# Feature Context: Real-time Synchronization


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- [1. Feature Context](#1-feature-context)
  - [1.1 Overview](#11-overview)
  - [1.2 Purpose](#12-purpose)
  - [1.3 Actors](#13-actors)
  - [1.4 References](#14-references)
- [2. Actor Flows (CDSL)](#2-actor-flows-cdsl)
- [3. Processes / Business Logic (CDSL)](#3-processes--business-logic-cdsl)
- [4. States (CDSL)](#4-states-cdsl)
- [5. Definitions of Done](#5-definitions-of-done)
  - [Sync Implementation Complete](#sync-implementation-complete)
- [6. Acceptance Criteria](#6-acceptance-criteria)
- [7. Additional Context (optional)](#7-additional-context-optional)

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- [ ] `p2` - **ID**: `cpt-examples-todo-app-featstatus-sync`

- [ ] `p2` - `cpt-examples-todo-app-feature-sync`

## 1. Feature Context

### 1.1 Overview

*Placeholder: Full feature specification to be developed.*

### 1.2 Purpose

Implement cross-device task synchronization via WebSocket with fallback to HTTP polling.

### 1.3 Actors

- `cpt-examples-todo-app-actor-user` - Works across multiple devices
- `cpt-examples-todo-app-actor-sync-service` - Manages real-time sync protocol

### 1.4 References

- Overall Design: [DESIGN.md](../DESIGN.md)
- PRD: [PRD.md](../PRD.md)
- Requirements: `cpt-examples-todo-app-nfr-data-persistence`, `cpt-examples-todo-app-contract-sync`
- Design elements: `cpt-examples-todo-app-interface-websocket`, `cpt-examples-todo-app-constraint-browser-compat`, `cpt-examples-todo-app-principle-offline-first`

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## 2. Actor Flows (CDSL)

*To be implemented: WebSocket connection flow, sync queue processing, conflict resolution*

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## 3. Processes / Business Logic (CDSL)

*To be implemented: Conflict resolution algorithm, connection fallback logic*

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## 4. States (CDSL)

*To be implemented: Sync state machine (connected/disconnected/syncing)*

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## 5. Definitions of Done

### Sync Implementation Complete

- [ ] `p2` - **ID**: `cpt-examples-todo-app-dod-sync`

**Acceptance Criteria**:
- [ ] WebSocket connection established on app load
- [ ] Task changes sync across devices within 5 seconds
- [ ] Offline changes queued and synced when connection restored
- [ ] Sync indicator shows current connection status
- [ ] Graceful fallback to HTTP polling if WebSocket unavailable
- [ ] Conflict resolution implemented (last-write-wins)
- [ ] Unit tests for sync queue and conflict resolution
- [ ] Integration tests for WebSocket protocol
- [ ] E2E tests for cross-device sync scenarios

## 6. Acceptance Criteria

See Definitions of Done (`cpt-examples-todo-app-dod-sync`) for acceptance criteria.

## 7. Additional Context (optional)

None
