P0Connectivity
iOS kills background BLE within minutes
Problem
iOS aggressively suspends background BLE. A ring or watch connected at lock time is likely disconnected within 5–15 minutes.
Why it happens
iOS reclaims CPU and radio from non-foreground apps. The connection token may persist while the app process is frozen — buffered notifications may or may not survive.
Saola's solution
- 01Per-source persisted sync cursor (last successful timestamp / record ID) on device + backend.
- 02On every sync opportunity, request only the delta since the cursor.
- 03Cursor advances only after atomic write to the ingest log.
- 04Multi-trigger orchestration: bluetooth-central, background-fetch (~15 min), silent push.
- 05UI never blocks on sync — render from local canonical cache, refresh optimistically.
Trade-off · Cursor logic adds adapter complexity and demands strict idempotency. A missed background window is never catastrophic — the next sync resumes.
Where in v3 · Stage 1 — incremental_pull(since_cursor); per-source sync-state table.