VibeUE is the MCP Expansion + AI Editor Toolset for Unreal Engine 5.8+. Unreal 5.8 added a built-in MCP server and AI toolsets; VibeUE is an MCP Expansion that plugs straight into them and adds a deep AI Editor Toolset — a library of editor capabilities — Blueprints, materials, landscape, foliage, animation, Niagara, UMG, audio, StateTree, Behavior Trees & Blackboards, gameplay tags, input, UVs, performance/profiling, and more — registered into the engine's own ToolsetRegistry and ModelContextProtocol server, plus rich domain skills served through Unreal's native AgentSkill system. Any MCP-capable agent (Claude Code, Cursor, Copilot, …) drives your editor through Unreal's standard MCP endpoint.

⚠️ VibeUE requires Unreal's native MCP to be set up first — enable the Unreal MCP plugin (which auto-enables Toolset Registry) and the Editor Tools plugin, then start the MCP server. Follow Epic's guide: Unreal MCP in the Unreal Editor. VibeUE then expands that endpoint — no separate server and no in-editor chat. A free API key (set in Editor Preferences → Plugins → VibeUE) unlocks the real-world terrain tools; everything else works without one.

✨ What VibeUE adds

Unreal 5.8 ships its own AI toolsets (Blueprints, materials, actors, assets, meshes, data tables, …). VibeUE complements them — it focuses on the domains and depth the engine doesn't cover:

• Terrain & world — Landscape sculpting/heightmaps/splines, landscape auto-materials + RVT, Foliage, procedural FPS Map Blockout, and real-world terrain (heightmaps + water from GPS).
• Audio — MetaSound and SoundCue graph authoring.
• Animation assets — AnimSequence keyframe editing, AnimMontage authoring, AnimBP state machines, Skeleton bone/socket/retarget/blend-profile editing.
• FX depth — Niagara emitter color/curve authoring and Custom-HLSL scratch-pad modules.
• UI — UMG widgets with MVVM bindings, animation authoring, and preview/PIE validation.
• Higher-order Blueprint authoring — timelines, event dispatchers, delegates, custom-event pins, comment boxes, and a batch build_graph builder.
• AI behavior authoring — Behavior Tree node/decorator/service editing by structural path with blackboard key binding, JSON tree round-trips, and validate/repair; full Blackboard asset + key CRUD. Writes go through the editor EdGraph with PIE- and open-editor-aware refusal guards.
• Editor safety — TransactionService wraps the editor's transaction buffer (undo / redo / checkpoints) so an agent can group and roll back its own edits — the engine's toolsets expose none.
• ⚡ Performance & profiling — VibeUE's standout: see the dedicated section below.
• Python-first access — run any unreal.* Python in the editor and introspect the whole API.
• Web research — search / fetch / geocode for in-context research and terrain workflows.

It deliberately does not duplicate the engine's general tools (basic asset/actor/blueprint/material CRUD, screenshots, logs, PIE) — agents use Unreal's native toolsets for those.

⚡ Performance & Profiling (flagship)

Unreal's native AI toolsets have zero performance tooling — they can start PIE/Simulate but can't measure anything. VibeUE's PerformanceService fills that gap so an agent can actually diagnose and fix frame rate:

• frame_timing() — Game/Render/GPU/RHI thread split + a CPU-vs-GPU-bound verdict and a concrete next-step hint. Run this first — optimising the GPU does nothing on a CPU-bound frame.
• Unreal Insights capture — start_trace / stop_trace / get_trace_status, with bookmark and region_start / region_end markers.
• analyse() — reads the trace and log back and returns a perf summary (frame stats, worst frames, hitches, notable log lines).
• Trace-attached start_standalone — profile a representative standalone build, not just the editor viewport.

import unreal
print(unreal.PerformanceService.frame_timing())   # CPU vs GPU bound — diagnose FIRST
unreal.PerformanceService.start_trace("cap", "")   # Insights trace
# … reproduce the workload (ideally under PIE / standalone) …
unreal.PerformanceService.stop_trace()
print(unreal.PerformanceService.analyse("both", ""))

Pair with the profiling and frame-rate skills for the full CPU/GPU drill-down.

🏗️ Architecture

VibeUE plugs into three native UE 5.8+ systems:

1. Toolsets (ToolsetRegistry) — VibeUE's services register as UToolsetDefinitions, so their methods become AICallable tools on the MCP endpoint. They're also BlueprintCallable, so the same methods are callable from Python as unreal.<Name>Service.<method>().
2. MCP server (ModelContextProtocol) — a small set of VibeUE utility tools are registered directly on the endpoint: execute_python_code, discover_python_module/_class/_function, list_python_subsystems, deep_research, terrain_data.
3. Skills (AgentSkillToolset) — ~36 markdown skill packs register as native UAgentSkills, discoverable via ListSkills and loaded lazily via GetSkills, alongside the engine's own skills.

Efficient usage (for agents): execute_python_code is the workhorse — it batches a whole multi-step task into one round-trip and reaches every VibeUE service plus the full unreal.* API. Use call_tool only for skills and the few engine toolsets with no Python path (screenshots, etc.). See Content/samples/AGENTS.md.sample for the full agent guide.

