From 8a6cf5ab5be865d7914da601444fac08492a9bab Mon Sep 17 00:00:00 2001
From: Tejas Deshpande <tdeshpande@google.com>
Date: Fri, 15 Aug 2025 13:47:52 -0400
Subject: [PATCH 01/14] Add TODO

---
 .../main/java/com/google/firebase/perf/FirebasePerfEarly.java    | 1 +
 1 file changed, 1 insertion(+)

diff --git a/firebase-perf/src/main/java/com/google/firebase/perf/FirebasePerfEarly.java b/firebase-perf/src/main/java/com/google/firebase/perf/FirebasePerfEarly.java
index 5b89deaad82..1436c863977 100644
--- a/firebase-perf/src/main/java/com/google/firebase/perf/FirebasePerfEarly.java
+++ b/firebase-perf/src/main/java/com/google/firebase/perf/FirebasePerfEarly.java
@@ -48,6 +48,7 @@ public FirebasePerfEarly(
     if (startupTime != null) {
       AppStartTrace appStartTrace = AppStartTrace.getInstance();
       appStartTrace.registerActivityLifecycleCallbacks(context);
+      // TODO(b/339891952): Investigate why this runs *before* the activity lifecycle callbacks.
       uiExecutor.execute(new AppStartTrace.StartFromBackgroundRunnable(appStartTrace));
     }
 

From f4434c2f34b10884bc0868675a177fc481cdbfa9 Mon Sep 17 00:00:00 2001
From: Tejas Deshpande <tdeshpande@google.com>
Date: Tue, 19 Aug 2025 17:25:37 -0400
Subject: [PATCH 02/14] Add a delay to detect background starts

---
 .../firebase/perf/metrics/AppStartTrace.java  | 37 ++++++++++++++++---
 1 file changed, 31 insertions(+), 6 deletions(-)

diff --git a/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java b/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
index 7574f989d92..233c3367aca 100644
--- a/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
+++ b/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
@@ -75,6 +75,8 @@ public class AppStartTrace implements ActivityLifecycleCallbacks, LifecycleObser
   private static final @NonNull Timer PERF_CLASS_LOAD_TIME = new Clock().getTime();
   private static final long MAX_LATENCY_BEFORE_UI_INIT = TimeUnit.MINUTES.toMicros(1);
 
+  private static final long MAX_BACKGROUND_THREAD_DELAY = TimeUnit.MILLISECONDS.toMicros(100);
+
   // Core pool size 0 allows threads to shut down if they're idle
   private static final int CORE_POOL_SIZE = 0;
   private static final int MAX_POOL_SIZE = 1; // Only need single thread
@@ -111,6 +113,8 @@ public class AppStartTrace implements ActivityLifecycleCallbacks, LifecycleObser
   private final @Nullable Timer processStartTime;
   private final @Nullable Timer firebaseClassLoadTime;
   private Timer onCreateTime = null;
+
+  private Timer mainThreadRunnableTime = null;
   private Timer onStartTime = null;
   private Timer onResumeTime = null;
   private Timer firstForegroundTime = null;
@@ -319,10 +323,28 @@ private void recordOnDrawFrontOfQueue() {
     logExperimentTrace(this.experimentTtid);
   }
 
+  private boolean isStartedFromBackground() {
+    // This a fix for b/339891952 where the runnable on the background thread can run before the
+    // activity lifecycle callbacks.
+    if (mainThreadRunnableTime == null) {
+      return false;
+    }
+
+    if (isStartedFromBackground
+        && (mainThreadRunnableTime.getDurationMicros() < MAX_BACKGROUND_THREAD_DELAY)) {
+      // Reset it to false as it was executed pre-emptively.
+      isStartedFromBackground = false;
+    }
+
+    return isStartedFromBackground;
+  }
+
   @Override
   public synchronized void onActivityCreated(Activity activity, Bundle savedInstanceState) {
-    if (isStartedFromBackground || onCreateTime != null // An activity already called onCreate()
+    if (isStartedFromBackground() || onCreateTime != null // An activity already called onCreate()
     ) {
+      AndroidLogger.getInstance()
+          .debug("onActivityCreated: isStartedFromBackground - " + isStartedFromBackground());
       return;
     }
 
