diff --git a/sentry-android-core/src/main/java/io/sentry/android/core/ActivityFramesTracker.java b/sentry-android-core/src/main/java/io/sentry/android/core/ActivityFramesTracker.java
index 4dd16e03e00..80374b839a4 100644
--- a/sentry-android-core/src/main/java/io/sentry/android/core/ActivityFramesTracker.java
+++ b/sentry-android-core/src/main/java/io/sentry/android/core/ActivityFramesTracker.java
@@ -5,7 +5,7 @@
 import androidx.core.app.FrameMetricsAggregator;
 import io.sentry.MeasurementUnit;
 import io.sentry.SentryLevel;
-import io.sentry.android.core.internal.util.MainThreadChecker;
+import io.sentry.android.core.internal.util.AndroidMainThreadChecker;
 import io.sentry.protocol.MeasurementValue;
 import io.sentry.protocol.SentryId;
 import java.util.HashMap;
@@ -208,7 +208,7 @@ public synchronized void stop() {
 
   private void runSafelyOnUiThread(final Runnable runnable, final String tag) {
     try {
-      if (MainThreadChecker.isMainThread()) {
+      if (AndroidMainThreadChecker.getInstance().isMainThread()) {
         runnable.run();
       } else {
         handler.post(
diff --git a/sentry-android-core/src/main/java/io/sentry/android/core/AndroidOptionsInitializer.java b/sentry-android-core/src/main/java/io/sentry/android/core/AndroidOptionsInitializer.java
index 821f1471195..5429b6e6250 100644
--- a/sentry-android-core/src/main/java/io/sentry/android/core/AndroidOptionsInitializer.java
+++ b/sentry-android-core/src/main/java/io/sentry/android/core/AndroidOptionsInitializer.java
@@ -13,6 +13,7 @@
 import io.sentry.SentryLevel;
 import io.sentry.android.core.cache.AndroidEnvelopeCache;
 import io.sentry.android.core.internal.modules.AssetsModulesLoader;
+import io.sentry.android.core.internal.util.AndroidMainThreadChecker;
 import io.sentry.android.core.internal.util.SentryFrameMetricsCollector;
 import io.sentry.android.fragment.FragmentLifecycleIntegration;
 import io.sentry.android.timber.SentryTimberIntegration;
@@ -130,6 +131,7 @@ static void initializeIntegrationsAndProcessors(
     options.setTransactionProfiler(
         new AndroidTransactionProfiler(context, options, buildInfoProvider, frameMetricsCollector));
     options.setModulesLoader(new AssetsModulesLoader(context, options.getLogger()));
+    options.setMainThreadChecker(AndroidMainThreadChecker.getInstance());
   }
 
