Offline sync

Mobile is offline-first. The server remains the source of truth. Clients keep a local SQLite/Drift cache for reads and a write outbox for offline work, then converge with pull and push.

Goals

• Keep working through long disconnects without silently losing data.
• Detect conflicts with row versions and server timestamps.
• Propagate soft deletes as tombstones.
• Keep posted financial/stock documents immutable — corrections use amend, cancel, reverse, or adjustment flows.

Endpoints

Method	Path	Purpose
GET	/v1/sync/manifest	Entity sync capabilities
GET	/v1/sync/pull?since=<cursor>	Paginated changes since cursor
POST	/v1/sync/push	Upload buffered local mutations
POST	/v1/sync/reset	Rebuild local cache from server

Business-scoped variants exist under /v1/businesses/:business_id/sync/....

How it works

1. Every business resource has a sync_version bumped on every update (including soft delete).
2. Pull uses a stable opaque cursor (base64url JSON over (updated_at, id)).
3. Push applies a batch of local mutations; conflicts surface deterministically.
4. POS sales use an idempotent client_sale_id so retries after reconnect are safe.

Operator tips

• Leave the Windows cashier tray process running so background sync can drain the outbox.
• After a device reset, run sync pull before taking payments.
• Never “edit” a posted invoice in place — use credit notes / reverse / adjust.

Related

• POS & cashier
• Backups
• Deep dive in the repo: docs/sync.md