@@ -337,7 +359,7 @@ public synchronized void onActivityCreated(Activity activity, Bundle savedInstan
 
   @Override
   public synchronized void onActivityStarted(Activity activity) {
-    if (isStartedFromBackground
+    if (isStartedFromBackground()
         || onStartTime != null // An activity already called onStart()
         || isTooLateToInitUI) {
       return;
@@ -347,7 +369,7 @@ public synchronized void onActivityStarted(Activity activity) {
 
   @Override
   public synchronized void onActivityResumed(Activity activity) {
-    if (isStartedFromBackground || isTooLateToInitUI) {
+    if (isStartedFromBackground() || isTooLateToInitUI) {
       return;
     }
 
@@ -440,7 +462,7 @@ private void logAppStartTrace() {
 
   @Override
   public void onActivityPaused(Activity activity) {
-    if (isStartedFromBackground
+    if (isStartedFromBackground()
         || isTooLateToInitUI
         || !configResolver.getIsExperimentTTIDEnabled()) {
       return;
@@ -458,7 +480,7 @@ public void onActivityStopped(Activity activity) {}
   @Keep
   @OnLifecycleEvent(Lifecycle.Event.ON_START)
   public void onAppEnteredForeground() {
-    if (isStartedFromBackground || isTooLateToInitUI || firstForegroundTime != null) {
+    if (isStartedFromBackground() || isTooLateToInitUI || firstForegroundTime != null) {
       return;
     }
     // firstForeground is equivalent to the first Activity onStart. This marks the beginning of
@@ -476,7 +498,7 @@ public void onAppEnteredForeground() {
   @Keep
   @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
   public void onAppEnteredBackground() {
-    if (isStartedFromBackground || isTooLateToInitUI || firstBackgroundTime != null) {
+    if (isStartedFromBackground() || isTooLateToInitUI || firstBackgroundTime != null) {
       return;
     }
     firstBackgroundTime = clock.getTime();
@@ -574,6 +596,9 @@ public StartFromBackgroundRunnable(final AppStartTrace trace) {
     public void run() {
       // if no activity has ever been created.
       if (trace.onCreateTime == null) {
+        trace.mainThreadRunnableTime = new Timer();
+        AndroidLogger.getInstance()
+            .debug("StartFromBackgroundThreadRunnable: " + trace.onCreateTime);
         trace.isStartedFromBackground = true;
       }
     }

From ad64ce903c89412bb73e9386d47ec7e6901a7937 Mon Sep 17 00:00:00 2001
From: Tejas Deshpande <tdeshpande@google.com>
Date: Tue, 19 Aug 2025 17:28:24 -0400
Subject: [PATCH 03/14] Remove logs

---
 .../java/com/google/firebase/perf/metrics/AppStartTrace.java  | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java b/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
index 233c3367aca..c011853476e 100644
--- a/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
+++ b/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
@@ -343,8 +343,6 @@ private boolean isStartedFromBackground() {
   public synchronized void onActivityCreated(Activity activity, Bundle savedInstanceState) {
     if (isStartedFromBackground() || onCreateTime != null // An activity already called onCreate()
     ) {
-      AndroidLogger.getInstance()
-          .debug("onActivityCreated: isStartedFromBackground - " + isStartedFromBackground());
       return;
     }
 
@@ -597,8 +595,6 @@ public void run() {
       // if no activity has ever been created.
       if (trace.onCreateTime == null) {
         trace.mainThreadRunnableTime = new Timer();
-        AndroidLogger.getInstance()
-            .debug("StartFromBackgroundThreadRunnable: " + trace.onCreateTime);
         trace.isStartedFromBackground = true;
       }
     }

From 5e50f5eea017cc10397ba5df9707c582bd58ceaf Mon Sep 17 00:00:00 2001
From: Tejas Deshpande <tdeshpande@google.com>
Date: Tue, 19 Aug 2025 17:49:15 -0400
Subject: [PATCH 04/14] Add unit test

