Entity Watchdog

Vanilla Minecraft silently discards entities when loading fails (unregistered entity ids, exceptions thrown by an entity constructor or Entity.load, or client-side packet creation failures), printing only a "Skipping Entity" warning, which makes creatures vanish and data corrupt with no way to trace the cause. Entity Watchdog pins mixins to the lowest-level entity-loading entry points (EntityType.create / loadStaticEntity / loadEntityRecursive and the client's ClientboundAddEntityPacket handling) with injection priority 100000

— above any normal mod —

and crashes by throwing an Error, so other mods' catch(Exception) fallbacks cannot swallow it.

The crash report includes the failure scenario, entity id, registry resolution, dimension/side/thread, the full stack trace of the swallowed original exception, a complete dump of the entity NBT, the nearest matching registered entity ids (rename detection), the full list of loaded mods, and fix instructions —

making it immediately clear which mod and what caused the failure.