NexusPay

The PYUSD Cross-Chain Nexus Bridge is a revolutionary DeFi application that solves the critical problem of fragmented liquidity across blockchain networks. Built for ETH Online 2025, this next-generation bridge enables seamless PYUSD token transfers between different chains with a single transaction, eliminating the complexity of traditional bridge mechanisms. Key Features:

Unified Cross-Chain Portfolio: Real-time PYUSD balance aggregation across Ethereum Sepolia, Arbitrum Sepolia, and Polygon Amoy testnets with live updates and automatic refreshing One-Click Cross-Chain Transfers: Transfer PYUSD between chains using Avail Nexus SDK's intent-based architecture for optimal routing and minimal friction Advanced Nexus Integration: Full lifecycle management of cross-chain intents with real-time monitoring, event hooks, and failsafe mechanisms Production-Ready PYUSD Support: Direct ERC-20 contract interactions with actual PYUSD testnet deployments (0xCaC524BcA292aaade2DF8A05cC58F0a65B1B3bB9 on Sepolia, 0x637A1259C6afd7E3AdF63993cA7E58BB438aB1B1 on Arbitrum Sepolia)

How it's made

This project showcases cutting-edge Web3 technology integration, combining multiple advanced frameworks and protocols to create a seamless cross-chain experience.

Frontend Architecture: Built with Next.js 15.5.4 and React 19.1.0 using the latest App Router pattern, providing server-side rendering and optimal performance. The entire codebase is written in TypeScript 5 for complete type safety and superior developer experience with modern React concurrent features.

Web3 Infrastructure: The application leverages Wagmi 2.18.2 and Viem 2.38.3 for type-safe Ethereum interactions with a lightweight client architecture. ConnectKit 1.9.1 provides a beautiful, accessible wallet connection UI with automatic provider detection. The system manages simultaneous connections to multiple testnets including Ethereum Sepolia, Arbitrum Sepolia, and Polygon Amoy.

Avail Nexus SDK Integration (Core Innovation): The heart of the application is the deep integration with Avail Nexus Core v0.0.1, implementing the complete intent-based cross-chain architecture. The system creates a sophisticated Nexus Provider that manages the SDK lifecycle with real-time intent monitoring and event hook management. The implementation includes advanced features like intent approval/denial UI with fee calculations, token allowance management for cross-chain operations, and comprehensive error handling for development environments including certificate issues.

PYUSD Multi-Chain Implementation: Created a custom PYUSDMultiChainSDK that aggregates balances across all supported testnets using parallel balance fetching across multiple chains. The system implements direct ERC-20 interactions with actual PYUSD testnet contracts on Ethereum Sepolia and Arbitrum Sepolia. The multi-chain balance manager provides real-time synchronization and automatic cache invalidation for optimal performance.

Smart Contract Integration: The application features direct ERC-20 interactions with actual PYUSD testnet contracts deployed on multiple networks. Contract addresses are dynamically managed with support for Ethereum Sepolia and Arbitrum Sepolia testnets. The system includes robust error handling for unsupported chains and automatic contract validation.

Hardhat 3.0+ Development Environment: Leveraged Hardhat v3.0.9 with advanced network forking capabilities for comprehensive testing. The development environment supports local testing with real contract states without spending testnet gas fees through sophisticated network forking configuration. This enables rapid iteration and cost-effective testing of complex cross-chain scenarios.

Real-Time Transaction Monitoring: Implemented comprehensive transaction listening with custom hooks that provide step-by-step progress updates for bridge operations. The system tracks swap completion, verification steps, and automatically generates explorer links. Transaction status updates are provided in real-time with visual progress indicators and detailed error reporting.

UI/UX Design System: The application features a modern lavender-themed design system built with Tailwind CSS 4 and Radix UI accessible component primitives. The design implements glass morphism effects with backdrop blur, gradient overlays for visual depth, and mobile-first responsive layouts. The interface includes micro-interactions, smooth hover states, and comprehensive error prevention through smart form validation.

Cross-Chain State Management: Developed sophisticated state management for multi-chain operations including synchronized balance updates across multiple blockchain networks, automatic cache invalidation, and real-time transaction status tracking. The system handles complex scenarios like chain switching, allowance management, and cross-chain transfer orchestration.

Particularly Notable Technical Achievements:

Intent-Based Architecture Implementation: Full implementation of Nexus SDK's intent system with real-time status updates, automatic retry mechanisms, and comprehensive lifecycle management from creation to execution.

Certificate Handling & Error Recovery: Robust error handling specifically designed for Nexus backend certificate issues in development environments, ensuring smooth developer experience while maintaining production readiness.

Multi-Chain Balance Aggregation: Sophisticated balance management system that aggregates PYUSD holdings across multiple testnets with real-time updates and intelligent caching strategies.

Transaction Flow Orchestration: Seamless integration of wallet management, chain switching, allowance handling, and cross-chain transfer execution in a unified user experience.

Production-Ready Architecture: The entire system is designed for scalability with modular components, comprehensive error handling, and easy network addition capabilities for future expansion.

The project demonstrates production-ready integration of emerging cross-chain technologies while maintaining excellent user experience, comprehensive error handling, and scalable architecture that can easily accommodate additional blockchain networks and features.