---
 .../firebase/perf/FirebasePerfEarly.java      |  1 -
 .../firebase/perf/metrics/AppStartTrace.java  |  5 ++++
 .../perf/metrics/AppStartTraceTest.java       | 29 +++++++++++++++++++
 3 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/firebase-perf/src/main/java/com/google/firebase/perf/FirebasePerfEarly.java b/firebase-perf/src/main/java/com/google/firebase/perf/FirebasePerfEarly.java
index 1436c863977..5b89deaad82 100644
--- a/firebase-perf/src/main/java/com/google/firebase/perf/FirebasePerfEarly.java
+++ b/firebase-perf/src/main/java/com/google/firebase/perf/FirebasePerfEarly.java
@@ -48,7 +48,6 @@ public FirebasePerfEarly(
     if (startupTime != null) {
       AppStartTrace appStartTrace = AppStartTrace.getInstance();
       appStartTrace.registerActivityLifecycleCallbacks(context);
-      // TODO(b/339891952): Investigate why this runs *before* the activity lifecycle callbacks.
       uiExecutor.execute(new AppStartTrace.StartFromBackgroundRunnable(appStartTrace));
     }
 
diff --git a/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java b/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
index c011853476e..2283bf45a3e 100644
--- a/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
+++ b/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
@@ -638,4 +638,9 @@ Timer getOnResumeTime() {
   void setIsStartFromBackground() {
     isStartedFromBackground = true;
   }
+
+  @VisibleForTesting
+  void setMainThreadRunnableTime(Timer timer) {
+    mainThreadRunnableTime = timer;
+  }
 }
diff --git a/firebase-perf/src/test/java/com/google/firebase/perf/metrics/AppStartTraceTest.java b/firebase-perf/src/test/java/com/google/firebase/perf/metrics/AppStartTraceTest.java
index 36ae3d10116..264f4bc22d3 100644
--- a/firebase-perf/src/test/java/com/google/firebase/perf/metrics/AppStartTraceTest.java
+++ b/firebase-perf/src/test/java/com/google/firebase/perf/metrics/AppStartTraceTest.java
@@ -18,6 +18,7 @@
 import static org.mockito.ArgumentMatchers.isA;
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
@@ -258,6 +259,34 @@ public void testStartFromBackground() {
             ArgumentMatchers.nullable(ApplicationProcessState.class));
   }
 
+  @Test
+  public void testStartFromBackground_invertedOrder() {
+    FakeScheduledExecutorService fakeExecutorService = new FakeScheduledExecutorService();
+    Timer fakeTimer = spy(new Timer(currentTime));
+    AppStartTrace trace =
+        new AppStartTrace(transportManager, clock, configResolver, fakeExecutorService);
+    trace.registerActivityLifecycleCallbacks(appContext);
+    trace.setIsStartFromBackground();
+    trace.setMainThreadRunnableTime(fakeTimer);
+
+    when(fakeTimer.getDurationMicros()).thenReturn(99L);
+    trace.onActivityCreated(activity1, bundle);
+    Assert.assertNotNull(trace.getOnCreateTime());
+    ++currentTime;
+    trace.onActivityStarted(activity1);
+    Assert.assertNotNull(trace.getOnStartTime());
+    ++currentTime;
+    trace.onActivityResumed(activity1);
+    Assert.assertNotNull(trace.getOnResumeTime());
+    // There should be a trace sent since the delay between the main thread and onActivityCreated
+    // is limited.
+    fakeExecutorService.runAll();
+    verify(transportManager, times(1))
+        .log(
+            traceArgumentCaptor.capture(),
+            ArgumentMatchers.nullable(ApplicationProcessState.class));
+  }
+
   @Test
   @Config(sdk = 26)
   public void timeToInitialDisplay_isLogged() {

