GraphRAG Guide

What Is UE-GraphRAG?

AgentUX ships with UE-GraphRAG, a knowledge base of 19.1M+ indexed nodes covering 27 UE5 releases (5.0.0 through 5.7.3). It gives Claude source-code-level understanding of every class, function, property, module, plugin, CVar, and documentation page in the engine, all with full version awareness.

AI models have a training cutoff. They don't know about APIs added or changed in the latest Unreal Engine releases, and they can't look up exact property names on the fly. GraphRAG fills that gap: it's built directly from your UE source tree, so your AI always has version-accurate knowledge, not stale training data.

Key Statistics

How It Works

GraphRAG combines two storage backends for different query types:

• Neo4j: Graph database for structural queries: class hierarchies, module relationships, function signatures, inheritance chains, and version-scoped lookups
• LanceDB: Vector database for semantic queries: natural language search over source code and documentation using ONNX embeddings

When Claude needs to verify a property name or explore an API, it calls the appropriate MCP tool. Structural queries (get_class_details, get_class_hierarchy) run directly against Neo4j and return in 4–45ms. Semantic queries (search_ue_source, search_ue_docs) embed the query and search LanceDB vectors, returning in under 300ms.

MCP Tool Reference

GraphRAG is exposed through 20 MCP tools organized into five categories:

All tools accept an optional ue_version parameter for version-scoped queries. See Multi-Version Queries below.

Source Code Tools

search_ue_source: Semantic Source Code Search

Search the entire UE source tree using natural language. Uses vector embeddings to find the most relevant classes, functions, and module summaries.

# Find how actors are spawned
search_ue_source(query="how to spawn an actor in the world")

# Find Niagara particle system creation code
search_ue_source(query="create particle system emitter", plugin_name="Niagara")

# Find editor subsystem classes only
search_ue_source(query="editor subsystem for asset management", chunk_type="class", category="Editor")

get_class_details: Full Class Information

Get complete details for a UE class: inheritance chain, all functions with signatures, properties, delegates, module, and file path. Always use this before guessing UPROPERTY or UFUNCTION names.

# Get all properties and functions on a fog component
get_class_details(class_name="UExponentialHeightFogComponent")
# Returns: FogDensity (float), bEnableVolumetricFog (bool), VolumetricFogAlbedo (FLinearColor), etc.

Important: Property names are case-sensitive. FogDensity is correct; fogDensity, Density, and fog_density are all wrong and will silently fail.

get_class_hierarchy: Inheritance Tree

Get ancestors, descendants, or both for any class. Essential for finding where inherited properties are defined.

# Find where Intensity is defined in the light hierarchy
get_class_hierarchy(class_name="USpotLightComponent", direction="up")
# Returns: USpotLightComponent -> UPointLightComponent -> ULocalLightComponent -> ULightComponent
# Intensity, LightColor, Temperature are on ULightComponent (parent)

find_api_surface: Blueprint/Exec Callable Functions

Find functions with specific UFUNCTION specifiers on a class or module.

# Find all BlueprintCallable functions on a fog component
find_api_surface(target="UExponentialHeightFogComponent", specifiers=["BlueprintCallable"])
# Returns: SetFogDensity(float), SetVolumetricFog(bool), etc.

Documentation Tools

search_ue_docs: Semantic Documentation Search

Search ~14,857 doc chunks from C++ API descriptions, UDN tooltips, Blueprint API docs, and community guides.

# How does dynamic lighting work?
search_ue_docs(query="how to set up dynamic lighting")

# Actor lifecycle
search_ue_docs(query="actor lifecycle initialization order")

get_ue_guidance: Best Practices & Patterns

Search curated guidance: community guides, best practices, code examples, and design patterns.

# GAS best practices
get_ue_guidance(query="Gameplay Ability System best practices", topic="gameplay-ability-system")

# Plugin architecture patterns
get_ue_guidance(query="how to structure a UE5 C++ plugin")

Versioning Tools

get_version_diff: Compare Class Between Versions

Compare a class between two UE versions, showing added/removed/changed functions and properties.

# What changed in AActor between UE 5.4 and 5.5?
get_version_diff(class_name="AActor", from_version="5.4.0", to_version="5.5.0")

get_version_history: Class Lifecycle Across All Versions

Track when a class was introduced, removed, and how it evolved across all 27 indexed releases.

