Worker affinity

Worker affinity — contract and behavior

• A backend kind can have many physical workers, but a stateful chat remains bound to the worker that owns its device state.
• The affinity record persists in storage and survives service restarts.
• If the assigned worker is offline, the request fails rather than moving the chat to a different Apple identity or device.
• Operators repair, reconnect, or deliberately migrate affinity; the scheduler does not guess equivalence between workers.