   private static void installDefaultIntegrations(
diff --git a/sentry-android-core/src/main/java/io/sentry/android/core/AppLifecycleIntegration.java b/sentry-android-core/src/main/java/io/sentry/android/core/AppLifecycleIntegration.java
index fc9b48377f3..28aad388f48 100644
--- a/sentry-android-core/src/main/java/io/sentry/android/core/AppLifecycleIntegration.java
+++ b/sentry-android-core/src/main/java/io/sentry/android/core/AppLifecycleIntegration.java
@@ -5,7 +5,7 @@
 import io.sentry.Integration;
 import io.sentry.SentryLevel;
 import io.sentry.SentryOptions;
-import io.sentry.android.core.internal.util.MainThreadChecker;
+import io.sentry.android.core.internal.util.AndroidMainThreadChecker;
 import io.sentry.util.Objects;
 import java.io.Closeable;
 import java.io.IOException;
@@ -56,7 +56,7 @@ public void register(final @NotNull IHub hub, final @NotNull SentryOptions optio
       try {
         Class.forName("androidx.lifecycle.DefaultLifecycleObserver");
         Class.forName("androidx.lifecycle.ProcessLifecycleOwner");
-        if (MainThreadChecker.isMainThread()) {
+        if (AndroidMainThreadChecker.getInstance().isMainThread()) {
           addObserver(hub);
         } else {
           // some versions of the androidx lifecycle-process require this to be executed on the main
@@ -115,7 +115,7 @@ private void removeObserver() {
   @Override
   public void close() throws IOException {
     if (watcher != null) {
-      if (MainThreadChecker.isMainThread()) {
+      if (AndroidMainThreadChecker.getInstance().isMainThread()) {
         removeObserver();
       } else {
         // some versions of the androidx lifecycle-process require this to be executed on the main
diff --git a/sentry-android-core/src/main/java/io/sentry/android/core/DefaultAndroidEventProcessor.java b/sentry-android-core/src/main/java/io/sentry/android/core/DefaultAndroidEventProcessor.java
index bf17d90aab6..5fcccb36428 100644
--- a/sentry-android-core/src/main/java/io/sentry/android/core/DefaultAndroidEventProcessor.java
+++ b/sentry-android-core/src/main/java/io/sentry/android/core/DefaultAndroidEventProcessor.java
@@ -26,9 +26,9 @@
 import io.sentry.SentryBaseEvent;
 import io.sentry.SentryEvent;
 import io.sentry.SentryLevel;
+import io.sentry.android.core.internal.util.AndroidMainThreadChecker;
 import io.sentry.android.core.internal.util.ConnectivityChecker;
 import io.sentry.android.core.internal.util.DeviceOrientations;
-import io.sentry.android.core.internal.util.MainThreadChecker;
 import io.sentry.android.core.internal.util.RootChecker;
 import io.sentry.protocol.App;
 import io.sentry.protocol.Device;
@@ -217,7 +217,7 @@ private void setThreads(final @NotNull SentryEvent event) {
     if (event.getThreads() != null) {
       for (SentryThread thread : event.getThreads()) {
         if (thread.isCurrent() == null) {
-          thread.setCurrent(MainThreadChecker.isMainThread(thread));
+          thread.setCurrent(AndroidMainThreadChecker.getInstance().isMainThread(thread));
         }
       }
     }
diff --git a/sentry-android-core/src/main/java/io/sentry/android/core/internal/util/AndroidMainThreadChecker.java b/sentry-android-core/src/main/java/io/sentry/android/core/internal/util/AndroidMainThreadChecker.java
new file mode 100644
index 00000000000..a893fa87d16
--- /dev/null
+++ b/sentry-android-core/src/main/java/io/sentry/android/core/internal/util/AndroidMainThreadChecker.java
@@ -0,0 +1,23 @@
+package io.sentry.android.core.internal.util;
+
+import android.os.Looper;
+import io.sentry.util.thread.IMainThreadChecker;
+import org.jetbrains.annotations.ApiStatus;
+
+/** Class that checks if a given thread is the Android Main/UI thread */
+@ApiStatus.Internal
+public final class AndroidMainThreadChecker implements IMainThreadChecker {
+
+  private static final AndroidMainThreadChecker instance = new AndroidMainThreadChecker();
+
+  public static AndroidMainThreadChecker getInstance() {
+    return instance;
+  }
+
+  private AndroidMainThreadChecker() {}
+
+  @Override
+  public boolean isMainThread(final long threadId) {
+    return Looper.getMainLooper().getThread().getId() == threadId;
+  }
+}
diff --git a/sentry-android-core/src/main/java/io/sentry/android/core/internal/util/MainThreadChecker.java b/sentry-android-core/src/main/java/io/sentry/android/core/internal/util/MainThreadChecker.java
deleted file mode 100644
index c4c389134c3..00000000000
--- a/sentry-android-core/src/main/java/io/sentry/android/core/internal/util/MainThreadChecker.java
+++ /dev/null
@@ -1,47 +0,0 @@
-package io.sentry.android.core.internal.util;
-
-import android.os.Looper;
-import io.sentry.protocol.SentryThread;
-import org.jetbrains.annotations.ApiStatus;
-import org.jetbrains.annotations.NotNull;
-
-/** Class that checks if a given thread is the Android Main/UI thread */
-@ApiStatus.Internal
-public final class MainThreadChecker {
-
-  private MainThreadChecker() {}
-
-  /**
-   * Checks if a given thread is the Android Main/UI thread
-   *
-   * @param thread the Thread
-   * @return true if it is the main thread or false otherwise
-   */
-  public static boolean isMainThread(final @NotNull Thread thread) {
-    return isMainThread(thread.getId());
-  }
-
-  /**
-   * Checks if the calling/current thread is the Android Main/UI thread
-   *
-   * @return true if it is the main thread or false otherwise
-   */
-  public static boolean isMainThread() {
-    return isMainThread(Thread.currentThread());
-  }
-
-  /**
-   * Checks if a given thread is the Android Main/UI thread
-   *
-   * @param sentryThread the SentryThread
-   * @return true if it is the main thread or false otherwise
-   */
-  public static boolean isMainThread(final @NotNull SentryThread sentryThread) {
-    final Long threadId = sentryThread.getId();
-    return threadId != null && isMainThread(threadId);
-  }
-
-  private static boolean isMainThread(final long threadId) {
-    return Looper.getMainLooper().getThread().getId() == threadId;
-  }
-}
diff --git a/sentry-android-core/src/test/java/io/sentry/android/core/internal/util/MainThreadCheckerTest.kt b/sentry-android-core/src/test/java/io/sentry/android/core/internal/util/AndroidMainThreadCheckerTest.kt
similarity index 72%
rename from sentry-android-core/src/test/java/io/sentry/android/core/internal/util/MainThreadCheckerTest.kt
rename to sentry-android-core/src/test/java/io/sentry/android/core/internal/util/AndroidMainThreadCheckerTest.kt
index 391074325ac..c759bdf79e0 100644
--- a/sentry-android-core/src/test/java/io/sentry/android/core/internal/util/MainThreadCheckerTest.kt
+++ b/sentry-android-core/src/test/java/io/sentry/android/core/internal/util/AndroidMainThreadCheckerTest.kt
@@ -8,23 +8,23 @@ import kotlin.test.assertFalse
 import kotlin.test.assertTrue
 
