Gradle was chosen to build Fabric mods. This document will dive into the details of the pipeline steps, and the tools used.

Yarn is an open-source repository that contains all the mappings used to turn Minecraft obfuscated names into the useful names Fabric mod developers use.

For more information on how to contribute mappings take a look here: Yarn

Enigma is a tool to deobfuscate Java applications, like Minecraft. Fabric uses a fork of Enigma that has been heavily modified to work more effectively with Yarn.

The code is not for the faint of heart but can be seen here Source