unreal-mcp-ue4-for-OHD

UE4.25.4-first MCP server for Operation Harsh Doorstop modding via Unreal Python Remote Execution (stdio transport)

Fork of runreal/unreal-mcp, heavily refactored UE4-first (via a UE4.27.2 stage) and retargeted here to UE4.25.4 for the OHDCore Mod Kit: same transport and tool surface, with version pins, docs links, and Python-dialect constraints adjusted for the kit's embedded Python 2.7.14. Port, tool, docs, and smoke-test work were developed with assistance from OpenAI Codex.

Contents

• Requirements · Setup · Migrating from unreal-mcp-ue4 · Editor remote execution · Usage · Sidebar tab · Internals · Testing · Publishing · Available Tools · Contributing · Troubleshooting · Notes and Limitations · Roadmap · License

Requirements

Reference: Unreal Engine Python API 4.25. No custom C++ plugin is required — the server uses the editor's built-in Python Remote Execution. UE5-only scripting features are not reintroduced; unreliable graph/binding flows are excluded from the MCP surface or return a clear message instead of failing silently.

graph TD
    A[MCP client] --> B[unreal-mcp-ue4-for-ohd stdio server]
    B --> C[manage_* namespaces + direct tools]
    C --> D[Python 2.7 payloads]
    D --> E[Unreal Editor via Remote Execution]

Setup

Autonomous agents setting up unattended: follow the ordered guide in docs/agent-setup.md.

npm install -g unreal-mcp-ue4-for-ohd   # recommended; then reference the `unreal-mcp-ue4-for-ohd` binary
npx unreal-mcp-ue4-for-ohd              # one-off invocation

Local source checkout:

git clone https://github.com/RibatTRW/unreal-mcp-ue4-for-OHD.git
cd unreal-mcp-ue4-for-OHD
npm install
npm run build   # produces `dist/bin.js`, `dist/index.js`, `dist/editor/tools.js`

One install, then one line per client (global vs local-checkout variants). All clients call the same 34 tools over stdio (3 session-info + 3 direct actor CRUD primitives + 28 manage_* namespaces):

Copilot docs: Extending GitHub Copilot Chat with MCP servers · About Model Context Protocol in GitHub Copilot

Migrating from unreal-mcp-ue4

This fork was renamed to its own identity so it can ship independently of upstream. Upstream credit: the UE4 line derives from conaman/unreal-mcp-ue4 (itself forked from runreal/unreal-mcp).

Re-add the server in your client (local server labels such as unreal-ue4 are unchanged — only the command changes):

claude mcp add --scope user unreal-mcp-ue4-for-ohd -- unreal-mcp-ue4-for-ohd
codex mcp add unreal-ue4 -- unreal-mcp-ue4-for-ohd

Copilot .vscode/mcp.json: change "command" to "unreal-mcp-ue4-for-ohd", keeping the unreal-ue4 server key.

Editor remote execution

Verified live against the kit. In the OHD editor (LaunchEditor.bat → HarshDoorstop.uproject):

1. Edit -> Plugins: enable Python Editor Script Plugin (ships disabled). Editor Scripting Utilities is already enabled — no action needed. Enable SequencerScripting (ships disabled) only for advanced manage_sequence actions: actor binding, track/key edits, camera cuts, playback ranges, speed-track analysis.

2. Restart if prompted → Edit -> Project Settings -> Plugins -> Python → enable Enable Remote Execution (endpoint 239.0.0.1:6766, bind 0.0.0.0, raise Multicast TTL from kit default 0 to 1). Restart again if needed.

3. Keep the project open while using the server or tests; restart the editor after any plugin/Python setting change.

4. No UMG plugin to install (tooling uses shipped editor modules). Do mod experiments in a throwaway content-only mod (Create Mod in the editor); never edit shipped Plugins/*, HDAssets, or engine content.

Connection env overrides (UNREAL_MCP_*):

Usage

• Prefer manage_* namespace tools (action-specific input schemas are exposed over MCP). Namespaces dispatch through action + params. Canonical reads: manage_editor.project_info (project), manage_editor.map_info + manage_level.world_outliner (map/level). Discover the surface with manage_tools (list_namespaces).

• Direct tools (get_unreal_*, editor_create/update/delete_object) are low-level primitives for session path discovery and actor CRUD.

• manage_editor.run_python is the escape hatch for debugging, prototyping, and UE4.25 API gaps — still Python 2.7-compatible.

First run: open the kit project and wait for load → confirm plugins + remote execution → npm install -g unreal-mcp-ue4-for-ohd (or npm run build) → open/start the client session → run something read-only:

• unreal-mcp-ue4-for-ohd --version (prints version, no stdio transport)

• manage_editor + action: "project_info" / "map_info" · manage_level + "world_outliner" · manage_tools + "list_namespaces"

• In prose: Get project info from the unreal-ue4 server. · List the actors in the current level. · Spawn a StaticMeshActor named TestCube at 0,0,100.

What the server can do: read project/map/asset/actor info; spawn, inspect, move, delete level actors; search assets and inspect references/metadata; create DataAsset/StringTable and other common UE4 data assets; create/edit Blueprint assets and Widget Blueprint trees where UE4.25 Python exposes the APIs.

Sidebar tab

One call sets up the EUW (Editor Utility Widget) sidebar tab end to end — an EUW asset plus a WebBrowser child hosting a web page beside the viewport:

manage_widget + action: "setup_sidebar_tab", params widget_blueprint_path (e.g. /Game/DSHSidebar), url (any page URL; the DSH web GUI is the convention), use_template: true (missing target is duplicated from the golden template — full-fill DSHBrowser + verified On Key Down shortcut fix — instead of built from scratch; re-runs are idempotent, reusing existing targets while refreshing URL/layout).

