Imported from ManageXR/claude-unity-bridge (skill/SKILL.md). Install upstream with npx skills add ManageXR/claude-unity-bridge --skill skill. Copyright stays with the author.

Unity Bridge Skill

Control Unity Editor operations from Claude Code using a reliable file-based communication protocol.

Overview

The Unity Bridge enables Claude Code to trigger operations in a running Unity Editor instance without network configuration or port conflicts. It uses a simple file-based protocol where commands are written to .unity-bridge/command.json and responses are read from .unity-bridge/response-{id}.json.

Key Features:

• Execute EditMode and PlayMode tests
• Trigger script compilation
• Refresh asset database
• Check editor status (compilation, play mode, etc.)
• Retrieve Unity console logs
• Control Play Mode (play, pause, step)
• Build projects (direct or custom pipeline)

Multi-Project Support: Each Unity project has its own .unity-bridge/ directory, allowing multiple projects to be worked on simultaneously.

Requirements

1. Unity Package: Install com.mxr.claude-bridge in your Unity project

   • Via Package Manager: https://github.com/ManageXR/claude-unity-bridge.git?path=package
   • See main package README for installation instructions

2. Unity Editor: Must be open with your project loaded

3. Python 3: The skill uses a Python script for reliable command execution

How It Works

The skill uses a CLI tool (unity-bridge) that handles:

• UUID generation for command tracking
• Atomic file writes to prevent corruption
• Exponential backoff polling for responses
• File locking handling
• Automatic cleanup of old response files
• Formatted, human-readable output

This approach ensures deterministic, rock-solid execution - the script is tested once and behaves identically every time, handling all edge cases (timeouts, file locking, malformed responses, etc.) without requiring Claude to manage these details in-context.

Usage

Basic Pattern

When you need to interact with Unity, use the CLI directly:

unity-bridge [command] [options]

All commands automatically:

• Generate a unique UUID for tracking
• Write the command atomically
• Poll for response with timeout
• Format output for readability
• Cleanup response files

Command Examples

Run Tests

Execute Unity tests in EditMode or PlayMode:

# Run all EditMode tests
unity-bridge run-tests --mode EditMode

# Run tests with filter
unity-bridge run-tests --mode EditMode --filter "MXR.Tests"

# Run all tests (both modes)
unity-bridge run-tests

Output:

✓ Tests Passed: 410
✗ Tests Failed: 2
○ Tests Skipped: 0
Duration: 1.25s

Failed Tests:
  - MXR.Tests.AuthTests.LoginWithInvalidCredentials
    Expected: success, Actual: failure
  - MXR.Tests.NetworkTests.TimeoutHandling
    NullReferenceException: Object reference not set

Parameters:

• --mode - EditMode or PlayMode (optional, defaults to both)
• --filter - Test name filter pattern (optional)
• --timeout - Override default 30s timeout

Compile Scripts

Trigger Unity script compilation:

unity-bridge compile

Output (Success):

✓ Compilation Successful
Duration: 2.3s

Output (Failure):

✗ Compilation Failed

Assets/Scripts/Player.cs:25: error CS0103: The name 'invalidVar' does not exist
Assets/Scripts/Enemy.cs:67: error CS0246: Type 'MissingClass' could not be found

Get Console Logs

Retrieve Unity console output:

# Get last 20 logs
unity-bridge get-console-logs --limit 20

# Get only errors
unity-bridge get-console-logs --limit 10 --filter Error

# Get warnings
unity-bridge get-console-logs --filter Warning

Output:

Console Logs (last 10, filtered by Error):

[Error] NullReferenceException: Object reference not set
  at Player.Update() in Assets/Scripts/Player.cs:34

[Error] Failed to load asset: missing_texture.png

[Error] (x3) Shader compilation failed
  See Console for details

Parameters:

• --limit - Maximum number of logs (default: 50)
• --filter - Filter by type: Log, Warning, or Error

Get Editor Status

Check Unity Editor state:

unity-bridge get-status

Output:

Unity Editor Status:
  - Compilation: ✓ Ready
  - Play Mode: ✏ Editing
  - Updating: No

Possible States:

• Compilation: ✓ Ready or ⏳ Compiling...
• Play Mode: ✏ Editing, ▶ Playing, or ⏸ Paused
• Updating: Yes or No

