Generate stand-alone, opaque identifiers for whatever sessions you want to analyse. Make sure these tags are ephemeral and decoupled from anything else. Then,

Generate stand-alone, opaque identifiers for whatever sessions you want to analyse. Make sure these tags are ephemeral and decoupled from anything else. Then, store only the flow data, discard everything else. Or if you need to keep some data around for the test duration, delete all of it once your A/B test has concluded.