diff --git a/wp-includes/class-wp-user.php b/wp-includes/class-wp-user.php
index 8fd5e5cd21..27f49b2e86 100644
--- a/wp-includes/class-wp-user.php
+++ b/wp-includes/class-wp-user.php
@@ -37,6 +37,9 @@
  * @property string $rich_editing
  * @property string $syntax_highlighting
  * @property string $use_ssl
+ * @property array<string, bool> $caps
+ * @property string[] $roles
+ * @property array<string, bool> $allcaps
  */
 #[AllowDynamicProperties]
 class WP_User {
@@ -60,10 +63,10 @@ class WP_User {
 	 * Capabilities that the individual user has been granted outside of those inherited from their role.
 	 *
 	 * @since 2.0.0
-	 * @var bool[] Array of key/value pairs where keys represent a capability name
-	 *             and boolean values represent whether the user has that capability.
+	 * @var array<string, bool>|null Array of key/value pairs where keys represent a capability name
+	 *                               and boolean values represent whether the user has that capability.
 	 */
-	public $caps = array();
+	protected $caps = null;
 
 	/**
 	 * User metadata option name.
@@ -79,16 +82,16 @@ class WP_User {
 	 * @since 2.0.0
 	 * @var string[]
 	 */
-	public $roles = array();
+	protected $roles = array();
 
 	/**
 	 * All capabilities the user has, including individual and role based.
 	 *
 	 * @since 2.0.0
-	 * @var bool[] Array of key/value pairs where keys represent a capability name
-	 *             and boolean values represent whether the user has that capability.
+	 * @var array<string, bool> Array of key/value pairs where keys represent a capability name
+	 *                          and boolean values represent whether the user has that capability.
 	 */
-	public $allcaps = array();
+	protected $allcaps = array();
 
 	/**
 	 * The filter context applied to user data fields.
@@ -288,6 +291,10 @@ class WP_User {
 			$key = 'ID';
 		}
 
+		if ( in_array( $key, array( 'caps', 'allcaps', 'roles' ), true ) ) {
+			return true;
+		}
+
 		if ( isset( $this->data->$key ) ) {
 			return true;
 		}
@@ -321,6 +328,11 @@ class WP_User {
 			return $this->ID;
 		}
 
+		if ( in_array( $key, array( 'caps', 'allcaps', 'roles' ), true ) ) {
+			$this->load_capability_data();
+			return $this->$key;
+		}
+
 		if ( isset( $this->data->$key ) ) {
 			$value = $this->data->$key;
 		} else {
@@ -363,6 +375,13 @@ class WP_User {
 			return;
 		}
 
+		// Ensure capability data is loaded before setting related properties.
+		if ( in_array( $key, array( 'caps', 'allcaps', 'roles' ), true ) ) {
+			$this->load_capability_data();
+			$this->$key = $value;
+			return;
+		}
+
 		$this->data->$key = $value;
 	}
 
@@ -386,6 +405,10 @@ class WP_User {
 			);
 		}
 
+		if ( in_array( $key, array( 'caps', 'allcaps', 'roles' ), true ) ) {
+			$this->$key = null;
+		}
+
 		if ( isset( $this->data->$key ) ) {
 			unset( $this->data->$key );
 		}
@@ -515,6 +538,11 @@ class WP_User {
 
 		$wp_roles = wp_roles();
 
+		// Edge case: In case someone calls this method before lazy initialization, we need to initialize on demand.
+		if ( ! isset( $this->caps ) ) {
+			$this->caps = $this->get_caps_data();
+		}
+
 		// Filter out caps that are not role names and assign to $this->roles.
 		if ( is_array( $this->caps ) ) {
 			$this->roles = array_filter( array_keys( $this->caps ), array( $wp_roles, 'is_role' ) );
@@ -548,6 +576,7 @@ class WP_User {
 		if ( empty( $role ) ) {
 			return;
 		}
+		$this->load_capability_data();
 
 		if ( in_array( $role, $this->roles, true ) ) {
 			return;
@@ -577,6 +606,7 @@ class WP_User {
 	 * @param string $role Role name.
 	 */
 	public function remove_role( $role ) {
+		$this->load_capability_data();
 		if ( ! in_array( $role, $this->roles, true ) ) {
 			return;
 		}
@@ -609,6 +639,7 @@ class WP_User {
 	 * @param string $role Role name.
 	 */
 	public function set_role( $role ) {
+		$this->load_capability_data();
 		if ( 1 === count( $this->roles ) && current( $this->roles ) === $role ) {
 			return;
 		}
@@ -710,6 +741,7 @@ class WP_User {
 	 * @param bool   $grant Whether to grant capability to user.
 	 */
 	public function add_cap( $cap, $grant = true ) {
+		$this->load_capability_data();
 		$this->caps[ $cap ] = $grant;
 		update_user_meta( $this->ID, $this->cap_key, $this->caps );
 		$this->get_role_caps();
@@ -724,6 +756,7 @@ class WP_User {
 	 * @param string $cap Capability name.
 	 */
 	public function remove_cap( $cap ) {
+		$this->load_capability_data();
 		if ( ! isset( $this->caps[ $cap ] ) ) {
 			return;
 		}
@@ -742,10 +775,10 @@ class WP_User {
 	 */
 	public function remove_all_caps() {
 		global $wpdb;
-		$this->caps = array();
+		$this->caps = null;
 		delete_user_meta( $this->ID, $this->cap_key );
 		delete_user_meta( $this->ID, $wpdb->get_blog_prefix() . 'user_level' );
-		$this->get_role_caps();
+		$this->load_capability_data();
 	}
 
 	/**
@@ -776,6 +809,8 @@ class WP_User {
 	 *              the given capability for that object.
 	 */
 	public function has_cap( $cap, ...$args ) {
+		$this->load_capability_data();
+
 		if ( is_numeric( $cap ) ) {
 			_deprecated_argument( __FUNCTION__, '2.0.0', __( 'Usage of user levels is deprecated. Use capabilities instead.' ) );
 			$cap = $this->translate_level_to_cap( $cap );
@@ -877,10 +912,7 @@ class WP_User {
 		}
 
 		$this->cap_key = $wpdb->get_blog_prefix( $this->site_id ) . 'capabilities';
-
-		$this->caps = $this->get_caps_data();
-
-		$this->get_role_caps();
+		$this->caps    = null;
 	}
 
 	/**
@@ -911,4 +943,17 @@ class WP_User {
 
 		return $caps;
 	}
+
+	/**
+	 * Loads capability data if it has not been loaded yet.
+	 *
+	 * @since 6.9.0
+	 */
+	private function load_capability_data() {
+		if ( isset( $this->caps ) ) {
+			return;
+		}
+		$this->caps = $this->get_caps_data();
+		$this->get_role_caps();
+	}
 }
diff --git a/wp-includes/version.php b/wp-includes/version.php
index ca6e84f93a..3e72d732b0 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.9-alpha-60914';
+$wp_version = '6.9-alpha-60915';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.