diff --git a/media/java/android/media/MediaSession2.java b/media/java/android/media/MediaSession2.java
index 4437cca..e2e314c 100644
--- a/media/java/android/media/MediaSession2.java
+++ b/media/java/android/media/MediaSession2.java
@@ -116,18 +116,20 @@
     /**
      * Command code for {@link MediaController2#skipToNextItem()}.
      * <p>
-     * Command would be sent directly to the player if the session doesn't reject the request
-     * through the {@link SessionCallback#onCommandRequest(MediaSession2, ControllerInfo, Command)}.
+     * Command would be sent directly to the playlist agent if the session doesn't reject the
+     * request through the {@link SessionCallback#onCommandRequest(
+     * MediaSession2, ControllerInfo, Command)}.
      */
-    public static final int COMMAND_CODE_PLAYBACK_SKIP_NEXT_ITEM = 4;
+    public static final int COMMAND_CODE_PLAYLIST_SKIP_NEXT_ITEM = 4;
 
     /**
      * Command code for {@link MediaController2#skipToPreviousItem()}.
      * <p>
-     * Command would be sent directly to the player if the session doesn't reject the request
-     * through the {@link SessionCallback#onCommandRequest(MediaSession2, ControllerInfo, Command)}.
+     * Command would be sent directly to the playlist agent if the session doesn't reject the
+     * request through the {@link SessionCallback#onCommandRequest(
+     * MediaSession2, ControllerInfo, Command)}.
      */
-    public static final int COMMAND_CODE_PLAYBACK_SKIP_PREV_ITEM = 5;
+    public static final int COMMAND_CODE_PLAYLIST_SKIP_PREV_ITEM = 5;
 
     /**
      * Command code for {@link MediaController2#prepare()}.
@@ -275,48 +277,60 @@
     /**
      * Command code for {@link MediaController2#playFromMediaId(String, Bundle)}.
      */
-    public static final int COMMAND_CODE_PLAY_FROM_MEDIA_ID = 22;
+    public static final int COMMAND_CODE_SESSION_PLAY_FROM_MEDIA_ID = 22;
 
     /**
      * Command code for {@link MediaController2#playFromUri(Uri, Bundle)}.
      */
-    public static final int COMMAND_CODE_PLAY_FROM_URI = 23;
+    public static final int COMMAND_CODE_SESSION_PLAY_FROM_URI = 23;
 
     /**
      * Command code for {@link MediaController2#playFromSearch(String, Bundle)}.
      */
-    public static final int COMMAND_CODE_PLAY_FROM_SEARCH = 24;
+    public static final int COMMAND_CODE_SESSION_PLAY_FROM_SEARCH = 24;
 
     /**
      * Command code for {@link MediaController2#prepareFromMediaId(String, Bundle)}.
      */
-    public static final int COMMAND_CODE_PREPARE_FROM_MEDIA_ID = 25;
+    public static final int COMMAND_CODE_SESSION_PREPARE_FROM_MEDIA_ID = 25;
 
     /**
      * Command code for {@link MediaController2#prepareFromUri(Uri, Bundle)}.
      */
-    public static final int COMMAND_CODE_PREPARE_FROM_URI = 26;
+    public static final int COMMAND_CODE_SESSION_PREPARE_FROM_URI = 26;
 
     /**
      * Command code for {@link MediaController2#prepareFromSearch(String, Bundle)}.
      */
-    public static final int COMMAND_CODE_PREPARE_FROM_SEARCH = 27;
+    public static final int COMMAND_CODE_SESSION_PREPARE_FROM_SEARCH = 27;
 
     /**
      * Command code for {@link MediaController2#setRating(String, Rating2)}.
      * @hide
      */
-    // TODO(jaewan): Unhide
-    public static final int COMMAND_CODE_SET_RATING = 29;
+    public static final int COMMAND_CODE_SESSION_SET_RATING = 28;
 
