Preloading Tricks

Overview

Preloading Tricks is a developer-only mod that enables advanced operations during the very early stage of the mod loader.
It provides early hooks, Java Instrumentation-based class transformation, and SPI-driven callbacks for loader extension.

Supported environments:

• Fabric – 1.20.1, 1.21+
• Forge (LexForge) – 1.20.1
• NeoForge – 1.20.6, 1.21+

You can test on more versions since it depends on the loader version instead of the Minecraft version.

Features

• Early loader entrypoint via PreloadingEntrypoint (SPI-based)

  • Register callbacks using PreloadingTricksCallbacks events:
    • SETUP_LANGUAGE_ADAPTER – early language adapter setup stage
    • COLLECT_MOD_CANDIDATES – dynamically add mod candidate paths before discovery
    • SETUP_MODS – modify mod list (add/remove/query via ModManager API)

• Instrumentation-powered ClassTransform
  Can transform already-loaded classes, including Java core and classloader classes.
  Configure via MANIFEST.MF on all platforms (see below).

• Forge variant detection (Forge-like only)

  • Access ForgeVariants to detect specific Forge/NeoForge versions at runtime

Usage (Gradle)

Add the Maven repository and dependency to your build:

Kotlin DSL:

repositories {
    maven("https://raw.githubusercontent.com/settingdust/maven/main/repository/")
}

dependencies {
  // Recommended: use the base artifact (no classifier).
  // Gradle variant matching / cloche will resolve the correct platform artifact automatically.
  implementation("settingdust.preloading_tricks:PreloadingTricks:VERSION")

  // Optional: pin to a specific classifier when you want to avoid accidentally using APIs
  // from other platforms.
  // implementation("settingdust.preloading_tricks:PreloadingTricks:VERSION:fabric")
  // implementation("settingdust.preloading_tricks:PreloadingTricks:VERSION:forge-service")
  // implementation("settingdust.preloading_tricks:PreloadingTricks:VERSION:neoforge-modlauncher")
  // implementation("settingdust.preloading_tricks:PreloadingTricks:VERSION:neoforge-fancy-mod-loader")
}

Replace VERSION with the latest release (e.g. 3.5.9).

If you are using cloche, the corresponding variant is selected automatically based on loader/minecraft attributes.

ClassTransform Configuration

For all platforms, add the following attribute to your MANIFEST.MF:

ClassTransformConfig: xxxx.classtransform.json

Multiple configs can be specified as comma-separated values:

ClassTransformConfig: first.classtransform.json,second.classtransform.json

Example config (xxxx.classtransform.json):

{
  "package": "settingdust.preloading_tricks.neoforge.transformer",
  "transformers": [
    "mod_setup_hook.FMLLoaderTransformer"
  ]
}

Forge Variant Detection (Forge-like only)

Allows a mod to load only on a specific Forge-like loader variant. This enables bundling both LexForge and NeoForge JARs together via jar-in-jar in a single mod file.

Configuration:

Specify your mod's target variant in MANIFEST.MF:

ForgeVariant: LexForge

or

ForgeVariant: NeoForge

Mods with a ForgeVariant specified will only load when running on the matching loader variant, allowing safe coexistence of variant-specific implementations.

For developers who need to reach into the earliest moments of Minecraft’s loading process.