divine-mobile: Skill for Claude Code

Flutter Startup Network Blocking

Problem

Flutter app startup is slow because network operations (WebSocket connections, API calls, service initialization) run sequentially during the initialization phase, blocking the first frame from rendering. With multiple relay/server connections, worst-case startup time becomes O(n × timeout) instead of O(max timeout).

Context / Trigger Conditions

• App takes 3+ seconds to show first frame on fresh launch
• Startup logs show sequential "connecting to relay X... connecting to relay Y..."
• Services that require authentication initialize even for unauthenticated users
• _initializeCoreServices() or similar contains multiple awaited network operations
• Riverpod providers eagerly initialize network-dependent services in their build() method

Solution

1. Identify Blocking Operations

Look for sequential awaits in startup code:

// BAD: Sequential - each connection blocks the next
for (final url in relays) {
  await connectToRelay(url);  // Blocks startup!
}

2. Convert Sequential to Parallel

Use Future.wait() to run all connections simultaneously:

// GOOD: Parallel - all connections run at once
final results = await Future.wait(
  relays.map((url) async {
    final success = await connectToRelay(url);
    return MapEntry(url, success);
  }),
);

3. Defer Non-Critical Service Initialization

Move network-dependent services out of the critical startup path:

Before (blocking startup):

Future<void> _initializeCoreServices(ProviderContainer container) async {
  await container.read(authServiceProvider).initialize();
  await container.read(nostrServiceProvider).initialize();  // BLOCKS for relay connections!
  await container.read(otherServiceProvider).initialize();
}

After (lazy initialization):

Future<void> _initializeCoreServices(ProviderContainer container) async {
  // NOTE: NostrService initializes lazily when user authenticates
  await container.read(authServiceProvider).initialize();
  await container.read(seenVideosServiceProvider).initialize();
  // NostrService NOT initialized here - happens when auth state changes
}