 @RunWith(AndroidJUnit4::class)
-class MainThreadCheckerTest {
+class AndroidMainThreadCheckerTest {
 
     @Test
     fun `When calling isMainThread from the same thread, it should return true`() {
-        assertTrue(MainThreadChecker.isMainThread())
+        assertTrue(AndroidMainThreadChecker.getInstance().isMainThread)
     }
 
     @Test
     fun `When calling isMainThread with the current thread, it should return true`() {
         val thread = Thread.currentThread()
-        assertTrue(MainThreadChecker.isMainThread(thread))
+        assertTrue(AndroidMainThreadChecker.getInstance().isMainThread(thread))
     }
 
     @Test
     fun `When calling isMainThread from a different thread, it should return false`() {
         val thread = Thread()
-        assertFalse(MainThreadChecker.isMainThread(thread))
+        assertFalse(AndroidMainThreadChecker.getInstance().isMainThread(thread))
     }
 
     @Test
@@ -33,7 +33,7 @@ class MainThreadCheckerTest {
         val sentryThread = SentryThread().apply {
             id = thread.id
         }
-        assertTrue(MainThreadChecker.isMainThread(sentryThread))
+        assertTrue(AndroidMainThreadChecker.getInstance().isMainThread(sentryThread))
     }
 
     @Test
@@ -42,6 +42,6 @@ class MainThreadCheckerTest {
         val sentryThread = SentryThread().apply {
             id = thread.id
         }
-        assertFalse(MainThreadChecker.isMainThread(sentryThread))
+        assertFalse(AndroidMainThreadChecker.getInstance().isMainThread(sentryThread))
     }
 }
diff --git a/sentry-samples/sentry-samples-android/proguard-rules.pro b/sentry-samples/sentry-samples-android/proguard-rules.pro
index 95c4bb7bbca..1165340c893 100644
--- a/sentry-samples/sentry-samples-android/proguard-rules.pro
+++ b/sentry-samples/sentry-samples-android/proguard-rules.pro
@@ -16,7 +16,6 @@
 # https://developer.android.com/studio/build/shrink-code#decode-stack-trace
 -keepattributes LineNumberTable,SourceFile
 
-
 # For native methods, see http://proguard.sourceforge.net/manual/examples.html#native
 -keepclasseswithmembernames,includedescriptorclasses class * {
     native <methods>;
diff --git a/sentry-samples/sentry-samples-android/src/main/java/io/sentry/samples/android/MainActivity.java b/sentry-samples/sentry-samples-android/src/main/java/io/sentry/samples/android/MainActivity.java
index 6f3c4016339..72c6a4810fe 100644
--- a/sentry-samples/sentry-samples-android/src/main/java/io/sentry/samples/android/MainActivity.java
+++ b/sentry-samples/sentry-samples-android/src/main/java/io/sentry/samples/android/MainActivity.java
@@ -9,6 +9,7 @@
 import io.sentry.Sentry;
 import io.sentry.SpanStatus;
 import io.sentry.UserFeedback;
+import io.sentry.instrumentation.file.SentryFileOutputStream;
 import io.sentry.protocol.SentryId;
 import io.sentry.protocol.User;
 import io.sentry.samples.android.compose.ComposeActivity;
@@ -79,7 +80,7 @@ protected void onCreate(Bundle savedInstanceState) {
         view -> {
           String fileName = Calendar.getInstance().getTimeInMillis() + "_file.txt";
           File file = getApplication().getFileStreamPath(fileName);
-          try (final FileOutputStream fileOutputStream = new FileOutputStream(file);
+          try (final FileOutputStream fileOutputStream = new SentryFileOutputStream(file);
               final OutputStreamWriter outputStreamWriter =
                   new OutputStreamWriter(fileOutputStream);
               final Writer writer = new BufferedWriter(outputStreamWriter)) {
diff --git a/sentry-samples/sentry-samples-android/src/main/java/io/sentry/samples/android/ThirdFragment.kt b/sentry-samples/sentry-samples-android/src/main/java/io/sentry/samples/android/ThirdFragment.kt
index f9047f100b2..449b667fdac 100644
--- a/sentry-samples/sentry-samples-android/src/main/java/io/sentry/samples/android/ThirdFragment.kt
+++ b/sentry-samples/sentry-samples-android/src/main/java/io/sentry/samples/android/ThirdFragment.kt
@@ -12,6 +12,9 @@ import retrofit2.Response
 class ThirdFragment : Fragment(R.layout.third_fragment) {
 
