Bia

Share grocery lists instantly, even when the signal drops.

Bia is a mobile grocery list app for households, roommates, and small families who need to create and update shopping lists together in real time. It combines fast collaboration, barcode scanning, and offline-first syncing so the list stays accurate in the aisle, at home, and across devices.

Business Goals

  • Launch an MVP in 3 weeks with 90% of core flows complete and stable on iOS and Android.
  • Achieve 40% week-1 retention and 20% week-4 retention among activated users within 60 days of launch.
  • Reach 60% of new users creating or joining a shared list within their first session.
  • Keep onboarding completion under 2 minutes for at least 80% of new signups.
  • Maintain App Store and Play Store crash-free sessions above 99.5% in the first 90 days.

User Goals

  • Create a new grocery list in under 30 seconds.
  • Share a list with family or roommates with one tap.
  • Add items quickly using typing, barcode scan, or recent items.
  • See list updates from other devices within a few seconds when online.
  • Keep using the list offline and have changes sync automatically later.

Non-Goals

  • Meal planning, recipes, or pantry inventory management.
  • Advanced budgeting, coupon clipping, or price comparison.
  • E-commerce checkout or first-party grocery delivery.
  • Complex permission hierarchies beyond owner and collaborator roles in MVP.

Busy Parent Lena, 34 - Manages groceries for a family of four while balancing work and school pickups. She needs a fast way to keep a shared list updated without texting everyone repeatedly.

Busy Parent Lena, 34

  • As a parent, I want to add items while I am in the kitchen, so that I do not forget them later.
  • As a parent, I want my partner to see edits instantly, so that we do not buy duplicates.
  • As a parent, I want to scan a barcode to add an item, so that I can create the list faster while holding products in store.

Roommate Chris, 27 - Shares grocery responsibilities with roommates and often shops on the way home. He needs an app that works well on a phone with spotty connectivity in stores.

Roommate Chris, 27

  • As a roommate, I want to join a shared list with a link, so that I can start contributing immediately.
  • As a roommate, I want offline changes to sync later, so that I can keep shopping in dead zones.
  • As a roommate, I want completed items to stay visible in history, so that I can avoid repurchasing mistakes.

Organizer Maya, 42 - Keeps lists for an older parent and a partner who uses multiple devices. She wants a dependable experience that is easy to explain and quick to learn.

Organizer Maya, 42

  • As an organizer, I want a simple onboarding flow, so that I can get another person using the app in under two minutes.
  • As an organizer, I want to manage list members, so that I can remove access if needed.
  • As an organizer, I want the app to recover from sync conflicts gracefully, so that the list stays trustworthy.

List Creation and Collaboration · High priority

  • Users can create, join, edit, and share grocery lists in real time across devices.
  • Create a personal list in one tap after signup or guest entry.
  • Generate share links and invite collaborators by phone number or email.
  • Broadcast updates to all connected devices within 2 seconds under normal network conditions.
  • Display clear ownership and collaborator indicators on each list.
  • Resolve simultaneous edits using last-write-wins for text fields with visible conflict notices when needed.

Fast Item Entry · High priority

  • Users can add items quickly using typing, suggestions, recent items, and barcode scanning.
  • Autocomplete item names from a curated grocery item dictionary and user history.
  • Support barcode scanning with camera permission prompt and fallback to manual entry if denied.
  • Allow quantity, unit, and note entry in the add-item flow.
  • Provide one-handed controls optimized for mobile use.
  • Accept partial input and normalize common variants like pluralization and casing.

Offline-First Sync · High priority

  • The app remains usable without network connectivity and syncs changes automatically when connection returns.
  • Store pending creates, updates, and deletes locally on device.
  • Show offline status and last successful sync time.
  • Retry sync automatically with exponential backoff and clear error states.
  • Prevent duplicate item creation when a queued action replays after reconnect.
  • Warn users when a change cannot sync due to authorization or deleted list state.

List Management and Status · Medium priority

  • Users can organize items and keep the list readable during shopping trips.
  • Mark items as checked off, uncheck them, or delete them.
  • Sort unchecked items above checked items by default.
  • Allow optional sections such as Produce, Dairy, and Pantry in MVP if time allows.
  • Show recent activity so collaborators can see who changed what.
  • Support archiving completed lists for future reference.

Authentication and Future Monetization · Low priority

  • The foundation supports secure login now and future paid plans later.
  • Support email magic link or phone-based signup in MVP.
  • Prepare user and household records for Stripe customer mapping.
  • Keep premium gating out of MVP but create feature flags for future subscriptions.
  • Store billing-ready metadata without requiring checkout at launch.

2-Minute Onboarding

  • Open Bia and choose Create New List or Join Existing List.
  • Sign in with email magic link or continue with a guest session.
  • Name the list and optionally add one collaborator.
  • Add the first item or scan a barcode to confirm value immediately.
  • See the live list view with sync status and a short tip overlay.
  • Reach first useful action in under 120 seconds for at least 80% of new users.

