unity-cli

English | Korean

Control Unity Editor from the command line. Built for AI agents, works with anything.

No server to run. No config to write. No process to manage. Just type a command.

Why this exists

I wanted to control Unity from the terminal. The existing MCP-based integrations required Python runtimes, WebSocket relays, JSON-RPC protocol layers, config files, server processes that need to be started and stopped, tool registration ceremonies, and tens of thousands of lines of over-engineered code. All just to send a simple command to Unity.

On top of that, every AI agent that wanted to use it needed its own MCP config and integration setup. The CLI doesn't care — any agent that can run a shell command can use it immediately.

That felt wrong. If I can curl a URL, why do I need all that?

So I built the opposite: a single binary that talks directly to Unity via HTTP. No server to run — the Unity package listens automatically. No config to write — it discovers Unity instances on its own. No tool registration — just call by name. No caching, no protocol layers, no ceremony.

The entire CLI is ~800 lines of Go (plus ~300 lines of help text). The Unity-side connector is ~1,700 lines of C#. It's just a thin layer that lets you control Unity from the shell — nothing more. You install the binary, add the Unity package, and it works.

Install

Linux / macOS

curl -fsSL https://raw.githubusercontent.com/youngwoocho02/unity-cli/master/install.sh | sh

Windows (PowerShell)

irm https://raw.githubusercontent.com/youngwoocho02/unity-cli/master/install.ps1 | iex

Other options

# Go install (any platform with Go)
go install github.com/youngwoocho02/unity-cli@latest
Manual download (pick your platform)
Linux amd64 / Linux arm64 / macOS amd64 / macOS arm64 / Windows amd64
curl -fsSL https://github.com/youngwoocho02/unity-cli/releases/latest/download/unity-cli-linux-amd64 -o unity-cli
chmod +x unity-cli && sudo mv unity-cli /usr/local/bin/

Supported platforms: Linux (amd64, arm64), macOS (Intel, Apple Silicon), Windows (amd64).

Update

# Update to the latest version
unity-cli update
Check for updates without installing
unity-cli update --check

Unity Setup

Add the Unity Connector package via Package Manager → Add package from git URL:

https://github.com/youngwoocho02/unity-cli.git?path=unity-connector

Or add directly to Packages/manifest.json:

"com.youngwoocho02.unity-cli-connector": "https://github.com/youngwoocho02/unity-cli.git?path=unity-connector"

To pin a specific version, append a tag to the URL (e.g. #v0.2.21).

Once added, the Connector starts automatically when Unity opens. No configuration needed.

Recommended: Disable Editor Throttling

By default, Unity throttles editor updates when the window is unfocused. This means CLI commands may not execute until you click back into Unity.

To fix this, go to Edit → Preferences → General → Interaction Mode and set it to No Throttling.

This ensures CLI commands are processed immediately, even when Unity is in the background.

Quick Start

# Check Unity connection
unity-cli status
Enter play mode and wait
unity-cli editor play --wait
Run C# code inside Unity
unity-cli exec "Application.dataPath"
Read console logs
unity-cli console --filter all

How It Works

Terminal                              Unity Editor
────────                              ────────────
$ unity-cli editor play --wait
    │
    ├─ reads ~/.unity-cli/instances.json
    │  → finds Unity on port 8090
    │
    ├─ POST http://127.0.0.1:8090/command
    │  { "command": "manage_editor",
    │    "params": { "action": "play",
    │                "wait_for_completion": true }}
    │                                      │
    │                                  HttpServer receives
    │                                      │
    │                                  CommandRouter dispatches
    │                                      │
    │                                  ManageEditor.HandleCommand()
    │                                  → EditorApplication.isPlaying = true
    │                                  → waits for PlayModeStateChange
    │                                      │
    ├─ receives JSON response  ←───────────┘
    │  { "success": true,
    │    "message": "Entered play mode (confirmed)." }
    │
    └─ prints: Entered play mode (confirmed).

The Unity Connector:

1. Opens an HTTP server on localhost:8090 when the Editor starts
2. Registers itself in ~/.unity-cli/instances.json so the CLI knows where to connect
3. Writes a heartbeat to ~/.unity-cli/status/{port}.json every 0.5s with the current state
4. Discovers all [UnityCliTool] classes via reflection on each request
5. Routes incoming commands to the matching handler on the main thread
6. Survives domain reloads (script recompilation)

Before compiling or reloading, the Connector records the state (compiling, reloading) to the status file. When the main thread freezes, the timestamp stops updating. The CLI detects this and waits for a fresh timestamp before sending commands.