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        view.findViewById<View>(R.id.third_button).setOnClickListener {
+            throw RuntimeException("Test")
+        }
         val span = Sentry.getSpan()
         val child = span?.startChild("calc")
 
diff --git a/sentry-samples/sentry-samples-android/src/main/res/layout/third_fragment.xml b/sentry-samples/sentry-samples-android/src/main/res/layout/third_fragment.xml
index c721c414425..98cd9b3921f 100644
--- a/sentry-samples/sentry-samples-android/src/main/res/layout/third_fragment.xml
+++ b/sentry-samples/sentry-samples-android/src/main/res/layout/third_fragment.xml
@@ -4,6 +4,7 @@
     android:layout_width="match_parent"
     android:layout_height="match_parent">
     <Button
+      android:id="@+id/third_button"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:text="@string/tap_me"/>
diff --git a/sentry/api/sentry.api b/sentry/api/sentry.api
index d5141451786..2b299fb1a85 100644
--- a/sentry/api/sentry.api
+++ b/sentry/api/sentry.api
@@ -1375,6 +1375,7 @@ public class io/sentry/SentryOptions {
 	public fun getInAppIncludes ()Ljava/util/List;
 	public fun getIntegrations ()Ljava/util/List;
 	public fun getLogger ()Lio/sentry/ILogger;
+	public fun getMainThreadChecker ()Lio/sentry/util/thread/IMainThreadChecker;
 	public fun getMaxAttachmentSize ()J
 	public fun getMaxBreadcrumbs ()I
 	public fun getMaxCacheItems ()I
@@ -1454,6 +1455,7 @@ public class io/sentry/SentryOptions {
 	public fun setHostnameVerifier (Ljavax/net/ssl/HostnameVerifier;)V
 	public fun setIdleTimeout (Ljava/lang/Long;)V
 	public fun setLogger (Lio/sentry/ILogger;)V
+	public fun setMainThreadChecker (Lio/sentry/util/thread/IMainThreadChecker;)V
 	public fun setMaxAttachmentSize (J)V
 	public fun setMaxBreadcrumbs (I)V
 	public fun setMaxCacheItems (I)V
@@ -1532,6 +1534,11 @@ public abstract interface class io/sentry/SentryOptions$TracesSamplerCallback {
 	public abstract fun sample (Lio/sentry/SamplingContext;)Ljava/lang/Double;
 }
 
+public final class io/sentry/SentryStackTraceFactory {
+	public fun <init> (Ljava/util/List;Ljava/util/List;)V
+	public fun getStackFrames ([Ljava/lang/StackTraceElement;)Ljava/util/List;
+}
+
 public final class io/sentry/SentryTraceHeader {
 	public static final field SENTRY_TRACE_HEADER Ljava/lang/String;
 	public fun <init> (Lio/sentry/protocol/SentryId;Lio/sentry/SpanId;Ljava/lang/Boolean;)V
@@ -3335,6 +3342,7 @@ public abstract class io/sentry/transport/TransportResult {
 }
 
 public final class io/sentry/util/CollectionUtils {
+	public static fun filterListEntries (Ljava/util/List;Lio/sentry/util/CollectionUtils$Predicate;)Ljava/util/List;
 	public static fun filterMapEntries (Ljava/util/Map;Lio/sentry/util/CollectionUtils$Predicate;)Ljava/util/Map;
 	public static fun map (Ljava/util/List;Lio/sentry/util/CollectionUtils$Mapper;)Ljava/util/List;
 	public static fun newArrayList (Ljava/util/List;)Ljava/util/List;
@@ -3445,6 +3453,24 @@ public final class io/sentry/util/StringUtils {
 	public static fun removeSurrounding (Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;
 }
 
+public abstract interface class io/sentry/util/thread/IMainThreadChecker {
+	public fun isMainThread ()Z
+	public abstract fun isMainThread (J)Z
+	public fun isMainThread (Lio/sentry/protocol/SentryThread;)Z
+	public fun isMainThread (Ljava/lang/Thread;)Z
+}
+
+public final class io/sentry/util/thread/MainThreadChecker : io/sentry/util/thread/IMainThreadChecker {
+	public static fun getInstance ()Lio/sentry/util/thread/MainThreadChecker;
+	public fun isMainThread (J)Z
+}
+
+public final class io/sentry/util/thread/NoOpMainThreadChecker : io/sentry/util/thread/IMainThreadChecker {
+	public fun <init> ()V
+	public static fun getInstance ()Lio/sentry/util/thread/NoOpMainThreadChecker;
+	public fun isMainThread (J)Z
+}
+
 public class io/sentry/vendor/Base64 {
 	public static final field CRLF I
 	public static final field DEFAULT I
diff --git a/sentry/src/main/java/io/sentry/Sentry.java b/sentry/src/main/java/io/sentry/Sentry.java
index 2f43ea60ae7..6e97b0aeb47 100644
--- a/sentry/src/main/java/io/sentry/Sentry.java
+++ b/sentry/src/main/java/io/sentry/Sentry.java
@@ -10,6 +10,9 @@
 import io.sentry.protocol.User;
 import io.sentry.transport.NoOpEnvelopeCache;
 import io.sentry.util.FileUtils;
+import io.sentry.util.thread.IMainThreadChecker;
+import io.sentry.util.thread.MainThreadChecker;
+import io.sentry.util.thread.NoOpMainThreadChecker;
 import java.io.File;
 import java.lang.reflect.InvocationTargetException;
 import java.util.List;
@@ -279,6 +282,12 @@ private static boolean initConfigurations(final @NotNull SentryOptions options)
       options.setModulesLoader(new ResourcesModulesLoader(options.getLogger()));
     }
 