1. Start a List

  • The user creates a new grocery list or opens one from an invite link.
  • Pre-fill list name suggestions like Weekly Groceries or Costco Run.
  • If invite link opens on an unregistered device, route to join flow before list access.
  • If network is unavailable, create a local draft list and sync later.

2. Add Items Fast

  • The user adds items through typeahead, barcode scan, or recent items.
  • Show inline validation for empty items, too-long notes, or invalid quantities.
  • Keep the add-item action above the keyboard and reachable with one thumb.
  • If barcode lookup fails, let the user save the scanned code as a manual item and retry in background.

3. Collaborate in Real Time

  • Edits from other devices appear quickly and clearly without manual refresh.
  • Display small presence indicators for active collaborators when online.
  • Animate new items and completion state changes so updates are noticeable but not distracting.
  • If sync lags, show a discreet pending badge rather than blocking input.

4. Shop Offline and Recover

  • The user continues shopping even with weak or no signal.
  • Queue local edits and preserve order of actions.
  • Show a visible offline banner and queued change count.
  • On reconnection, reconcile changes and surface any conflicts in a simple review state.

5. Close the Loop

  • The user finishes the trip and archives or reuses the list next time.
  • Allow list duplication for recurring trips.
  • Move completed lists into archive without deleting history.
  • If a list is shared, preserve access rules when duplicating only if the owner chooses to copy members.

Power Features and Edge Cases

  • Barcode history for frequently purchased items.
  • Duplicate list templates for recurring shops.
  • List activity log with timestamps and actor names.
  • Invite acceptance through deep links and fallback copy link.
  • Conflict resolution state for simultaneous edits on the same item.
  • Graceful handling of deleted users, revoked invites, and expired links.

Mobile-First Clarity

  • Large tap targets and high-contrast text for kitchen and store use.
  • Bottom-sheet add-item flow optimized for one-handed operation.
  • Accessible labels for every icon, barcode scanner, and completion control.
  • Sub-2-second perceived response for common actions through local optimistic updates.
  • Clear offline, syncing, and synced states using color plus text, not color alone.

Lena is juggling work and school pickup when she remembers milk, diapers, and pasta. She opens Bia, taps create list, and adds the first few items before the app even finishes syncing. In less than two minutes, her partner has the list on their phone and starts checking off items while at the store.

Later that evening, Lena scans a cereal barcode and Bia recognizes it instantly. When the supermarket basement loses signal, the app keeps working offline and quietly queues changes. By the time she gets home, the list is fully synced, duplicates are avoided, and the family has a single source of truth for groceries instead of scattered texts.

User-Centric Metrics

  • 80% of new users create or join a list in under 2 minutes.
  • 60% of activated users add at least 3 items in their first session.
  • 50% of shared-list users have a second collaborator join within 24 hours.
  • 70% of shopping sessions include at least one completed item check-off.
  • Less than 3% of users report sync confusion or duplicate items in post-session feedback.

Business Metrics

  • 40% week-1 retention within 60 days of launch.
  • 20% week-4 retention within 60 days of launch.
  • 25% of signups convert to a shared household or collaborator workflow.
  • Organic referral rate of 15% of new signups through invite links.
  • Feature adoption of barcode scanning reaches 30% of active users by month 3.

Technical Metrics

  • 99.5% crash-free sessions on iOS and Android.
  • P95 list view and item add latency under 300 ms on device.
  • P95 real-time sync propagation under 2 seconds on stable connectivity.
  • Authentication and list access endpoints maintain 99.9% service availability.

Tracking Plan

  • signup_started and signup_completed
  • list_created
  • invite_link_generated
  • invite_joined
  • item_added
  • barcode_scan_started and barcode_scan_succeeded
  • item_checked_off
  • offline_mode_entered and offline_changes_synced
  • sync_conflict_detected
  • list_archived

Technical Needs

  • React Native mobile app with TypeScript.
  • Supabase Auth for email magic links or phone-based sign-in.
  • Supabase Postgres with row-level security for shared lists.
  • Supabase Realtime for list update broadcasting.
  • Local persistence with SQLite or MMKV for offline queue and cached lists.
  • Camera permissions and barcode scanning via a native React Native scanning library such as Expo Camera or VisionCamera with barcode support.
  • Feature flags and remote config to safely enable future Stripe monetization.

