Connector Server Mixin Fix

A tiny server-side library that fixes dedicated-server crashes caused by Sinytra Connector not removing client-only members from Fabric mixin classes.

Just drop it in your server's mods/ folder next to Connector — the crash is gone. It does nothing on clients, so it's safe to ship in the same pack.

Symptoms it fixes

If a Fabric mod loaded through Connector has a mixin with a client-only method, your dedicated server crashes during startup with something like:

MixinPreProcessorException: Attach error for .mixins.json:SomeMixin
&nbsp; -> INVOKESTATIC net/minecraft/client/Minecraft::getInstance
Caused by: java.lang.ClassNotFoundException: net.minecraft.client.Minecraft

Note the key detail: no crash report is generated (it dies during class loading), so all you get is this stack trace in the console — which is exactly what this mod prevents.

Why it happens

Connector correctly strips Fabric @Environment(CLIENT) members from regular classes, but it skips this step for mixin classes. A common mixin carrying a client-only method (correctly annotated by the mod author) therefore survives on the server, and the mixin processor later tries to resolve a net.minecraft.client.* class that doesn't exist server-side → crash.

This is a Connector limitation, not a bug in the affected mod — the mod works fine in singleplayer and on native Fabric servers.

What it does

Runs just before the mixin processor reads each mixin class and removes any @Mixin member marked @Environment(CLIENT) on a dedicated server, exactly like the Fabric loader does natively. It's generic — it fixes every Fabric mod hitting this pattern, not one specific mod.

You'll see this line on server startup confirming it's active:

[ConnectorEnvStrip/]: Registered 'connector_env_strip' launch plugin

ℹ️ This is a low-level library, so it does not appear in the in-game mod list. Check the startup log line above to confirm it loaded.

Requirements

Minecraft 1.21.1, NeoForge 21.1.x
Sinytra Connector (without it, this mod simply does nothing)
Server-side only (harmless on clients)