+    final IMainThreadChecker mainThreadChecker = options.getMainThreadChecker();
+    // only override the MainThreadChecker if it's not already set by Android
+    if (mainThreadChecker instanceof NoOpMainThreadChecker) {
+      options.setMainThreadChecker(MainThreadChecker.getInstance());
+    }
+
     return true;
   }
 
diff --git a/sentry/src/main/java/io/sentry/SentryOptions.java b/sentry/src/main/java/io/sentry/SentryOptions.java
index e7c0980c2b2..9e7a0f01c44 100644
--- a/sentry/src/main/java/io/sentry/SentryOptions.java
+++ b/sentry/src/main/java/io/sentry/SentryOptions.java
@@ -15,6 +15,8 @@
 import io.sentry.util.Platform;
 import io.sentry.util.SampleRateUtils;
 import io.sentry.util.StringUtils;
+import io.sentry.util.thread.IMainThreadChecker;
+import io.sentry.util.thread.NoOpMainThreadChecker;
 import java.io.File;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -361,6 +363,8 @@ public class SentryOptions {
   /** Modules (dependencies, packages) that will be send along with each event. */
   private @NotNull IModulesLoader modulesLoader = NoOpModulesLoader.getInstance();
 
+  private @NotNull IMainThreadChecker mainThreadChecker = NoOpMainThreadChecker.getInstance();
+
   /**
    * Adds an event processor
    *
@@ -1766,6 +1770,14 @@ public void setModulesLoader(final @Nullable IModulesLoader modulesLoader) {
     this.modulesLoader = modulesLoader != null ? modulesLoader : NoOpModulesLoader.getInstance();
   }
 
+  public @NotNull IMainThreadChecker getMainThreadChecker() {
+    return mainThreadChecker;
+  }
+
+  public void setMainThreadChecker(final @NotNull IMainThreadChecker mainThreadChecker) {
+    this.mainThreadChecker = mainThreadChecker;
+  }
+
   /** The BeforeSend callback */
   public interface BeforeSendCallback {
 
diff --git a/sentry/src/main/java/io/sentry/SentryStackTraceFactory.java b/sentry/src/main/java/io/sentry/SentryStackTraceFactory.java
index e194015bbf6..c2ef60c3cec 100644
--- a/sentry/src/main/java/io/sentry/SentryStackTraceFactory.java
+++ b/sentry/src/main/java/io/sentry/SentryStackTraceFactory.java
@@ -4,11 +4,13 @@
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.annotations.TestOnly;
 
 /** class responsible for converting Java StackTraceElements to SentryStackFrames */
-final class SentryStackTraceFactory {
+@ApiStatus.Internal
+public final class SentryStackTraceFactory {
 
   /** list of inApp excludes */
   private final @Nullable List<String> inAppExcludes;
@@ -29,7 +31,7 @@ public SentryStackTraceFactory(
    * @return list of SentryStackFrames or null if none
    */
   @Nullable
-  List<SentryStackFrame> getStackFrames(@Nullable final StackTraceElement[] elements) {
+  public List<SentryStackFrame> getStackFrames(@Nullable final StackTraceElement[] elements) {
     List<SentryStackFrame> sentryStackFrames = null;
 
     if (elements != null && elements.length > 0) {
diff --git a/sentry/src/main/java/io/sentry/instrumentation/file/FileIOSpanManager.java b/sentry/src/main/java/io/sentry/instrumentation/file/FileIOSpanManager.java
index ee64417c800..478f5c3953f 100644
--- a/sentry/src/main/java/io/sentry/instrumentation/file/FileIOSpanManager.java
+++ b/sentry/src/main/java/io/sentry/instrumentation/file/FileIOSpanManager.java
@@ -2,7 +2,11 @@
 
 import io.sentry.IHub;
 import io.sentry.ISpan;
+import io.sentry.SentryOptions;
+import io.sentry.SentryStackTraceFactory;
 import io.sentry.SpanStatus;
+import io.sentry.protocol.SentryStackFrame;
+import io.sentry.util.CollectionUtils;
 import io.sentry.util.Platform;
 import io.sentry.util.StringUtils;
 import java.io.Closeable;
@@ -10,6 +14,7 @@
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
+import java.util.List;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
@@ -17,7 +22,7 @@ final class FileIOSpanManager {
 
