Already updated the Fabric API to fabric-api-0.46.2+1.18 and cloth-config-6.1.50-fabric.jar
Single is ok, but the server crashed.

[main/ERROR]: Minecraft has crashed!
net.fabricmc.loader.impl.FormattedException: java.lang.BootstrapMethodError: java.lang.RuntimeException: Mixin transformation of net.minecraft.class_1792 failed
at Not Enough Crashes deobfuscated stack trace.(1.18.1+build.22) ~[?:?]
at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.launch(MinecraftGameProvider.java:610) ~[fabric-loader-0.12.12.jar:?]
at net.fabricmc.loader.impl.launch.knot.Knot.launch(Knot.java:77) [fabric-loader-0.12.12.jar:?]
at net.fabricmc.loader.impl.launch.knot.KnotServer.main(KnotServer.java:23) [fabric-loader-0.12.12.jar:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?]
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?]
at net.fabricmc.loader.impl.launch.server.FabricServerLauncher.main(FabricServerLauncher.java:66) [fabric-loader-0.12.12.jar:?]
Caused by: java.lang.BootstrapMethodError: java.lang.RuntimeException: Mixin transformation of net.minecraft.class_1792 failed
at net.minecraft.util.registry.Registry.(Registry:177) ~[?:?]
at net.minecraft.Bootstrap.initialize(Bootstrap:49) ~[?:?]
at net.minecraft.server.Main.main(Main:101) ~[server-intermediary.jar:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?]
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?]
at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.launch(MinecraftGameProvider.java:608) ~[fabric-loader-0.12.12.jar:?]
... 7 more
Caused by: java.lang.RuntimeException: Mixin transformation of net.minecraft.class_1792 failed
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.getPostMixinClassByteArray(KnotClassDelegate.java:252) ~[fabric-loader-0.12.12.jar:?]
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.tryLoadClass(KnotClassDelegate.java:150) ~[fabric-loader-0.12.12.jar:?]
at net.fabricmc.loader.impl.launch.knot.KnotClassLoader.loadClass(KnotClassLoader.java:155) ~[fabric-loader-0.12.12.jar:?]
at java.lang.ClassLoader.loadClass(ClassLoader.java:520) ~[?:?]
at net.minecraft.util.registry.Registry.(Registry:177) ~[?:?]
at net.minecraft.Bootstrap.initialize(Bootstrap:49) ~[?:?]
at net.minecraft.server.Main.main(Main:101) ~[server-intermediary.jar:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?]
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?]
at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.launch(MinecraftGameProvider.java:608) ~[fabric-loader-0.12.12.jar:?]
... 7 more

What are all the mods you have? I will look into this today.

I found and fixed the crash, new version uploading soon.

If this crash persists, please reopen this issue.

Thanks for your prompt efficiency