fix(android): Align foreground app start measurements

Use the foreground app start fallback for foreground standalone app
start transactions so measurements match the transaction timestamp.
Keep the headless-only span source limited to true headless starts.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: buenaflor

sentry-android-core/src/main/java/io/sentry/android/core/ActivityLifecycleIntegration.java

@@ -64,7 +64,7 @@ public final class ActivityLifecycleIntegration
   static final String TTFD_OP = "ui.load.full_display";
   static final long TTFD_TIMEOUT_MILLIS = 25000;
   private static final String TRACE_ORIGIN = "auto.ui.activity";
-  private static final String APP_START_SCREEN_DATA = "app.vitals.start.screen";
+  static final String APP_START_SCREEN_DATA = "app.vitals.start.screen";
 
   private final @NotNull Application application;
   private final @NotNull BuildInfoProvider buildInfoProvider;

sentry-android-core/src/main/java/io/sentry/android/core/PerformanceAndroidEventProcessor.java

@@ -1,6 +1,7 @@
 package io.sentry.android.core;
 
 import static io.sentry.android.core.ActivityLifecycleIntegration.APP_START_COLD;
+import static io.sentry.android.core.ActivityLifecycleIntegration.APP_START_SCREEN_DATA;
 import static io.sentry.android.core.ActivityLifecycleIntegration.APP_START_WARM;
 import static io.sentry.android.core.ActivityLifecycleIntegration.STANDALONE_APP_START_OP;
 import static io.sentry.android.core.ActivityLifecycleIntegration.UI_LOAD_OP;
@@ -85,15 +86,19 @@ public SentryEvent process(@NotNull SentryEvent event, @NotNull Hint hint) {
       // the app start measurement is only sent once and only if the transaction has
       // the app.start span, which is automatically created by the SDK.
       if (hasAppStartSpan(transaction)) {
-        // For headless starts, appLaunchedInForeground is false, so standalone app start
-        // transactions bypass only the foreground check, not the duplicate-send guard.
+        // For headless starts, appLaunchedInForeground is false, so only headless standalone app
+        // start transactions bypass the foreground check, not the duplicate-send guard.
         final @Nullable SpanContext traceContext = transaction.getContexts().getTrace();
         final boolean isStandaloneAppStartTxn =
             traceContext != null && STANDALONE_APP_START_OP.equals(traceContext.getOperation());
+        final boolean isHeadlessStandaloneAppStartTxn =
+            traceContext != null
+                && isStandaloneAppStartTxn
+                && !traceContext.getData().containsKey(APP_START_SCREEN_DATA);
 
-        if (appStartMetrics.shouldSendStartMeasurements(isStandaloneAppStartTxn)) {
+        if (appStartMetrics.shouldSendStartMeasurements(isHeadlessStandaloneAppStartTxn)) {
           final @NotNull TimeSpan appStartTimeSpan =
-              isStandaloneAppStartTxn
+              isHeadlessStandaloneAppStartTxn
                   ? appStartMetrics.getAppStartTimeSpanForHeadless()
                   : appStartMetrics.getAppStartTimeSpanWithFallback(options);
           final long appStartUpDurationMs = appStartTimeSpan.getDurationMs();

sentry-android-core/src/test/java/io/sentry/android/core/PerformanceAndroidEventProcessorTest.kt

@@ -13,6 +13,7 @@ import io.sentry.SpanStatus
 import io.sentry.TracesSamplingDecision
 import io.sentry.TransactionContext
 import io.sentry.android.core.ActivityLifecycleIntegration.APP_START_COLD
+import io.sentry.android.core.ActivityLifecycleIntegration.APP_START_SCREEN_DATA
 import io.sentry.android.core.ActivityLifecycleIntegration.APP_START_WARM
 import io.sentry.android.core.ActivityLifecycleIntegration.STANDALONE_APP_START_OP
 import io.sentry.android.core.ActivityLifecycleIntegration.UI_LOAD_OP
@@ -169,6 +170,30 @@ class PerformanceAndroidEventProcessorTest {
     }
   }
 
+  @Test
+  fun `foreground standalone app start measurement uses foreground fallback time span`() {
+    val sut = fixture.getSut(enablePerformanceV2 = false)
+    AppStartMetrics.getInstance().apply {
+      appStartType = AppStartType.COLD
+      isAppLaunchedInForeground = true
+      appStartTimeSpan.apply {
+        setStartedAt(1)
+        setStoppedAt(101)
+      }
+      sdkInitTimeSpan.apply {
+        setStartedAt(10)
+        setStoppedAt(30)
+      }
+    }
+
+    var tr = getTransaction(AppStartType.COLD)
+    tr.contexts.trace!!.setData(APP_START_SCREEN_DATA, "MainActivity")
+
+    tr = sut.process(tr, Hint())
+
+    assertEquals(20f, tr.measurements[MeasurementValue.KEY_APP_START_COLD]?.value)
+  }
+
   @Test
   fun `add cold start measurement for performance-v2`() {
     val sut = fixture.getSut(enablePerformanceV2 = true)