Synk

Expense Tracking & Splitting
Add expenses to trips or as direct (non-trip) expenses between any two users.
Flexible cost splitting: equal, custom amounts, or custom participant subsets.
Supports multiple currencies per trip.
Receipt attachments with OCR scanning for auto-fill.

Debt Settlement
Per-trip debt view: pairwise net balances or simplified/minimized transfers (toggle per trip via simplified_debt).
Direct (non-trip) debt between any two users, settled via global "Settle Up" payments.
Unified settlement timeline per user pair showing shared trip rows, direct expenses, and payment records.
Trip Management

Create and manage trips with members (invite by email).
Trip admin controls, soft-delete with tombstone propagation to all members.
Per-trip to-do lists with assignees.
Shared trip documents (file storage).
Itinerary / POI Planning

Build day-by-day itineraries with points of interest.
POI search powered by OpenStreetMap/Overpass (no Google Maps).
Attach images to itinerary stops.
Activity Feed

Real-time-style activity log per trip: expense added/updated/deleted, member left, trip deleted.
Persists deleted-trip activity locally so history survives after a trip is removed.
Push notifications via FCM for expense activity and trip deletions.
Offline-First

A sync queue drains automatically on connectivity restore or manually via pull-to-refresh.