Built-in Commands

Editor Control

# Enter play mode
unity-cli editor play
Enter play mode and wait until fully loaded
unity-cli editor play --wait
Stop play mode
unity-cli editor stop
Toggle pause (only works during play mode)
unity-cli editor pause
Refresh assets
unity-cli editor refresh
Refresh and recompile scripts (waits for compilation to finish)
unity-cli editor refresh --compile

Console Logs

# Read error and warning logs (default)
unity-cli console
Read last 20 log entries of all types
unity-cli console --lines 20 --filter all
Read only errors
unity-cli console --filter error
Include stack traces (short: filtered, full: raw)
unity-cli console --stacktrace short
Clear console
unity-cli console --clear

Execute C# Code

Run arbitrary C# code inside the Unity Editor at runtime. This is the most powerful command — it gives you full access to UnityEngine, UnityEditor, ECS, and every loaded assembly. No need to write a custom tool for one-off queries or mutations.

Single expressions auto-return their result. Multi-statement code needs an explicit return.

# Simple expressions
unity-cli exec "Time.time"
unity-cli exec "Application.dataPath"
unity-cli exec "EditorSceneManager.GetActiveScene().name" --usings UnityEditor.SceneManagement
Query game objects
unity-cli exec "GameObject.FindObjectsOfType<Camera>().Length"
unity-cli exec "Selection.activeGameObject?.name ?? &quot;nothing selected&quot;"
Multi-statement (explicit return)
unity-cli exec "var go = new GameObject(&quot;Marker&quot;); go.tag = &quot;EditorOnly&quot;; return go.name;"
ECS world inspection with extra usings
unity-cli exec "World.All.Count" --usings Unity.Entities
unity-cli exec "var sb = new System.Text.StringBuilder(); foreach(var w in World.All) sb.AppendLine(w.Name); return sb.ToString();" --usings Unity.Entities
Modify project settings at runtime
unity-cli exec "PlayerSettings.bundleVersion = &quot;1.2.3&quot;; return PlayerSettings.bundleVersion;"

Because exec compiles and runs real C#, it can do anything a custom tool can — inspect ECS entities, modify assets, call internal APIs, run editor utilities. For AI agents, this means zero-friction access to Unity's entire runtime without writing a single line of tool code.

Menu Items

# Execute any Unity menu item by path
unity-cli menu "File/Save Project"
unity-cli menu "Assets/Refresh"
unity-cli menu "Window/General/Console"

Note: File/Quit is blocked for safety.

Asset Reserialize

AI agents (and humans) can edit Unity asset files — .prefab, .unity, .asset, .mat — as plain text YAML. But Unity's YAML serializer is strict: a missing field, wrong indent, or stale fileID will corrupt the asset silently.

reserialize fixes this. After a text edit, it tells Unity to load the asset into memory and write it back out through its own serializer. The result is a clean, valid YAML file — as if you had edited it through the Inspector.

# Reserialize the entire project (no arguments)
unity-cli reserialize
After editing a prefab's transform values in a text editor
unity-cli reserialize Assets/Prefabs/Player.prefab
After batch-editing multiple scenes
unity-cli reserialize Assets/Scenes/Main.unity Assets/Scenes/Lobby.unity
After modifying material properties
unity-cli reserialize Assets/Materials/Character.mat

This is what makes text-based asset editing safe. Without it, a single misplaced YAML field can break a prefab with no visible error until runtime. With it, AI agents can confidently modify any Unity asset through plain text — add components to prefabs, adjust scene hierarchies, change material properties — and know the result will load correctly.