From c187fa7dc59636a164ad23fc1e69be6be71308eb Mon Sep 17 00:00:00 2001
From: Tejas Deshpande <tdeshpande@google.com>
Date: Tue, 19 Aug 2025 17:52:21 -0400
Subject: [PATCH 05/14] Additional unit test

---
 .../perf/metrics/AppStartTraceTest.java       | 30 ++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/firebase-perf/src/test/java/com/google/firebase/perf/metrics/AppStartTraceTest.java b/firebase-perf/src/test/java/com/google/firebase/perf/metrics/AppStartTraceTest.java
index 264f4bc22d3..f0b342c6af5 100644
--- a/firebase-perf/src/test/java/com/google/firebase/perf/metrics/AppStartTraceTest.java
+++ b/firebase-perf/src/test/java/com/google/firebase/perf/metrics/AppStartTraceTest.java
@@ -252,6 +252,7 @@ public void testStartFromBackground() {
     ++currentTime;
     trace.onActivityResumed(activity1);
     Assert.assertNull(trace.getOnResumeTime());
+    fakeExecutorService.runAll();
     // There should be no trace sent.
     verify(transportManager, times(0))
         .log(
@@ -278,10 +279,37 @@ public void testStartFromBackground_invertedOrder() {
     ++currentTime;
     trace.onActivityResumed(activity1);
     Assert.assertNotNull(trace.getOnResumeTime());
+    fakeExecutorService.runAll();
+    // There should be no trace sent.
+    verify(transportManager, times(1))
+        .log(
+            traceArgumentCaptor.capture(),
+            ArgumentMatchers.nullable(ApplicationProcessState.class));
+  }
+
+  @Test
+  public void testStartFromBackground_delayedInvertedOrder() {
+    FakeScheduledExecutorService fakeExecutorService = new FakeScheduledExecutorService();
+    Timer fakeTimer = spy(new Timer(currentTime));
+    AppStartTrace trace =
+        new AppStartTrace(transportManager, clock, configResolver, fakeExecutorService);
+    trace.registerActivityLifecycleCallbacks(appContext);
+    trace.setIsStartFromBackground();
+    trace.setMainThreadRunnableTime(fakeTimer);
+
+    when(fakeTimer.getDurationMicros()).thenReturn(TimeUnit.MILLISECONDS.toMicros(100) + 1);
+    trace.onActivityCreated(activity1, bundle);
+    Assert.assertNull(trace.getOnCreateTime());
+    ++currentTime;
+    trace.onActivityStarted(activity1);
+    Assert.assertNull(trace.getOnStartTime());
+    ++currentTime;
+    trace.onActivityResumed(activity1);
+    Assert.assertNull(trace.getOnResumeTime());
     // There should be a trace sent since the delay between the main thread and onActivityCreated
     // is limited.
     fakeExecutorService.runAll();
-    verify(transportManager, times(1))
+    verify(transportManager, times(0))
         .log(
             traceArgumentCaptor.capture(),
             ArgumentMatchers.nullable(ApplicationProcessState.class));

From b90accd1a3f372c3d027bf1f55fcfe98ef3f7921 Mon Sep 17 00:00:00 2001
From: Tejas Deshpande <tdeshpande@google.com>
Date: Tue, 19 Aug 2025 17:58:20 -0400
Subject: [PATCH 06/14] Refactor

---
 .../firebase/perf/metrics/AppStartTrace.java  | 20 +++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java b/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
index 2283bf45a3e..fc8f106fb4e 100644
--- a/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
+++ b/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
@@ -323,11 +323,11 @@ private void recordOnDrawFrontOfQueue() {
     logExperimentTrace(this.experimentTtid);
   }
 
-  private boolean isStartedFromBackground() {
+  private void resolveIsStartedFromBackground() {
     // This a fix for b/339891952 where the runnable on the background thread can run before the
     // activity lifecycle callbacks.
     if (mainThreadRunnableTime == null) {
-      return false;
+      return;
     }
 
     if (isStartedFromBackground
@@ -335,13 +335,13 @@ private boolean isStartedFromBackground() {
       // Reset it to false as it was executed pre-emptively.
       isStartedFromBackground = false;
     }
-
-    return isStartedFromBackground;
   }
 
