A production rollout exposes a contract mismatch between the UI boundary and the owning service. The affected area is outbox worker.
Repair the outbox worker activity stream implementation so it splits activity after the configured inactivity gap and counts sessions per actor.
Evidence
- Affected surface: Full-stack backend focus / outbox worker.
- Observed failure family: sessionize event activity.
- Scope policy: region must equal eu-west.