🪙 SplitMon — Onchain Bill Splitter on Monad

Split expenses with friends, settle via smart contract. No more chasing people for money.

Built for the BuildAnything Spark Hackathon — vibecoded with ❤️

The Problem

You go out for dinner with 5 friends. The bill is 3 MON. You pay upfront... and then spend the next week DMing everyone "hey, can you send me 0.6 MON?"

SplitMon fixes this. One person creates a split, friends pay their share to a smart contract, and funds are released automatically. No awkward reminders. No forgotten IOUs.

How It Works

Step	Action	Description
1	Create	Set amount, add friends' addresses, fund the split
2	Share	Give friends the Split ID — they pay directly
3	Settle	All paid? Funds auto-release to creator
4	Refund	Deadline passed? Everyone gets their money back

Partial Release

If at least 2 people have paid but not everyone, the creator can release partial funds — collect what's been paid so far while the rest stays open for refunds.

Smart Contract

Address: 0x9f8b012407bF1D84055828dA60aD0B6F7D6891e5
Network: Monad Testnet (Chain ID: 10143)
Explorer: Monad Testnet Explorer

Functions

Function	Description
createSplit(participants[], deadline, title)	Create a new split (payable)
payShare(splitId)	Pay your share
releaseFunds(splitId)	Creator releases partial funds (≥2 paid)
refund(splitId)	Claim refund after deadline
getSplit(splitId)	View full split details
splitCount()	Total splits created

Events

• SplitCreated — New split created
• PaymentMade — Participant paid their share
• PartialRelease — Creator released partial funds
• SplitSettled — All paid, funds released
• SplitRefunded — Everyone refunded
• ParticipantRefunded — Individual refund claimed

Tech Stack

• Smart Contract: Solidity 0.8.20 + Foundry
• Frontend: Next.js 14 + TypeScript + Tailwind CSS
• Web3: Wagmi v2 + Viem

Quick Start

# Clone
git clone https://github.com/EVM0x/splitmon.git
cd splitmon

# Smart contract
forge build

# Frontend
cd frontend
npm install
npm run dev

Deploy

forge create \
  --rpc-url https://testnet-rpc.monad.xyz \
  --private-key $PRIVATE_KEY \
  contracts/SplitMon.sol:SplitMon

Security

• ✅ No reentrancy vectors (checks-effects-interactions pattern)
• ✅ Timeout protection prevents locked funds
• ✅ Only creator can release funds
• ✅ Only participants can pay or refund

License

MIT — Built for the BuildAnything Spark Hackathon