   @Override
   public synchronized void onActivityCreated(Activity activity, Bundle savedInstanceState) {
-    if (isStartedFromBackground() || onCreateTime != null // An activity already called onCreate()
+    resolveIsStartedFromBackground();
+
+    if (isStartedFromBackground || onCreateTime != null // An activity already called onCreate()
     ) {
       return;
     }
@@ -357,7 +357,7 @@ public synchronized void onActivityCreated(Activity activity, Bundle savedInstan
 
   @Override
   public synchronized void onActivityStarted(Activity activity) {
-    if (isStartedFromBackground()
+    if (isStartedFromBackground
         || onStartTime != null // An activity already called onStart()
         || isTooLateToInitUI) {
       return;
@@ -367,7 +367,7 @@ public synchronized void onActivityStarted(Activity activity) {
 
   @Override
   public synchronized void onActivityResumed(Activity activity) {
-    if (isStartedFromBackground() || isTooLateToInitUI) {
+    if (isStartedFromBackground || isTooLateToInitUI) {
       return;
     }
 
@@ -460,7 +460,7 @@ private void logAppStartTrace() {
 
   @Override
   public void onActivityPaused(Activity activity) {
-    if (isStartedFromBackground()
+    if (isStartedFromBackground
         || isTooLateToInitUI
         || !configResolver.getIsExperimentTTIDEnabled()) {
       return;
@@ -478,7 +478,7 @@ public void onActivityStopped(Activity activity) {}
   @Keep
   @OnLifecycleEvent(Lifecycle.Event.ON_START)
   public void onAppEnteredForeground() {
-    if (isStartedFromBackground() || isTooLateToInitUI || firstForegroundTime != null) {
+    if (isStartedFromBackground || isTooLateToInitUI || firstForegroundTime != null) {
       return;
     }
     // firstForeground is equivalent to the first Activity onStart. This marks the beginning of
@@ -496,7 +496,7 @@ public void onAppEnteredForeground() {
   @Keep
   @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
   public void onAppEnteredBackground() {
-    if (isStartedFromBackground() || isTooLateToInitUI || firstBackgroundTime != null) {
+    if (isStartedFromBackground || isTooLateToInitUI || firstBackgroundTime != null) {
       return;
     }
     firstBackgroundTime = clock.getTime();

From 82d705bc97d5aecb866e579c9cc52f47dbd1144c Mon Sep 17 00:00:00 2001
From: Tejas Deshpande <tdeshpande@google.com>
Date: Tue, 19 Aug 2025 18:01:42 -0400
Subject: [PATCH 07/14] Add changelog

---
 firebase-perf/CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/firebase-perf/CHANGELOG.md b/firebase-perf/CHANGELOG.md
index b4db8bb6bc4..c7f69f22a43 100644
--- a/firebase-perf/CHANGELOG.md
+++ b/firebase-perf/CHANGELOG.md
@@ -1,5 +1,6 @@
 # Unreleased
 * [fixed] Fixed an ANR on app launch. [#4831]
+* [fixed] Fix app start traces on API 34+. [#5920]
 
 # 22.0.0
 * [changed] **Breaking Change**: Updated minSdkVersion to API level 23 or higher.

From a7e7239c38df90aed15b287f78f307f5c6db48bb Mon Sep 17 00:00:00 2001
From: Tejas Deshpande <tdeshpande@google.com>
Date: Tue, 19 Aug 2025 18:05:27 -0400
Subject: [PATCH 08/14] Rename

---
 .../java/com/google/firebase/perf/metrics/AppStartTrace.java  | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java b/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
index fc8f106fb4e..3e8f0b03457 100644
--- a/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
+++ b/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
@@ -75,7 +75,7 @@ public class AppStartTrace implements ActivityLifecycleCallbacks, LifecycleObser
   private static final @NonNull Timer PERF_CLASS_LOAD_TIME = new Clock().getTime();
   private static final long MAX_LATENCY_BEFORE_UI_INIT = TimeUnit.MINUTES.toMicros(1);
 
