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fix(android): Improve app start type detection with main thread timing #4999

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e7047cb
fix(android): Improve app start type detection with main thread timing
markushi Dec 29, 2025
4164619
Update CHANGELOG.md
markushi Dec 29, 2025
70879c1
Reduce number of foreground checks and add maestro tests
markushi Jan 15, 2026
1547b1f
Merge branch 'main' into fix/app-start-warm-detection
markushi Jan 15, 2026
acf7e58
Merge branch 'main' into fix/app-start-warm-detection
markushi Jan 15, 2026
b0722d3
Merge branch 'main' into fix/app-start-warm-detection
markushi Jan 16, 2026
7034d95
Update Changelog
markushi Jan 16, 2026
ef2b3bf
Switch to MessageQueue.IdleHandler
markushi Jan 16, 2026
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4 changes: 4 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,10 @@

## Unreleased

### Fixes

- Fix warm app start type detection for edge cases ([#4999](https://github.com/getsentry/sentry-java/pull/4999))

### Features

- Added `io.sentry.ndk.sdk-name` Android manifest option to configure the native SDK's name ([#5027](https://github.com/getsentry/sentry-java/pull/5027))
Expand Down
130 changes: 88 additions & 42 deletions sentry-android-core/src/main/java/io/sentry/android/core/performance/AppStartMetrics.java
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Original file line number Diff line number Diff line change
Expand Up @@ -3,9 +3,11 @@
import android.app.Activity;
import android.app.Application;
import android.content.ContentProvider;
import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.MessageQueue;
import android.os.SystemClock;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
Expand All @@ -21,6 +23,7 @@
import io.sentry.android.core.SentryAndroidOptions;
import io.sentry.android.core.internal.util.FirstDrawDoneListener;
import io.sentry.util.AutoClosableReentrantLock;
import io.sentry.util.LazyEvaluator;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
Expand Down Expand Up @@ -56,7 +59,15 @@ public enum AppStartType {
new AutoClosableReentrantLock();

private @NotNull AppStartType appStartType = AppStartType.UNKNOWN;
private boolean appLaunchedInForeground;
private final LazyEvaluator<Boolean> appLaunchedInForeground =
new LazyEvaluator<>(
new LazyEvaluator.Evaluator<Boolean>() {
@Override
public @NotNull Boolean evaluate() {
return ContextUtils.isForegroundImportance();
}
});
private volatile long firstIdle = -1;

private final @NotNull TimeSpan appStartSpan;
private final @NotNull TimeSpan sdkInitTimeSpan;
Expand Down Expand Up @@ -89,7 +100,6 @@ public AppStartMetrics() {
applicationOnCreate = new TimeSpan();
contentProviderOnCreates = new HashMap<>();
activityLifecycles = new ArrayList<>();
appLaunchedInForeground = ContextUtils.isForegroundImportance();
}

/**
Expand Down Expand Up @@ -140,12 +150,12 @@ public void setAppStartType(final @NotNull AppStartType appStartType) {
}

public boolean isAppLaunchedInForeground() {
return appLaunchedInForeground;
return appLaunchedInForeground.getValue();
}

@VisibleForTesting
public void setAppLaunchedInForeground(final boolean appLaunchedInForeground) {
this.appLaunchedInForeground = appLaunchedInForeground;
this.appLaunchedInForeground.setValue(appLaunchedInForeground);
}

/**
Expand Down Expand Up @@ -176,7 +186,7 @@ public void onAppStartSpansSent() {
}

public boolean shouldSendStartMeasurements() {
return shouldSendStartMeasurements && appLaunchedInForeground;
return shouldSendStartMeasurements && appLaunchedInForeground.getValue();
}

public long getClassLoadedUptimeMs() {
Expand All @@ -191,7 +201,7 @@ public long getClassLoadedUptimeMs() {
final @NotNull SentryAndroidOptions options) {
// If the app start type was never determined or app wasn't launched in foreground,
// the app start is considered invalid
if (appStartType != AppStartType.UNKNOWN && appLaunchedInForeground) {
if (appStartType != AppStartType.UNKNOWN && appLaunchedInForeground.getValue()) {
if (options.isEnablePerformanceV2()) {
// Only started when sdk version is >= N
final @NotNull TimeSpan appStartSpan = getAppStartTimeSpan();
Expand All @@ -212,6 +222,16 @@ public long getClassLoadedUptimeMs() {
return new TimeSpan();
}

@TestOnly
void setFirstIdle(final long firstIdle) {
this.firstIdle = firstIdle;
}

@TestOnly
long getFirstIdle() {
return firstIdle;
}

@TestOnly
public void clear() {
appStartType = AppStartType.UNKNOWN;
Expand All @@ -229,11 +249,12 @@ public void clear() {
}
appStartContinuousProfiler = null;
appStartSamplingDecision = null;
appLaunchedInForeground = false;
appLaunchedInForeground.resetValue();
isCallbackRegistered = false;
shouldSendStartMeasurements = true;
firstDrawDone.set(false);
activeActivitiesCounter.set(0);
firstIdle = -1;
}

public @Nullable ITransactionProfiler getAppStartProfiler() {
Expand Down Expand Up @@ -301,7 +322,8 @@ public static void onApplicationPostCreate(final @NotNull Application applicatio
}

/**
* Register a callback to check if an activity was started after the application was created
* Register a callback to check if an activity was started after the application was created. Must
* be called from the main thread.
*
* @param application The application object to register the callback to
*/
Expand All @@ -310,61 +332,85 @@ public void registerLifecycleCallbacks(final @NotNull Application application) {
return;
}
isCallbackRegistered = true;
appLaunchedInForeground = appLaunchedInForeground || ContextUtils.isForegroundImportance();
appLaunchedInForeground.resetValue();
application.registerActivityLifecycleCallbacks(instance);
// We post on the main thread a task to post a check on the main thread. On Pixel devices
// (possibly others) the first task posted on the main thread is called before the
// Activity.onCreate callback. This is a workaround for that, so that the Activity.onCreate
// callback is called before the application one.
new Handler(Looper.getMainLooper()).post(() -> checkCreateTimeOnMain());