     /**
-     * Command code for {@link MediaBrowser2} specific functions that allows navigation and search
-     * from the {@link MediaLibraryService2}. This would be ignored for a {@link MediaSession2},
-     * not {@link android.media.MediaLibraryService2.MediaLibrarySession}.
+     * Command code for {@link android.media.MediaLibraryService2.MediaLibrarySession} specific
+     * functions. With or without this, a {@link MediaSession2} that isn't
+     * {@link android.media.MediaLibraryService2.MediaLibrarySession} would automatically reject
+     * the calls.
      *
+     * @see android.media.MediaLibraryService2.MediaLibrarySession
      * @see MediaBrowser2
+     * @hide
      */
-    public static final int COMMAND_CODE_BROWSER = 28;
+    // TODO(jaewan): Remove
+    public static final int COMMAND_CODE_BROWSER = 29;
+
+    // TODO(jaewan): Add javadoc
+    public static final int COMMAND_CODE_LIBRARY_GET_CHILDREN = 29;
+    public static final int COMMAND_CODE_LIBRARY_GET_ITEM = 30;
+    public static final int COMMAND_CODE_LIBRARY_GET_LIBRARY_ROOT = 31;
+    public static final int COMMAND_CODE_LIBRARY_GET_SEARCH_RESULT = 32;
+    public static final int COMMAND_CODE_LIBRARY_SEARCH = 33;
+    public static final int COMMAND_CODE_LIBRARY_SUBSCRIBE = 34;
+    public static final int COMMAND_CODE_LIBRARY_UNSUBSCRIBE = 35;
 
     /**
      * @hide
@@ -627,8 +641,8 @@
          * @see #COMMAND_CODE_PLAYBACK_PLAY
          * @see #COMMAND_CODE_PLAYBACK_PAUSE
          * @see #COMMAND_CODE_PLAYBACK_STOP
-         * @see #COMMAND_CODE_PLAYBACK_SKIP_NEXT_ITEM
-         * @see #COMMAND_CODE_PLAYBACK_SKIP_PREV_ITEM
+         * @see #COMMAND_CODE_PLAYLIST_SKIP_NEXT_ITEM
+         * @see #COMMAND_CODE_PLAYLIST_SKIP_PREV_ITEM
          * @see #COMMAND_CODE_PLAYBACK_PREPARE
          * @see #COMMAND_CODE_PLAYBACK_FAST_FORWARD
          * @see #COMMAND_CODE_PLAYBACK_REWIND
@@ -683,7 +697,7 @@
          * @param controller controller information
          * @param mediaId media id
          * @param extras optional extra bundle
-         * @see #COMMAND_CODE_PLAY_FROM_MEDIA_ID
+         * @see #COMMAND_CODE_SESSION_PLAY_FROM_MEDIA_ID
          */
         public void onPlayFromMediaId(@NonNull MediaSession2 session,
                 @NonNull ControllerInfo controller, @NonNull String mediaId,
@@ -700,7 +714,7 @@
          * @param controller controller information
          * @param query query string. Can be empty to indicate any suggested media
          * @param extras optional extra bundle
-         * @see #COMMAND_CODE_PLAY_FROM_SEARCH
+         * @see #COMMAND_CODE_SESSION_PLAY_FROM_SEARCH
          */
         public void onPlayFromSearch(@NonNull MediaSession2 session,
                 @NonNull ControllerInfo controller, @NonNull String query,
@@ -714,7 +728,7 @@
          * @param controller controller information
          * @param uri uri
          * @param extras optional extra bundle
-         * @see #COMMAND_CODE_PLAY_FROM_URI
+         * @see #COMMAND_CODE_SESSION_PLAY_FROM_URI
          */
         public void onPlayFromUri(@NonNull MediaSession2 session,
                 @NonNull ControllerInfo controller, @NonNull Uri uri,
@@ -738,7 +752,7 @@
          * @param controller controller information
          * @param mediaId media id to prepare
          * @param extras optional extra bundle
-         * @see #COMMAND_CODE_PREPARE_FROM_MEDIA_ID
+         * @see #COMMAND_CODE_SESSION_PREPARE_FROM_MEDIA_ID
          */
         public void onPrepareFromMediaId(@NonNull MediaSession2 session,
                 @NonNull ControllerInfo controller, @NonNull String mediaId,
@@ -762,7 +776,7 @@
          * @param controller controller information
          * @param query query string. Can be empty to indicate any suggested media
          * @param extras optional extra bundle
-         * @see #COMMAND_CODE_PREPARE_FROM_SEARCH
+         * @see #COMMAND_CODE_SESSION_PREPARE_FROM_SEARCH
          */
         public void onPrepareFromSearch(@NonNull MediaSession2 session,
                 @NonNull ControllerInfo controller, @NonNull String query,
@@ -786,7 +800,7 @@
          * @param controller controller information
          * @param uri uri
          * @param extras optional extra bundle
-         * @see #COMMAND_CODE_PREPARE_FROM_URI
+         * @see #COMMAND_CODE_SESSION_PREPARE_FROM_URI
          */
         public void onPrepareFromUri(@NonNull MediaSession2 session,
                 @NonNull ControllerInfo controller, @NonNull Uri uri, @Nullable Bundle extras) { }