diff -r 48c4eec2b7e6 -r 8c2e4d02f4ef wp/wp-includes/class-wp-feed-cache-transient.php
--- a/wp/wp-includes/class-wp-feed-cache-transient.php	Fri Sep 05 18:40:08 2025 +0200
+++ b/wp/wp-includes/class-wp-feed-cache-transient.php	Fri Sep 05 18:52:52 2025 +0200
@@ -11,9 +11,10 @@
  * Core class used to implement feed cache transients.
  *
  * @since 2.8.0
+ * @since 6.7.0 Now properly implements the SimplePie\Cache\Base interface.
  */
 #[AllowDynamicProperties]
-class WP_Feed_Cache_Transient {
+class WP_Feed_Cache_Transient implements SimplePie\Cache\Base {
 
 	/**
 	 * Holds the transient name.
@@ -42,18 +43,20 @@
 	public $lifetime = 43200;
 
 	/**
-	 * Constructor.
+	 * Creates a new (transient) cache object.
 	 *
 	 * @since 2.8.0
 	 * @since 3.2.0 Updated to use a PHP5 constructor.
+	 * @since 6.7.0 Parameter names have been updated to be in line with the `SimplePie\Cache\Base` interface.
 	 *
-	 * @param string $location  URL location (scheme is used to determine handler).
-	 * @param string $filename  Unique identifier for cache object.
-	 * @param string $extension 'spi' or 'spc'.
+	 * @param string                           $location URL location (scheme is used to determine handler).
+	 * @param string                           $name     Unique identifier for cache object.
+	 * @param Base::TYPE_FEED|Base::TYPE_IMAGE $type     Either `TYPE_FEED` ('spc') for SimplePie data,
+	 *                                                   or `TYPE_IMAGE` ('spi') for image data.
 	 */
-	public function __construct( $location, $filename, $extension ) {
-		$this->name     = 'feed_' . $filename;
-		$this->mod_name = 'feed_mod_' . $filename;
+	public function __construct( $location, $name, $type ) {
+		$this->name     = 'feed_' . $name;
+		$this->mod_name = 'feed_mod_' . $name;
 
 		$lifetime = $this->lifetime;
 		/**
@@ -62,21 +65,22 @@
 		 * @since 2.8.0
 		 *
 		 * @param int    $lifetime Cache duration in seconds. Default is 43200 seconds (12 hours).
-		 * @param string $filename Unique identifier for the cache object.
+		 * @param string $name     Unique identifier for the cache object.
 		 */
-		$this->lifetime = apply_filters( 'wp_feed_cache_transient_lifetime', $lifetime, $filename );
+		$this->lifetime = apply_filters( 'wp_feed_cache_transient_lifetime', $lifetime, $name );
 	}
 
 	/**
-	 * Sets the transient.
+	 * Saves data to the transient.
 	 *
 	 * @since 2.8.0
 	 *
-	 * @param SimplePie $data Data to save.
+	 * @param array|SimplePie\SimplePie $data Data to save. If passed a SimplePie object,
+	 *                                        only cache the `$data` property.
 	 * @return true Always true.
 	 */
 	public function save( $data ) {
-		if ( $data instanceof SimplePie ) {
+		if ( $data instanceof SimplePie\SimplePie ) {
 			$data = $data->data;
 		}
 
@@ -86,11 +90,11 @@
 	}
 
 	/**
-	 * Gets the transient.
+	 * Retrieves the data saved in the transient.
 	 *
 	 * @since 2.8.0
 	 *
-	 * @return mixed Transient value.
+	 * @return array Data for `SimplePie::$data`.
 	 */
 	public function load() {
 		return get_transient( $this->name );
@@ -101,7 +105,7 @@
 	 *
 	 * @since 2.8.0
 	 *
-	 * @return mixed Transient value.
+	 * @return int Timestamp.
 	 */
 	public function mtime() {
 		return get_transient( $this->mod_name );