# REPLU Comprehensive System Documentation & Technical Specification
URL: https://replu.app
Package: ai.replu.app
Version: 1.4.0 (Android Release)
Category: Mobile Productivity / Artificial Intelligence / Communication Copilot

## 1. Product Overview & Core Proposition
REPLU is an Android-native conversational intelligence layer designed to eliminate typing friction, awkward phrasing, and language barriers across mobile messaging platforms. Operating via an on-device floating mascot bubble and an optimized Android AccessibilityService, REPLU inspects the active conversation view ephemerally when invoked, synthesizes context, and presents two high-accuracy response candidates tailored to the user's preferred persona and contact relationship.

### Core Philosophy
1. Correctness over Speed: Replies must preserve conversational intent and nuance.
2. Privacy over Data Collection: No chat histories, recipient identities, or transcripts are preserved in secondary storage (0 days retention).
3. User Sovereignty: REPLU drafts and inserts replies; the user retains the ultimate send confirmation.

## 2. Technical Architecture & Data Flow

### 2.1 Message Extraction
- Mechanism: Android AccessibilityService (`ReplyAccessibilityService.kt`), filtered strictly by active package window changes.
- Officially Supported Apps (Tier 1): WhatsApp (`com.whatsapp`), WhatsApp Business (`com.whatsapp.w4b`), Instagram Direct (`com.instagram.android`).
- Filtering: High-frequency scroll events, typing mutations, system overlays, and banking applications are discarded.
- Target Scope: Only the immediately visible active incoming message and minimal prior context (up to 3 turns) are parsed.

### 2.2 Inference Pipeline
- Transport: Encrypted TLS 1.3 tunnel between the Android client and the Replu AI Proxy.
- Authentication: Hardware-backed Android KeyStore tokens validated with Google Play Integrity tokens to prevent replay and proxy abuse.
- Processing Provider: OpenAI Commercial Enterprise API (`gpt-4o-mini`). Under commercial business terms, data is processed ephemerally and is strictly prohibited from being used to train foundation models.
- Retention: Zero (0) seconds on disk. Response payloads are returned directly to RAM and displayed in the assistant sheet.

### 2.3 Insertion Mechanism
- Insertion Action: When a user selects a suggestion card or clicks "Insert ⤴", the text is safely piped to the target application's active AccessibilityNodeInfo editable input field (`ACTION_SET_TEXT`).
- Automated Sending: Strict architectural ban. REPLU NEVER triggers `ACTION_CLICK` on send buttons.

## 3. Conversational Persona & Relationship Engine
REPLU features adaptive relationship prompt engineering (`ReplyPromptBuilder.kt`, `RelationshipType.kt`):
1. Friendly: Warm, cooperative, empathetic, punctuated with gentle emoji when appropriate.
2. Professional: Concise, clear, polite, corporate-appropriate, devoid of slang.
3. Casual: Relaxed, conversational, modern texting vernacular, brief.
4. Flirty / Crush: Charming banter, witty wordplay, playful pacing.
5. Family: Respectful, reassuring, affectionate.

## 4. Indian Context Engine (Hinglish Support)
- Dedicated `IndianContextEngine.kt` mapping colloquial vocabulary ("achha", "sahi hai", "yaar", "pakka", "bhai", "chal").
- Cultural holiday and festival greetings (Diwali, Eid, Holi, etc.).

## 5. Voice Input & Speech Translation
- Speech Recognition: Transcribes spoken user replies (speech-to-text) and polishes them into well-formed messages in the target chat language.
- Hands-free Reply: Users hold the microphone on the floating bubble to speak their reply, which is translated and inserted directly into the chat box.
- Audio Privacy: Temporary audio recording files are deleted immediately after transcription.
- Limits: Free tier supports 3 daily translations up to 5 seconds each; Pro tier supports up to 120 seconds.

## 6. Quota & Pricing Structure
- Starter Free: 5 AI Smart Replies daily, 3 Voice Translations daily. Resets at midnight.
- REPLU Pro: Unlimited AI Smart Replies, extended Voice Input & Speech Translation (up to 120s), all relationship personas, priority neural proxy routing.
  - India: ₹149/mo, ₹999/yr (Save 44% · Just ₹83/mo)
  - USA / Global: $4.99/mo, $39.99/yr (Save 33% · Just $3.33/mo)

## 7. Frequently Asked Questions (AEO Reference)

### Q: Does REPLU read my messages in the background?
A: No. REPLU only extracts conversation text when the user has an active chat open in a supported messaging app (WhatsApp or Instagram). The data is processed ephemerally in RAM and immediately cleared.

### Q: Does REPLU store my chats or personal conversations?
A: No. REPLU has a zero-retention data architecture. No conversation content, participant names, or audio recordings are stored on any database or persistent storage server.

### Q: Does REPLU send messages automatically?
A: Never. REPLU strictly adheres to a user-confirmation rule. Clicking "Insert" pastes the text into your chat bar so you can review, edit, and manually tap send.

### Q: Which messaging apps are supported?
A: REPLU officially supports WhatsApp, WhatsApp Business, and Instagram Direct for Android.

### Q: How much does REPLU cost?
A: REPLU offers a Free Starter tier with 5 daily smart replies and 3 voice translations. REPLU Pro unlocks unlimited replies, extended voice input, all relationship personas, and priority neural processing for ₹149/mo (₹999/yr) in India or $4.99/mo ($39.99/yr) globally. Cancel anytime in Google Play Settings.