iOS Multi-Simulator MCP Server

Forked from joshuayoes/ios-simulator-mcp — all foundational work by Joshua Yoes.

An MCP server that lets AI agents create, control, and destroy iOS simulators through session-based lifecycle management. Each session owns its own simulator, enabling multiple agents to work in parallel on separate simulators without conflicts.

┌──────────────┐  ┌──────────────┐  ┌──────────────┐
│   Agent A    │  │   Agent B    │  │   Agent C    │
│  (id: "qa1") │  │  (id: "qa2") │  │  (id: "dev") │
└──────┬───────┘  └──────┬───────┘  └──────┬───────┘
       │                 │                 │
       └────────────┬────┴────┬────────────┘
                    │         │
              ┌─────┴─────────┴──────┐
              │    MCP Server        │
              │  (single process)    │
              └──┬─────────┬──────┬──┘
                 │         │      │
          ┌──────┴──┐ ┌────┴───┐ ┌┴────────┐
          │ iPhone  │ │ iPad   │ │ iPhone  │
          │ 16 Pro  │ │ Air    │ │ 16 Pro  │
          │ (qa1)   │ │ (qa2)  │ │ (dev)   │
          └─────────┘ └────────┘ └─────────┘

What this fork adds:

• Session-based lifecycle — start_simulator / destroy_simulator create and tear down simulators on demand, with automatic cleanup on server exit
• Multi-agent support — each session gets an isolated simulator, so parallel agents don't collide
• Attach to existing simulators — attach_simulator lets you control a simulator that was created externally (e.g. by Xcode)
• Removed get_booted_sim_id / open_simulator / IDB_UDID — the session model replaces all of these

Tools

All tools take a required id (session identifier) parameter.

ui_describe_all — the key navigation tool

ui_view lets the agent visually see the screen with a compressed jpg image. While this is sufficient for the agent to determine where to click, it will not work if the screen is rotated. But ui_describe_all uses logical coordinates and will work fine for finding buttons to tap. Unless there is a good reason to do otherwise, I'd suggest telling agents to use ui_describe_all for navigation (though ui_view will work so long as the screen is in portrait)

ui_describe_all returns a nested JSON accessibility tree. This is another way the agent can "see" the screen to decide what to tap. Example (abbreviated):

[
  {
    "type": "Application",
    "frame": { "x": 0, "y": 0, "width": 393, "height": 852 },
    "role_description": "application",
    "title": "Settings",
    "children": [
      {
        "type": "NavigationBar",
        "frame": { "x": 0, "y": 59, "width": 393, "height": 96 },
        "children": [
          {
            "type": "StaticText",
            "frame": { "x": 152, "y": 75, "width": 89, "height": 25 },
            "title": "Settings"
          }
        ]
      },
      {
        "type": "Cell",
        "frame": { "x": 0, "y": 200, "width": 393, "height": 44 },
        "title": "General",
        "AXAccessibilityElement": true
      }
    ]
  }
]

The frame coordinates map directly to ui_tap coordinates — to tap "General", use the centre of its frame.

Example usage

Hot Tip:

You can use cheap agents like Haiku to do navigation and even visual comparison. You do not need Opus to navigate around your app, saving you tons of money and time. Haiku is almost fast enough that you can record demo videos without speeding up ;)

Launch an app and navigate:

Start an iPhone 16 Pro simulator, open Settings, and navigate to General > About.

Compare a screenshot against expected state:

Take a screenshot of the simulator and check whether the login screen is showing the "Welcome back" message.

Multi-step agent workflow (great for Haiku subagents):

You are a QA agent. Start a simulator, install the app at ./build/MyApp.app, launch it (com.example.myapp), then:

1. Tap "Sign Up"
2. Fill in the email field with "test@example.com" and password with "password123"
3. Tap "Submit"
4. Take a screenshot and verify the success message appears

Prerequisites

• Node.js (v18+)
• macOS (iOS simulators are macOS-only)
• Xcode with iOS simulators installed
• Facebook IDB —

Facebook IDB (Important)

This dependency is a little more involved. The official install guide can be a little difficult, the easiest way to install it (imo) is to use pipx.

MacOS:

# Install pipx to make installing python packages easier
brew install pipx
pipx ensurepath

brew tap facebook/fb
brew install idb-companion
pipx install fb-idb

Installation

Please note the fb-idb dependecy above!

Cursor

Add to ~/.cursor/mcp.json:

{
  "mcpServers": {
    "ios-multi-simulator": {
      "command": "npx",
      "args": ["-y", "github:zafnz/ios-multi-simulator-mcp"]
    }
  }
}

For local development, build from source and point to the built file:

{
  "mcpServers": {
    "ios-multi-simulator": {
      "command": "node",
      "args": ["/path/to/ios-multi-simulator-mcp/build/index.js"]
    }
  }
}

Claude Code

claude mcp add ios-multi-simulator npx -y github:zafnz/ios-multi-simulator-mcp

For local development:

claude mcp add ios-multi-simulator -- node /path/to/ios-multi-simulator-mcp/build/index.js

Troubleshooting

Rotated screen

The rotated screen is a problem when using ui_view due to the tapping and swipping using logical coordinate space, but the ui_view returning the pixel space, which when rotated don't align. Tell the agent to use ui_describe_all to navigate -- it uses less tokens anyhow.

Configuration

Environment Variables

Example with env vars:

{
  "mcpServers": {
    "ios-multi-simulator": {
      "command": "npx",
      "args": ["-y", "ios-multi-simulator-mcp"],
      "env": {
        "IOS_SIMULATOR_MCP_DEFAULT_OUTPUT_DIR": "~/Code/project/tmp",
        "IOS_SIMULATOR_MCP_IDB_PATH": "/opt/homebrew/bin/idb"
      }
    }
  }
}

License

MIT