Universal Modder (universal-modder on GitHub, by rehan-remade) is a free, MIT-licensed toolkit that lets AI coding agents such as Claude Code and Codex mod PC games you own. This page is a quick install and usage guide; the full, always-updated version lives at universal-modder.dev.
GitHub: github.com/rehan-remade/universal-modder
Maintainer: rehan-remade
Stars / forks: 5.7k+ stars, 540+ forks (October 2026)
License: MIT, free
Last commit: 2026-10-09
Agents: 7 install routes: Claude Code, Codex, Gemini CLI, VS Code Copilot, Cursor, OpenCode, and any Agent Skills agent
It's a kit of 11 Agent Skills, the um command-line tool, a fal MCP server for generated sprites, 3D models and sound, and a shared knowledge base of field notes that agents write for each other. Agents have used it to put real Minecraft inside GTA V, build a new Age of Empires II civilization and add a tactical nuke to Terraria. It is not a one-click mod generator: your agent does the work, following a tested method.
1. Plugin (Claude Code), run inside a Claude Code session:
/plugin marketplace add rehan-remade/universal-modder
/plugin install universal-modder@universal-modder
Codex: codex plugin marketplace add rehan-remade/universal-modder then codex plugin add universal-modder@universal-modder. Gemini CLI: gemini extensions install https://github.com/rehan-remade/universal-modder.
2. Clone the repo and start your agent inside it:
git clone https://github.com/rehan-remade/universal-modder
3. The um CLI only (it is installed from GitHub, not from PyPI):
uv tool install git+https://github.com/rehan-remade/universal-modder
pipx install git+https://github.com/rehan-remade/universal-modder
Requirements: Git, Python 3.10+, ffmpeg, uv (recommended), Blender (optional, for 3D to sprites). Step-by-step install guide for every agent.
um scan (find games, engine, anti-cheat, saves) · um fal (sprites, textures, 3D, SFX, music, voice) · um comfy (local images, no key) · um sprite · um render3d · um win (launch, screenshot, input, record on Windows/WSL) · um video · um backup · um publish check · um kb (knowledge base).
Generated assets need a fal API key from fal.ai/dashboard/keys: export FAL_KEY="your-key" (Windows: setx FAL_KEY "your-key"). A default sprite costs about $0.21, a 3D model $0.25–0.35. Cost breakdown and calculator.
The mod-any-game skill runs the same loop every time: 1) search the knowledge base, 2) recon and pick a route, 3) set up a safe lab with saves backed up, 4) read the actual code, 5) build one working slice, 6) generate assets, 7) verify in the real game, 8) record, 9) package, 10) write a field note.
Engine playbooks: Unity, Unreal, .NET/XNA, Godot, Source, Bethesda, Minecraft, AoE2/Genie, big frameworks (RE Engine, FromSoft, GTA, Cyberpunk, BG3), native C++, indie engines, retro decomps. Browse the games modded with it.
Git/SSH error when adding the marketplace: run git config --global url."https://github.com/".insteadOf git@github.com:
Skills don't appear: run /reload-plugins or restart the agent.
um: command not found: open a new terminal, or run uv tool update-shell.
fal key missing: set FAL_KEY, then restart the agent.
um win refuses to run: game control works on Windows or WSL only.
Mod only games you own: single-player, offline, or servers you host.
No anti-cheat bypass, no cheats against other players, no DRM tampering.
Never redistribute game files or decompiled code; ship your own code, assets or patches.
Install only from the official GitHub repository.