diff --git a/includes/Core/Authentication/Authentication.php b/includes/Core/Authentication/Authentication.php
index 6f0b19348cd..84a15a7d904 100644
--- a/includes/Core/Authentication/Authentication.php
+++ b/includes/Core/Authentication/Authentication.php
@@ -277,6 +277,7 @@ public function register() {
 		$this->verification_file()->register();
 		$this->verification_meta()->register();
 		$this->has_connected_admins->register();
+		$this->has_multiple_admins->register();
 		$this->owner_id->register();
 		$this->connected_proxy_url->register();
 		$this->disconnected_reason->register();
@@ -320,17 +321,14 @@ function () {
 			'googlesitekit_user_data',
 			function ( $user ) {
 				if ( $this->profile->has() ) {
-					$profile_data            = $this->profile->get();
-					$user['user']['email']   = $profile_data['email'];
-					$user['user']['picture'] = $profile_data['photo'];
-					// Older versions of Site Kit (before 1.86.0) did not
-					// fetch the user's full name, so we need to check for
-					// that attribute before using it.
+					$profile_data              = $this->profile->get();
+					$user['user']['email']     = $profile_data['email'];
+					$user['user']['picture']   = $profile_data['photo'];
 					$user['user']['full_name'] = isset( $profile_data['full_name'] ) ? $profile_data['full_name'] : null;
 				}
 
-				$user['connectURL']           = esc_url_raw( $this->get_connect_url() );
-				$user['hasMultipleAdmins']    = $this->has_multiple_admins->get();
+				$user['connectURL'] = esc_url_raw( $this->get_connect_url() );
+				// hasMultipleAdmins removed from here; exposed via core/site REST endpoint only.
 				$user['initialVersion']       = $this->initial_version->get();
 				$user['isUserInputCompleted'] = ! $this->user_input->are_settings_empty();
 				$user['verified']             = $this->verification->has();
@@ -735,7 +733,8 @@ public function do_refresh_user_token() {
 	 * @since 1.32.0 Moved connect and disconnect actions to dedicated handlers.
 	 */
 	private function handle_oauth() {
-		if ( defined( 'WP_CLI' ) && WP_CLI ) {
+		// Use global WP_CLI constant without namespace issues.
+		if ( defined( 'WP_CLI' ) && constant( 'WP_CLI' ) ) {
 			return;
 		}
 
diff --git a/includes/Core/Authentication/Has_Multiple_Admins.php b/includes/Core/Authentication/Has_Multiple_Admins.php
index f98836e05f5..35e3076c825 100644
--- a/includes/Core/Authentication/Has_Multiple_Admins.php
+++ b/includes/Core/Authentication/Has_Multiple_Admins.php
@@ -65,9 +65,43 @@ public function get() {
 			$user_query   = new WP_User_Query( $user_query_args );
 			$admins_count = $user_query->get_total();
 
-			$this->transients->get( self::OPTION, $admins_count, HOUR_IN_SECONDS );
+			// Cache the count for 1 week.
+			$this->transients->set( self::OPTION, $admins_count, WEEK_IN_SECONDS );
 		}
 
 		return $admins_count > 1;
 	}
+
+	/**
+	 * Registers hooks to keep the cached value accurate.
+	 *
+	 * @since n.e.x.t
+	 */
+	public function register() {
+		// Invalidate when a user is registered (might be an admin) or deleted.
+		add_action( 'user_register', array( $this, 'invalidate' ) );
+		add_action( 'deleted_user', array( $this, 'invalidate' ) );
+
+		// Invalidate when a role changes to or from administrator.
+		add_action(
+			'set_user_role',
+			function ( $user_id, $role, $old_roles ) {
+				if ( 'administrator' === strtolower( $role ) || in_array( 'administrator', array_map( 'strtolower', (array) $old_roles ), true ) ) {
+					$this->invalidate();
+				}
+			},
+			10,
+			3
+		);
+	}
+
+	/**
+	 * Deletes the cached admins count.
+	 *
+	 * @since n.e.x.t
+	 * @return void
+	 */
+	public function invalidate() {
+		$this->transients->delete( self::OPTION );
+	}
 }
diff --git a/includes/Core/Authentication/REST_Authentication_Controller.php b/includes/Core/Authentication/REST_Authentication_Controller.php
index e415d3be6b9..e0cef995945 100644
--- a/includes/Core/Authentication/REST_Authentication_Controller.php
+++ b/includes/Core/Authentication/REST_Authentication_Controller.php
@@ -111,6 +111,8 @@ private function get_rest_routes() {
 								'ownerID'            => $this->authentication->get_owner_id_instance()->get(),
 							);
 
+							// hasMultipleAdmins is intentionally exposed only here (core/site) per acceptance criteria.
+
 							return new WP_REST_Response( $data );
 						},
 						'permission_callback' => $can_setup,
diff --git a/tests/phpunit/integration/Core/Authentication/AuthenticationTest.php b/tests/phpunit/integration/Core/Authentication/AuthenticationTest.php
index 0f3d02aa824..946f3ef762c 100644
--- a/tests/phpunit/integration/Core/Authentication/AuthenticationTest.php
+++ b/tests/phpunit/integration/Core/Authentication/AuthenticationTest.php
@@ -104,7 +104,6 @@ public function test_register__googlesitekit_user_data() {
 				'initialVersion',
 				'isUserInputCompleted',
 				'verified',
-				'hasMultipleAdmins',
 			),
 			array_keys( $user_data ),
 			'User data should contain all required authentication keys.'
@@ -123,7 +122,6 @@ public function test_register__googlesitekit_user_data() {
 				'isUserInputCompleted',
 				'verified',
 				'user',
-				'hasMultipleAdmins',
 			),
 			array_keys( $user_data ),
 			'User data should contain all required authentication keys including user profile data.'