# When was PCGGraph introduced?
get_version_history(class_name="UPCGGraph")
# Returns: first appeared in 5.2.0, per-version function/property counts

Common Workflows

Before Writing UE C++ Code

Always verify names before writing code that references UE types:

# 1. Find the class
search_ue_class(pattern="ExponentialHeightFog")
# -> AExponentialHeightFog

# 2. Get exact property names
get_class_details(class_name="UExponentialHeightFogComponent")
# -> FogDensity (float), NOT "Density" or "fogDensity"

# 3. Find callable functions
find_api_surface(target="UExponentialHeightFogComponent", specifiers=["BlueprintCallable"])
# -> SetFogDensity(float), SetVolumetricFog(bool)

# 4. Check parent classes for inherited properties
get_class_hierarchy(class_name="UExponentialHeightFogComponent", direction="up")

Combining Editor Control with GraphRAG

Use GraphRAG to look up the correct API, then use AgentUX editor commands:

# 1. Look up the correct property name
get_class_details(class_name="UDirectionalLightComponent")
# -> Intensity is on parent ULightComponent

# 2. Verify via hierarchy
get_class_hierarchy(class_name="UDirectionalLightComponent", direction="up")

# 3. Use AgentUX to set it
{"method": "editor.rc.property", "params": {
  "path": "/Game/Maps/Main.Main:PersistentLevel.DirectionalLight.LightComponent0",
  "property": "Intensity", "value": 10.0, "access": "WRITE"
}}

Exploring a Plugin

# 1. Browse plugin contents
search_by_plugin(plugin_name="PCG", limit=50)

# 2. Drill into a specific class
get_class_details(class_name="UPCGGraph")

# 3. Find related classes
find_related_classes(class_name="UPCGGraph")

Understanding a System

# 1. Semantic search for the concept
search_ue_source(query="world partition streaming levels")

# 2. Read the documentation
search_ue_docs(query="world partition streaming setup")

# 3. Get best practices
get_ue_guidance(query="world partition best practices")

# 4. Find relevant CVars
search_params(query="world partition streaming", system="CVar")

Multi-Version Queries

All tools accept a ue_version parameter with these values:

# Get AActor's API in UE 5.4
get_class_details(class_name="AActor", ue_version="5.4.0")

# Cross-version search
search_ue_class(pattern="NaniteStaticMesh*", ue_version="all")

Safety Enhancement

GraphRAG powers the second layer of AgentUX's safety system. With 7,350+ indexed assertions from the engine source, your AI gets warned about dangerous preconditions before triggering them.

• Layer 1 (Hardcoded Guards) (always active): Block known unsafe operations like saving during PIE
• Layer 2 (GraphRAG-Enhanced) (when connected): Queries the knowledge base for check() and ensure() calls, covering thousands of additional edge cases per session

Without GraphRAG, Layer 1 still provides core safety. With GraphRAG, coverage expands dramatically, especially for operations on less-common classes where hardcoded guards may not exist.

Performance

Structural graph queries (get_class_details, get_class_hierarchy) are fast from the start since they don't use embeddings. The one-time ~18s delay only applies to the first semantic search tool call.

Tip: Start Neo4j as a Windows service (neo4j install-service && neo4j start) so it's always running when the editor launches.

Neo4j Setup

GraphRAG requires Neo4j Community Server 5.x. If you haven't installed it yet:

1. Download Neo4j Community Edition 5.x
2. Ensure Java 21+ is installed
3. Extract and start:

   neo4j console

4. Verify at bolt://localhost:7687
5. Run the AgentUX installer to populate the database:

   python install.py

For persistent background operation on Windows:

neo4j install-service
neo4j start

Troubleshooting

Neo4j connection errors

• Verify Neo4j is running: neo4j status
• Check that bolt://localhost:7687 is accessible
• Verify Java 21+ is installed: java -version

Slow first query

The first semantic query loads the ONNX embedding model (~600MB). This is a one-time cost per session. Subsequent queries complete in under 300ms. If Neo4j is cold, add ~6 seconds for JVM startup.

MCP server not connecting

• Verify GRAPHRAG_CONFIG env var points to the correct config.yaml
• Run python install.py --skip-deps to reconfigure
• Check that LanceDB data is present at the configured path

Stale or missing data

If the knowledge base seems incomplete or outdated, rebuild it from the source docs. See the Installation Guide's GraphRAG Setup section.

Tips

• Always verify names: UE property and function names are case-sensitive. A wrong name silently fails. Use get_class_details before guessing.
• Check parent classes: Many properties are inherited. Use get_class_hierarchy(direction="up") to find where a property is defined.
• Use semantic search for concepts: search_ue_source and search_ue_docs understand natural language.
• Struct parameters: Functions with struct parameters often can't be called via editor.rc.call. Use editor.rc.property WRITE instead.
• Combine tools: Use search_ue_docs for "how it works", get_ue_guidance for "how to do it well", and search_ue_source for "show me the code".
• Version shorthand: Use "5.5" instead of "5.5.0". It auto-resolves to the latest patch.
• Default version: If you omit ue_version, queries run against the configured default. You usually don't need to specify a version for current-engine work.

Related

• Quick Start: Get running in under 10 minutes
• Installation: Detailed setup including Neo4j
• API Reference: All 558+ editor control methods