update: I had issue an emergency bugfix just now msebald, switching back to the action hooking into template_redirect, due to multiple others having issues (with e.g. some JS and/or CSS not being optimized or CDN rewrite not working correctly).
You can however force AO to load early by adding this to your wp-config.php;
define("AUTOPTIMIZE_INIT_EARLIER","true");
in which case the code picks up on that;
if (defined('AUTOPTIMIZE_INIT_EARLIER')) {
add_action('init','autoptimize_start_buffering',-1);
} else {
add_action('template_redirect','autoptimize_start_buffering',2);
}
frank