   private final @Nullable ISpan currentSpan;
   private final @Nullable File file;
-  private final boolean isSendDefaultPii;
+  private final @NotNull SentryOptions options;
 
   private @NotNull SpanStatus spanStatus = SpanStatus.OK;
   private long byteCount;
@@ -30,10 +35,10 @@ final class FileIOSpanManager {
   FileIOSpanManager(
       final @Nullable ISpan currentSpan,
       final @Nullable File file,
-      final boolean isSendDefaultPii) {
+      final @NotNull SentryOptions options) {
     this.currentSpan = currentSpan;
     this.file = file;
-    this.isSendDefaultPii = isSendDefaultPii;
+    this.options = options;
   }
 
   /**
@@ -87,17 +92,44 @@ private void finishSpan() {
       if (file != null) {
         final String description = file.getName() + " " + "(" + byteCountToString + ")";
         currentSpan.setDescription(description);
-        if (Platform.isAndroid() || isSendDefaultPii) {
+        if (Platform.isAndroid() || options.isSendDefaultPii()) {
           currentSpan.setData("file.path", file.getAbsolutePath());
         }
       } else {
         currentSpan.setDescription(byteCountToString);
       }
       currentSpan.setData("file.size", byteCount);
+      currentSpan.setData("blocked_ui_thread", options.getMainThreadChecker().isMainThread());
+      attachStacktrace();
       currentSpan.finish(spanStatus);
     }
   }
 
+  private void attachStacktrace() {
+    final SentryStackTraceFactory sentryStackTraceFactory =
+        new SentryStackTraceFactory(options.getInAppExcludes(), options.getInAppIncludes());
+    final StackTraceElement[] stacktrace = new Exception().getStackTrace();
+    final List<SentryStackFrame> frames = sentryStackTraceFactory.getStackFrames(stacktrace);
+    if (currentSpan != null && frames != null) {
+      final List<SentryStackFrame> relevantFrames =
+          CollectionUtils.filterListEntries(
+              frames,
+              (frame) -> {
+                final String module = frame.getModule();
+                boolean isSystemFrame = false;
+                if (module != null) {
+                  isSystemFrame =
+                      module.startsWith("sun.")
+                          || module.startsWith("java.")
+                          || module.startsWith("android.")
+                          || module.startsWith("com.android.");
+                }
+                return Boolean.TRUE.equals(frame.isInApp()) || !isSystemFrame;
+              });
+      currentSpan.setData("call_stack", relevantFrames);
+    }
+  }
+
   /**
    * A task that returns a result and may throw an IOException. Implementors define a single method
    * with no arguments called {@code call}.
diff --git a/sentry/src/main/java/io/sentry/instrumentation/file/FileInputStreamInitData.java b/sentry/src/main/java/io/sentry/instrumentation/file/FileInputStreamInitData.java
index d91b6cef760..e3621980af8 100644
--- a/sentry/src/main/java/io/sentry/instrumentation/file/FileInputStreamInitData.java
+++ b/sentry/src/main/java/io/sentry/instrumentation/file/FileInputStreamInitData.java
@@ -1,6 +1,7 @@
 package io.sentry.instrumentation.file;
 
 import io.sentry.ISpan;
+import io.sentry.SentryOptions;
 import java.io.File;
 import java.io.FileInputStream;
 import org.jetbrains.annotations.NotNull;
@@ -11,16 +12,16 @@ final class FileInputStreamInitData {
   final @Nullable File file;
   final @Nullable ISpan span;
   final @NotNull FileInputStream delegate;
-  final boolean isSendDefaultPii;
+  final @NotNull SentryOptions options;
 
   FileInputStreamInitData(
       final @Nullable File file,
       final @Nullable ISpan span,
       final @NotNull FileInputStream delegate,
-      final boolean isSendDefaultPii) {
+      final @NotNull SentryOptions options) {
     this.file = file;
     this.span = span;
     this.delegate = delegate;
-    this.isSendDefaultPii = isSendDefaultPii;
+    this.options = options;
   }
 }
diff --git a/sentry/src/main/java/io/sentry/instrumentation/file/FileOutputStreamInitData.java b/sentry/src/main/java/io/sentry/instrumentation/file/FileOutputStreamInitData.java
index 95872106a90..422304128b4 100644
--- a/sentry/src/main/java/io/sentry/instrumentation/file/FileOutputStreamInitData.java
+++ b/sentry/src/main/java/io/sentry/instrumentation/file/FileOutputStreamInitData.java
@@ -1,6 +1,7 @@
 package io.sentry.instrumentation.file;
 
 import io.sentry.ISpan;
+import io.sentry.SentryOptions;
 import java.io.File;
 import java.io.FileOutputStream;
 import org.jetbrains.annotations.NotNull;
@@ -12,18 +13,18 @@ final class FileOutputStreamInitData {
   final @Nullable ISpan span;
   final boolean append;
   final @NotNull FileOutputStream delegate;
-  final boolean isSendDefaultPii;
+  final @NotNull SentryOptions options;
 
