* Add server-side ping/pong heartbeat to detect dead WebSocket connections On Windows, WebSocket connections can die silently (OSError 64) without either side being notified. This causes commands to fail with "Unity session not available" until Unity eventually detects the dead connection. Changes: - Add PingMessage model for server->client pings - Add ping loop in PluginHub that sends pings every 10 seconds - Track last pong time per session; close connection if no pong within 20s - Include session_id in pong messages from Unity for server-side tracking - Clean up debug/timing logs from Issue #654 investigation The server will now proactively detect dead connections within 20 seconds instead of waiting indefinitely for the next command to fail. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com> * Fix connection recovery after Unity domain reloads (#654) When Unity performs a domain reload (after script changes, test runs, or large payload transfers), the MCP connection drops and needs to reconnect. The previous reconnection timeout (2s) was too short for domain reloads which can take 10-30s. Changes: - Increase UNITY_MCP_RELOAD_MAX_WAIT_S default from 2s to 30s - Increase backoff cap when reloading from 0.8s to 5.0s - Skip PluginHub session resolution for stdio transport (was causing unnecessary waits on every command) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com> * Fix ping/pong heartbeat, reduce timeout to 20s, fix test flakiness - Add server-side ping loop to detect dead WebSocket connections - Include session_id in pong messages for tracking - Reduce domain reload timeout from 30s to 20s - Add ClassVar annotations for mutable class attributes - Add lock protection for _last_pong access - Change debug stack trace log from Warn to Debug level - Remove unused TIMING-STDIO variable - Fix flaky async duration test (allow 20% timer variance) - Fix Python test that cleared HOME env var on Windows - Skip Unix-path test on Windows (path separator difference) - Add LogAssert.Expect to PropertyConversion tests Fixes #654, #643 Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com> --------- Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com> |
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| .claude | ||
| .github | ||
| CustomTools/RoslynRuntimeCompilation | ||
| MCPForUnity | ||
| Server | ||
| TestProjects | ||
| docs | ||
| scripts | ||
| tools | ||
| .dockerignore | ||
| .gitignore | ||
| .mcpbignore | ||
| CLAUDE.md | ||
| LICENSE | ||
| README.md | ||
| docker-compose.yml | ||
| manifest.json | ||
| mcp_source.py | ||
README.md
| English | 简体中文 |
|---|
Proudly sponsored and maintained by Coplay -- the best AI assistant for Unity.
Create your Unity apps with LLMs! MCP for Unity bridges AI assistants (Claude, Cursor, VS Code, etc.) with your Unity Editor via the Model Context Protocol. Give your LLM the tools to manage assets, control scenes, edit scripts, and automate tasks.
Quick Start
Prerequisites
- Unity 2021.3 LTS+ — Download Unity
- Python 3.10+ and uv — Install uv
- An MCP Client — Claude Desktop | Cursor | VS Code Copilot | GitHub Copilot CLI | Windsurf
1. Install the Unity Package
In Unity: Window > Package Manager > + > Add package from git URL...
[!TIP]
https://github.com/CoplayDev/unity-mcp.git?path=/MCPForUnity#main
Want the latest beta? Use the beta branch:
https://github.com/CoplayDev/unity-mcp.git?path=/MCPForUnity#beta
Other install options (Asset Store, OpenUPM)
Unity Asset Store:
- Visit MCP for Unity on the Asset Store
- Click
Add to My Assets, then import viaWindow > Package Manager
OpenUPM:
openupm add com.coplaydev.unity-mcp
2. Start the Server & Connect
- In Unity:
Window > MCP for Unity - Click Start Server (launches HTTP server on
localhost:8080) - Select your MCP Client from the dropdown and click Configure
- Look for 🟢 "Connected ✓"
- Connect your client: Some clients (Cursor, Windsurf, Antigravity) require enabling an MCP toggle in settings, while others (Claude Desktop, Claude Code) auto-connect after configuration.
That's it! Try a prompt like: "Create a red, blue and yellow cube" or "Build a simple player controller"
Features & Tools
Key Features
- Natural Language Control — Instruct your LLM to perform Unity tasks
- Powerful Tools — Manage assets, scenes, materials, scripts, and editor functions
- Automation — Automate repetitive Unity workflows
- Extensible — Works with various MCP Clients
Available Tools
manage_asset • manage_editor • manage_gameobject • manage_components • manage_material • manage_prefabs • manage_scene • manage_script • manage_scriptable_object • manage_shader • manage_vfx • manage_texture • batch_execute • find_gameobjects • find_in_file • read_console • refresh_unity • run_tests • get_test_job • execute_menu_item • apply_text_edits • script_apply_edits • validate_script • create_script • delete_script • get_sha
Available Resources
custom_tools • unity_instances • menu_items • get_tests • gameobject • gameobject_components • prefab_api • prefab_info • prefab_hierarchy • editor_state • editor_selection • editor_prefab_stage • project_info • project_tags • project_layers
Performance Tip: Use batch_execute for multiple operations — it's 10-100x faster than individual calls!
