session_regenerate_id - what behaviors trigger a regenerate of session id?

[boxes]

how is a session_regenerate_id triggered?

what cart/user/browser behaviors occur to make this happen?

gotta write something to an external system that changes the session id of the external tool when the cart changes its session to keep both the same

thx

[DrByte]

It happens whenever zen_session_recreate() is called. And that happens whenever the user does something that requires that function to be called. You can see where that function is called by looking at the code using your favorite editor and text-search tool or the Developers Toolkit.
But if you really need to update an external system "whenever" it changes, then it really doesn't matter "what" causes the change, right? So you'll need to hack your custom code into the function.