diff --git a/Android.bp b/Android.bp
index e89aee0..2af7ca4 100644
--- a/Android.bp
+++ b/Android.bp
@@ -563,6 +563,7 @@
         "core/java/android/annotation/Nullable.java",
         "core/java/android/annotation/IntDef.java",
         "core/java/android/annotation/IntRange.java",
+        "core/java/android/annotation/SystemApi.java",
         "core/java/android/annotation/UnsupportedAppUsage.java",
         "core/java/com/android/internal/annotations/GuardedBy.java",
         "core/java/com/android/internal/annotations/VisibleForTesting.java",
diff --git a/apex/sdkext/framework/java/android/os/ext/SdkExtensions.java b/apex/sdkext/framework/java/android/os/ext/SdkExtensions.java
index c039a82..331ef21 100644
--- a/apex/sdkext/framework/java/android/os/ext/SdkExtensions.java
+++ b/apex/sdkext/framework/java/android/os/ext/SdkExtensions.java
@@ -17,13 +17,23 @@
 package android.os.ext;
 
 import android.annotation.IntDef;
+import android.annotation.SystemApi;
 import android.os.Build.VERSION_CODES;
 import android.os.SystemProperties;
 
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 
-/** @hide */
+/**
+ * Methods for interacting with the extension SDK.
+ *
+ * This class provides information about the extension SDK version present
+ * on this device. Use the {@link #getExtensionVersion(int) getExtension} to
+ * query for the extension version for the given SDK version.
+
+ * @hide
+ */
+@SystemApi
 public class SdkExtensions {
 
     private static final int R_EXTENSION_INT;
@@ -31,11 +41,16 @@
         R_EXTENSION_INT = SystemProperties.getInt("persist.com.android.sdkext.sdk_info", 0);
     }
 
-    /** Values suitable as parameters for {@link #getExtensionVersion(int)}. */
+    /**
+     * Values suitable as parameters for {@link #getExtensionVersion(int)}.
+     * @hide
+     */
     @IntDef(value = { VERSION_CODES.R })
     @Retention(RetentionPolicy.SOURCE)
     public @interface SdkVersion {}
 
+    private SdkExtensions() { }
+
     /**
      * Return the version of the extension to the given SDK.
      *
diff --git a/api/system-current.txt b/api/system-current.txt
index c459412..8e64f0e 100644
--- a/api/system-current.txt
+++ b/api/system-current.txt
@@ -6019,6 +6019,14 @@
 
 }
 
+package android.os.ext {
+
+  public class SdkExtensions {
+    method public static int getExtensionVersion(int);
+  }
+
+}
+
 package android.os.image {
 
   public class DynamicSystemClient {