Monolith

One plugin. Every Unreal domain. Zero Python bridges.

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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

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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/

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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

Namespace	Tool	Actions	Description
monolith	monolith_discover	—	List available actions per namespace
monolith	monolith_status	—	Server health, version, index status
monolith	monolith_reindex	—	Trigger full project re-index
monolith	monolith_update	—	Check or install updates
blueprint	blueprint.query	5	Graph topology, variables, execution flow, node search
material	material.query	14	Inspection, editing, graph building, previews, validation
animation	animation.query	23	Montages, blend spaces, ABPs, skeletons, bone tracks
niagara	niagara.query	39	Systems, emitters, modules, parameters, renderers, HLSL
editor	editor.query	13	Build triggers, error logs, compile output, crash context
config	config.query	6	INI resolution, explain, diff, search
project	project.query	5	Deep project search — FTS5 across all indexed assets
source	source.query	10	Engine source lookup, call graphs, class hierarchy

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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

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Troubleshooting / FAQ

Problem	Solution
Plugin doesn't appear in editor	Verify the folder is at YourProject/Plugins/Monolith/ and contains Monolith.uplugin. Check you're on UE 5.7+.
MCP connection refused	Make sure the editor is open and running. Check Output Log for port conflicts. Verify .mcp.json is in your project root.
Index shows 0 assets	Run monolith_reindex or restart the editor. Check Output Log for indexing errors.
Source tools return empty results	The Python engine source indexer hasn't been run. See Step 5 above.
Claude can't find any tools	Check that .mcp.json has "type": "streamableHttp" (not "http" or "sse"). Restart Claude Code after creating the file.
Tools fail on first try	Restart Claude Code to refresh the MCP connection. This is a known quirk with initial connection timing.
Port 9316 already in use	Change the port in Editor Preferences > Plugins > Monolith, then update the port in .mcp.json to match.
Mac/Linux not working	Monolith currently supports Windows only. Mac and Linux support is planned for a future release.

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Configuration

Plugin settings are at Editor Preferences > Plugins > Monolith:

Setting	Default	Description
MCP Server Port	9316	Port for the embedded HTTP server
Auto-Update	On	Check GitHub Releases on editor startup
Module Toggles	All enabled	Enable/disable individual domain modules
Database Path	Project-local	Override SQLite database storage location

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Skills

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

Skill	Description
unreal-blueprints	Graph reading, variable inspection, execution flow
unreal-materials	PBR setup, graph building, validation
unreal-animation	Montages, ABP state machines, blend spaces
unreal-niagara	Particle system creation, HLSL modules, scalability
unreal-debugging	Build errors, log search, crash context
unreal-performance	Config auditing, shader stats, INI tuning
unreal-project-search	FTS5 search syntax, reference tracing
unreal-cpp	API lookup, include paths, Build.cs gotchas
unreal-build	Smart build decision-making, Live Coding vs full rebuild

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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

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Contributing

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

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License

MIT — See ATTRIBUTION.md for credits.