https://hastebin.com/ocinebeyaf.makefile

Happens when Cloth's config is clicked (via modlist or REI)

Please update / downgrade your cloth to your respective snapshot

They were already 19w14b, but Cloth Event API got updated 5 hours ago.
After updating Cloth Event API, the client doesn't boot:
java.lang.NoClassDefFoundError: me/shedaniel/cloth/api/ConfigScreenBuilder at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Unknown Source) at me.shedaniel.rei.RoughlyEnoughItemsCore.onInitializeClient(RoughlyEnoughItemsCore.java:96) at java.util.ArrayList.forEach(Unknown Source) at net.fabricmc.loader.entrypoint.hooks.EntrypointClient.start(EntrypointClient.java:35) at net.minecraft.class_310.method_1503(class_310.java) at net.minecraft.class_310.method_1514(class_310.java:395) at net.minecraft.client.main.Main.main(Main.java:154) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at net.fabricmc.loader.launch.knot.Knot.init(Knot.java:130) at net.fabricmc.loader.launch.knot.KnotClient.main(KnotClient.java:26) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.multimc.onesix.OneSixLauncher.launchWithMainClass(OneSixLauncher.java:196) at org.multimc.onesix.OneSixLauncher.launch(OneSixLauncher.java:231) at org.multimc.EntryPoint.listen(EntryPoint.java:143) at org.multimc.EntryPoint.main(EntryPoint.java:34) Caused by: java.lang.ClassNotFoundException: me.shedaniel.cloth.api.ConfigScreenBuilder at java.net.URLClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at net.fabricmc.loader.launch.knot.KnotClassLoader.loadClass(KnotClassLoader.java:148) at java.lang.ClassLoader.loadClass(Unknown Source) ... 22 more

Also added Cloth Config API afterwards, but it doesn't change anything for the time being.

Cloth Config holds a different API, get versions before 0.3.0 in Cloth Event for now