This seems to work:
<?php
if(!function_exists('panel')) return;
panel()->routes(array(
array(
'pattern' => '(logout)', // the trick here is the parens around the route pattern
'method' => 'GET|POST',
'filter' => array('auth'),
'action' => function() {
if($user = panel()->user()) {
$user->logout();
}
go('/');
},
),
));
Thanks to @lukaskleinschmidt’s post