What is Universal Modder?
Universal Modder is an open-source collection of skills, tools and shared modding knowledge for AI coding agents. It is not a standalone game editor: you use it with an agent such as Claude Code or Codex and a game you own.
Searching for Universal Modder AI? This is the toolkit that helps an agent investigate a game, choose a modding route, work with its code and assets, and verify a change in the running game. The agent can also prepare recordings, package the result and document what worked.
How to install Universal Modder
Choose the setup for the agent you already use. The installation guide includes the full command table, dependencies, asset setup and troubleshooting.
Claude Code
Add the marketplace, then install the plugin inside Claude Code.
View instructions →02 / PLUGINCodex
Use the Codex CLI marketplace and plugin commands.
View instructions →03 / MORE AGENTSCursor & Gemini CLI
Use a clone or extension. VS Code and OpenCode routes are included.
Choose your agent →Which AI agent should you use?
Start with an agent you can already run. Changing agents does not remove game-specific setup or guarantee a better mod.
- Claude Code
- A plugin workflow inside Claude Code. Set up Claude Code →
- Codex
- A CLI plugin route for an existing Codex workflow. Set up Codex →
- Gemini CLI
- An extension install from the upstream repository. Set up Gemini CLI →
- Cursor
- A marketplace or repository-based editor workflow. Set up Cursor →
- VS Code & Copilot
- The source-plugin route uses VS Code’s plugin setting. Set up VS Code →
- OpenCode
- Start the agent inside a clone to use its project configuration. Set up OpenCode →
What can it mod?
The upstream project organizes its guidance into the following engine and ecosystem playbooks. This is not a tested list of every supported game. Begin with recon and look for a field note for your exact title.
| Engine / ecosystem | What to check first |
|---|---|
| Unity | Investigate the scripting backend before selecting a loader or patching route. |
| Unreal | Identify the engine build and the game’s available modding interfaces. |
| .NET & XNA | Managed-code routes include games such as Terraria, Stardew Valley and Celeste. |
| Godot | Work from the game’s packaging and the resources available to inspect. |
| Source 1 & 2 | Choose tooling for the correct engine generation and game. |
| Bethesda | Use the game-specific ecosystem; loaders and tools differ between titles. |
| Minecraft | Select the edition, game version and mod loader first. |
| Age of Empires II / Genie | Data and sprite formats need a route matched to the edition. |
| RE Engine / FromSoft / GTA / Cyberpunk / BG3 | These share a playbook grouping, not a universal loader or install command. |
| Native C++ | Expect deeper investigation; a workable route is not guaranteed. |
| Indie engines | Playbooks cover GameMaker, RPG Maker, Ren’Py, Paradox, Doom, HTML5, LÖVE and Java routes. |
| Retro decomps | A decompilation project can offer a different route when available and appropriate. |
Browse the upstream playbooks ↗ · Search documented game sessions ↗
Real examples from the upstream repository
These are upstream examples, not results produced or independently reproduced by this site.
Fal Arsenal
A mod with five weapons, three enemies and a two-phase Drone Mothership boss, including guided missiles, a crater-making nuke and a black-hole weapon. The sprites were generated with fal. Use a spare world: explosions change terrain. Multiplayer is not tested.
Read the code and build instructions ↗San Franciscans
A civilization example featuring a Robotaxi unit, Delivery Drones and a Transamerica Pyramid wonder. It includes a sprite-writing route and renders generated 3D models to the game’s camera angle.
Explore the civilization example ↗Two games, one composited scene
Minecraft runs alongside GTA V, with camera and event synchronization and a depth-aware compositor. This is a game-specific passthrough implementation, not a one-click merger. The example targets GTA V Legacy story mode; Enhanced is not supported.
Read the mashup’s requirements and architecture ↗Requirements and costs
- Core tools: Git, Python 3.10+ and ffmpeg. The upstream recommends uv.
- An AI coding agent: its access, subscription or API costs are separate.
- A game you own: game-specific tools and loaders may also be required.
- Generated assets: fal needs an API key and may incur usage charges. Local ComfyUI is an alternative for image workflows, with its own setup and hardware requirements.
- 3D-to-sprite rendering: Blender is needed for that route, not every mod.
- Platform: Windows games can be driven natively or from WSL. That does not make all Windows-only tooling work on macOS or Linux.
Safety rules and limits
The project’s instructions require owned games and permitted modding routes. They reject injection into anti-cheat-protected online games, cheats targeting other players, and bypasses of anti-cheat, DRM or ownership checks.
They also require save backups, process termination by exact PID, and permission before driving input, installing loaders into game folders or publishing, including pull requests. Packages should contain mod code, permitted original assets, patches or converters—not game files or decompiled dumps.
Universal Modder FAQ
Is Universal Modder free?
The toolkit is open source under MIT. Your game, AI agent, asset-generation services and any other paid tools are separate costs.
Which games does it support?
There is no blanket compatibility guarantee. Use the engine playbooks as candidate routes and the knowledge base as evidence for specific game versions.
Can it merge any two games?
No universal merger is promised. Existing mashups use different approaches, such as content ports or two running games connected by custom code. Their setup and restrictions are specific to the pair of games.
Do I need a fal API key?
Only for fal-backed operations. Recon and code work are separate. Local ComfyUI can supply images, but it does not replace every fal feature.
Where should I start?
Install for your agent, then follow the first-session quick start. Aim for one small, verifiable change.