CLI Overview

Commands

Lanterna provides three commands for different performance profiling workflows:

Command	Description
`measure`	Collect performance metrics for a running app
`test`	Run a Maestro E2E flow and collect performance metrics in parallel
`monitor`	Start a live monitoring dashboard via WebSocket

See the dedicated page for each command for full option details:

Global Behavior

Platform Auto-Detection

When --platform is not specified, Lanterna checks for connected devices in the following order:

Query adb devices for connected Android devices or emulators.
Query xcrun simctl list devices booted for running iOS Simulators.
Select the first available device from whichever platform responds.

If devices are connected on both platforms, Android is selected by default. Use --platform ios or --platform android to override.

Device Selection

When multiple devices are connected on the same platform, Lanterna auto-selects the first one listed. To target a specific device, pass its ID:

# Android: use the device serial from `adb devices`
lanterna measure com.example.app --device emulator-5554

# iOS: use the simulator UDID from `xcrun simctl list`
lanterna measure com.example.app --device 3A4B5C6D-7E8F-9A0B-C1D2-E3F4A5B6C7D8

Exit Codes

Code	Meaning
`0`	Measurement completed successfully and the score is not in the Poor range
`1`	Score is Poor, or a regression was detected (when using `--baseline`)

This behavior makes Lanterna suitable as a CI gate — a non-zero exit code signals that performance has degraded below acceptable thresholds.

Full Help Output

lanterna — Performance profiler for React Native apps

Usage:
  lanterna measure <package> [options]
  lanterna test --maestro <flow.yaml> [options]
  lanterna monitor [options]

Commands:
  measure    Collect performance metrics for a running app
  test       Run a Maestro E2E flow and collect performance metrics
  monitor    Start live monitoring dashboard (WebSocket server)

Options (measure):
  --duration <seconds>    Measurement duration (default: 10)
  --platform <ios|android> Force platform (auto-detect if omitted)
  --device <id>           Target device ID (auto-select if omitted)
  --output <path>         Export JSON report to file
  --baseline <path>       Compare against a previous JSON report
  --help                  Show this help message

Options (test):
  --maestro <flow.yaml>   Path to Maestro flow YAML (required)
  --duration <seconds>    Measurement duration (default: 10)
  --platform <ios|android> Force platform (auto-detect if omitted)
  --device <id>           Target device ID (auto-select if omitted)
  --output <path>         Export JSON report to file

Options (monitor):
  --port <number>         WebSocket server port (default: 8347)

Examples:
  lanterna measure com.example.app
  lanterna measure com.example.app --duration 15
  lanterna measure com.example.app --platform ios --output report.json
  lanterna test --maestro login-flow.yaml
  lanterna test --maestro login-flow.yaml --duration 30 --output report.json
  lanterna monitor
  lanterna monitor --port 9000