-  private static final long MAX_BACKGROUND_THREAD_DELAY = TimeUnit.MILLISECONDS.toMicros(100);
+  private static final long MAX_BACKGROUND_RUNNABLE_DELAY = TimeUnit.MILLISECONDS.toMicros(100);
 
   // Core pool size 0 allows threads to shut down if they're idle
   private static final int CORE_POOL_SIZE = 0;
@@ -331,7 +331,7 @@ private void resolveIsStartedFromBackground() {
     }
 
     if (isStartedFromBackground
-        && (mainThreadRunnableTime.getDurationMicros() < MAX_BACKGROUND_THREAD_DELAY)) {
+        && (mainThreadRunnableTime.getDurationMicros() < MAX_BACKGROUND_RUNNABLE_DELAY)) {
       // Reset it to false as it was executed pre-emptively.
       isStartedFromBackground = false;
     }

From 98986f036f3ff7b079a065add50a98c21507d977 Mon Sep 17 00:00:00 2001
From: Tejas Deshpande <tdeshpande@google.com>
Date: Tue, 19 Aug 2025 18:16:05 -0400
Subject: [PATCH 09/14] nit

---
 firebase-perf/CHANGELOG.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/firebase-perf/CHANGELOG.md b/firebase-perf/CHANGELOG.md
index c7f69f22a43..4954be336b5 100644
--- a/firebase-perf/CHANGELOG.md
+++ b/firebase-perf/CHANGELOG.md
@@ -1,6 +1,6 @@
 # Unreleased
 * [fixed] Fixed an ANR on app launch. [#4831]
-* [fixed] Fix app start traces on API 34+. [#5920]
+* [fixed] Fixed app start traces on API 34+. [#5920]
 
 # 22.0.0
 * [changed] **Breaking Change**: Updated minSdkVersion to API level 23 or higher.

From 4f853fa96d7700c5ab6eda889bc5e30cbb3e46d4 Mon Sep 17 00:00:00 2001
From: Tejas Deshpande <tdeshpande@google.com>
Date: Wed, 20 Aug 2025 10:05:05 -0400
Subject: [PATCH 10/14] Update method documentation.

---
 .../java/com/google/firebase/perf/metrics/AppStartTrace.java   | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java b/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
index 3e8f0b03457..4c51d73f942 100644
--- a/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
+++ b/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
@@ -580,8 +580,7 @@ public static boolean isScreenOn(Context appContext) {
    * We use StartFromBackgroundRunnable to detect if app is started from background or foreground.
    * If app is started from background, we do not generate AppStart trace. This runnable is posted
    * to main UI thread from FirebasePerfEarly. If app is started from background, this runnable will
-   * be executed before any activity's onCreate() method. If app is started from foreground,
-   * activity's onCreate() method is executed before this runnable.
+   * be executed earlier than 100ms of any activity's onCreate() method.
    */
   public static class StartFromBackgroundRunnable implements Runnable {
     private final AppStartTrace trace;

From 65aba3239df37d365c3afe99fd14d5f82f23832e Mon Sep 17 00:00:00 2001
From: Tejas Deshpande <tdeshpande@google.com>
Date: Wed, 20 Aug 2025 10:15:43 -0400
Subject: [PATCH 11/14] Simplify change

---
 .../firebase/perf/metrics/AppStartTrace.java  | 15 +++-------
 .../perf/metrics/AppStartTraceTest.java       | 28 ++-----------------
 2 files changed, 6 insertions(+), 37 deletions(-)

diff --git a/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java b/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
index 4c51d73f942..189e6c95106 100644
--- a/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
+++ b/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
@@ -324,16 +324,14 @@ private void recordOnDrawFrontOfQueue() {
   }
 
   private void resolveIsStartedFromBackground() {
-    // This a fix for b/339891952 where the runnable on the background thread can run before the
-    // activity lifecycle callbacks.
+    // If the runnable hasn't run, it isn't a background start.
     if (mainThreadRunnableTime == null) {
       return;
     }
 