🚀 Installation & setup

Requirements: Unreal Engine 5.8+ · Git

Step 1 — Set up Unreal's native MCP (do this FIRST)

VibeUE is an expansion of Unreal's built-in MCP support, so enable that first. Full details in Epic's guide: Unreal MCP in the Unreal Editor.

1. Edit → Plugins → enable Unreal MCP (this auto-enables Toolset Registry) and Editor Tools (the engine's own AI toolsets, so agents get both). These are Experimental. Restart when prompted.
2. Edit → Editor Preferences → General → Model Context Protocol → enable Auto Start Server (or run the console command ModelContextProtocol.StartServer). Default endpoint http://127.0.0.1:8000/mcp (port/path configurable). Enabling Tool Search keeps an agent's context small — it sees list_toolsets / describe_toolset / call_tool and loads tools on demand.

Step 2 — Install VibeUE

cd /path/to/YourProject/Plugins
git clone https://github.com/kevinpbuckley/VibeUE.git

Build with the project script:

Plugins/VibeUE/BuildAndLaunchGame.ps1                  # builds + launches the editor
Plugins/VibeUE/BuildAndLaunchGame.ps1 -StrictRebuild   # full recompile (warnings-as-errors)
Plugins/VibeUE/BuildAndLaunchGame.ps1 -Map /Game/Maps/MyMap   # open a specific map (issue #554)

On Linux or macOS, use the platform-detecting shell script:

Plugins/VibeUE/BuildAndLaunchGame.sh --engine /path/to/UE5
Plugins/VibeUE/BuildAndLaunchGame.sh --engine /path/to/UE5 --strict-rebuild
Plugins/VibeUE/BuildAndLaunchGame.sh --engine /path/to/UE5 --map /Game/Maps/MyMap

Then Edit → Plugins → enable VibeUE and restart. Its services, tools, and skills now register onto the same endpoint, alongside the engine's own.

Step 3 — Connect your agent

Two console commands from the editor (open the console with `):

1. Write the MCP server config (.mcp.json at the project root):

ModelContextProtocol.GenerateClientConfig ClaudeCode

(supports ClaudeCode, Cursor, VSCode, Gemini, Codex, or All.)

2. Write VibeUE's agent guide so the assistant uses the efficient patterns:

VibeUE.GenerateAgentConfig ClaudeCode

This writes the guide to the correct file for your agent — CLAUDE.md (Claude Code), GEMINI.md (Gemini), AGENTS.md (Codex / Hermes / Cursor), or .github/copilot-instructions.md (Copilot) — or pass All to write CLAUDE.md + GEMINI.md + AGENTS.md at once. It resolves the plugin location automatically, so it works whether VibeUE was installed from FAB or Git. The guide goes in a managed block, so re-run any time to refresh without disturbing your own notes. Pass import to link the guide with a one-line @import instead of copying it (Claude Code / Gemini only — other agents don't resolve imports, so they always get a copy).

The MCP server is loopback-only with no authentication — same-machine use only (per Epic's docs).

The guide teaches: discover before you call (discover_python_class), batch with execute_python_code, load skills via ListSkills/GetSkills, and when to reach for deep_research / terrain_data.

🎯 Skills

Skills are lazy-loaded domain knowledge (workflows, gotchas, property formats) served by Unreal's native AgentSkillToolset:

# discover (summaries only — cheap)
call_tool(tool_name="ListSkills", toolset_name="ToolsetRegistry.AgentSkillToolset")

# load the packs you need (full markdown, lazy)
call_tool(tool_name="GetSkills", toolset_name="ToolsetRegistry.AgentSkillToolset",
          arguments={"skillPaths": ["/VibeUE/Python/init_unreal_PY.VibeUE_blueprints"]})

ListSkills is the live source of truth for what's available (it reads each pack's SKILL.md). Skills tell you what to do and why; use discover_python_class('unreal.<Name>Service', method_filter='…') for exact signatures before writing code.

🔧 Plugin dependencies

Native engine prerequisites (enable in Step 1 — Epic's MCP stack):

Enabled automatically by VibeUE: PythonScriptPlugin (the unreal.* API), EditorScriptingUtilities, and the domain plugins its services need — Niagara, MetaSound, EnhancedInput, ModelViewViewModel, StateTree, MeshModelingToolset, GameplayTagsEditor. (VibeUE also depends on ToolsetRegistry + ModelContextProtocol, so enabling VibeUE pulls them in — but you still enable Editor Tools and start the server per Step 1.)

🛠️ Build & launch script

BuildAndLaunchGame.ps1 (project root or Plugins/VibeUE/) stops the running editor, builds, and relaunches:

• -StrictRebuild — full plugin recompile under warnings-as-errors
• -Clean — wipe intermediate/binaries first
• -SkipBuild — relaunch only

📚 The live API

VibeUE intentionally keeps no static method catalog in this README — the surface evolves with the engine. The authoritative, always-current references are:

• ListSkills → which domains exist and when to use them.
• discover_python_class('unreal.<Name>Service') → exact method signatures.
• describe_toolset('VibeUE.<Name>Service') → the toolset's tools + JSON schemas (token-heavy; prefer skills + discovery).

License

MIT — see LICENSE. Project home: https://www.vibeue.com/