vibeue

name vibeue description Unreal Engine 5 development using the VibeUE Python API. Use when working in Unreal Engine — blueprints, state trees, materials, actors, landscapes, animation, niagara, widgets, sound, foliage, gameplay tags, enhanced input, skeletons, PCG (procedural content generation), and more. VibeUE is an extension of Unreal's native MCP endpoint. VibeUE is an extension on Unreal Engine's native MCP endpoint ( http://localhost:8000/mcp ). There is no separate VibeUE server, no API key, and no in-editor chat — VibeUE simply registers extra Python services ( unreal.<Service> ) and skill packs on top of the engine's own toolsets. Wait for VibeUE readiness after launch BuildAndLaunchGame.ps1 / .sh print Editor-PID=<pid> — treat that as the process identity. Check once, then watch the filesystem for <ProjectDir>/Saved/VibeUE/Signals/editor-<pid>-true.json before using MCP. Wait at most 180 seconds, do not poll MCP while waiting, and fail if that Editor process exits or the timeout expires. Ignore signal files for other or dead PIDs. The signal only means RegisterToolsets() reached its end; Python, World, and level readiness remain separate checks. The file is JSON, written atomically, so it is complete the moment it appears: { "signal" : "toolsets-registered" , "pid" : 21044 , "createdUtc" : "2026-08-03T17:04:11.921Z" , "sessionStartUtc" : "2026-08-03T17:03:22.108Z" , "pluginVersion" : "3.0" , "currentMap" : "/Game/Maps/Level1_FullBody" } Process IDs get recycled. The launch scripts clear a matching stale signal right after starting the Editor, but if you launch it some other way, verify sessionStartUtc is later than the moment you started the process before trusting the signal. currentMap is the loaded map's package name and the signal is re-published on every map open (issue #554) — gate world-edit scripts on it . A relaunch opens the project default map unless you pass -Map /Game/Maps/YourMap ( --map on the .sh) to the launch script; editing "the current world" after a relaunch without checking has silently modified the wrong level before. Health heartbeat — dead or wedged editor detection Signals/editor-<pid>-health.json is rewritten every ~5s by a background thread (issue #555): { "signal" : "health" , "pid" : 21044 , "updatedUtc" : "2026-08-03T17:09:00.000Z" , "sessionStartUtc" : "2026-08-03T17:03:22.108Z" , "gameThreadStallSeconds" : 0.03 } Epic's MCP endpoint runs on the game thread with no request timeout, so a dead or wedged editor hangs MCP calls for the client's full timeout — and even JSON-RPC ping hangs with it. Read the health file instead: file missing or updatedUtc older than ~15s → the process is gone (relaunch); gameThreadStallSeconds above ~10 → alive but wedged (modal dialog / crash handler; MCP will hang — relaunch); fresh and small → the editor is healthy, debug something else. Skill packs (this file and its siblings) are loaded through the engine's AgentSkillToolset . Each skill carries exact API patterns and gotchas; load the relevant skill before writing any code in a domain, or you will guess wrong property names and spiral into discovery loops. Discover and load skills Skills are discovered and read through the engine AgentSkillToolset , invoked with call_tool : # List every available skill (full path → description) call_tool(toolset_name="ToolsetRegistry.AgentSkillToolset", tool_name="ListSkills", arguments={}) # Read one or more skills — GetSkills takes the FULL paths that ListSkills returns call_tool(toolset_name="ToolsetRegistry.AgentSkillToolset", tool_name="GetSkills", arguments={"skillPaths": ["/VibeUE/Python/init_unreal_PY.VibeUE_pcg", "/VibeUE/Python/init_unreal_PY.VibeUE_materials"]}) Naming rule (verified live): skill pack <slug> registers as VibeUE_<slug> (hyphens → underscores) and sub-doc <slug>/<file>.md as VibeUE_<slug>__<file> , all under the path prefix /VibeUE/Python/init_unreal_PY. . Short names such as "pcg" or "state-trees/api-reference" return an empty result with no error — always pass full paths, taking them from ListSkills when unsure. Run describe_toolset on ToolsetRegistry.AgentSkillToolset if the call signature differs in your build. The old vibeue-skills-manager tool no longer exists. Route by functional area. Find the area whose scope matches the task, then GetSkills the listed skill(s) — full paths per the naming rule above. The NOT for column is the disambiguator — when two areas seem to fit, the one that excludes your task is telling you where to go instead. Functional area Use for — NOT for… Load skill(s) Scene & actors place / move / arrange / organize / tag actors in a level — NOT gameplay logic (→ Blueprints), NOT world-scale terrain/foliage (→ Environment), NOT attaching a Niagara/particle component (→ VFX) level-actors Blueprints & gameplay logic author Blueprint classes & graphs, Enhanced Input, gameplay tags, Gameplay Ability System (abilities/attributes/effects/cues) — NOT AI behavior (→ AI), NOT AnimBP graphs (→ Animation), NOT C++/source (coding-agent handoff) blueprints , blueprint-graphs , enhanced-input , gameplay-tags , gas AI author StateTree logic — states, tasks, transitions, event payloads, delegate bindings — NOT character body animation (→ Animation), NOT generic