Godot Agent Loop

Build it. Play it. Prove it.

An MCP automation loop for Godot 4.

npm version Godot integration tests

E2E tools: 171/171

MCP Server Made with Godot MIT License

Other integrations give agents tools. Godot Agent Loop gives them a tested feedback loop to author, run, observe, playtest, and independently verify Godot games:

author → validate → run → observe → playtest → verify → refine

Watch the 65-second cold-agent demo

Watch the 65-second demo · Read the exact run evidence · Inspect the resulting project

Quickstart

claude mcp add godot-agent-loop -- npx -y @beremaran/godot-agent-loop

Then point the agent at a project directory—or an empty directory—and describe the playable result. The compact default surface exposes 40 tools for the loop above; the godot_tools meta-tool searches, describes, and dispatches the full 171-tool catalog on demand. Runtime injection is transient; watched projects can use the optional persistent editor addon.

Using Cline, Cursor, or another MCP client? See Configuration.

Proof before claims

• 171/171 tools exercised through the complete MCP-to-Godot path, with 365 public actions traced to resolving tests; see the generated coverage report.
• 171/171 tools have full-path MCP E2E coverage, with the complete serial real-Godot matrix enforced in CI.
• A cold agent built and independently verified a playable win/lose game with zero human corrections, in under seven minutes, using 103 MCP calls and no built-in tools; see the launch evidence and deterministic acceptance record.
• Privileged reflection, code execution, and networking groups are denied by default, and the editor provides a human Pause Agent control.

Support is deliberately bounded: Godot 4.7 is both the compatibility floor and the primary target. Editor attachment is verified on Linux CI and in a headed macOS 4.7.1 acceptance run; Windows retains the documented portable acceptance path but not an editor-UI claim. Full debugger automation, native extension builds, and unbounded engine control are not claimed. Details in the verified support boundary.

Highlights

• Author with or without an editor — attach securely to a normally opened project for undoable scene/resource transactions, or retain detached and CI authoring with explicit synchronization metadata.
• Run and observe — launch the game, capture logs and errors incrementally, take screenshots, and run visual-regression comparisons with baselines, masks, and retained diffs.
• Playtest like a player — mouse, keyboard, key-hold, drag, scroll, touch, and gamepad input against the running game.
• Verify independently — headless GDScript validation (validate_script, validate_scripts), test runners for native/GUT/GdUnit4 (run_project_tests), bounded runtime evidence (verify_project), export checks (verify_export_readiness), and static integrity analysis (analyze_project_integrity).
• Reach into the runtime — inspect and manipulate any node, signal, animation, physics body, or UI control through 100+ runtime tools; game_eval executes GDScript with await support (privileged, opt-in).
• Drive the editor — editor_session ensure discovers the matching project, editor-routed tools and editor_transaction apply reversible edits through EditorUndoRedoManager, and the Agent Activity dock replays the bounded correlated trace with a human Pause Agent lock.
• .NET / C# support — scaffold C# projects with a Godot.NET.Sdk matched to your installed Godot, generate idiomatic scripts, and restore/build/run via verify_dotnet_project.
• Bounded by design — deterministic pagination and size caps on large responses, structured correlated diagnostics, and least-privilege security defaults.

Tool catalog

The full inventory of 171 tools — runtime interaction, scene authoring, project management, verification, 2D/3D rendering, audio, UI, networking, and more — lives in docs/tools.md. Per-tool verification status and test references are in the generated coverage report.

Requirements

• Godot Engine 4.7 or later
• (Optional) .NET SDK 8.0+ and the Godot .NET (C#) build, only if you use create_project's dotnet: true flag or create_csharp_script
• Node.js >= 22.0.0 (active LTS)
• An AI assistant that supports MCP (Claude Code, Cline, Cursor, etc.)

Godot compatibility policy

Development targets the latest stable Godot release. Godot 4.7 is the current compatibility floor and primary target, and CI covers that exact release. The floor may be raised when it blocks useful features or creates meaningful maintenance cost. In that case, the last compatible release remains available, and an older-version maintenance branch will be created only when user demand justifies maintaining it. Such a branch would receive critical fixes rather than new features.