   FileOutputStreamInitData(
       final @Nullable File file,
       final boolean append,
       final @Nullable ISpan span,
       final @NotNull FileOutputStream delegate,
-      final boolean isSendDefaultPii) {
+      final @NotNull SentryOptions options) {
     this.file = file;
     this.append = append;
     this.span = span;
     this.delegate = delegate;
-    this.isSendDefaultPii = isSendDefaultPii;
+    this.options = options;
   }
 }
diff --git a/sentry/src/main/java/io/sentry/instrumentation/file/SentryFileInputStream.java b/sentry/src/main/java/io/sentry/instrumentation/file/SentryFileInputStream.java
index 1c65de2a694..04bb87ae7c2 100644
--- a/sentry/src/main/java/io/sentry/instrumentation/file/SentryFileInputStream.java
+++ b/sentry/src/main/java/io/sentry/instrumentation/file/SentryFileInputStream.java
@@ -48,14 +48,14 @@ public SentryFileInputStream(final @NotNull FileDescriptor fdObj) {
   private SentryFileInputStream(
       final @NotNull FileInputStreamInitData data, final @NotNull FileDescriptor fd) {
     super(fd);
-    spanManager = new FileIOSpanManager(data.span, data.file, data.isSendDefaultPii);
+    spanManager = new FileIOSpanManager(data.span, data.file, data.options);
     delegate = data.delegate;
   }
 
   private SentryFileInputStream(final @NotNull FileInputStreamInitData data)
       throws FileNotFoundException {
     super(getFileDescriptor(data.delegate));
-    spanManager = new FileIOSpanManager(data.span, data.file, data.isSendDefaultPii);
+    spanManager = new FileIOSpanManager(data.span, data.file, data.options);
     delegate = data.delegate;
   }
 
@@ -66,7 +66,7 @@ private static FileInputStreamInitData init(
     if (delegate == null) {
       delegate = new FileInputStream(file);
     }
-    return new FileInputStreamInitData(file, span, delegate, hub.getOptions().isSendDefaultPii());
+    return new FileInputStreamInitData(file, span, delegate, hub.getOptions());
   }
 
   private static FileInputStreamInitData init(
@@ -77,7 +77,7 @@ private static FileInputStreamInitData init(
     if (delegate == null) {
       delegate = new FileInputStream(fd);
     }
-    return new FileInputStreamInitData(null, span, delegate, hub.getOptions().isSendDefaultPii());
+    return new FileInputStreamInitData(null, span, delegate, hub.getOptions());
   }
 
   @Override
diff --git a/sentry/src/main/java/io/sentry/instrumentation/file/SentryFileOutputStream.java b/sentry/src/main/java/io/sentry/instrumentation/file/SentryFileOutputStream.java
index 791e2dcdc3a..9424710d71d 100644
--- a/sentry/src/main/java/io/sentry/instrumentation/file/SentryFileOutputStream.java
+++ b/sentry/src/main/java/io/sentry/instrumentation/file/SentryFileOutputStream.java
@@ -53,14 +53,14 @@ public SentryFileOutputStream(final @NotNull FileDescriptor fdObj) {
   private SentryFileOutputStream(
       final @NotNull FileOutputStreamInitData data, final @NotNull FileDescriptor fd) {
     super(fd);
-    spanManager = new FileIOSpanManager(data.span, data.file, data.isSendDefaultPii);
+    spanManager = new FileIOSpanManager(data.span, data.file, data.options);
     delegate = data.delegate;
   }
 
   private SentryFileOutputStream(final @NotNull FileOutputStreamInitData data)
       throws FileNotFoundException {
     super(getFileDescriptor(data.delegate));
-    spanManager = new FileIOSpanManager(data.span, data.file, data.isSendDefaultPii);
+    spanManager = new FileIOSpanManager(data.span, data.file, data.options);
     delegate = data.delegate;
   }
 
@@ -74,8 +74,7 @@ private static FileOutputStreamInitData init(
     if (delegate == null) {
       delegate = new FileOutputStream(file, append);
     }
-    return new FileOutputStreamInitData(
-        file, append, span, delegate, hub.getOptions().isSendDefaultPii());
+    return new FileOutputStreamInitData(file, append, span, delegate, hub.getOptions());
   }
 
   private static FileOutputStreamInitData init(
@@ -84,8 +83,7 @@ private static FileOutputStreamInitData init(
     if (delegate == null) {
       delegate = new FileOutputStream(fd);
     }
-    return new FileOutputStreamInitData(
-        null, false, span, delegate, hub.getOptions().isSendDefaultPii());
+    return new FileOutputStreamInitData(null, false, span, delegate, hub.getOptions());
   }
 
