diff --git a/core/api/system-current.txt b/core/api/system-current.txt
index 3a5954dfb58d1..d21b525aab362 100644
--- a/core/api/system-current.txt
+++ b/core/api/system-current.txt
@@ -1395,7 +1395,10 @@ package android.app.ambientcontext {
 
 package android.app.assist {
 
-  public class ActivityId {
+  public final class ActivityId implements android.os.Parcelable {
+    method public int describeContents();
+    method public void writeToParcel(@NonNull android.os.Parcel, int);
+    field @NonNull public static final android.os.Parcelable.Creator<android.app.assist.ActivityId> CREATOR;
   }
 
   public static class AssistStructure.ViewNode {
diff --git a/core/api/test-current.txt b/core/api/test-current.txt
index fd5e23f2e9864..5ad106c78697f 100644
--- a/core/api/test-current.txt
+++ b/core/api/test-current.txt
@@ -569,9 +569,13 @@ package android.app.admin {
 
 package android.app.assist {
 
-  public class ActivityId {
+  public final class ActivityId implements android.os.Parcelable {
+    ctor public ActivityId(int, @Nullable android.os.IBinder);
+    method public int describeContents();
     method public int getTaskId();
     method @Nullable public android.os.IBinder getToken();
+    method public void writeToParcel(@NonNull android.os.Parcel, int);
+    field @NonNull public static final android.os.Parcelable.Creator<android.app.assist.ActivityId> CREATOR;
   }
 
 }
diff --git a/core/java/android/app/assist/ActivityId.java b/core/java/android/app/assist/ActivityId.java
index fb0d056c2a34e..1cc4b024d42df 100644
--- a/core/java/android/app/assist/ActivityId.java
+++ b/core/java/android/app/assist/ActivityId.java
@@ -22,6 +22,7 @@ import android.annotation.SystemApi;
 import android.annotation.TestApi;
 import android.os.IBinder;
 import android.os.Parcel;
+import android.os.Parcelable;
 import android.service.contentcapture.ContentCaptureService;
 import android.view.contentcapture.ContentCaptureContext;
 import android.view.translation.UiTranslationManager;
@@ -38,7 +39,8 @@ import com.android.internal.annotations.Immutable;
  */
 @Immutable
 @SystemApi
-public class ActivityId {
+@TestApi
+public final class ActivityId implements Parcelable {
 
     /**
      * The identifier of the task this activity is in.
@@ -53,6 +55,7 @@ public class ActivityId {
     /**
      * @hide
      */
+    @TestApi
     public ActivityId(int taskId, @Nullable IBinder activityId) {
         mTaskId = taskId;
         mActivityId = activityId;
@@ -87,13 +90,39 @@ public class ActivityId {
     }
 
     /**
-     * @hide
+     * {@inheritDoc}
      */
-    public void writeToParcel(@NonNull Parcel dest, int parcelableFlags) {
+    @Override
+    public int describeContents() {
+        return 0;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public void writeToParcel(@NonNull Parcel dest, int flags) {
         dest.writeInt(mTaskId);
         dest.writeStrongBinder(mActivityId);
     }
 
+    /**
+     * Creates {@link ActivityId} instances from parcels.
+     */
+    @NonNull
+    public static final Parcelable.Creator<ActivityId> CREATOR =
+            new Parcelable.Creator<ActivityId>() {
+                @Override
+                public ActivityId createFromParcel(Parcel parcel) {
+                    return new ActivityId(parcel);
+                }
+
+                @Override
+                public ActivityId[] newArray(int size) {
+                    return new ActivityId[size];
+                }
+            };
+
     @Override
     public String toString() {
         return "ActivityId { taskId = " + mTaskId + ", activityId = " + mActivityId + " }";