Refresh Asset Database

Force Unity to refresh assets:

unity-bridge refresh

Output:

✓ Asset Database Refreshed
Duration: 0.5s

Play Mode Control

Toggle Play Mode, pause, and step through frames:

# Enter/exit Play Mode (toggle)
unity-bridge play

# Pause/unpause (while in Play Mode)
unity-bridge pause

# Step one frame (while in Play Mode)
unity-bridge step

Output (play):

✓ play completed
Play Mode: ▶ Playing
Duration: 0.01s

Output (pause):

✓ pause completed
Play Mode: ⏸ Paused
Duration: 0.01s

Output (step):

✓ step completed
Play Mode: ⏸ Paused
Duration: 0.02s

Notes:

• play toggles Play Mode on/off (like the Play button in Unity)
• pause and step require Play Mode to be active; returns error if not playing
• All three return the resulting editorStatus so the caller knows the current state

Build Project

Build the Unity project using either direct BuildPipeline.BuildPlayer() or a custom build method:

# Direct build with current active target
unity-bridge build

# Direct build for specific target
unity-bridge build --target Android --development

# Custom build pipeline via static method invocation
unity-bridge build --method MXR.Builder.BuildEntryPoints.BuildQuest

# With environment variables
unity-bridge build --method MXR.Builder.BuildEntryPoints.BuildQuest --env BUILD_TYPE=production --env SCRIPTING_BACKEND=il2cpp

# Using a named build profile (from .unity-bridge/build.json)
unity-bridge build --profile quest

Output (Success):

✓ Build Succeeded
Errors: 0
Warnings: 3
Build Time: 45.2s
Output: /path/to/Build_Android.apk
Size: 50.0 MB
Duration: 45.50s

Output (Failure):

✗ Build Failed
Errors: 5
Warnings: 2
Build Time: 30.0s
Duration: 30.50s

Build Failed: 5 error(s), 2 warning(s)

Parameters:

• --method - Fully qualified static method (e.g., MXR.Builder.BuildEntryPoints.BuildQuest)
• --target - BuildTarget enum name (e.g., Android, StandaloneWindows64, iOS)
• --development - Enable development build flag
• --env - Environment variable KEY=VALUE (repeatable)
• --profile - Named profile from .unity-bridge/build.json
• --output - Override output path
• --timeout - Override default 300s timeout

Build Profiles:

For projects with custom build pipelines, create .unity-bridge/build.json to define named profiles:

{
  "profiles": {
    "quest": {
      "method": "MXR.Builder.BuildEntryPoints.BuildQuest",
      "env": { "BUILD_TYPE": "development", "SCRIPTING_BACKEND": "il2cpp" },
      "timeout": 600
    },
    "pico": {
      "method": "MXR.Builder.BuildEntryPoints.BuildPico"
    }
  }
}

Notes:

• Default timeout is 5 minutes (300s) — builds are long-running operations
• Direct builds use the currently active build target if --target is not specified
• Environment variables are set before method invocation and cleaned up after
• Profile settings are defaults; CLI arguments override them

Advanced Options

Timeout Configuration

Override the default 30-second timeout:

unity-bridge run-tests --timeout 60

Use longer timeouts for:

• Large test suites
• PlayMode tests (which start/stop Play Mode)
• Full project compilation

Cleanup Old Responses

Automatically remove old response files before executing:

unity-bridge compile --cleanup

This removes response files older than 1 hour. Useful for maintaining a clean workspace.

Verbose Output

See detailed execution progress:

unity-bridge run-tests --verbose

Prints:

• Command ID
• Polling attempts
• Response file detection
• Cleanup operations

Error Handling

The script provides clear error messages for common issues:

Unity Not Running:

Error: Unity Editor not detected. Ensure Unity is open with the project loaded.

Command Timeout:

Error: Command timed out after 30s. Check Unity Console for errors.

Invalid Parameters:

Error: Failed to write command file: Invalid mode 'InvalidMode'

Exit Codes:

• 0 - Success
• 1 - Error (Unity not running, invalid params, etc.)
• 2 - Timeout

Integration with Claude Code

When you're working in a Unity project directory, you can ask Claude Code to perform Unity operations naturally:

• "Run the Unity tests in EditMode"
• "Check if there are any compilation errors"
• "Show me the last 10 error logs from Unity"
• "Refresh the Unity asset database"
• "Enter Play Mode"
• "Pause the editor"
• "Step one frame"
• "Build for Android"
• "Run the Quest build"
• "Set up build profiles for my project"

Claude Code will automatically use this skill to execute the commands via the Python script.

