Monolith

One plugin. Every Unreal domain. Zero Python bridges.

What is Monolith?

Monolith is an Unreal Engine editor plugin that gives AI assistants full read/write access to your project through the Model Context Protocol (MCP). Install one plugin, point your AI client at one endpoint, and it can work with Blueprints, Materials, Animation, Niagara, project configuration, and more.

It works with Claude Code, Cursor, or any MCP-compatible client. If your AI tool speaks MCP, it can drive Monolith.

Platform: Windows only. Mac and Linux support is coming soon.

Why Monolith?

Most MCP integrations register every action as a separate tool, which floods the AI's context window with tool descriptions. Monolith uses a namespace dispatch pattern instead: each domain exposes a single {namespace}.query(action, params) tool, and a central monolith.discover() call lists what's available. This keeps the tool list small (around a dozen entries) while still exposing over a hundred actions across nine domains.

Features

• Full Blueprint inspection — Graph topology, variables, execution flow, node search
• Material graph editing — Read, build, and validate material graphs with preview support
• Animation coverage — Montages, blend spaces, ABP state machines, skeletons, bone tracks
• Niagara particle systems — Create and edit systems, emitters, modules, parameters, renderers, and HLSL
• Editor integration — Build triggers, log capture, compile output, crash context, Live Coding support
• Config management — INI resolution, diff, search, and explain
• Deep project search — SQLite FTS5 full-text search across all indexed assets
• Engine source intelligence — Tree-sitter C++ parsing of the UE source tree with call graphs and class hierarchy
• Auto-updater — Checks GitHub Releases on editor startup, one-click update
• Claude Code skills — Domain-specific workflow guides bundled with the plugin
• Pure C++ — Direct UE API access, embedded Streamable HTTP server

Installation for Dummies (Step-by-Step)

Prerequisites

• Unreal Engine 5.7+ — Launcher or source build (unrealengine.com)

Platform: Windows only. Mac and Linux support is coming soon.

• Claude Code, Cursor, or another MCP client — Any tool that supports the Model Context Protocol
• (Optional) Python 3.10+ — Only needed if you want engine source code lookups

Step 1: Download Monolith

Every Unreal project has a Plugins/ folder. If yours doesn't exist yet, create it. It lives at the same level as your .uproject file:

YourProject/
  YourProject.uproject
  Content/
  Source/
  Plugins/          <-- here
    Monolith/

Option A: Git clone (recommended)

cd YourProject/Plugins
git clone https://github.com/tumourlove/monolith.git Monolith

Option B: Download ZIP

Download the latest release from GitHub Releases, extract it, and place the folder at YourProject/Plugins/Monolith/.

Step 2: Configure the MCP Connection

Create a file called .mcp.json in your project root — the same directory as your .uproject file:

YourProject/
  YourProject.uproject
  .mcp.json          <-- create this file
  Plugins/
    Monolith/

Paste this exact content into .mcp.json:

{
  "mcpServers": {
    "monolith": {
      "type": "streamableHttp",
      "url": "http://localhost:9316/mcp"
    }
  }
}

This tells your AI client where to find Monolith's MCP server. You can also copy the template:

cp Plugins/Monolith/Templates/.mcp.json.example .mcp.json

Step 3: Launch Unreal Editor

Open your .uproject file as normal. On first launch:

1. Monolith auto-indexes your entire project (takes 30-60 seconds depending on project size)
2. Open the Output Log (Window > Developer Tools > Output Log)
3. Filter for LogMonolith — you should see messages about the server starting and indexing completing

If you see Monolith MCP server listening on port 9316, you're good.

Step 4: Connect Your AI

1. Open Claude Code (or your MCP client) in your project directory — the one containing .mcp.json
2. Claude Code auto-detects .mcp.json and connects to Monolith
3. Verify it works by asking: "What Monolith tools do you have?"

Your AI should list the Monolith namespace tools (blueprint.query, material.query, etc.).

Step 5: (Optional) Engine Source Index

If you want your AI to look up Unreal Engine C++ APIs, function signatures, call graphs, and class hierarchies:

1. Install Python 3.10+
2. Run the source indexer script (see Source/MonolithSource/ for details)
3. This builds a local SQLite database of the entire UE source tree
4. Once indexed, source.query actions become available

Verify Everything Works

With the editor open, run this curl command from any terminal:

curl -X POST http://localhost:9316/mcp \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/list"}'

You should get a JSON response listing all available Monolith tools. If you get "connection refused", make sure the editor is running and check the Output Log for errors.

(Optional) Install Claude Code Skills

Monolith ships with domain-specific workflow skills for Claude Code:

cp -r Plugins/Monolith/Skills/* ~/.claude/skills/

Architecture

Monolith.uplugin
  MonolithCore          — HTTP server, tool registry, discovery, auto-updater (4 actions)
  MonolithBlueprint     — Blueprint graph reading (5 actions)
  MonolithMaterial      — Material inspection + graph editing (14 actions)
  MonolithAnimation     — Animation sequences, montages, ABPs (23 actions)
  MonolithNiagara       — Niagara particle systems (39 actions)
  MonolithEditor        — Build triggers, log capture, compile output, crash context (13 actions)
  MonolithConfig        — Config/INI resolution and search (6 actions)
  MonolithIndex         — SQLite FTS5 deep project indexer (5 actions)
  MonolithSource        — Engine source + API lookup (10 actions)

119 actions total across 9 modules, exposed through ~14 namespace tools.

Tool Reference

Auto-Updater

Monolith includes a built-in auto-updater:

1. On editor startup — Checks GitHub Releases for a newer version
2. Downloads and stages — If an update is found, it downloads and stages the new version
3. Auto-swaps on exit — The plugin is replaced when you close the editor
4. Manual check — Use the monolith_update tool to check for updates at any time
5. Disable — Toggle off in Editor Preferences > Plugins > Monolith

Troubleshooting / FAQ

Configuration

Plugin settings are at Editor Preferences > Plugins > Monolith:

Skills

Monolith bundles 9 Claude Code skills in Skills/ for domain-specific workflows:

Documentation

• API_REFERENCE.md — Full action reference with parameters
• SPEC.md — Technical specification and design decisions
• CONTRIBUTING.md — Development setup, coding conventions, PR process
• CHANGELOG.md — Version history and release notes

Contributing

Contributions are welcome! See CONTRIBUTING.md for dev environment setup, coding conventions, how to add new actions, and the PR process.

License

MIT — See ATTRIBUTION.md for credits.