Verified support boundary

Configuration

The quickstart npx command is all most setups need. The sections below cover other clients and a source checkout.

Interactive editor setup

For a project the user watches, copy addons/godot_agent_loop into the project at that same path, enable Godot Agent Loop under Project > Project Settings > Plugins, and restart Godot once. Thereafter Godot may be opened normally; editor_session discovers the matching project without launching a duplicate. The dock remains visible and waits cleanly when no agent is connected.

The addon publishes a private, untracked record at .godot/godot_agent_loop/editor-session.json with a fresh token and ephemeral loopback port for each editor start. The token is never returned or logged. Multiple editors are routed by canonical project path. To uninstall, disable the plugin, close Godot, remove addons/godot_agent_loop, and optionally remove a stale .godot/godot_agent_loop directory. MCP cleanup removes only its own unmodified transient bridge, never this persistent addon.

An editor already started without an enabled compatible addon cannot receive a new EditorPlugin safely at runtime. Install/enable once and restart. See the interaction architecture for states, protocol migration, unsaved-conflict recovery, and fallback semantics.

Portable agent bundle

The repository ships one neutral bundle that starts the matching npm MCP server and provides the same build, debug, verify, and ship skills to Claude Code, Codex, OpenCode, and Pi. For Claude Code:

/plugin marketplace add beremaran/godot-agent-loop
/plugin install godot-agent-loop@godot-agent-loop

For a local checkout, use claude --plugin-dir ./agent-plugin. See the portable agent bundle guide for verified Claude Code, Codex, OpenCode, and Pi install paths.

MCP client configuration

{
  "mcpServers": {
    "godot": {
      "command": "npx",
      "args": ["-y", "@beremaran/godot-agent-loop"],
      "env": {
        "GODOT_PATH": "/path/to/godot",
        "DEBUG": "true"
      }
    }
  }
}

{
  "mcpServers": {
    "godot": {
      "command": "npx",
      "args": ["-y", "@beremaran/godot-agent-loop"],
      "disabled": false
    }
  }
}

{
  "mcpServers": {
    "godot": {
      "command": "npx",
      "args": ["-y", "@beremaran/godot-agent-loop"]
    }
  }
}

For a source checkout, use node as the executable and pass the built server path as a separate argument:

{
  "command": "node",
  "args": ["/absolute/path/to/godot-agent-loop/build/index.js"]
}

Installation from source

git clone https://github.com/beremaran/godot-agent-loop.git
cd godot-agent-loop
npm install
npm run build

Runtime Tools Setup

No setup is required when the game is started through run_project: the server installs the interaction autoload automatically by generating an override.cfg (which Godot merges over project.godot at startup) and copying the runtime scripts into the project, then removes them again on stop_project, game exit, or server shutdown. project.godot is never modified. If an earlier server crashed or was killed before cleaning up, the next server detects and removes the leftover files on first contact with the project; an installation you manage yourself (declared in project.godot) is never touched.

To run the interaction server without run_project, copy build/scripts/mcp_interaction_server.gd to your project and register it as an autoload:

1. Copy build/scripts/mcp_interaction_server.gd to your project's scripts folder
2. In Godot: Project > Project Settings > Autoload
3. Add the script with the name McpInteractionServer

The server listens on 127.0.0.1:9090. Each MCP server launch generates a cryptographic runtime secret, passes it only to the Godot child process, and authenticates it during capability negotiation before any runtime command is accepted. A manually managed runtime should set the same GODOT_MCP_RUNTIME_SECRET value in both processes; leaving it unset retains legacy unauthenticated behavior and is suitable only for a trusted machine.

