mobile-analytics

name	mobile-analytics
description	Add crash reporting and event tracking to a React Native/Expo or Flutter app. Covers Sentry, Firebase Crashlytics, PostHog, source map upload, user identification, session recording, and GDPR compliance. Use when the user wants visibility into crashes, user behavior, or app performance in production.
standards-version	1.10.0

Mobile Analytics

Trigger

Use this skill when the user:

• Wants crash reporting or error tracking in production
• Needs event analytics or user behavior tracking
• Asks about Sentry, Firebase Crashlytics, PostHog, or Mixpanel
• Wants to understand how users interact with their app
• Mentions "analytics", "crash reporting", "crashlytics", "sentry", "tracking", "events", or "session recording"

Required Inputs

• Analytics type: crash reporting only, event tracking only, or both
• Provider: Sentry (recommended for crash + performance), Firebase Crashlytics, PostHog, or Mixpanel
• Framework: Expo (React Native) or Flutter

Workflow

1. Choose a provider. Each has different strengths:

   Provider	Best for	Free tier	Source maps	Session recording
   Sentry	Crashes + performance monitoring	5K errors/month	Yes	Yes (beta)
   Firebase Crashlytics	Crash-only, Google ecosystem	Unlimited	Yes (via CLI)	No
   PostHog	Product analytics + feature flags	1M events/month	No	Yes
   Mixpanel	Event funnels and retention	20M events/month	No	No

   You can combine providers. A common pattern is Sentry for crashes + PostHog for product analytics.

2. Set up Sentry (recommended). For Expo:

   npx expo install @sentry/react-native
   

   Add the config plugin in app.json:

   {
     "expo": {
       "plugins": [
         [
           "@sentry/react-native/expo",
           {
             "organization": "your-org",
             "project": "your-project"
           }
         ]
       ]
     }
   }
   

3. Initialize Sentry. In app/_layout.tsx or your entry point:

   import * as Sentry from "@sentry/react-native";
   
   Sentry.init({
     dsn: process.env.EXPO_PUBLIC_SENTRY_DSN!,
     environment: __DEV__ ? "development" : "production",
     tracesSampleRate: __DEV__ ? 1.0 : 0.2,
     enabled: !__DEV__,
   });
   

   Wrap your root component:

   export default Sentry.wrap(function RootLayout() {
     return <Stack />;
   });
   

4. Upload source maps for readable stack traces. With EAS Build, add a post-publish hook in app.json:

   {
     "expo": {
       "hooks": {
         "postPublish": [
           {
             "file": "@sentry/react-native/expo",
             "config": {
               "organization": "your-org",
               "project": "your-project"
             }
           }
         ]
       }
     }
   }
   

   Set the auth token in your EAS secrets:

   eas secret:create --name SENTRY_AUTH_TOKEN --value "your-token" --scope project
   

5. Track custom events. Beyond automatic crash reporting:

   import * as Sentry from "@sentry/react-native";
   
   Sentry.addBreadcrumb({
     category: "navigation",
     message: "User opened profile screen",
     level: "info",
   });
   
   Sentry.captureMessage("User completed onboarding");
   
   Sentry.captureException(new Error("Payment failed"), {
     tags: { payment_provider: "stripe" },
     extra: { amount: 999, currency: "usd" },
   });
   

6. Set up PostHog for product analytics (optional). Install:

   npx expo install posthog-react-native
   

   Initialize in your app:

   import { PostHogProvider } from "posthog-react-native";
   
   export default function RootLayout() {
     return (
       <PostHogProvider
         apiKey={process.env.EXPO_PUBLIC_POSTHOG_KEY!}
         options={{
           host: "https://us.i.posthog.com",
           enableSessionReplay: true,
         }}
       >
         <Stack />
       </PostHogProvider>
     );
   }
   

   Track events:

   import { usePostHog } from "posthog-react-native";
   
   function CheckoutScreen() {
     const posthog = usePostHog();
   
     const handlePurchase = () => {
       posthog.capture("purchase_completed", {
         product_id: "premium_yearly",
         price: 39.99,
       });
     };
   }
   

7. Identify users. Link analytics to authenticated users:

   // Sentry
   Sentry.setUser({ id: user.id, email: user.email });
   
   // PostHog
   posthog.identify(user.id, { email: user.email, plan: "premium" });
   
   // On sign-out, clear the user
   Sentry.setUser(null);
   posthog.reset();
   

8. GDPR and privacy compliance. Respect user privacy:

   import * as Sentry from "@sentry/react-native";
   
   function disableTracking() {
     Sentry.init({ enabled: false });
     posthog.optOut();
   }
   
   function enableTracking() {
     Sentry.init({ enabled: true, dsn: process.env.EXPO_PUBLIC_SENTRY_DSN! });
     posthog.optIn();
   }
   

   Add a privacy settings screen where users can opt out of analytics. Required for EU users under GDPR and recommended for App Store review.

Key References

• Sentry: React Native
• Sentry: Expo integration
• Firebase Crashlytics: React Native
• PostHog: React Native
• Mixpanel: React Native

Example Interaction

User: "I want crash reporting in production and event tracking for my checkout flow."

Agent:

1. Recommends Sentry for crashes + PostHog for event analytics
2. Installs @sentry/react-native and posthog-react-native with mobile_installDependency
3. Configures Sentry plugin in app.json with org and project
4. Initializes Sentry in _layout.tsx with production-only mode and 20% trace sampling
5. Sets up source map uploads via EAS Build hooks
6. Wraps app in PostHogProvider
7. Adds purchase event tracking in checkout flow: posthog.capture("purchase_completed", {...})
8. Implements user identification on login and reset on logout
9. Reminds user to set EXPO_PUBLIC_SENTRY_DSN and EXPO_PUBLIC_POSTHOG_KEY in .env

MCP Usage

Step	MCP Tool	Description
Install SDKs	mobile_installDependency	Install @sentry/react-native, posthog-react-native
Check build	mobile_checkBuildHealth	Verify project builds with native Sentry module
Validate config	mobile_checkBuildHealth	Ensure app.json plugins are correctly configured
Build for testing	mobile_buildForStore	Create a production build to verify source map upload

Common Pitfalls

1. Leaving analytics enabled in development - Set enabled: !__DEV__ to avoid polluting production data with dev crashes and test events.
2. Missing source maps - Without source maps, crash stack traces show minified code. Configure the Sentry post-publish hook and set the auth token in EAS secrets.
3. Over-sampling performance traces - A tracesSampleRate of 1.0 in production generates too much data and slows the app. Use 0.1-0.2 for production.
4. Not identifying users - Anonymous crash reports are hard to debug. Call Sentry.setUser() after authentication to associate crashes with user accounts.
5. Tracking PII in events - Do not log emails, passwords, or payment details in event properties. Sentry and PostHog both have data scrubbing options, but prevention is better.
6. Ignoring session recording consent - Session recording captures screen content. Require explicit user consent before enabling it, especially for EU users.
7. Firebase Crashlytics requires a dev build - Like most native modules, Crashlytics does not work in Expo Go.

See Also

• Mobile Monetization - track purchase and subscription events
• Mobile OTA Updates - track update adoption and crash rates per release
• Mobile Auth Setup - identify users for analytics after authentication