Quote Originally Posted by webchills View Post
Known spiders are definitively prevented from creating sessions

As you are not using the page_not_found redirect, you could change in the observer class from

Code:
// Do not execute the check for the 'page_not_found' page
		if ($current_page_base == 'page_not_found') {
			return;
		}
to

Code:
// Do not execute the check for known spiders
		if (isset($spider_flag) && $spider_flag === true) {
			return;
		}
to disable the whole thing for known spiders

I'm not using this on a live site at the moment so cannot really test if its working
I've changed the code as suggested, but I'll have to wait until tomorrow when my api quota resets to see if it works for spiders. If it works that is quite an elegant fix as I manually block bad bot useragents via .htaccess before they load anything from my site.