java.lang.OutOfMemoryError: Java heap space
at me.modmuss50.optifabric.patcher.ClassCache.read(ClassCache.java:94)
at me.modmuss50.optifabric.mod.OptifineSetup.getRuntime(OptifineSetup.java:77)
at me.modmuss50.optifabric.mod.OptifabricSetup.run(OptifabricSetup.java:41)
at com.chocohead.mm.Plugin$$Lambda$86/1594039997.accept(Unknown Source)
at java.util.ArrayList.forEach(Unknown Source)
at com.chocohead.mm.Plugin.getMixins(Plugin.java:340)
at org.spongepowered.asm.mixin.transformer.PluginHandle.getMixins(PluginHandle.java:128)
at org.spongepowered.asm.mixin.transformer.MixinConfig.postInitialise(MixinConfig.java:667)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.prepareConfigs(MixinProcessor.java:542)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.select(MixinProcessor.java:439)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.checkSelect(MixinProcessor.java:415)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.applyMixins(MixinProcessor.java:285)
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClass(MixinTransformer.java:208)
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClassBytes(MixinTransformer.java:178)
at org.spongepowered.asm.mixin.transformer.FabricMixinTransformerProxy.transformClassBytes(FabricMixinTransformerProxy.java:23)
at net.fabricmc.loader.launch.knot.KnotClassDelegate.getPostMixinClassByteArray(KnotClassDelegate.java:162)
at net.fabricmc.loader.launch.knot.KnotClassLoader.loadClass(KnotClassLoader.java:154)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at net.fabricmc.loader.util.DefaultLanguageAdapter.create(DefaultLanguageAdapter.java:50)
at net.fabricmc.loader.EntrypointStorage$NewEntry.lambda$getOrCreate$0(EntrypointStorage.java:106)
at net.fabricmc.loader.EntrypointStorage$NewEntry$$Lambda$72/483797427.apply(Unknown Source)
at java.util.HashMap.computeIfAbsent(Unknown Source)
at net.fabricmc.loader.EntrypointStorage$NewEntry.getOrCreate(EntrypointStorage.java:104)
at net.fabricmc.loader.EntrypointStorage.lambda$getEntrypointContainers$1(EntrypointStorage.java:191)
at net.fabricmc.loader.EntrypointStorage$$Lambda$71/1414967210.get(Unknown Source)
at net.fabricmc.loader.entrypoint.EntrypointContainerImpl.getEntrypoint(EntrypointContainerImpl.java:37)
at net.fabricmc.loader.entrypoint.minecraft.hooks.EntrypointUtils.invoke0(EntrypointUtils.java:47)
at net.fabricmc.loader.entrypoint.minecraft.hooks.EntrypointUtils.invoke(EntrypointUtils.java:33)
at net.fabricmc.loader.launch.knot.Knot.init(Knot.java:143)
at net.fabricmc.loader.launch.knot.KnotClient.main(KnotClient.java:28)

yea i am also having the same problem idk why this is happening i asked some people on reddit they told me to use different fabric mods which work as same as optifine so i guess that is the only solution

this isnt a issue with "optifabric" your out of memory on your client allocate more RAM to your minecraft if you cant? or dont know how this would be a support you would raise with the maker of your launcher

As mentioned above, this is from Minecraft not having enough RAM rather than an issue with OptiFabric