AuthBack

Evidence

Ran on Kiln's test stand (2026-11-04): AuthBackClientInitializer did not start: java.lang.NoClassDefFoundError: com/mojang/authlib/minecraft/client/ObjectMapper.

What it needs from Kiln

• an access widener
• Mixin
• com.mojang.authlib.minecraft.client.ObjectMapper
• com.mojang.authlib.properties.PropertyMap
• com.mojang.authlib.properties.PropertyMap.Serializer
• com.mojang.authlib.services.response.ProfileSearchResultsResponse
• com.mojang.authlib.services.response.ProfileSearchResultsResponse.Serializer
• com.mojang.util.ByteBufferTypeAdapter
• com.mojang.util.UUIDTypeAdapter
• io.netty.buffer.Unpooled
• net.fabricmc.fabric.api.client.networking.v1.ClientConfigurationNetworking
• net.fabricmc.fabric.api.client.networking.v1.ClientConfigurationNetworking.ConfigurationPayloadHandler
• net.fabricmc.fabric.api.client.networking.v1.ClientConfigurationNetworking.Context
• net.fabricmc.fabric.api.client.networking.v1.ClientLoginNetworking
• net.fabricmc.fabric.api.client.networking.v1.ClientLoginNetworking.LoginQueryRequestHandler
• net.fabricmc.fabric.api.networking.v1.PayloadTypeRegistry
• net.minecraft.client.User
• net.minecraft.client.multiplayer.ClientConfigurationPacketListenerImpl
• net.minecraft.network.FriendlyByteBuf
• net.minecraft.network.protocol.common.ServerboundCustomPayloadPacket
• net.minecraft.network.protocol.common.custom.CustomPacketPayload
• net.minecraft.network.protocol.common.custom.CustomPacketPayload.Type
• net.minecraft.network.protocol.common.custom.CustomPacketPayload.TypeAndCodec
• org.apache.commons.lang3.function.TriConsumer
• org.apache.commons.lang3.function.TriFunction
• Minecraft.getUser()

On the roadmap: Minecraft's libraries and client API (0.2), Code next to data (0.3), Mixin (0.5)

In the author's words

Allows you play normally even when authentication servers are down

Scan

Scanned on 4 November 2026 against Kiln 0.2.0, file authback-1.9.0.jar. The scan reads the mod's classes; it does not run them.