Lightsplit

Lightsplit is a convenient bill-splitting tool that uses USDC payments, allowing users to easily share expenses in group chats. No additional app download is required—create a split group, track expenses, and it automatically calculates each person’s share. It’s ideal for scenarios like traveling with friends, splitting household costs with roommates, or group purchases with colleagues, making the process quick and simple.

Our project, Lightsplit, solves a real-world pain point: splitting bills with friends without the mess of multiple transactions or copying wallet addresses. Picture this: you’re at dinner with three friends, and the bill’s $100. With Lightsplit, we use USDC to split it—$25 each—settled on-chain in one smooth move. The secret sauce? We built a multicall contract with ERC-7702 to pack all USDC transfers into one transaction. Normally, you’d send USDC to each friend individually, pasting their addresses one by one—a total drag. Our multicall contract batches it (25 USDC to Alice, Bob, and Charlie) and fires it off together. ERC-7702 takes it up a notch by letting your wallet temporarily act as a smart contract, embedding the multicall logic right into the transaction. No copying addresses, no extra steps—just sign once, and everyone’s paid. We hooked this up with ethers.js and Circle’s USDC API, running on Ethereum’s Sepolia testnet. For the hackathon, we got hacky: we pre-loaded friends’ addresses into the ERC-7702 contract_code field from a quick JSON config—zero manual input. Real-world case? A $100 dinner bill split four ways in seconds—faster than cash apps, cheaper than separate gas fees, and way slicker than passing around wallet QR codes.