Payos

Payos is a decentralized, cross-chain bill splitting platform that enables groups to split expenses across Ethereum, Arbitrum, Optimism, and Base networks. Users create a split with multiple contributors, define amounts per person, and recipients receive funds once targets are met. Contributors can use ETH, USDC, or PYUSD from any supported chain, with Avail Nexus SDK handling bridging and conversions. The platform solves the problem of cross-chain bill splitting by allowing: No coordination - create on one chain, contribute from any chain Multi-token support for flexibility Automatic settlement when targets are reached Trustless operation via immutable smart contracts No platform fees - users only pay gas

Smart Contract Layer (Solidity + Foundry) PayosSplit.sol — Solidity 0.8.20 deployed with CREATE2 at 0x3bdeD6E96eeeB7858701A0291dBA9A84c8b9D801 across all chains Uses OpenZeppelin (Ownable, ReentrancyGuard, SafeERC20) Oracle/relayer pattern: owner-only contributeToBill() for off-chain contribution recording

Frontend (Next.js 15 + React 19 + TypeScript)

Next.js 15 App Router, React 19 with TypeScript Privy for wallet auth; Wagmi + Viem for Ethereum MongoDB for split metadata Tailwind CSS 4 with custom theme variables TanStack Query for server state

Integrations: Avail Nexus SDK: handles cross-chain token bridging and execution PYUSD: settlement currency configured on all four testnets

Architecture Highlights: Deterministic deployment ensures the same contract address on all chains Oracle pattern bridges on-chain state with cross-chain transactions MongoDB caching for quick queries while verifying against on-chain data Focus on UX with clear flows and sensible theme design

The hybrid system manages cross-chain splits, handles bridging/conversion, and settles funds without centralized intermediaries.