Build your own WhatsApp.

# Build an original app inspired by WhatsApp

You are an experienced mobile product designer and mobile engineer. Build a working, polished MVP from the brief below. Implement the core journeys end to end; a static mockup is not sufficient. Inspect the current environment, make sensible implementation decisions, and get started. Ask a question only if a missing answer genuinely blocks implementation.

Starting platform: iOS / Android. Explicit customized Product & audience and Tech stack requirements take precedence over this starting target.

## Product & audience
Build an original native mobile messenger called Circlechat, inspired by WhatsApp. Use Flutter for iOS and Android and start with an invite-only pilot. People join using verified app accounts, open a direct or small-group conversation, send messages, and recover after losing connectivity. It is an independent messaging service, with no WhatsApp interoperability.

## Design
Create an original mobile conversation list, chat screen, group detail, and attachment picker. Use readable message bubbles, explicit pending/sent/delivered/read states, accessible touch targets, and platform-appropriate navigation. Avoid exposing message previews on the lock screen without a user preference.

## Features
1. Accounts and invitations: support verified sign-in and revocable invitations. Let users choose who can contact them. Keep address-book access optional and omit bulk contact uploading from the starting version.

2. Direct and group messaging: create private conversations, invite/remove members, and send ordered text messages through an authenticated real-time backend. Check membership on history, uploads, and real-time subscriptions.

3. Offline outbox: store pending messages locally with client IDs, retry on reconnect without duplicates, and acknowledge durable server acceptance. Delivered and read indicators must represent explicit recipient acknowledgments.

4. Attachments and notifications: upload bounded images with progress and cancellation, store them behind authorized URLs, and configure genuine mobile push notifications or clearly report setup-required status. Remove device tokens after sign-out.

5. User controls: mute, block, report, leave a group, and delete your own local history with clear semantics. Preserve group ownership and make blocked-user checks apply to the API as well as the interface.

## Tech stack
Use Flutter/Dart, SQLite for the mobile outbox/cache, an authenticated TypeScript API with PostgreSQL, WebSocket delivery, and private object storage. Use APNs/FCM through configured credentials for push. TLS and server access controls are required; do not advertise end-to-end encryption unless a reviewed established protocol is separately integrated and verified.

## Data & behavior
User; Device {pushToken}; Conversation {type}; Membership {role, joinedAt, leftAt}; Message {clientId, conversationId, senderId, sequence, text}; Attachment; DeliveryReceipt; ReadCursor; Block; Report; local Outbox. Use unique sender/client IDs and server-assigned ordering.

Acceptance checks and scope:
Test on iOS/Android emulators or devices: send between two accounts, go offline and retry, reconnect after termination, remove a group member, block a sender, and fetch an attachment without membership. Exclude calls, status stories, phone-number discovery, WhatsApp integration, and unverified encryption claims. Document message retention and notification setup.

## Originality and assets
The named product is a reference for general workflows only. Use an original product name, visual identity, wording, layout, and assets. Do not copy proprietary code, branded logos, distinctive screens, private APIs, paid templates, or protected media. Use original or appropriately licensed sample data and assets. Build from this brief rather than scraping the reference service. Do not imply affiliation with the referenced company.

## Implementation quality
- Make every visible control work, with clear loading, success, empty, validation, and failure states. Remove controls for unimplemented features.
- Support the target platform and responsive or resizable layouts where appropriate. Use platform-appropriate accessibility semantics, labels, keyboard operation, visible focus, sufficient contrast, and reduced-motion preferences. Provide alternatives for drag-only interactions.
- Validate inputs at the relevant boundary. Treat imported or user-generated content as untrusted; render it safely. Confirm destructive actions or offer undo.
- Keep state changes reliable across navigation and reloads. Never silently lose edits. Handle persistence and network errors with an actionable message.
- Keep the scope realistic. Prioritize the complete primary journey. If a custom Features section differs from the baseline, update the data model, design, and acceptance checks to match it; explicit custom requirements take precedence over baseline assumptions.
- Provide realistic original sample content and a useful empty state. Keep sample data clearly separate from user-created data.

## Delivery and verification
1. Inspect the repository and outline the implementation in a few sentences.
2. Implement the app and connect its actual data flow. Continue until the primary journey works.
3. Run appropriate checks and test the acceptance cases above on the target platform. Verify responsive layouts and keyboard navigation when browser tools are available. For native projects, build with the available SDK and test an emulator or device when possible; report any missing native verification honestly. For games, verify the rules and gameplay loop, not only the menus.
4. Fix observed failures, then provide the runnable result, setup/run instructions, a brief explanation of what is implemented, and any specific configuration or verification limits.

This is a focused MVP. Do not add billing, AI services, or unrelated features unless explicitly requested in the brief. Start building now.