Integration Points

  • Supabase Auth
  • Supabase Postgres and Realtime
  • Barcode scanning library
  • Apple App Store and Google Play distribution
  • Stripe customer and payment setup for future subscription plans

Data Storage & Privacy

  • Store only necessary personal data for collaboration: name, email or phone, list membership, and shopping item content.
  • Use row-level security so only invited collaborators can read or write a list.
  • Encrypt sensitive data in transit with TLS and rely on platform secure storage for tokens.
  • Provide account deletion and data export support to satisfy GDPR and CCPA expectations.
  • Avoid storing payment data in MVP; delegate all future payment handling to Stripe hosted components.

Scalability & Performance

  • Design sync payloads to send only changed rows, not full lists.
  • Paginate archive and activity history to keep list load time fast.
  • Cache the active list locally so the app opens instantly after launch.
  • Limit realtime subscriptions to the active list and currently visible screens.

Potential Challenges

  • Concurrent edits may overwrite each other; mitigate with optimistic UI plus conflict detection on item deletes and quantity changes.
  • Barcode recognition can fail in poor lighting; mitigate with manual entry fallback and flashlight toggle.
  • Offline queues can duplicate actions after reconnect; mitigate with idempotent client action IDs and server-side deduplication.
  • Invite links can be forwarded unintentionally; mitigate with revocable links and expiration settings.
  • Three-week timeline is tight; mitigate by shipping a strict MVP focused on one shared list, fast add-item flow, and robust sync before extras.

Team & resourcing - Small team - 2 mobile engineers, 1 backend engineer, 1 product designer, part-time PM/QA

Phase 1: MVP Foundation · Week 1

  • App shell and navigation
  • Supabase auth and user profile setup
  • Create and view a single grocery list
  • Basic data model for lists, items, members, and invites
  • Local persistence scaffold and optimistic updates

Phase 2: Collaboration and Offline · Week 2

  • Real-time shared list updates
  • Invite links and collaborator join flow
  • Offline queue for add, edit, check-off, and delete actions
  • Sync status indicators and conflict handling
  • Activity log for recent changes

Phase 3: Fast Item Entry · Week 3

  • Barcode scanning with camera permission handling
  • Typeahead suggestions and recent items
  • List archive and duplicate list
  • Accessibility polish and onboarding completion optimization
  • Analytics events and crash monitoring

Phase 4: Launch Hardening · Post-launch Week 1–2

  • Bug fixes from beta feedback
  • Performance tuning for cold start and sync latency
  • Store submission updates and release notes
  • Monitoring dashboard for retention, sync failures, and activation
  • Stripe-ready feature flags and subscription data model placeholders

Paste this into Cursor, Bolt, Lovable, or v0 to start building.

Build a mobile grocery list app called Bia using React Native and TypeScript with Supabase as the backend. The app must let users create, edit, share, and collaborate on grocery lists in real time, with offline-first support, barcode scanning via camera, fast sync, and a clean one-handed mobile UI.

Core requirements:
1. Auth: email magic link or phone sign-in with Supabase Auth. Allow guest creation first if needed, then prompt to sign in to keep syncing.
2. Main screens: onboarding, list home, shared list detail, add item bottom sheet, barcode scanner, invite/share modal, activity/history, offline/sync status, settings/profile.
3. List behavior: create a list, invite collaborators by link, see live updates from other users, check items off, reorder unchecked above checked, archive and duplicate lists.
4. Offline support: cache current list locally using SQLite or MMKV, queue mutations while offline, sync automatically when connectivity returns, dedupe actions with client-generated IDs.
5. Barcode scanning: open camera scanner, support flashlight, manual fallback if scan fails, and save scanned barcodes to an item. If a barcode matches a known item, prefill the name.
6. Data model in Supabase Postgres: users, households/lists, list_members, list_items, invites, item_events/activity_log, device_sync_state. Use row-level security so only members can read/write shared lists.
7. Realtime: subscribe only to the active list and update UI instantly on insert/update/delete events.
8. Analytics: instrument signup_started, signup_completed, list_created, invite_generated, invite_joined, item_added, barcode_scan_succeeded, item_checked_off, offline_mode_entered, sync_conflict_detected, list_archived.
9. Future-proofing: include a Stripe-ready billing customer_id field on the user or household model, but do not build payments UI yet.
10. Quality: make the app fast, accessible, and resilient. Use optimistic updates, loading skeletons, clear sync banners, error states, and empty states. Aim for sub-300ms local UI response and a polished MVP suitable for App Store and Google Play.

Please scaffold the codebase with a sensible project structure, reusable components, Supabase client setup, state management, local persistence layer, example screens, and seed mock data. Include environment variable placeholders and clear TODOs where backend credentials or platform-specific permissions are required.

Business Idea

Bia is a mobile grocery list app that lets users create, edit, and share shopping lists in real time, including barcode scanning with the camera, offline support, and fast sync between devices. The MVP ships in 3 weeks, must onboard 80% of new users in under 2 minutes, and is built with React Native, Supabase, and Stripe for future payments. Generate a detailed mobile app PRD for this project and sprint plan

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