Opto

Opto is an innovative cross-chain atomic swap solution built for the ETH Sepolia ↔ Sui testnet. It successfully extends the 1inch Fusion+ protocol to the Sui ecosystem, enabling bidirectional atomic swaps between Ethereum and Sui using a Hashed Timelock Contract (HTLC) mechanism. This approach provides a secure and efficient decentralized trading experience.

We also built a comprehensive UI that visualizes all ETH Sepolia ↔ Sui testnet swap activities, ensuring everything works correctly and remains easy to understand.

Our cross-chain swap implementation merges two distinct on-chain environments:

Ethereum (Sepolia) We integrate 1inch’s Limit Order Protocol and Dutch-auction smart contracts to handle intent-based order creation, competitive bidding, partial fills, and settlement. All contracts enforce a hashlock/timelock escrow: funds are locked against a SHA-256 preimage and automatically refunded if unclaimed before timeout.

Sui (Testnet) We developed parallel Move modules—packaged in our sui-fusion-sdk(https://github.com/abcd5251/1inch-on-sui/tree/main/packages/sui-fusion-sdk)—that replicate the same HTLC escrow guarantees in Sui’s non-EVM execution model. Each module exposes functions to initiate swaps, verify secrets, and enforce timeouts.

Off-Chain Relayer At the core lies a unified Node.js relayer service (relayer)[https://github.com/abcd5251/1inch-on-sui/tree/main/packages/relayer] that continuously monitors both Ethereum and Sui full-nodes:

Event Detection

Listens for AuctionStarted or HTLC creation events on the source chain.

Preimage Handling

Fetches the secret from on-chain logs or computes it via the SDK’s intent parameters.

Cross-Chain Transaction Generation

Serializes and signs the claim transaction for the target chain, converting between EVM ABI and Sui BCS.

Conclusion By combining proven 1inch Fusion+ auction mechanics on Ethereum with bespoke Move-based HTLC logic on Sui, and orchestrating them via our custom relayer, we deliver a robust, end-to-end cross-chain swap engine. The comprehensive TypeScript SDK and clear abstractions empower developers to integrate this functionality seamlessly into any dApp.