Legacy Bugs

Evidence

Ran on Kiln's test stand (2026-11-04): LegacyBugs did not start: java.lang.NoClassDefFoundError: net/minecraft/network/protocol/common/custom/CustomPacketPayload; LegacyBugsClient did not start: java.lang.NoClassDefFoundError: net/minecraft/network/protocol/common/custom/CustomPacketPayload.

What it needs from Kiln

• Mixin
• net.fabricmc.fabric.api.client.networking.v1.ClientPlayConnectionEvents
• net.fabricmc.fabric.api.client.networking.v1.ClientPlayConnectionEvents.Disconnect
• net.fabricmc.fabric.api.client.networking.v1.ClientPlayConnectionEvents.Join
• net.fabricmc.fabric.api.client.networking.v1.ClientPlayNetworking
• net.fabricmc.fabric.api.client.networking.v1.ClientPlayNetworking.Context
• net.fabricmc.fabric.api.client.networking.v1.ClientPlayNetworking.PlayPayloadHandler
• net.fabricmc.fabric.api.command.v2.CommandRegistrationCallback
• net.fabricmc.fabric.api.networking.v1.PayloadTypeRegistry
• net.fabricmc.fabric.api.networking.v1.ServerPlayNetworking
• net.fabricmc.fabric.api.networking.v1.ServerPlayNetworking.Context
• net.fabricmc.fabric.api.networking.v1.ServerPlayNetworking.PlayPayloadHandler
• net.minecraft.client.gui.components.Button
• net.minecraft.client.gui.components.Button.Builder
• net.minecraft.client.gui.components.Button.OnPress
• net.minecraft.commands.CommandSourceStack
• net.minecraft.commands.Commands
• net.minecraft.commands.Commands.CommandSelection
• net.minecraft.network.codec.ByteBufCodecs
• net.minecraft.network.codec.StreamCodec
• net.minecraft.network.protocol.common.custom.CustomPacketPayload
• net.minecraft.network.protocol.common.custom.CustomPacketPayload.Type
• net.minecraft.network.protocol.common.custom.CustomPacketPayload.TypeAndCodec
• net.minecraft.server.MinecraftServer
• net.minecraft.server.dedicated.DedicatedServer
• net.minecraft.server.permissions.PermissionLevel
• net.minecraft.server.permissions.PermissionSet
• net.minecraft.server.permissions.Permissions
• Font.width()
• Screen.extractBackground()
• Screen.extractRenderState()
• Screen.tick()
• Component.copy()
• ServerPlayer.checkPermission()

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

Restores selected historical Minecraft bugs as accurately as possible.

Scan

Scanned on 4 November 2026 against Kiln 0.2.0, file legacy-bugs-1.3.0.jar. The scan reads the mod's classes; it does not run them.