A question about layer 3 wireless roaming?

My understanding of L3 wireless roaming is that you can keep your IP address you started with when you roam onto an AP that doesn't offer the SSID/VLAN you are anchored to. So for example, you start off on an IP that is say, 192.168.100.10 on vlan 100 with an SSID of "Users" then you roam into an AP that is connected to a controller that doesn't have that SSID/VLAN so you join say SSID "engineering" which is tied to VLAN 200. So the new controller you roamed into (the foreign controller) will build a capwap tunnel to the controller you started at (the anchor controller) so you can keep your IP address even though the SSID/VLAN isn't natively offered by this AP/ controller.

I think this is how it works? It's very confusing to me. If you roam onto an AP that doesn't have the SSID you were originally attached to, then it's going to break the connection when you move to the new SSID right? And when you connect to the new one, you'll just get a new IP in whatever subnet that SSID is tied to right? How does the controller know to build a tunnel to your anchor controller and keep your existing IP address?