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
Looper.getMainLooper()
.getQueue()
.addIdleHandler(
new MessageQueue.IdleHandler() {
@Override
public boolean queueIdle() {
firstIdle = SystemClock.uptimeMillis();
checkCreateTimeOnMain();
return false;
}
});
} else {
// We post on the main thread a task to post a check on the main thread. On Pixel devices
// (possibly others) the first task posted on the main thread is called before the
// Activity.onCreate callback. This is a workaround for that, so that the Activity.onCreate
// callback is called before the application one.
final Handler handler = new Handler(Looper.getMainLooper());
handler.post(
new Runnable() {
@Override
public void run() {
// not technically correct, but close enough for pre-M
firstIdle = SystemClock.uptimeMillis();
handler.post(() -> checkCreateTimeOnMain());
}
});
}
}

private void checkCreateTimeOnMain() {
new Handler(Looper.getMainLooper())
.post(
() -> {
// if no activity has ever been created, app was launched in background
if (activeActivitiesCounter.get() == 0) {
appLaunchedInForeground = false;

// we stop the app start profilers, as they are useless and likely to timeout
if (appStartProfiler != null && appStartProfiler.isRunning()) {
appStartProfiler.close();
appStartProfiler = null;
}
if (appStartContinuousProfiler != null && appStartContinuousProfiler.isRunning()) {
appStartContinuousProfiler.close(true);
appStartContinuousProfiler = null;
}
}
});
// if no activity has ever been created, app was launched in background
if (activeActivitiesCounter.get() == 0) {
appLaunchedInForeground.setValue(false);

// we stop the app start profilers, as they are useless and likely to timeout
if (appStartProfiler != null && appStartProfiler.isRunning()) {
appStartProfiler.close();
appStartProfiler = null;
}
if (appStartContinuousProfiler != null && appStartContinuousProfiler.isRunning()) {
appStartContinuousProfiler.close(true);
appStartContinuousProfiler = null;
}
}
}

@Override
public void onActivityCreated(@NonNull Activity activity, @Nullable Bundle savedInstanceState) {
final long activityCreatedUptimeMillis = SystemClock.uptimeMillis();
CurrentActivityHolder.getInstance().setActivity(activity);

// the first activity determines the app start type
if (activeActivitiesCounter.incrementAndGet() == 1 && !firstDrawDone.get()) {
final long nowUptimeMs = SystemClock.uptimeMillis();
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@romtsn romtsn Jan 19, 2026

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do we still need this variable given it's just few microseconds apart from activityCreatedUptimeMillis?


// If the app (process) was launched more than 1 minute ago, it's likely wrong
// If the app (process) was launched more than 1 minute ago, consider it a warm start
final long durationSinceAppStartMillis = nowUptimeMs - appStartSpan.getStartUptimeMs();
if (!appLaunchedInForeground || durationSinceAppStartMillis > TimeUnit.MINUTES.toMillis(1)) {
if (!appLaunchedInForeground.getValue()
|| durationSinceAppStartMillis > TimeUnit.MINUTES.toMillis(1)) {
appStartType = AppStartType.WARM;

shouldSendStartMeasurements = true;
appStartSpan.reset();
appStartSpan.start();
appStartSpan.setStartedAt(nowUptimeMs);
CLASS_LOADED_UPTIME_MS = nowUptimeMs;
appStartSpan.setStartedAt(activityCreatedUptimeMillis);
CLASS_LOADED_UPTIME_MS = activityCreatedUptimeMillis;
contentProviderOnCreates.clear();
applicationOnCreate.reset();
} else if (savedInstanceState != null) {
appStartType = AppStartType.WARM;
} else if (firstIdle != -1 && activityCreatedUptimeMillis > firstIdle) {
appStartType = AppStartType.WARM;
} else {
appStartType = savedInstanceState == null ? AppStartType.COLD : AppStartType.WARM;
appStartType = AppStartType.COLD;
}
}
appLaunchedInForeground = true;
appLaunchedInForeground.setValue(true);
}

@Override
Expand Down Expand Up @@ -403,9 +449,9 @@ public void onActivityDestroyed(@NonNull Activity activity) {

final int remainingActivities = activeActivitiesCounter.decrementAndGet();
// if the app is moving into background
// as the next Activity is considered like a new app start
// as the next onActivityCreated will treat it as a new warm app start
if (remainingActivities == 0 && !activity.isChangingConfigurations()) {
appLaunchedInForeground = false;
appLaunchedInForeground.setValue(true);
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@cursor cursor bot Jan 16, 2026

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Incorrect boolean value in onActivityDestroyed sets wrong foreground state

Medium Severity

In onActivityDestroyed(), appLaunchedInForeground.setValue(true) is set when the app moves to background, but the original code set it to false. The comment explicitly states "if the app is moving into background", yet the value is inverted. This causes warm starts to potentially be misclassified as cold starts when a user returns from background very quickly (within the same millisecond as firstIdle), because the !appLaunchedInForeground.getValue() check that previously caught this case now fails, and the firstIdle timing check uses strict > comparison which can miss edge cases.

Fix in Cursor Fix in Web

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@romtsn romtsn Jan 19, 2026

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hmm, this sounds legit I think?

shouldSendStartMeasurements = true;
firstDrawDone.set(false);
}
Expand Down
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