A stable Fabric installation depends on matching four pieces: the Minecraft version, Fabric loader environment, Supplementaries Fabric build and its required Moonlight Lib dependency.
Prepare the Fabric instance
Create or select a Fabric instance for the exact Minecraft version you intend to use. Keep it separate from NeoForge or Forge instances to prevent loader-specific files from being mixed together.
Launch the clean loader instance once before adding mods so basic loader problems are easier to identify.
Add the dependency first
Install a compatible Moonlight Lib build for the same Minecraft version and Fabric environment. If the loader reports that Moonlight is missing, do not bypass the message; correct the dependency instead.
Add Supplementaries and test
Place the matching compiled Fabric Supplementaries JAR in the instance mods folder, then launch with only the required dependency and a small trusted set of mods. Add other mods back gradually if you are diagnosing a conflict.
Related guides
Continue with the focused guides in the sidebar or return to the full Supplementaries Mod guide library.