Cross-handset sharing of A/B experiment bucket identifiers

Determine whether the A/B experiment bucket identifier assigned by Apple is shared by many handsets or is specific to an individual handset.

Background

The paper observes that the server assigns an A/B experiment bucket identifier and that the identifier persists across multiple requests. Because the measurements involve only one handset, they cannot determine whether the same bucket identifier is assigned broadly to many devices or uniquely to this handset. Establishing its scope is relevant to assessing its identifying and tracking implications.

References

The A/B experiment bucketId (Section \ref{sec:telemetry}) is assigned by the server and so is probably shared by many handsets, but we cannot establish this from measurements on a single handset.

— Decoding What iOS Location Services Send to Apple: An LLM Is an Unreliable Analyst but a Useful Toolmaker  (2610.21597 - Leith, 15 Oct 2026) in Section 3.4.2, “Session Identifiers”