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Fabric Client Mod on Server

A Fabric server crashes because a client-only Fabric mod was added to it. The mod's client entrypoint tries to load rendering classes the dedicated server does not have.

Que signifie cette erreur ?
Fabric mods can declare a 'client' environment in their fabric.mod.json. When such a mod is on the server, it attempts to load client classes for the DEDICATED_SERVER dist and fails, because those classes are client-only. 
Attempted to load class net/minecraft/client/... for invalid dist DEDICATED_SERVER
Causes les plus fréquentes
  • A client-environment Fabric mod placed on the server.
  • Copying the full client mods folder to the server.
  • A visual/UI Fabric mod with no server role.
  • Not checking the mod's environment field.
  • A pack that did not separate client mods.
Comment diagnostiquer
  1. Read the crash for the failing mod and client class.
  2. Check the mod's fabric.mod.json or page for a client-only environment.
  3. Decide whether the mod has any server function.
  4. Review the server mods folder for other client-only entries.
Correctifs recommandés
  • Remove it from the server
    Delete the client-only Fabric mod from the server, leave it on clients.
  • Keep server-safe mods only
    On the server, run only mods that work in or do not require the client environment.
  • Use environment metadata
    Trust the mod's declared environment (client/server/*) when deciding where it goes.
  • Separate the pack sides
    Maintain distinct client and server mod sets for the modpack.
Analyser mon log
Questions fréquentes

In fabric.mod.json, mods declare client, server, or both. Client-only ones must not run on a server.

Yes, it stays on clients. It just cannot be on the dedicated server.

No, this is about the mod's side, not a missing library, the fix is to remove it from the server.