Commands that execute arbitrary GDScript, invoke arbitrary node properties or methods, mutate scripts, call multiplayer peers, or make HTTP/WebSocket connections remain disabled by default even after authentication. Grant only the required group with GODOT_MCP_PRIVILEGED_GROUPS: reflection enables arbitrary property/method access, code-execution enables eval/script control, and network enables RPC, HTTP, and WebSocket. The legacy GODOT_MCP_ALLOW_PRIVILEGED_COMMANDS=true grants all three groups. Use either only for a trusted local developer workflow. Authentication and policy denials never echo secrets, source, property values, URLs, headers, or engine errors. Authentication success/failure emits a structured audit event containing only the event name, runtime component, numeric session ID, and timestamp.

Environment Variables

Structured runtime evidence

With DEBUG=true, the MCP server emits JSON request lifecycle events to stderr. The Godot runtime emits matching events to its captured stdout. Both use an internal mcp_<number> correlation ID and controlled event fields; parameters, response values, secrets, source, URLs, and malformed payloads are never copied into logs. Runtime process output is capped at the latest 1,000 stdout and stderr lines. Stable JSON-RPC error codes remain the authoritative machine-readable failure classification.

Large-project response limits

Large responses are bounded rather than allowed to grow with project size. list_project_files returns deterministic cursor pages of at most 1,000 files; game_get_scene_tree returns deterministic pre-order trees of 1,000 nodes by default (configurable up to 10,000) and reports truncation. game_get_logs and game_get_errors return at most 1,000 unread lines per call with hasMore and remaining, while retaining the latest 1,000 lines per stream. Runtime JSON responses are capped at 8 MiB, screenshots additionally enforce pixel and 6 MiB PNG limits, and short-lived subprocess/import commands cap captured output at 16 MiB. Limit failures are explicit; callers can narrow resource/import queries instead of receiving partial unlabelled data.

Architecture

The server uses three bounded execution paths:

1. Persistent authoring session - The primary scene/resource authoring path. It owns a headed, deterministic Godot main loop and serves authenticated JSON-RPC commands without paying engine startup cost per edit.

2. Running-game socket - run_project launches the user's game headed and injects the authenticated mcp_interaction_server.gd autoload through override.cfg for high-fidelity runtime interaction.

3. One-shot subprocess fallback - Isolated authoring, validation, import, and export operations may invoke Godot once and exit. Commands that do not render may internally use --headless; this is not a supported display-less agent-loop tier. Authoring sessions, running games, screenshots, and visual verification require a desktop display, Xvfb, or another reachable rendering context and fail fast when none exists.

Source layout

Testing

The project uses Vitest plus direct Godot and full MCP-to-Godot suites. The source-derived tool, action, command, and suite inventory is published in the coverage report.

npm run check       # TypeScript tests, lint, build, and coverage drift
npm run test:e2e    # built MCP server through a real client and Godot
npm run test:golden-agent # cold-agent game build acceptance gate
npm run test:godot  # strict parsing, subprocess operations, runtime protocol
npm run test:watch  # watch mode

Example Prompts

"Run my Godot project and check for errors"

"Create a new Godot project called 'MyGame' and write a player script"

"Read the test_level.tscn scene and show me the node tree"

"Check all my changed GDScript files for syntax errors before I run the game"

"Hold down the W key for 2 seconds to test walking"

"Pause the game and take a screenshot"

"Get performance metrics - what's my FPS and draw call count?"

"Set the player's health to 100"

"Connect the enemy's 'died' signal to the game manager's 'on_enemy_died' method"

"Create a new C# (.NET) Godot project and add a CharacterBody2D script"

Community

• Contributing guide — development workflow, checks, and PR expectations
• Security policy — how to report vulnerabilities
• Code of conduct
• Changelog and release notes
• Issues — bug reports and feature requests

License

This project is licensed under the MIT License - see the LICENSE file for details.

Lineage

• Original project: godot-mcp by Solomon Elias (Coding-Solo), which provided the foundational TypeScript MCP server, headless GDScript operations, and TCP runtime interaction architecture.
• Inherited from: Tugcan Topaloglu's godot-mcp, which extended the original project across networking, 3D/2D rendering, UI controls, audio, animation, file I/O, runtime code execution, project creation, and physics while preserving the MIT license.
• Godot Agent Loop: maintained and substantially extended by Berke Arslan, preserving the complete Git history and every inherited MIT notice.