What problem does it solve? Mobile teams lack visibility into how their production Expo apps actually start up and navigate in the field. This Skill guides adding EAS Observe instrumentation to an Expo project, querying the collected telemetry from the terminal, and interpreting metrics like cold launch, TTR, and TTI to diagnose slow startups. ## Core Features & Use Cases - Instrumentation setup: Add expo-observe to an Expo project with the correct SDK-specific API (AppMetricsRoot on SDK 55, ObserveRoot and useObserve on SDK 56+), plus per-route navigation metrics via Expo Router or React Navigation integrations, custom events with Observe.logEvent, and error reporting with ObserveErrorBoundary. - CLI querying: Run the six eas observe:* commands (metrics-summary, metrics, routes, events, session, versions) with correct flags, aliases, pagination, and JSON output shapes. - Metrics interpretation: Apply target thresholds and diagnostic patterns using automatic TTI params (frame rate, device state, network state) to distinguish slow-but-smooth launches from main-thread contention or environmental throttling. - Use Case: After users report slow startup, run eas observe:metrics tti --sort slowest --days 7, pull a sessionId from the JSON output, and replay the full session timeline with eas observe:session to find the blocking request. ## Quick Start Ask the assistant to add EAS Observe instrumentation to your Expo project's root layout and mark the app interactive after initial data loading finishes.
