diff --git a/runner/monitor/CHANGELOG.md b/runner/monitor/CHANGELOG.md
index 92c24cb64..43979c96b 100644
--- a/runner/monitor/CHANGELOG.md
+++ b/runner/monitor/CHANGELOG.md
@@ -5,6 +5,7 @@
 `androidx.test:monitor:{version}` is released.
 
 **Bug Fixes**
+* Activities can be started from any thread.
 
 **New Features**
 
@@ -14,6 +15,7 @@
 
 * Update to minSdkVersion 21
 * Make ReflectionException a RuntimeException
+* Hid IntentStubberRegistry.getInstance()
 
 **Breaking API Changes**
 
diff --git a/runner/monitor/java/androidx/test/runner/MonitoringInstrumentation.java b/runner/monitor/java/androidx/test/runner/MonitoringInstrumentation.java
index 67954ce60..7b23fb96e 100644
--- a/runner/monitor/java/androidx/test/runner/MonitoringInstrumentation.java
+++ b/runner/monitor/java/androidx/test/runner/MonitoringInstrumentation.java
@@ -677,7 +677,7 @@ private static class StubResultCallable implements Callable<ActivityResult> {
 
     @Override
     public ActivityResult call() {
-      return IntentStubberRegistry.getInstance().getActivityResultForIntent(intent);
+      return IntentStubberRegistry.getActivityResultForIntent(intent);
     }
   }
 
@@ -707,7 +707,7 @@ private ActivityResult stubResultFor(Intent intent) {
           throw new RuntimeException(e);
         }
       } else {
-        return IntentStubberRegistry.getInstance().getActivityResultForIntent(intent);
+        return IntentStubberRegistry.getActivityResultForIntent(intent);
       }
     }
     return null;
diff --git a/runner/monitor/java/androidx/test/runner/intent/IntentStubberRegistry.java b/runner/monitor/java/androidx/test/runner/intent/IntentStubberRegistry.java
index 6ed313ec6..9058e3e1c 100644
--- a/runner/monitor/java/androidx/test/runner/intent/IntentStubberRegistry.java
+++ b/runner/monitor/java/androidx/test/runner/intent/IntentStubberRegistry.java
@@ -19,15 +19,17 @@
 import static androidx.test.internal.util.Checks.checkNotNull;
 import static androidx.test.internal.util.Checks.checkState;
 
-import android.os.Looper;
+import android.app.Instrumentation.ActivityResult;
+import android.content.Intent;
 import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicReference;
 
 /** Exposes an implementation of {@link IntentStubber}. */
 public final class IntentStubberRegistry {
 
-  private static IntentStubber instance;
+  private static final AtomicReference<IntentStubber> instance = new AtomicReference<>();
 
-  private static AtomicBoolean isLoaded = new AtomicBoolean();
+  private static final AtomicBoolean isLoaded = new AtomicBoolean();
 
   /**
    * Loads an {@link IntentStubber} into this registry. There can only be one active stubber at a
@@ -37,44 +39,51 @@ public final class IntentStubberRegistry {
    *
    * <p>This method can be called from any thread.
    */
-  public static void load(IntentStubber intentStubber) {
+  public static synchronized void load(IntentStubber intentStubber) {
     checkNotNull(intentStubber, "IntentStubber cannot be null!");
     checkState(
         !isLoaded.getAndSet(true),
         "Intent stubber already registered! Multiple stubbers are not"
             + "allowedAre you running under an ");
-    instance = intentStubber;
+    instance.set(intentStubber);
   }
 
-  /** @return if an {@link IntentStubber} has been loaded. */
+  /** Returns if an {@link IntentStubber} has been loaded. */
   public static boolean isLoaded() {
     return isLoaded.get();
   }
 
+  /** Clears the current instance of Intent Stubber. */
+  public static synchronized void reset() {
+    instance.set(null);
+    isLoaded.set(false);
+  }
+
+  /**
+   * Returns the activity result for the given intent..
+   *
+   * <p>This method can be called from any thread.
+   *
+   * @throws IllegalStateException if no Intent Stubber has been loaded.
+   */
+  public static ActivityResult getActivityResultForIntent(Intent intent) {
+    return getInstance().getActivityResultForIntent(intent);
+  }
+
   /**
    * Returns the loaded Intent Stubber instance.
    *
-   * @throws IllegalStateException if this method is not called on the main thread.
+   * <p>This method can be called from any thread.
+   *
    * @throws IllegalStateException if no Intent Stubber has been loaded.
    */
-  public static IntentStubber getInstance() {
-    checkMain();
-    checkState(
-        null != instance,
+  private static IntentStubber getInstance() {
+    checkNotNull(
+        instance,
         "No intent monitor registered! Are you running under an "
             + "Instrumentation which registers intent monitors?");
-    return instance;
-  }
-
-  private static void checkMain() {
-    checkState(Looper.myLooper() == Looper.getMainLooper(), "Must be called on main thread.");
+    return instance.get();
   }
 
   private IntentStubberRegistry() {}
-
-  /** Clears the current instance of Intent Stubber. */
-  public static synchronized void reset() {
-    instance = null;
-    isLoaded.set(false);
-  }
 }
diff --git a/runner/monitor/javatests/androidx/test/runner/intent/IntentStubberRegistryTest.java b/runner/monitor/javatests/androidx/test/runner/intent/IntentStubberRegistryTest.java
index 1de1d0d04..334c5d0d2 100644
--- a/runner/monitor/javatests/androidx/test/runner/intent/IntentStubberRegistryTest.java
+++ b/runner/monitor/javatests/androidx/test/runner/intent/IntentStubberRegistryTest.java
@@ -58,8 +58,6 @@ public void tearDown() throws Exception {
   public void testIntentStubberLoading() {
     IntentStubberRegistry.load(mIntentStubber);
     assertThat(IntentStubberRegistry.isLoaded()).isTrue();
-
-    assertThat(IntentStubberRegistry.getInstance()).isNotNull();
   }
 
   @Test
@@ -83,22 +81,17 @@ public void testLoadPassingNullThrows() {
   }
 
   @Test
-  public void testGetInstanceCanOnlyBeCalledOnMainThread() {
+  public void testGetActivityResultForIntent_loaded_returnsActivityResult() {
     IntentStubberRegistry.load(mIntentStubber);
-    try {
-      IntentStubberRegistry.getInstance();
-      fail(
-          "IllegalStateException expected. getInstance() should only be allowed on main"
-              + "thread!");
-    } catch (IllegalStateException expected) {
-    }
+
+    assertThat(IntentStubberRegistry.getActivityResultForIntent(new Intent())).isNotNull();
   }
 
   @Test
-  public void testNoInstanceLoadedThrows() {
+  public void testGetActivityResultForIntent_notLoaded_throws() {
     try {
-      IntentStubberRegistry.getInstance();
-      fail("IllegalStateException expected. No instance available, load must be called" + "first");
+      IntentStubberRegistry.getActivityResultForIntent(new Intent());
+      fail("IllegalStateException expected. No instance available, load must be called first");
     } catch (IllegalStateException expected) {
     }
   }