlustfusions.client.mixins.json:RegisterAbsoluteZeroEffectMixin from mod lowlustfusions] from phase [DEFAULT] in config [lowlustfusions.client.mixins.json] FAILED during PREPARE

How to fix Mixin apply failed on a Minecraft server

Fixing Mixin apply failed on a Minecraft server comes down to one file: the build of the mod named in the line. A mod build is made for one Minecraft release, so a file for 1.21.10 is not a file for 1.21.11. On Lodehost it goes like this:

Note the mod and the target
Open the Console tab, or the newest file in crash-reports on the Files tab, and find the Mixin apply for mod or MixinApplyError line. Note the mod after for mod or from mod, and the target after the arrow.
Compare the file with your versions
On the Mods tab, find the mod under Installed mods. If its file name mentions another Minecraft version or another loader than your server runs, that is the mismatch. With more than 20 mods, type part of the name in Filter installed mods above the list.
Swap in the build that fits
Press Remove next to the file. Then search the mod under Verified Modrinth catalog and press Verify & install. The catalog only offers stable server-side releases for exactly your loader and Minecraft version.
Match the other mod when the target is a mod
Update the mod it patches as well, or install the version that the mod's page asks for. For mods the panel installed, the Updates card on the Mods tab lists newer versions with an Update button.
Start the server and read the console again
If the same mod still fails on the right versions, the build may clash with another mod or have a bug of its own. Try another release of it, or take it off and send the line to the mod's author.

Players need the same version

When you swap a mod that players install too, such as one that adds blocks or items, they need the same build in their own game, or joining fails. Before you remove a mod for good, make a backup on the Backups tab: blocks and items from that mod can be lost once the world loads without it.

@Mixin target was not found: a warning, not the crash

@Mixin target ... was not found is a WARN line, not the crash: a mod carries a patch for something that is not installed, so Mixin leaves that patch out. On the Fabric 1.20.1 server below, the start went on after it.

Fabric 1.20.1, a warning

[main/WARN]: @Mixin target net.coderbot.iris.Iris was not found notenoughcrashes.fabric.mixins.json:iris.SilentNEC from mod notenoughcrashes

Here Not Enough Crashes has a patch for Iris, a shader mod that only runs on players' computers. Iris is not on the server, so the patch is skipped. Look for the ERROR line instead. When a crash names net.minecraft.class_310 or another part of the game client, see client-only mods.

Written and checked by the Lodehost team, last reviewed on 8 November 2026.

FAQ

Mixin crash questions

What does "Mixin apply for mod failed" mean?

A mod could not apply one of its patches to Minecraft or to another mod, so the server stopped. The mod is named after for mod, and the class it tried to change after the arrow.

What is a mixin in a Minecraft mod?

A small patch inside a mod that changes one method of the game, or of another mod, while it starts. Mods for Fabric, NeoForge and Forge can all use them.

What does "Critical injection failure" mean?

An @Inject patch in a mod found no method with the name it was written for. Check that the mod's build matches your Minecraft version, and the version of any mod it patches.

What does "An unexpected critical error was encountered" mean?

It is Mixin's general line for a patch that failed. The mod is in the Mixin apply for mod line above it, and the reason in the last Caused by line of the crash.