# Port A Mod

Port an existing mod to a newer game version or another mod loader while keeping its...

- Repository: https://github.com/rehan-remade/universal-modder (9317 stars)
- Category: Testing
- License: MIT
- Last updated: 2026-11-01
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add rehan-remade/universal-modder --skill port-a-mod -g -a claude-code -y`
Codex: `npx skills add rehan-remade/universal-modder --skill port-a-mod -g -a codex -y`
Cursor: `npx skills add rehan-remade/universal-modder --skill port-a-mod -g -a cursor -y`
Gemini CLI: `npx skills add rehan-remade/universal-modder --skill port-a-mod -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add rehan-remade/universal-modder`

## Description

Port an existing mod to a newer game version or another mod loader while keeping its behaviour, values and quirks. Typical cases are an old Forge 1.7.10 or 1.12 Minecraft mod moving to modern Fabric or NeoForge, a Skyrim LE plugin moving to SE/AE, or a tModLoader 1.3 mod moving to 1.4. It covers pinning one source version, a private decompiled reference, an adaptation matrix, extracting the mod's data with scripts instead of retyping it, porting unit by unit with tests that catch drift, real-client checks, audits against the original, and keeping a long port resumable across sessions and agents. Use when the user wants to update, port, revive or re-implement a mod that already exists, or to continue such a port.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Port a mod faithfully

When porting an existing mod, the original is the spec. A port rarely fails for lack of code. It fails by
**drift**:
- values recalled from memory or a wiki;
- mechanics borrowed from a later rewrite of the same mod;
- quiet "improvements";
- renderers that look roughly right;
- checks that the original made on the client and the port forgot.

The method below carried a Thaumcraft 4.2.3.5 port from Minecraft 1.7.10 Forge to 1.20.1 Fabric:
- 859 original classes became about 77,000 lines of port code;
- 323 GameTests cover it, and scripted real-client scenarios check what tests can't reach;
- the work spanned many sessions and two agent accounts.

The field note `knowledge/games/minecraft/porting-thaumcraft-4-1-7-10-forge-to-minecraft-1-20-1-fabric.md` has
its gotchas. Minecraft-specific mappings are in `references/minecraft-1-7-10-forge-to-1-20-fabric.md`.

Run the **mod-any-game** loop around this skill (intake, recon, lab, verify, publish, field note). This
skill replaces its "vertical slice" step with a long series of slices, one per unit of the original.
Bringing one game's content or mechanics into another game is the **mashup-mods** skill, not this one.

The rest: https://github.com/rehan-remade/universal-modder/blob/HEAD/.agents/skills/port-a-mod/SKILL.md