A Claude Code plugin called universal-modder mods PC games from one-line prompts, and hit 703 stars in its first day on GitHub

Ask an AI agent to add a homing missile launcher to Terraria, and it now has a recipe to follow. A Claude Code plugin called universal-modder, published on GitHub on 2026-09-30 under the handle rehan-remade, drives the whole loop from a one-line prompt: pick the game, work out the engine, read the actual code, build one working slice, generate the art on fal, test it in the running game, and package the mod. It reached 703 stars in the 16 hours after it went live, per the GitHub API stargazers_count field checked at 21:14 UTC. The repository is MIT-licensed and written in Python.

What the loop looks like

The plugin ships nine skills. The top one, mod-any-game, is the safety and workflow policy plus twelve engine playbooks: Unity, Unreal, .NET or XNA (which covers Terraria, Stardew Valley and Celeste), Godot, Source, Bethesda, Minecraft, Age of Empires II, RE Engine games (FromSoft, Cyberpunk), native C++, indie engines and retro decompilation. Others cover reverse engineering (ILSpy, Ghidra, Frida, RenderDoc), asset generation on fal, art-to-engine pipelines, safe process control, showcase video and packaging.

The mechanics sit in a command called um. um scan finds Steam, Epic and Xbox installs and fingerprints the engine, anti-cheat, installed loaders and save folders, then ranks the modding routes. um fal runs the fal API for sprites, textures, PBR maps, image-to-3D, rigging, sound effects, music, voice and video, logging a manifest of every generation. um render3d turns a .glb from fal into sprite frames at the game's camera angle, using Blender. um win handles Windows work: screenshotting through the GPU, recording the game window with only the game's audio, and driving mouse and keyboard input that only reaches the game.

Two mods that were built with it

The repo ships two example mods, both listed as starting from a one-line prompt.

Fal Arsenal for Terraria adds a homing missile launcher, a tactical nuke that leaves a crater and a mushroom cloud, a chain-lightning rifle, a black-hole gun, an orbital strike, three new enemies and a two-phase Drone Mothership boss. Every sprite came from fal.

San Franciscans for Age of Empires II Definitive Edition adds a civilization with a Robotaxi unique unit and Delivery Drones, rendered from fal image-to-3D models at AoE2's camera angle, a Transamerica Pyramid wonder, and a reverse-engineered writer for AoE2's .sld sprite format.

The rules the author wrote in

Because a modding agent that can inject code into any running game is a risky primitive to hand a language model, the README states the rules up front. Universal-modder will not work with online games that have anti-cheat, will not write multiplayer cheats, and will not bypass anti-cheat, DRM or ownership checks. It backs up save folders before touching them and kills processes by PID only. It asks the user before it takes over the mouse and keyboard, installs a loader into a game folder or publishes a mod. It refuses to ship game files or decompiled code, so a mod leaves the machine as code plus the user's own assets plus a patch or converter.

For a team looking at AI-driven creative tools, the pattern outside the games is what to notice. A coding agent with an engine playbook, a real asset API, a safe way to reach the running program, and a written rule sheet can now do end-to-end work on software it has never seen before.

Source

• Primary: rehan-remade/universal-modder, created 2026-09-30, MIT licence. Star count 703 as of 2026-09-30 21:14 UTC, from the GitHub API stargazers_count field.