A cross-platform mobile/web app for managing stablecoin portfolios with AI-powered optimization. Built with React Native (Expo) for MadHacks 2025.

Devpost Link: https://devpost.com/software/stablepay-5l8jeu

• Multi-chain Wallet: Solana-based stablecoin management (USDC, USDT) with encrypted storage
• Smart Transfers: Send to crypto addresses or PayPal with automatic path optimization (still WIP)
• Currency Conversion: Real-time rates with multi-hop path finding for minimal fees
• Transaction History: Complete activity log with on-chain sync
• Portfolio Optimizer: AI-powered recommendations for optimal allocations across chains

Analyzes your portfolio using:

• 90-day historical gas cost data from CoinGecko
• Real-time liquidity and TVL from DefiLlama
• Volatility patterns and day-of-week analysis
• Transaction frequency patterns

Provides recommendations for:

• Stablecoin Selection: Best stablecoin per chain based on liquidity and regional fit
• Bridge Recommendations: When to move assets between chains (with break-even analysis)
• Timing Optimization: Best days/times to execute conversions
• Fiat Distribution: Optimal allocation when converting fiat to stablecoins

Key calculations:

• Average monthly gas costs: mean(historicalGasCosts) × monthlyFrequency
• Volatility: stdDev(gasCosts) / avgGasCost
• Bridge savings: (currentMonthlyCost - targetMonthlyCost) × 6 - bridgeCost
• Stablecoin scoring: Liquidity (40%) + Fees (30%) + Regional fit (20%) + Stability (10%)

# Install dependencies
pnpm install
cd server && npm install && cd ..

# Set up environment (.env file)
ANTHROPIC_API_KEY=sk-ant-api03-...
EXPO_PUBLIC_COINGECKO_API_KEY=your-key
BACKEND_URL=http://localhost:8000

# Start proxy server and app
npm run dev

# Or separately:
npm run server  # Proxy on port 3000
npm start       # Expo dev server

Frontend (React Native + Expo)
    ↓ Proxy requests
Express Proxy (Port 3000)
    ↓ Forward to backend
Backend API (Port 8000)
    ↓ Fetch data
External APIs (CoinGecko, Solana RPC)

State Management: Context API (Wallet, Transactions, Settings, Theme)
Storage: expo-secure-store (encrypted wallets), AsyncStorage (preferences)

app/                    # Screens (Expo Router)
  (tabs)/              # Tab navigation
  send.tsx, receive.tsx, convert.tsx, etc.
contexts/              # State management
utils/                 # Core logic and APIs
server/                # Express proxy

POST /api/evaluate_path
{ "from_currency": "USDC", "to_currency": "ARS", "amount": 100 }

Response: { "path": ["USDC", "SOL", "ARS"], "final_amount": 110000, 
           "total_fee_ars": 2.50, "hops": [...] }

POST /api/claude
{ "model": "claude-3-haiku-20240307", "messages": [...] }

Web: npx expo export:web → deploy web-build/
Mobile: eas build --platform ios/android → eas submit

Required:

• ANTHROPIC_API_KEY - AI features
• BACKEND_URL - Backend API endpoint

Optional:

• EXPO_PUBLIC_COINGECKO_API_KEY - Higher API rate limits
• EXPO_PUBLIC_PROXY_URL - Custom proxy URL

• Proxy issues: Check port 3000 is free, verify firewall
• Wallet not loading: Clear app data, check password
• AI features failing: Verify ANTHROPIC_API_KEY
• Slow path evaluation: Check network and backend API

1. Fork → 2. Create feature branch → 3. Commit → 4. Push → 5. PR

Built for MadHacks 2025 | Stack: React Native, Expo, Solana, Claude AI