File Protocol Details

Command Format

Written to .unity-bridge/command.json:

{
  "id": "550e8400-e29b-41d4-a716-446655440000",
  "action": "run-tests",
  "params": {
    "testMode": "EditMode",
    "filter": "MyTests"
  }
}

Response Format

Read from .unity-bridge/response-{id}.json:

{
  "id": "550e8400-e29b-41d4-a716-446655440000",
  "status": "success",
  "action": "run-tests",
  "duration_ms": 1250,
  "result": {
    "passed": 410,
    "failed": 0,
    "skipped": 0,
    "failures": []
  }
}

Status Values:

• running - Command in progress (may see intermediate responses)
• success - Command completed successfully
• failure - Command completed with failures (e.g., failed tests)
• error - Command execution error

Project Structure

skill/
├── SKILL.md                    # This file
├── pyproject.toml              # Package configuration
├── src/
│   └── claude_unity_bridge/
│       ├── __init__.py         # Package version
│       └── cli.py              # CLI implementation
├── tests/
│   └── test_cli.py             # Unit tests
└── references/
    ├── COMMANDS.md             # Detailed command specifications
    └── EXTENDING.md            # Guide for adding custom commands

Detailed Documentation

For more information, see:

• COMMANDS.md - Complete command reference with all parameters, response formats, and edge cases
• EXTENDING.md - Tutorial for adding custom commands to the Unity Bridge for project-specific workflows

Troubleshooting

Unity Not Responding

Symptoms: Commands timeout or "Unity not detected" error

Solutions:

1. Ensure Unity Editor is open with the project loaded
2. Check that the package is installed (Window > Package Manager)
3. Verify .unity-bridge/ directory exists in project root
4. Check Unity Console for errors from ClaudeBridge package

Response File Issues

Symptoms: "Failed to parse response JSON" error

Solutions:

1. Check Unity Console for ClaudeBridge errors
2. Manually inspect .unity-bridge/response-*.json files
3. Try cleaning up old responses with --cleanup flag
4. Restart Unity Editor if file system is in bad state

Performance Issues

Symptoms: Slow response times, frequent timeouts

Solutions:

1. Increase timeout with --timeout 60 or higher
2. Close unnecessary Unity Editor windows
3. Reduce test scope with --filter parameter
4. Check system resources (CPU, memory)

File Locking Errors

Symptoms: Intermittent errors reading/writing files

Solutions:

1. The CLI handles file locking automatically with retries
2. If persistent, check for antivirus interference
3. Verify file permissions on .unity-bridge/ directory

Installation

Quick Install

pip install claude-unity-bridge
unity-bridge install-skill

This installs the CLI and the Claude Code skill.

Verify Setup

unity-bridge health-check

Updating

unity-bridge update

This upgrades the pip package and reinstalls the skill.

Uninstalling

unity-bridge uninstall-skill
pip uninstall claude-unity-bridge

Development Installation

cd claude-unity-bridge/skill
pip install -e ".[dev]"
unity-bridge install-skill

Why a CLI Tool?

The skill uses a CLI tool instead of implementing the protocol directly in Claude Code prompts for several critical reasons:

Consistency: UUID generation, polling logic, and error handling work identically every time. Without the CLI, Claude might implement these differently across sessions, leading to subtle bugs.

Reliability: All edge cases are handled once in tested code:

• File locking when Unity writes responses
• Exponential backoff for polling
• Atomic command writes to prevent corruption
• Graceful handling of malformed JSON
• Proper cleanup of stale files

Error Messages: Clear, actionable error messages for all failure modes. Claude doesn't have to figure out what went wrong each time.

Token Efficiency: The CLI handles complexity, so Claude doesn't need to manage low-level details in-context. The SKILL.md stays concise while providing full functionality.

Deterministic Exit Codes: Shell integration works reliably with standard exit codes (0=success, 1=error, 2=timeout).

Rock Solid: Test the CLI once, it works forever. No variability between Claude sessions.

Support

For issues or questions:

• Package Issues: https://github.com/ManageXR/claude-unity-bridge/issues
• Skill Issues: Report in the same repository with [Skill] prefix