Note

Will be released in 9.9.1

Description

Native app start spans (Cold Start, Process Initialization, Application.onCreate, etc.) are missing from the "root /" transaction when Time to Full Display (TTFD) tracking takes longer than 3 seconds to complete.

The app_start_cold/app_start_warm measurements are correctly reported, but the detailed span breakdown is missing.

Environment

• Platform: iOS and Android (both affected)
• SDK: sentry_flutter
• Affected versions: At least 9.8.0 (likely earlier versions too)

Root Cause

Race condition in NativeAppStartHandler where _attachAppStartSpans() is called after timeToDisplayTracker.track(), but the transaction can be sent inside the timeToDisplayTracker.track() await chain via _finishedCallback.

Timeline:

1. Transaction created with autoFinishAfter: 3 seconds
2. Timer fires at 3s, sets _finishStatus to "finishing"
3. When TTFD completes (>3s), _finishedCallback triggers finish() and sends the transaction
4. _attachAppStartSpans() runs after timeToDisplayTracker.track() returns — too late!

What's Present vs Missing

Reproduction

1. Enable TTFD tracking: options.enableTimeToFullDisplayTracing = true
2. Call reportFullyDisplayed() after 3+ seconds (or don't call it at all)
3. Check the "root /" transaction in Sentry
4. Native app start spans will be missing

// In your app's root widget initState:
Future.delayed(const Duration(seconds: 5), () {
  SentryFlutter.reportFullyDisplayed();
});
// Result: Native app start spans will be MISSING## Suggested Fix

// Move `_attachAppStartSpans()` **before** `timeToDisplayTracker.track()`:

// Current (buggy):
await options.timeToDisplayTracker.track(...);
await _attachAppStartSpans(...);  // Too late!

// Fixed:
await _attachAppStartSpans(...);  // Add spans first
await options.timeToDisplayTracker.track(...);Alternatively, use the `onFinish` callback to ensure spans are attached before the transaction is captured (as mentioned in the existing TODO comment).