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Offline behavior and caching

References: OFFLINE_FIRST_AND_CLIENT_SYNC.md, SPEC.md §2, AI offline note.

1. Principles​

The patient app is online-first for clinical writes and sensitive reads. Cached data is read-only convenience, not a second source of truth.

  • Writes (booking, demographics request, messages): require connectivity; queue only if product explicitly adds an idempotent outbox later—default is fail with retry UI.
  • Reads: TanStack Query (or equivalent) may cache GET responses with short staleTime; show last updated or pull to refresh on Home and lists.

2. Degradation​

  • When offline: show banner; disable booking and send; allow viewing cached appointments and messages if already fetched (stale indicator).
  • AI-assisted features: offline behavior per SPEC.md AI subsection—disable or show static education only.

3. PHI on device​

  • Minimize persistence; use encrypted storage if caching sensitive JSON; clear on logout.
  • Align with COMPLIANCE_SECURITY.md §7 for device-level expectations.

4. Sync conflicts​