[split] ajax killing sessions?

Yes, with that file in the location I specified you autoload 'session', CI see's MY_Session then uses that which extends the base session library and overloads the method defined in the new file. AJAX calls should not break your session unless one of them is closing it. Whats the error you're getting?

For reference our app uses both a queue for long running requests and 3+ subdomains to bypass the 2-per-domain concurrent AJAX request limit. It is normal for 5-10 concurrent requests to be running at any given time and we do not have any issues related to sessions closing.

We're moving to websockets for sanity sake but there's no reason concurrent AJAX requests should kill your session unless there's an unrelated bug somewhere. It's more likely you have a concurrency issue with database actions (deadlocks, timeouts from locks, etc).

What session driver are you using?