   @Override
diff --git a/sentry/src/main/java/io/sentry/util/CollectionUtils.java b/sentry/src/main/java/io/sentry/util/CollectionUtils.java
index 58afa657cac..2cbfe6a12a2 100644
--- a/sentry/src/main/java/io/sentry/util/CollectionUtils.java
+++ b/sentry/src/main/java/io/sentry/util/CollectionUtils.java
@@ -120,6 +120,23 @@ public static int size(final @NotNull Iterable<?> data) {
     return mappedList;
   }
 
+  /**
+   * Returns a new list which entries match a predicate specified by a parameter.
+   *
+   * @param predicate - the predicate
+   * @return a new list
+   */
+  public static @NotNull <T> List<T> filterListEntries(
+      final @NotNull List<T> list, final @NotNull Predicate<T> predicate) {
+    final List<T> filteredList = new ArrayList<>();
+    for (final T entry : list) {
+      if (predicate.test(entry)) {
+        filteredList.add(entry);
+      }
+    }
+    return filteredList;
+  }
+
   /**
    * A simplified copy of Java 8 Predicate.
    *
diff --git a/sentry/src/main/java/io/sentry/util/thread/IMainThreadChecker.java b/sentry/src/main/java/io/sentry/util/thread/IMainThreadChecker.java
new file mode 100644
index 00000000000..19cd1c76a0a
--- /dev/null
+++ b/sentry/src/main/java/io/sentry/util/thread/IMainThreadChecker.java
@@ -0,0 +1,41 @@
+package io.sentry.util.thread;
+
+import io.sentry.protocol.SentryThread;
+import org.jetbrains.annotations.ApiStatus;
+import org.jetbrains.annotations.NotNull;
+
+@ApiStatus.Internal
+public interface IMainThreadChecker {
+
+  boolean isMainThread(final long threadId);
+
+  /**
+   * Checks if a given thread is the Main/UI thread
+   *
+   * @param thread the Thread
+   * @return true if it is the main thread or false otherwise
+   */
+  default boolean isMainThread(Thread thread) {
+    return isMainThread(thread.getId());
+  }
+
+  /**
+   * Checks if the calling/current thread is the Main/UI thread
+   *
+   * @return true if it is the main thread or false otherwise
+   */
+  default boolean isMainThread() {
+    return isMainThread(Thread.currentThread());
+  }
+
+  /**
+   * Checks if a given thread is the Main/UI thread
+   *
+   * @param sentryThread the SentryThread
+   * @return true if it is the main thread or false otherwise
+   */
+  default boolean isMainThread(final @NotNull SentryThread sentryThread) {
+    final Long threadId = sentryThread.getId();
+    return threadId != null && isMainThread(threadId);
+  }
+}
diff --git a/sentry/src/main/java/io/sentry/util/thread/MainThreadChecker.java b/sentry/src/main/java/io/sentry/util/thread/MainThreadChecker.java
new file mode 100644
index 00000000000..0f61c29ce6f
--- /dev/null
+++ b/sentry/src/main/java/io/sentry/util/thread/MainThreadChecker.java
@@ -0,0 +1,28 @@
+package io.sentry.util.thread;
+
+import org.jetbrains.annotations.ApiStatus;
+
+/**
+ * Class that checks if a given thread is the Main/UI thread. The Main thread is denoted by the
+ * thread, where the `Sentry.init` method was called. If it was inited from a background thread,
+ * then this class is wrong, but it's a best effort.
+ *
+ * <p>We're gonna educate people through the docs.
+ */
+@ApiStatus.Internal
+public final class MainThreadChecker implements IMainThreadChecker {
+
+  private static final long mainThreadId = Thread.currentThread().getId();
+  private static final MainThreadChecker instance = new MainThreadChecker();
+
+  public static MainThreadChecker getInstance() {
+    return instance;
+  }
+
+  private MainThreadChecker() {}
+
+  @Override
+  public boolean isMainThread(long threadId) {
+    return mainThreadId == threadId;
+  }
+}
diff --git a/sentry/src/main/java/io/sentry/util/thread/NoOpMainThreadChecker.java b/sentry/src/main/java/io/sentry/util/thread/NoOpMainThreadChecker.java
new file mode 100644
index 00000000000..bc1b6e58963
--- /dev/null
+++ b/sentry/src/main/java/io/sentry/util/thread/NoOpMainThreadChecker.java
@@ -0,0 +1,18 @@
+package io.sentry.util.thread;
+
+import org.jetbrains.annotations.ApiStatus;
+
+@ApiStatus.Internal
+public final class NoOpMainThreadChecker implements IMainThreadChecker {
+
+  private static final NoOpMainThreadChecker instance = new NoOpMainThreadChecker();
+
+  public static NoOpMainThreadChecker getInstance() {
+    return instance;
+  }
+
+  @Override
+  public boolean isMainThread(long threadId) {
+    return false;
+  }
+}