java-mod-rust-port-tool README

The project's README from github.com/Wallbycontact/java-mod-rust-port-tool. As one markdown file: README.md.

Smelt. Drop a Java mod, get it back in Rust.

Release v1.1.21 MIT license Windows and Linux, portable Horizon 26.3 Built with Rust

Download · How to use · What comes over · For mod developers · FAQ

A .jar is dragged into Smelt, turns into a Rust mod in a few seconds and is added to Horizon with one click

Smelt turns a Fabric or NeoForge mod into a mod for Minecraft on Rust: Horizon, the open-source rewrite of Minecraft: Java Edition 26.3. Java mods don't run there. Smelt rewrites them so they do.

Drop the .jar on the window, wait a few seconds, press Add to Horizon. That's the whole app.

Download

System File
Windows 10 and 11 java-mod-rust-port-tool.zip One zip. No installer, no admin rights

Unpack the whole folder and start Main.exe. No installer, no admin rights.

Main.exe is code-signed, so Windows starts it without a warning. Keep Smelt next to it: they ship together.

How to use

  1. Open Smelt.
  2. Drop a mod's .jar on the window, or press Choose a file.
  3. Press Add to Horizon.

The next time Horizon starts, it asks whether you trust the new mod. That's Horizon's own check for every mod that contains code. Mods made only of blocks and textures don't need it.

Ready for Minecraft on Rust Ready, with one gap
A client mod, rewritten in Rust Most of it comes over. The gap is named in one line
Blocks, recipes and textures This one can't come over yet
Blocks, recipes and textures. No code, nothing to trust Rendering mods can't come over yet. Nothing is installed

What comes over

Three mods in a row: one works, one comes over partly, one can't run yet

Every mod gets one of three verdicts:

Verdict What it means
Works Everything in the mod runs in Minecraft on Rust.
Partly Most of it runs. Smelt tells you which part doesn't, in one line.
Won't run The mod does something Minecraft on Rust can't load yet. Nothing gets installed.

What to expect, by kind of mod:

Kind of mod Usually
Blocks, items, recipes, loot, textures Works
HUD overlays, keybinds, zoom, chat tweaks, minimaps Works
Settings screens and custom menus Partly
Machines, pipes, new mob behaviour, world generation Partly or won't run
Shaders, rendering engines, performance mods Won't run

Smelt doesn't guess. If a piece of a mod can't be rewritten safely, it's left out and the verdict says so. You never get a mod that loads and then breaks your world.

How it works

mod.jar is read, rewritten in Rust and packed into a .hnmod for code and a .hmod for blocks and textures

  1. Reading the mod. Smelt opens the .jar and works out the loader (Fabric or NeoForge), the side (client, server or both), every class, and every game API those classes call. Blocks, items, recipes and textures are collected separately.
  2. Rewriting it in Rust. Loader events become Horizon hook points: native_tick, native_hud, native_key, native_command and the rest. Method bodies are translated line by line. Common mixins, like the ones zoom mods use, are swapped for the matching hook.
  3. Packing it for Horizon. The result is compile-checked against the Horizon revision Smelt targets, then packed. Code goes into a .hnmod; blocks, items and textures go into a .hmod.

Everything happens on your PC, and nothing is uploaded. The rules that map Java APIs to Horizon hooks are plain TOML files in mappings/, so anyone can read them and improve them.

For mod developers

Switch on Developer mode in the bottom-right corner to see the Java and the Rust side by side. Matching lines are highlighted, every hook the mod uses is listed, and anything Smelt rewrote from a known pattern is flagged for a quick look.

Developer mode shows Java and Rust side by side with matching lines highlighted

From there you can Export port plan (a Markdown checklist) or Open Rust project to keep working on the generated code yourself.

The same engine runs from the terminal:

smelt converts a mod and checks a whole mods folder in PowerShell 

smelt zoom.jar                         # convert one mod, add it to Horizon
smelt check ./mods                     # verdicts only, nothing written
smelt ./mods --out ./converted         # convert a folder, don't install
smelt zoom.jar --keep-project ./zoom   # keep the generated Cargo project
Option What it does
--out <dir> Write the .hnmod and .hmod files to a folder instead of Horizon
--keep-project <dir> Keep the generated Cargo project for hand editing
--horizon <dir> Use a specific Horizon install
--plan <file.md> Write the port plan as a Markdown checklist
--json Machine-readable verdicts, for CI

Build from source

You need Rust 1.85 or newer. The desktop app also needs the Tauri prerequisites for your system.

git clone https://github.com/Ropesehypnotize/java-mod-rust-port-tool.git
cd smelt
cargo build --release -p smelt-cli       # the smelt command
cargo test --workspace
cargo tauri build                        # the desktop app
Path What's inside
crates/smelt-core Reading jars, the Java to Rust rewrite, verdicts
crates/smelt-cli The smelt command
app/ The desktop window (Tauri) and its icons
mappings/ Java API to Horizon hook rules, one TOML file per loader
assets/ Images for this README

FAQ

Is this made by Mojang or by the Horizon team?