actor placement (→ Scene) state-trees Animation & rigging AnimBP state machines, AnimSequence keyframes, montages & AnimNotify wiring, bone/skeleton editing & retarget — NOT cinematic timelines (Epic Sequencer), NOT AI movement (→ AI), NOT authoring/adding sound assets — even a character's footstep sounds (→ Audio) animation-blueprint , animsequence , animation-editing , animation-montage , skeleton Materials & shading materials, instances, graph nodes, Custom HLSL — NOT Niagara particle materials (→ VFX), NOT landscape auto-materials (→ Environment) materials VFX (Niagara) particle systems, emitters, scratch-pad HLSL, attaching/placing a Niagara component on an actor — NOT surface materials (→ Materials) niagara-systems , niagara-emitters UI (UMG) widget blueprints, layout, fonts/brushes, MVVM — NOT the gameplay behind the UI (→ Blueprints) umg-widgets Environment (world-scale) landscape sculpt/paint, landscape materials, foliage, PCG, map blockout, real-world terrain — NOT single-actor placement (→ Scene), NOT sound/audio (→ Audio) landscape , landscape-materials , landscape-auto-material , foliage , pcg , map-blockout , terrain-data Audio MetaSound and SoundCue authoring — creating the sound asset itself: ambient, a character's footstep/foley, UI sounds — NOT triggering sounds from gameplay logic (→ Blueprints), NOT wiring an existing sound to anim-notify foot-plant frames (→ Animation) metasounds , sound-cues Assets, data & project import/export assets, UV mapping, enums/structs, engine & project settings — NOT actors placed in a level (→ Scene) asset-management , uv-mapping , enum-struct , engine-settings , project-settings Diagnostics, testing & run start/stop/query PIE, profile (CPU-vs-GPU / Insights), uncap frame rate — NOT fixing the logic a bug points to (→ its authoring area) pie-testing , profiling , frame-rate Camera & viewport viewport camera, view mode, FOV, exposure, layout — NOT material look (→ Materials), NOT placing/editing light actors (→ Scene) viewport Cinematics · Physics Sequencer cinematics and Physics assets (ragdoll/skeletal) are Epic-native — VibeUE adds no skill here — NOT enabling simulate-physics on a level actor (→ Scene) (none — use list_toolsets : animation_toolset.* / PhysicsToolsets ) A loaded skill gives you: workflows, gotchas, and property formats for the domain vibeue_classes / unreal_classes — class names to feed into discover_python_class for live method signatures sub-doc references ( <skill>/<section> ) you can fetch via GetSkills for deeper detail Always call discover_python_class on the classes in vibeue_classes before writing code — never guess method names from the skill content alone. Batch the discovery into ONE call instead of one call per class: # ONE call covers all classes and all topics: discover_python_class( class_name="unreal.MaterialService, unreal.WidgetService, unreal.MaterialNodeService", method_filter="create|delete|compile|property|color") # WRONG — three separate calls for three classes wastes round-trips and repeats boilerplate class_name accepts a comma-separated list (response gains a classes array, one entry per class); method_filter ORs keywords with | . How work gets done — execute_python_code is the workhorse VibeUE services are plain Python on the editor's unreal module. Run everything through execute_python_code : import unreal widgets = unreal.WidgetService.list_widget_blueprints() unreal.StateTreeService.create_state_tree( "/Game/AI/MyBehavior" ) You get the full unreal.* API plus every unreal.<Service> VibeUE adds. Reserve call_tool for engine toolsets and skills (e.g. AgentSkillToolset , EditorToolset.EditorAppToolset , LogsToolset , GameplayTagsToolset , AssetTools ). Tools — what each is for Tool Use it for execute_python_code Run unreal.* Python in the editor — the workhorse for every VibeUE service call_tool Invoke engine toolsets and skills (skills, PIE control, logs, assets, gameplay tags) describe_toolset / list_toolsets Discover engine toolsets and their actions/args discover_python_class / discover_python_function / discover_python_module Get live signatures before writing code list_python_subsystems Enumerate editor subsystems for unreal.get_editor_subsystem(...) terrain_data Real-world heightmaps + water splines (see terrain-data skill) deep_research Web research / page fetch / geocoding Engine toolsets replace the old VibeUE tools Several capabilities that used to be VibeUE-specific MCP tools are now the engine's native toolsets, called via call_tool (run describe_toolset for action names/params): Need Engine toolset (via call_tool ) Start / stop / query PIE EditorToolset.EditorAppToolset → StartPIE / StopPIE / IsPIERunning Capture a viewport screenshot EditorToolset.EditorAppToolset → CaptureViewport List / read / filter / tail UE logs LogsToolset Search / open / save / move / import assets AssetTools Single-tag gameplay-tag CRUD GameplayTagsToolset (see gameplay-tags skill) Inspect a live Ability System (attributes/tags/effects/abilities), attribute-set discovery, gameplay cues GASToolsets.* (see gas skill) Performance/Insights tracing is the one net-new VibeUE service — unreal.PerformanceService.* (see the profiling skill) — because Unreal 5.8 ships no performance toolset.