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Universal Modder
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Install Universal Modder in Claude Code

Quick install

Run these commands inside Claude Code, rather than in your ordinary shell:

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/plugin marketplace add rehan-remade/universal-modder
/plugin install universal-modder@universal-modder

You can select the code to copy it manually.

Before you start

Have Claude Code installed and authenticated, with Git available to the shell it uses. Check the current Claude Code setup instructions if you still need the agent itself. Universal Modder supplies modding tools; Claude's account and model access are separate.

Check the shared installation requirements for Python, ffmpeg and optional asset tools. On native Windows, Claude's Bash calls may need Git Bash; WSL has its own Git, Python and PATH. Use a project folder you own and plan your first change with the Universal Modder tutorial.

Step-by-step install

Step 1: Check the agent and Git

In the terminal where you launch Claude:

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git --version
claude --version
claude doctor

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Resolve a missing Git executable or agent setup error before installing the plugin. Open Claude in your project folder.

Step 2: Add the marketplace and plugin

Enter the two quick-install commands above. Review the repository source and choose the intended installation scope. A user-scope installation is useful across your projects; record your choice so removal targets the same scope.

You can alternatively install from the ordinary terminal:

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claude plugin marketplace add rehan-remade/universal-modder
claude plugin install universal-modder@universal-modder --scope user
claude plugin list --json

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Use one route, then inspect the result. The repository is rehan-remade/universal-modder and the plugin is universal-modder.

Step 3: Start a fresh session

Exit and reopen Claude in the same project. In /plugin, check that Universal Modder is installed and enabled and inspect any reported errors. Type /universal-modder: to find its available skills, including mod-any-game.

Step 4: Choose whether to enable assets

Use /mcp to inspect the plugin's fal connection. Asset generation needs your own FAL_KEY; if you want to begin with code and placeholder art, disable the fal connection for that project. Check its state again when opening a different project. The FAQ explains fal and model costs.

Check CLI

Ask Claude to run these read-only checks through its Bash tool:

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Run command -v um, um --help and um --version in your tool shell.
Report the actual command location and output. Do not edit game files
or start an asset generation.

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Check um --help in your ordinary terminal separately. The plugin's session hook can prepare the agent's environment without changing every terminal on your machine. If the ordinary terminal cannot find um, use the standalone CLI install.

Your first prompt

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Use the mod-any-game skill to investigate my Terraria installation.
Find the game version, tModLoader route, save directories and prior field notes.
Write MODDING_PLAN.md for one simple weapon in an isolated practice world.
Show the backup and restore steps before making game changes.

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This starter prompt keeps the first session to a small planning task. Continue through the tutorial checkpoints before expanding to the full Terraria example.

Common errors in Claude Code

  • No skill appears: inspect the enabled plugin and its errors, confirm the installation scope, and reopen the project session.
  • Git cannot start: check Git from the actual shell used by the agent. The Git diagnostic explains executable and working-directory checks.
  • The skill loads but um is absent: check the agent shell and terminal independently; use CLI PATH diagnosis.
  • fal is unavailable: confirm whether you disabled it intentionally. A fal configuration failure need not block a project using placeholder art.

Uninstall

Exit Claude. For the user-scope installation shown above:

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claude plugin uninstall universal-modder@universal-modder --scope user
claude plugin list --json

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Use the original scope if you chose project or local scope instead. Reopen the project to confirm removal. An independently installed um has its own uninstall step; keep mod source and game backups.

Other agents

Compare Codex, Cursor, Gemini CLI, VS Code / Copilot and OpenCode. The installation overview keeps all six agents and the skills-only route together.

Frequently asked questions

Do I need a fal key for the Claude plugin?

No. A key is only needed for fal asset generation. You can keep its MCP connection disabled while working with code, placeholder art or your own assets.

Why does um work in Claude but not my terminal?

The plugin prepares the environment for agent tool calls. Your ordinary terminal may use a different PATH, so check it separately and install the CLI with uv or pipx if needed.

Does installing the plugin modify my games?

Installation adds agent capabilities. A later task can read or change local files, so review the game plan and use an isolated practice environment with backups.