RetroConvert

RetroConvert

Drop your Babric mods into an Ornithe instance RetroConvert converts them automatically at launch.

Babric and Ornithe both run Fabric Loader on Minecraft Beta 1.7.3, but they use different intermediary mappings, so their mods aren't compatible with each other. RetroConvert fixes that: at launch it rewrites Babric mods' bytecode in place to Ornithe's Calamus gen2 mappings token for token, with no recompilation, no sources, and no internet required.

Features

• Fully automatic just put Babric .jar files in your mods folder alongside RetroConvert and launch. Converted mods appear as <name>-ornithe.jar; originals are safely archived in config/retroconvert/originals/.
• Deep conversion rewrites class bytecode, mixin annotations (including refmap-less string targets), refmap JSONs, access wideners, fabric.mod.json, string constants used for reflection, and nested jar-in-jar mods, recursively.
• No visible restart after converting, Fabric Loader is relaunched inside the same JVM over the converted mods folder. The game just starts.
• Smart detection already-ported Ornithe mods are left untouched, and umbrella mods with nested jars (like StationAPI) are handled per-jar.
• Official-build replacements a few mods (StationAPI, GlassConfigAPI) changed too much for a bytecode rewrite; for those, the official Ornithe build is downloaded instead, with bytecode conversion as the offline fallback.
• Cached jars are keyed by SHA-256, so only new files are scanned on later launches.

Usage

1. Install RetroConvert into an Ornithe b1.7.3 instance's mods folder.
2. Add your Babric mods to the same folder.
3. Launch. That's it.

Optional: Java agent mode (zero-restart, even on first launch)

Add this to your JVM arguments (Prism Launcher: instance → Settings → Java → JVM arguments):

-javaagent:mods/retroconvert-1.0.1+mcb1.7.3.jar

This converts mods before Fabric Loader scans the folder no relaunch logic needed at all. The same line works for every instance on Prism, MultiMC, and the vanilla launcher.

Headless usage

Convert any mods folder without launching the game:

./gradlew runConverter --args="/path/to/.minecraft/mods"

Limitations

• Only b1.7.3 is supported by design, since Babric only targets b1.7.3.
• A Babric mod that fails dependency resolution crashes before RetroConvert can run; remove that jar manually.
• Don't restore an archived original next to its converted output the loader will see two mods with the same id.

License & Source

Source code, issue tracker, and full technical details are available on GitHub.