Caveats: non-DSH pages get no editor-driving loop (typing in them does nothing to the viewport); the 4.25 CEF gate applies (a minimal page renders where a full app shows blank); first template use reports template_staged (the 4.25 Asset Registry can't see the staged /Game file until restart — restart, then re-run); a custom browser_widget_name is ignored on the template path with a warning and DSH asset/browser names stay; if the opened tab looks stale, Compile the widget blueprint in the designer, then dock it beside the viewport.

Internals

TypeScript 7 native toolchain (tsc -p tsconfig.json, ES2022, Node 20 proven), stdio transport, Effect-migrated dispatch/connection layers (Zod stays at the MCP SDK call-site — the SDK only accepts Zod). Recent performance work:

Testing

Runner options: --keep-assets (inspect results in the Content Browser), --skip-namespace (skip namespace-dispatch portion), --verbose (MCP server stderr), --help (options without rebuilding). Windows PowerShell:

cd C:\dev\unreal-mcp-ue4-for-OHD
npm install
npm run test:no-unreal
npm run test:e2e
npm run test:e2e -- --with-assets

Success = [PASS] on every step; actor tests visibly create then remove temp actors (both surfaces); asset tests create then remove temp Blueprint/DataAsset/StringTable/Texture/Widget assets. Workflow: test:no-unreal → test:e2e → test:e2e -- --with-assets → try the real client → use a test project before production content.

Publishing

Version format YYYY.M.D-N, unified everywhere (current 2026.9.9-1) — bump it, then:

npm run publish:check                                  # typecheck + rebuild + tarball dry-run
npm run test:e2e -- --with-assets --skip-build         # when an OHD (UE4.25) editor is available
npm publish --tag latest                               # explicit dist-tag required (semver prerelease suffix)

prepack runs npm run build, so the tarball always uses a fresh dist.

Available Tools

Notes call out important requirements or UE4.25 limitations when they matter. Empty notes mean there are no additional caveats beyond normal editor setup.

The recommended public surface is the manage_* namespace layer. Prefer manage_editor.project_info, manage_editor.map_info, and manage_level.world_outliner as canonical read entry points, and treat the small direct-tool set as low-level primitives for path discovery and actor CRUD.

Editor Session Info

Core Direct Tools

Core Tool Namespaces

World & Environment Tool Namespaces

Content & Authoring Tool Namespaces

Gameplay & Systems Tool Namespaces

Excluded Capability Areas

These capability areas are intentionally not exposed through the MCP surface in this UE4.25 port because they fail reliably in the current Python environment and only add prompt or context overhead until a native bridge exists.

Contributing

main is protected by the protect-main ruleset (PRs only — no direct pushes, force-pushes, or deletions; review threads must resolve). Branch off main, open a PR back, and before pushing run npm run typecheck + npm run check:py27 (plus npm run test:no-unreal when possible). Keep payloads Python 2.7-compatible; the tables above regenerate during build, so run npm run build before committing doc changes.

Troubleshooting

• Remote node is not available: open the editor fully first; verify Python Editor Script Plugin, Editor Scripting Utilities, and Enable Remote Execution are enabled; restart after changing any of them.

• Connection/discovery on Windows: allow UnrealEditor.exe and node.exe through Windows Defender Firewall. Discovery is UDP multicast on 239.0.0.1:6766, command channel on 6776. Override the bind address with UNREAL_MCP_BIND_ADDRESS or UNREAL_MCP_COMMAND_ADDRESS when the editor can't discover/connect. In JSON configs, escape backslashes or use forward slashes.

• Client can't find unreal-mcp-ue4-for-ohd or node: put the npm global binary dir on the client's PATH (or use the absolute unreal-mcp-ue4-for-ohd path); for source checkouts use the absolute node/node.exe path instead of relying on PATH.

• Blueprint graph / UMG binding commands unavailable: expected — Widget creation + tree editing work, but delegate bindings and runtime viewport flows don't; Blueprint asset/component/compile + summaries work, but graph inspection, pin wiring, and variable/function metadata are excluded (stock UE4.25 Python doesn't expose them). Full list under Excluded Capability Areas above.

Notes and Limitations

• World/structure tools use UE4.25-friendly preset builders on engine basic-shape assets.

• UMG editing works with native PanelWidget parents; absolute positioning targets CanvasPanel slots — run manage_widget.ensure_canvas_root first when the root isn't a Canvas. Reparenting the root widget and named-slot edits aren't handled; delegate bindings remain unavailable.

• Blueprint asset/component editing works; graph inspection, pin wiring, and variable/function metadata inspection are excluded.

• The surface mixes granular tools and action-based namespaces so clients can work at different abstraction levels.

Roadmap

• Improve Code Architecture (Effect-migration phases 0-7 landed)

• Add Dsh Harness Support (manage_widget.setup_sidebar_tab + golden template)

• Add a agent.md so agents can install it easily (landed as docs/agent-setup.md)

• Add GitHub Actions CI (.github/workflows/ci.yml green on main + Tests badge live; protect-main ruleset PR-only with required status checks)

• Cut a first fork release (tags exist, e.g. 2026.5.12-12; published to npm as unreal-mcp-ue4-for-ohd)

• Decide registry identity: renamed to the fork's own io.github.RibatTRW/unreal-mcp-ue4-for-ohd (see Migrating from unreal-mcp-ue4 above)

License

Licensed under the MIT License.