ProbeJS Legacy

ProbeJS Legacy

Unofficial continuation of ProbeJS for versions abandoned by official ProbeJS

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About this Mod

ProbeJS Legacy

is an unofficial continuation of ProbeJS for KubeJS versions abandoned by official ProbeJS.

Usage

  1. You need to install ProbeJS Legacy, obviously.
  2. Enter a singleplayer world. Use /probejs dump to export datas gathered by ProbeJS Legacy. For first-time users, this will be done automatically when you join the world.
  3. Open your game instance folder using VSCode.
  4. Enjoy!

Note0: type @item or @block_tag to see snippets generated.

Note1: game instance folder is where you can see the kubejs folder directly.

Note2: Other IDEs with support for TypeScript typing (.d.ts) should also work.

New Features

(Compared to ProbeJS)

  • Simulated Internal

    • ProbeJS Legacy will now generate a Internal namespace, allowing users to migrate from ProbeJS 6 or ProbeJS Legacy 3 easily.
    • Example: Internal.ItemStack and Internal.ItemStack_
  • Better Param Naming

    • Param names that conflict with TypeScript will now be renamed in a better way.
    • Param names in Method/Constructor, if in arg123 format, will be renamed to a new name generated from its type.

Example:

"mayUseItemAt"(arg0: $BlockPos$$Type, arg1: $Direction$$Type, arg2: $ItemStack$$Type): boolean

will be renamed to

"mayUseItemAt"(blockPos0: $BlockPos$$Type, direction1: $Direction$$Type, itemStack2: $ItemStack$$Type): boolean
  • Better $Class<T>

    • ProbeJS will transform $Class<T> into typeof T, but ignoring many conditions where this should not be done. ProbeJS Legacy makes it more correct.
    • Some basic classes, for example java.lang.String and java.lang.Character. can now be dumped.
    • The T in $Class<T> is now actually usable for type hint.
  • better instanceof

    • ProbeJS Legacy can now properly support obj instanceof $SomeClass, where $SomeClass is a class loaded via java(...) or Java.loadClass(...).

Example:

const $BoatItem = java("some.path.to.BoatItem")

let item = Item.of("boat").item; // here the type of `item` is `$Item`
if (item instanceof $BoatItem) {
    // here the type of `item` can be inferred to `$BoatItem`
}
  • Field Beaning

    • Some fields will be transformed into getter+setter, in order to provide better support for TypeWrapper
    • Consider a obj with a field like this: block: $Block, and obj.block = "minecraft:stone" is a valid syntax in KubeJS. This had no typing support before, but now ProbeJS Legacy can support it properly.
  • Typing files sharing

    • By extracting common parts in dumped classes, the total typing files size can be much smaller than before.
    • Another benefits is that TS server can now reuse common typings between 3 script types, improving IDE performance.
  • Better comment formatting

    • blank lines at the front/back will now be ignored
    • comments will be formatted as one line if there's only one valid line
  • Side only methods (marked by @OnlyIn) will have comments telling you that it's server-only or client-only.

  • xxx.d.ts file with too many modules in it will now be split into smaller files automatically, providing better IDE performance

  • Method/Field in declaration files are now naturally sorted.

  • gloabl resolving: values you put into global can be resolved now. Configure resolving depth via 'global' Resolving Depth config.

  • And many internal changes. This Readme will certainly be too long if I write them all down.

Collecting data

KubeJS Event

For 1.16.5, ProbeJS Legacy will record all posted event. If you're unable to find some common events, try triggering it before dumping data. Example: block.place event is triggered by placing a block.

For 1.20.1, all registered KJS events will be dumped automatically, no need for triggering.

Forge Event

ProbeJS Legacy will record all Forge events, regardless of whether they have been posted or not. This behaviour can be altered via Class Scanner config.

Java Classes

ProbeJS Legacy will use multiple approaches for collecting Java classes.

These classes will be recorded:

  • Classes loaded manually, aka those loaded via java(...) or Java.loadClass(...)
  • Classes referenced by JS bindings, for example AABB and Text.
  • Classes references by known classes, for example Item.class referenced by ItemStack.class.
  • Registry objects, for example BoatItem for vanilla boats. By default this will skip non-vanilla objects, and can be altered via Registry Object Filter config.
  • Classes from certain mods. See Mods with forced Full Scanning config.
  • Classes read from cache file. The cache file is saved to <your instance folder>/.probe/classes.txt.
  • Classes found by class scanner. See Class Scanner config.

Why

Initially, all I want to do is just find some sort of doc or helper for KubeJS script writing, so that I won't need to feel such pain in the arse when developing Enlightend6Expert(https://www.curseforge.com/minecraft/modpacks/enlightened-6-expert) .
But after some research, I realized that 1.16.5, despite being one of the hottest modded versions, didn't even have a proper KubeJS helper mod.
So there it is, a ProbeJS fork for 1.16.5.
This is my first Java project and first Minecraft Mod project, and to be honest, ProbeJS is too tough for a coding noob like me. Thankfully I made it.

This project is licensed under LGPLv3, the same as the original ProbeJS.

Available Versions

1.20.1-6.2.0release
MC 1.20.1forge
May 31, 2026
1.16.5-6.2.0release
MC 1.16.5forge
May 31, 2026
1.20.1-6.1.0release
MC 1.20.1forge
May 23, 2026
1.16.5-6.1.0release
MC 1.16.5forge
May 23, 2026
1.20.1-6.0.5release
MC 1.20.1forge
May 14, 2026

How to Install ProbeJS Legacy on Your Server

1

Order Server

Order a Minecraft Java server with at least 3 GB RAM (4 GB recommended).

2

Set forge Loader

In the panel under "Egg", select the forge loader and matching Minecraft version (1.20.6).

3

Install Mod

Open the mod browser in the dashboard and search for "ProbeJS Legacy". Click "Install" – done! Alternatively, upload the .jar via SFTP to the /mods folder.

Compatibility

Mod Loaders

forge

Minecraft Versions

1.20.6, 1.20.5, 1.20.4 (+4 more)

Server-side

Required

Recommended RAM

4 GB(min. 3 GB)

Frequently Asked Questions

ProbeJS Legacy server crashes on startup – what to do?

Most common cause: wrong forge version or insufficient RAM. Check the server log (latest.log) for "OutOfMemoryError" or "Mixin" errors. With Mado Hosting: ensure at least 3 GB RAM is allocated and the loader matches the mod version (1.20.6). You can switch loaders with one click in the panel.

Is ProbeJS Legacy compatible with forge?

ProbeJS Legacy officially supports forge for Minecraft 1.20.6, 1.20.5, 1.20.4. The Mado dashboard automatically detects incompatible loader combinations.

Server lagging with ProbeJS Legacy – how to optimize performance?

Recommended RAM: 4 GB (per 8 players). Use /spark profiler to check if ProbeJS Legacy consumes the most tick time. Common fixes: reduce server view-distance to 8-10, install "performant" or "starlight" as supplementary mods on Forge. With Mado Hosting, your server runs on NVMe SSDs with dedicated CPU cores for minimal latency.

Rent Modded Server

Install ProbeJS Legacy with just one click on your server.

Recommended RAM
4 GBab €8/mo
Min. 3 GB | +1 GB pro 8 Spieler
Create Server Now
1-Click Mod Install
NVMe SSD Storage
DDoS Protection included

Details

License
GNU General Public License v3.0 only
Server-side
Required

Supported Versions

1.20.61.20.51.20.41.20.31.20.21.20.11.16.5