Papyrus

Papyrus provides named mappings through the Fabric loader's MappingResolver, letting a mod use readable names for classes and members while the game runs. On first run it fetches the mappings for the game version and keeps them in the game directory as cached tiny v2 files, so later launches do not need to fetch them again. Papyrus injects the added mappings before launch, which means a mod that needs them has to be prepared before the game starts.

Developers can reach game internals through reflection using named classes, and the mod offers a more developer friendly route to mappings than working with intermediary names directly. Mojmap treats the members of parent classes in its own way, and Papyrus accounts for that when it resolves names. A project that needs access to Papyrus internals must add it with the modApi configuration rather than modRuntimeOnly, and its fabric.mod.json must declare which mappings and version it needs.

Papyrus is a library published for Fabric only, with 17 game versions across 1.18 – 1.21.1. It works on either side, and neither the client nor the server needs it. The code is open source under the MIT License, and the source code and issue tracker are public.