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iOS app crashes on iPhone 14 Pro with offline mode enabled

Bug Report

Description

iOS app crashes immediately when offline mode is enabled on iPhone 14 Pro devices.

Environment

  • Device: iPhone 14 Pro, iPhone 14 Pro Max
  • iOS Version: 17.0, 17.1
  • App Version: 2.3.0
  • Frequency: 100% reproduction rate
  • Impact: ~8% of iOS user base (iPhone 14 Pro users)

Steps to Reproduce

  1. Open app on iPhone 14 Pro
  2. Navigate to Settings → Offline Mode
  3. Toggle "Enable Offline Mode" ON
  4. App crashes immediately

Crash Log

Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Subtype: KERN_INVALID_ADDRESS at 0x0000000000000010
Triggered by Thread: 0

Thread 0 Crashed:
0   OfflineStorage         0x000000010423c4f8 -[AsyncStorageManager saveData:] + 120
1   RecommendationService  0x000000010425a3dc -[RecommendationService cacheRecommendations:] + 348
2   UIKit                  0x00000001a8e5c7b8 -[UIApplication _run] + 828

Root Cause Analysis

Initial findings:

  1. AsyncStorage memory issue

    • Allocating 180MB for offline cache
    • iPhone 14 Pro has aggressive memory limits
    • Not releasing memory properly

  2. Sync queue race condition

    • Background sync thread conflicts with UI thread
    • Not using proper locking mechanisms

  3. Database schema issue

    • WatermelonDB migration fails on new devices
    • Schema version mismatch

Affected Features

  • ✅ Offline recommendation caching: CRASHES
  • ✅ Offline reading mode: CRASHES
  • ⚠️ Sync when online: Untested (can't reach feature)

Impact Metrics

  • Crash rate: 8.2% of iOS sessions
  • Affected users: ~24,000 users
  • App Store rating: Dropped from 4.6 to 4.1
  • Support tickets: 340 in past week

Proposed Fix

Immediate (This week)

  1. Disable offline mode for iPhone 14 Pro:
const isIPhone14Pro = DeviceInfo.getModel().includes('iPhone15,2');
if (isIPhone14Pro) {
  // Hide offline mode setting
  return null;
}
  1. Release hotfix 2.3.1:
    • Remove offline mode for affected devices
    • Add analytics to track impact

Short-term (Week 2)

  1. Fix memory allocation:
// Chunk large data writes
const CHUNK_SIZE = 10 * 1024 * 1024; // 10MB chunks
for (let i = 0; i < data.length; i += CHUNK_SIZE) {
  await AsyncStorage.setItem(key, data.slice(i, i + CHUNK_SIZE));
  await new Promise(resolve => setTimeout(resolve, 100)); // Release event loop
}
  1. Add proper locking:
import { Mutex } from 'async-mutex';
const mutex = new Mutex();

await mutex.runExclusive(async () => {
  await AsyncStorage.setItem(key, value);
});
  1. Database migration fix:
await database.write(async () => {
  await database.unsafeResetDatabase();
  await migrateDatabase();
});

Testing Plan

  • Test on iPhone 14 Pro simulator
  • Test on physical iPhone 14 Pro device
  • Test with large offline cache (100MB+)
  • Test background sync scenarios
  • Memory profiling with Instruments

Rollout Plan

  1. Beta release (Oct 12): TestFlight to 100 users
  2. Phased rollout (Oct 15): 10% → 50% → 100%
  3. Monitor crash rates daily
  4. Rollback if crash rate > 2%

Related Issues

  • Relates to: #7 (closed) (offline mode implementation)
  • Relates to: #6 (closed) (AI recommendations - offline caching)
  • Blocked by: #3 (closed) (data sync implementation)

Priority: CRITICAL - 8% crash rate Type: Bug

cc: @michael_usanchenko @jean_gabriel @bill_staples