-    if (isStartedFromBackground
-        && (mainThreadRunnableTime.getDurationMicros() < MAX_BACKGROUND_RUNNABLE_DELAY)) {
-      // Reset it to false as it was executed pre-emptively.
-      isStartedFromBackground = false;
+    // Set it to true if the runnable ran more than 100ms prior to onActivityCreated()
+    if (mainThreadRunnableTime.getDurationMicros() >= MAX_BACKGROUND_RUNNABLE_DELAY) {
+      isStartedFromBackground = true;
     }
   }
 
@@ -633,11 +631,6 @@ Timer getOnResumeTime() {
     return onResumeTime;
   }
 
-  @VisibleForTesting
-  void setIsStartFromBackground() {
-    isStartedFromBackground = true;
-  }
-
   @VisibleForTesting
   void setMainThreadRunnableTime(Timer timer) {
     mainThreadRunnableTime = timer;
diff --git a/firebase-perf/src/test/java/com/google/firebase/perf/metrics/AppStartTraceTest.java b/firebase-perf/src/test/java/com/google/firebase/perf/metrics/AppStartTraceTest.java
index f0b342c6af5..3177eb310b5 100644
--- a/firebase-perf/src/test/java/com/google/firebase/perf/metrics/AppStartTraceTest.java
+++ b/firebase-perf/src/test/java/com/google/firebase/perf/metrics/AppStartTraceTest.java
@@ -239,35 +239,12 @@ public void testDelayedAppStart() {
   }
 
   @Test
-  public void testStartFromBackground() {
-    FakeScheduledExecutorService fakeExecutorService = new FakeScheduledExecutorService();
-    AppStartTrace trace =
-        new AppStartTrace(transportManager, clock, configResolver, fakeExecutorService);
-    trace.setIsStartFromBackground();
-    trace.onActivityCreated(activity1, bundle);
-    Assert.assertNull(trace.getOnCreateTime());
-    ++currentTime;
-    trace.onActivityStarted(activity1);
-    Assert.assertNull(trace.getOnStartTime());
-    ++currentTime;
-    trace.onActivityResumed(activity1);
-    Assert.assertNull(trace.getOnResumeTime());
-    fakeExecutorService.runAll();
-    // There should be no trace sent.
-    verify(transportManager, times(0))
-        .log(
-            traceArgumentCaptor.capture(),
-            ArgumentMatchers.nullable(ApplicationProcessState.class));
-  }
-
-  @Test
-  public void testStartFromBackground_invertedOrder() {
+  public void testStartFromBackground_within100ms() {
     FakeScheduledExecutorService fakeExecutorService = new FakeScheduledExecutorService();
     Timer fakeTimer = spy(new Timer(currentTime));
     AppStartTrace trace =
         new AppStartTrace(transportManager, clock, configResolver, fakeExecutorService);
     trace.registerActivityLifecycleCallbacks(appContext);
-    trace.setIsStartFromBackground();
     trace.setMainThreadRunnableTime(fakeTimer);
 
     when(fakeTimer.getDurationMicros()).thenReturn(99L);
@@ -288,13 +265,12 @@ public void testStartFromBackground_invertedOrder() {
   }
 
   @Test
-  public void testStartFromBackground_delayedInvertedOrder() {
+  public void testStartFromBackground_moreThan100ms() {
     FakeScheduledExecutorService fakeExecutorService = new FakeScheduledExecutorService();
     Timer fakeTimer = spy(new Timer(currentTime));
     AppStartTrace trace =
         new AppStartTrace(transportManager, clock, configResolver, fakeExecutorService);
     trace.registerActivityLifecycleCallbacks(appContext);
-    trace.setIsStartFromBackground();
     trace.setMainThreadRunnableTime(fakeTimer);
 
     when(fakeTimer.getDurationMicros()).thenReturn(TimeUnit.MILLISECONDS.toMicros(100) + 1);

