Music Triggers ReplayMod Compat

Client-side compat mod (Servers do not need it) for Minecraft 1.12.2 that stops Music Triggers from reacting to network traffic that ReplayMod plays back inside the replay viewer.

The problem

ReplayMod records every server-to-client packet, including the Forge custom-payload packets that Music Triggers (through The Impossible Library) uses to talk to its server half. When a replay is opened in the viewer, ReplayMod re-feeds those packets through an embedded netty pipeline. Music Triggers sees them as a live server talking to it, answers into a connection that does not exist, and the viewer disconnects a moment after it opens.

What this mod does

A single late mixin into ReplayMod's ReplayHandler#setup() inserts a small netty inbound handler into the replay pipeline, right before the vanilla packet_handler. Forge inserts its own fml:packet_handler at the same position later, so the final order is

replay sender -> mtreplaycompat_filter -> fml:packet_handler -> packet_handler

Any SPacketCustomPayload whose channel is in the blocked list is dropped before it can reach a mod channel. Outbound packets Music Triggers may still try to send during playback are already discarded by ReplayMod itself. The hook runs on every pipeline build, so replay restarts are covered too.