No. Smelt is an independent fan project. It isn't affiliated with Mojang, Microsoft or the Horizon project.

Will a converted mod work in normal Minecraft?

No. It's made for Minecraft on Rust only. Keep the original .jar for Java Edition.

Is it safe?

Smelt works offline and never uploads your mods. Mods with code run unsandboxed in Horizon, so Horizon asks you to trust each one. Only convert mods you would trust on Java Edition too.

Can I share a mod I converted?

Check the original mod's license first. A converted mod is still its author's work.

My mod says "Won't run". What now?

Usually it changes how the game draws or depends on parts of Java Minecraft that Minecraft on Rust doesn't have yet. Try again after Smelt or Horizon updates. If you think the verdict is wrong, open an issue and attach smelt check <mod>.jar --json.

Does it handle Forge or Quilt mods?

NeoForge and Fabric today. Quilt mods that only use the Fabric API usually work. Older Forge mods aren't supported.

License

Smelt is MIT licensed. The bundled fonts, Geist and Pixelify Sans, are under the SIL Open Font License 1.1.

Minecraft is a trademark of Mojang Synergies AB. Smelt isn't an official Minecraft product and isn't approved by or associated with Mojang or Microsoft.

java-mod-rust-port-tool (Wallbycontact/java-mod-rust-port-tool)

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409 ·GitHub
Java-mod-rust-port-tool
What is this?Smelt converts a Fabric or NeoForge Java mod .jar into a mod for Minecraft on Rust (Horizon). You drop the jar on the window, wait a few seconds, and press Add to Horizon.
Is it a launcher, a mod loader, or a converter?It's a converter. Java mods don't run in Horizon, so Smelt rewrites them into Rust mods that do. It's a Windows desktop app, and a command-line version runs the same engine.
How do I convert a mod?Download the zip, unpack the whole folder, and start Main.exe. There's no installer and no admin rights needed. Drop the .jar on the window and press Add to Horizon. The next time Horizon starts, it asks you to trust the new mod if it contains code.
Do I need Horizon or Rust to use it?You need Horizon installed, since converted mods are added to it. Using the app needs no installer. Building from source needs Rust 1.85 or newer, plus the Tauri prerequisites for your system.
Will every mod convert?No. Each mod gets a verdict of Works, Partly, or Won't run. Rendering mods, shaders and performance mods can't come over yet, and any part that can't be rewritten safely is left out and flagged.
Does it run on Mac or Linux?The published download is for Windows 10 and 11 only. The README doesn't mention a Mac or Linux build.
Does it upload my mods anywhere?No. Smelt works offline and never uploads your mods, and all conversion happens on your PC.
What does Developer mode show?It shows the Java and Rust code side by side with matching lines highlighted, lists every Horizon hook a mod uses, and flags lines rewritten from a known pattern. You can export a Markdown port plan or open the generated Rust project.
Can I use it from a terminal or in CI?Yes. The smelt command runs the same engine, with options to choose an output folder, keep the Cargo project, pick a Horizon install, write a port plan, or print machine-readable JSON verdicts for CI.
Which mod loaders are supported?NeoForge and Fabric today. Quilt mods that only use the Fabric API usually work, but older Forge mods aren't supported.
Is this made by Mojang or the Horizon team?No. Smelt is an independent fan project, not affiliated with Mojang, Microsoft or the Horizon project. Converted mods only work in Minecraft on Rust, so keep the original .jar for Java Edition.
What are similar projects?horizon-modpack-compatibility, ai-minecraft-modmaker, horizon-capes-skins-minecraft, minecraft-hack-menu-2026, mcopt, Rise-6.9.5, DLSS5oneclick, CircuitLordVRModInstaller
Which topics is it in?fabric, minecraft, game-modding, modding, tauri, game, gaming, offline, developers, command-line-tool, rust, desktop-app
Creator
Wallbycontact
Size
4.2 MB
Stars
409
Updated
CommitNov 04Releasev1.1.24Nov 05
Age
Today
Commits · 90 Days