Manual Configuration
If auto-setup doesn't work, add this to your MCP client's config file:
HTTP (default — works with Claude Desktop, Cursor, Windsurf):
{
"mcpServers": {
"unityMCP": {
"url": "http://localhost:8080/mcp"
}
}
}
VS Code:
{
"servers": {
"unityMCP": {
"type": "http",
"url": "http://localhost:8080/mcp"
}
}
}
Stdio configuration (uvx)
macOS/Linux:
{
"mcpServers": {
"unityMCP": {
"command": "uvx",
"args": ["--from", "mcpforunityserver", "mcp-for-unity", "--transport", "stdio"]
}
}
}
Windows:
{
"mcpServers": {
"unityMCP": {
"command": "C:/Users/YOUR_USERNAME/AppData/Local/Microsoft/WinGet/Links/uvx.exe",
"args": ["--from", "mcpforunityserver", "mcp-for-unity", "--transport", "stdio"]
}
}
}
Multiple Unity Instances
MCP for Unity supports multiple Unity Editor instances. To target a specific one:
- Ask your LLM to check the
unity_instancesresource - Use
set_active_instancewith theName@hash(e.g.,MyProject@abc123) - All subsequent tools route to that instance
Roslyn Script Validation (Advanced)
For Strict validation that catches undefined namespaces, types, and methods:
- Install NuGetForUnity
Window > NuGet Package Manager→ InstallMicrosoft.CodeAnalysisv5.0- Also install
SQLitePCLRaw.coreandSQLitePCLRaw.bundle_e_sqlite3v3.0.2 - Add
USE_ROSLYNtoPlayer Settings > Scripting Define Symbols - Restart Unity
Manual DLL installation (if NuGetForUnity isn't available)
- Download
Microsoft.CodeAnalysis.CSharp.dlland dependencies from NuGet - Place DLLs in
Assets/Plugins/folder - Ensure .NET compatibility settings are correct
- Add
USE_ROSLYNto Scripting Define Symbols - Restart Unity
Troubleshooting
- Unity Bridge Not Connecting: Check
Window > MCP for Unitystatus, restart Unity - Server Not Starting: Verify
uv --versionworks, check the terminal for errors - Client Not Connecting: Ensure the HTTP server is running and the URL matches your config
Detailed setup guides:
- Fix Unity MCP and Cursor, VSCode & Windsurf — uv/Python installation, PATH issues
- Fix Unity MCP and Claude Code — Claude CLI installation
- Common Setup Problems — macOS dyld errors, FAQ
Still stuck? Open an Issue or Join Discord
Contributing
See README-DEV.md for development setup. For custom tools, see CUSTOM_TOOLS.md.
- Fork → Create issue → Branch (
feature/your-idea) → Make changes → PR
Telemetry & Privacy
Anonymous, privacy-focused telemetry (no code, no project names, no personal data). Opt out with DISABLE_TELEMETRY=true. See TELEMETRY.md.
License: MIT — See LICENSE | Need help? Discord | Issues
Star History
Citation for Research
If you are working on research that is related to Unity-MCP, please cite us!@inproceedings{10.1145/3757376.3771417,
author = {Wu, Shutong and Barnett, Justin P.},
title = {MCP-Unity: Protocol-Driven Framework for Interactive 3D Authoring},
year = {2025},
isbn = {9798400721366},
publisher = {Association for Computing Machinery},
address = {New York, NY, USA},
url = {https://doi.org/10.1145/3757376.3771417},
doi = {10.1145/3757376.3771417},
series = {SA Technical Communications '25}
}
Unity AI Tools by Coplay
Coplay offers 3 AI tools for Unity:
- MCP for Unity is available freely under the MIT license.
- Coplay is a premium Unity AI assistant that sits within Unity and is more than the MCP for Unity.
- Coplay MCP a free-for-now MCP for Coplay tools.
(These tools have different tech stacks. See this blog post comparing Coplay to MCP for Unity.)
Disclaimer
This project is a free and open-source tool for the Unity Editor, and is not affiliated with Unity Technologies.