SettleOne

SettleOne is a unified payment interface designed to solve the fragmentation and high cost of DeFi transactions. It combines off-chain state channels, identity resolution, and batched settlement into a seamless "checkout" experience for crypto payments.

Instead of signing a transaction and paying gas for every single payment, users open a session (powered by Yellow Network state channels) where they can queue unlimited USDC payments off-chain instantly and gas-free. We integrate ENS deeply into the UI, allowing users to pay human-readable names like vitalik.eth instead of error-prone hex addresses.

When the session ends, SettleOne aggregates all pending transfers and executes a single, atomic transaction on Base Sepolia using our custom SessionSettlement smart contract. This reduces gas costs by up to 90% compared to individual transfers. For cross-chain needs, we integrate LI.FI to automatically route funds across networks.

SettleOne transforms crypto payments from a series of stressful transactions into a single, secure settlement.

We built SettleOne using a modern stack optimized for speed and security. Frontend: Built with Next.js 16, React 19, and Tailwind CSS. We use wagmi and viem for blockchain interactions. The core "magic" lies in our integration of the Yellow Network SDK (@erc7824/nitrolite).

We implemented a custom hook useYellow that manages WebSocket connections to Yellow's ClearNode, handling authentication (challenge-response), session creation, and state updates. This allows us to maintain a secure off-chain ledger of payments in real-time.

Backend: A robust Rust (Axum) server acts as our orchestrator. It handles:

1. Identity: A custom EnsService that queries the ensdata.net API with TTL-based caching to resolve names instantly without hitting rate limits or mainnet RPCs unnecessarily.
2. Cross-Chain: A proxy service for LI.FI API to fetch bridging quotes securely.
3. State: An in-memory session store (using Arc<RwLock>) that persists session state across UI reloads.

Smart Contracts: We deployed our SessionSettlement.sol contract on Base Sepolia using Hardhat. It features:

• Circle / Arc Compatibility: Designed for USDC.
• Security: ReentrancyGuard, SafeERC20, and explicit integer overflow checks (unchecked blocks with validation) to safely handle batched amounts.
• Gas Optimization: Custom errors instead of strings.

Partner Tech Highlights:

• Yellow Network: Their state channels enabled the "instant queuing" UX. We hacked around the WebSocket disconnect behavior by implementing a custom "confirmation wait" loop to ensure the off-chain state was fully synced before allowing on-chain settlement.
• ENS: We built a dual-layer resolution system (Frontend immediate + Backend verified) to ensure 100% uptime for name lookups.
• Circle: We utilized the transferFrom pattern to allow a single user signature to distribute funds to N recipients atomically.