From 713a0015519afcfb46bc0f1cbac4846b4309c2ac Mon Sep 17 00:00:00 2001
From: Tejas Deshpande <tdeshpande@google.com>
Date: Wed, 20 Aug 2025 10:18:19 -0400
Subject: [PATCH 12/14] Fix comment

---
 .../com/google/firebase/perf/metrics/AppStartTraceTest.java | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/firebase-perf/src/test/java/com/google/firebase/perf/metrics/AppStartTraceTest.java b/firebase-perf/src/test/java/com/google/firebase/perf/metrics/AppStartTraceTest.java
index 3177eb310b5..25ad845231a 100644
--- a/firebase-perf/src/test/java/com/google/firebase/perf/metrics/AppStartTraceTest.java
+++ b/firebase-perf/src/test/java/com/google/firebase/perf/metrics/AppStartTraceTest.java
@@ -257,7 +257,8 @@ public void testStartFromBackground_within100ms() {
     trace.onActivityResumed(activity1);
     Assert.assertNotNull(trace.getOnResumeTime());
     fakeExecutorService.runAll();
-    // There should be no trace sent.
+    // There should be a trace sent since the delay between the main thread and onActivityCreated
+    // is limited.
     verify(transportManager, times(1))
         .log(
             traceArgumentCaptor.capture(),
@@ -282,8 +283,7 @@ public void testStartFromBackground_moreThan100ms() {
     ++currentTime;
     trace.onActivityResumed(activity1);
     Assert.assertNull(trace.getOnResumeTime());
-    // There should be a trace sent since the delay between the main thread and onActivityCreated
-    // is limited.
+    // There should be no trace sent.
     fakeExecutorService.runAll();
     verify(transportManager, times(0))
         .log(

From 07495da4b38a0535be525053d5952e3042f8ab6d Mon Sep 17 00:00:00 2001
From: Tejas Deshpande <tdeshpande@google.com>
Date: Wed, 20 Aug 2025 10:21:45 -0400
Subject: [PATCH 13/14] Make change to always set the main thread runnable time

---
 .../com/google/firebase/perf/metrics/AppStartTrace.java     | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java b/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
index 189e6c95106..5e70bf864dd 100644
--- a/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
+++ b/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
@@ -589,11 +589,7 @@ public StartFromBackgroundRunnable(final AppStartTrace trace) {
 
     @Override
     public void run() {
-      // if no activity has ever been created.
-      if (trace.onCreateTime == null) {
-        trace.mainThreadRunnableTime = new Timer();
-        trace.isStartedFromBackground = true;
-      }
+      trace.mainThreadRunnableTime = new Timer();
     }
   }
 

From 03effc9a18b5654a2a63c195d53be1cfa9787e2a Mon Sep 17 00:00:00 2001
From: Tejas Deshpande <tdeshpande@google.com>
Date: Wed, 20 Aug 2025 10:32:35 -0400
Subject: [PATCH 14/14] Fix multiple checks

---
 .../com/google/firebase/perf/metrics/AppStartTrace.java   | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java b/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
index 5e70bf864dd..ceac4b39335 100644
--- a/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
+++ b/firebase-perf/src/main/java/com/google/firebase/perf/metrics/AppStartTrace.java
@@ -324,15 +324,19 @@ private void recordOnDrawFrontOfQueue() {
   }
 
   private void resolveIsStartedFromBackground() {
-    // If the runnable hasn't run, it isn't a background start.
+    // If the mainThreadRunnableTime is null, either the runnable hasn't run, or this check has
+    // already been made.
     if (mainThreadRunnableTime == null) {
       return;
     }
 
     // Set it to true if the runnable ran more than 100ms prior to onActivityCreated()
-    if (mainThreadRunnableTime.getDurationMicros() >= MAX_BACKGROUND_RUNNABLE_DELAY) {
+    if (mainThreadRunnableTime.getDurationMicros() > MAX_BACKGROUND_RUNNABLE_DELAY) {
       isStartedFromBackground = true;
     }
+
+    // Set this to null to prevent additional checks if `onActivityCreated()` is called again.
+    mainThreadRunnableTime = null;
   }
 
   @Override