Profiler

# Read profiler hierarchy (last frame, top-level)
unity-cli profiler hierarchy
Recursive drill-down
unity-cli profiler hierarchy --depth 3
Set root by name (substring match) — focus on a specific system
unity-cli profiler hierarchy --root SimulationSystem --depth 3
Drill into a specific item by ID
unity-cli profiler hierarchy --parent 4 --depth 2
Average over last 30 frames
unity-cli profiler hierarchy --frames 30 --min 0.5
Average over a specific frame range
unity-cli profiler hierarchy --from 100 --to 200
Filter and sort
unity-cli profiler hierarchy --min 0.5 --sort self --max 10
Enable/disable profiler recording
unity-cli profiler enable
unity-cli profiler disable
Show profiler state
unity-cli profiler status
Clear captured frames
unity-cli profiler clear

List Tools

# Show all available tools (built-in + project custom) with parameter schemas
unity-cli list

Custom Tools

# Call a custom tool directly by name
unity-cli my_custom_tool
Call with parameters
unity-cli my_custom_tool --params '{"key": "value"}'

Status

# Show Unity Editor state
unity-cli status
# Output: Unity (port 8090): ready
#   Project: /path/to/project
#   Version: 6000.1.0f1
#   PID:     12345

The CLI also checks Unity's state automatically before sending any command. If Unity is busy (compiling, reloading), it waits for Unity to become responsive.

Global Options

Flag	Description	Default
--port <N>	Override Unity instance port (skip auto-discovery)	auto
--project <path>	Select Unity instance by project path	latest
--timeout <ms>	HTTP request timeout	120000

# Connect to a specific Unity instance
unity-cli --port 8091 editor play
Select by project path when multiple Unity instances are open
unity-cli --project MyGame editor stop

Use --help on any command for detailed usage:

unity-cli editor --help
unity-cli exec --help
unity-cli profiler --help

Writing Custom Tools

Create a static class with [UnityCliTool] attribute in any Editor assembly. The Connector discovers it automatically on domain reload.

using UnityCliConnector;
using Newtonsoft.Json.Linq;
[UnityCliTool(Description = "Spawn an enemy at a position")]
public static class SpawnEnemy
{
// Command name auto-derived: "spawn_enemy"
// Call with: unity-cli spawn_enemy --params '{"x":1,"y":0,"z":5}'
public class Parameters
{
    [ToolParameter("X world position", Required = true)]
    public float X { get; set; }

    [ToolParameter("Y world position", Required = true)]
    public float Y { get; set; }

    [ToolParameter("Z world position", Required = true)]
    public float Z { get; set; }

    [ToolParameter("Prefab name in Resources folder")]
    public string Prefab { get; set; }
}

public static object HandleCommand(JObject parameters)
{
    float x = parameters["x"]?.Value<float>() ?? 0;
    float y = parameters["y"]?.Value<float>() ?? 0;
    float z = parameters["z"]?.Value<float>() ?? 0;
    string prefabName = parameters["prefab"]?.Value<string>() ?? "Enemy";

    var prefab = Resources.Load<GameObject>(prefabName);
    var instance = Object.Instantiate(prefab, new Vector3(x, y, z), Quaternion.identity);

    return new SuccessResponse("Enemy spawned", new
    {
        name = instance.name,
        position = new { x, y, z }
    });
}

}

The Parameters class is optional but recommended. When present, unity-cli list exposes parameter names, types, descriptions, and required flags — so AI assistants can discover how to call your tool without reading the source code.

Rules

• Class must be static
• Must have public static object HandleCommand(JObject parameters) or async Task<object> variant
• Return SuccessResponse(message, data) or ErrorResponse(message)
• Add a Parameters nested class with [ToolParameter] attributes for discoverability
• Class name is auto-converted to snake_case for the command name
• Override with [UnityCliTool(Name = "my_name")] if needed
• Runs on Unity main thread, so all Unity APIs are safe to call
• Discovered automatically on Editor start and after every script recompilation
• Duplicate tool names are detected and logged as errors — only the first discovered handler is used

Multiple Unity Instances

When multiple Unity Editors are open, each registers on a different port (8090, 8091, ...):

# See all running instances
cat ~/.unity-cli/instances.json
Select by project path
unity-cli --project MyGame editor play
Select by port
unity-cli --port 8091 editor play
Default: uses the most recently registered instance
unity-cli editor play

Compared to MCP

	MCP	unity-cli
Install	Python + uv + FastMCP + config JSON	Single binary
Dependencies	Python runtime, WebSocket relay	None
Protocol	JSON-RPC 2.0 over stdio + WebSocket	Direct HTTP POST
Setup	Generate MCP config, restart AI tool	Add Unity package, done
Reconnection	Complex reconnect logic for domain reloads	Stateless per request
Compatibility	MCP-compatible clients only	Anything with a shell
Custom tools	Same [Attribute] + HandleCommand pattern	Same

Author

Created by DevBookOfArray

License

MIT