Programmatic native-USDC payout splitter + cancellable time-locked vault for Arc Mainnet. Built for Circle's Arc Microgrants (DoraHacks).

Two primitives, one gas-cheap contract:

• executeSplit — atomic multi-recipient payout by percentage (basis points, so 33.33% works). Dust-safe: the final recipient absorbs any rounding remainder, so the contract never strands value.
• executeSplitAmounts — same, but by exact per-recipient USDC amounts; the sum must equal msg.value, so every payout is precise. The web app toggles between % and $ modes over these two functions.
• Escrow vault — sender locks USDC for a recipient until releaseTime.
  • After the lock: recipient (or sender) calls releaseEscrow → pays recipient.
  • Before the lock: sender calls refundEscrow → reclaims funds.
  • Honest scope: this is a cancellable time-locked vault, not milestone or multi-sig escrow. Don't market it as more than it is.

All value functions carry a nonReentrant guard and follow checks-effects-interactions.

Live dApp: https://splitpay-arc-eight.vercel.app (wired to the testnet contract below)

Verified on testnet: executeSplit (70/30 → exact payouts), createEscrow

• releaseEscrow (recipient paid after lock), and createEscrow + refundEscrow (sender reclaimed before lock). This also confirms Arc's native-USDC model works with msg.value / .call{value:} as assumed.

⚠️ Recipient addresses must be plain EOAs. executeSplit and releaseEscrow use push payments, so a recipient that is a contract rejecting value — or a swept public-key address (e.g. default Anvil/Hardhat accounts, whose keys are public and get drained by bots on live networks) — makes the transfer revert with "Transfer failed". Use real wallets.

Gas token = USDC. Native gas is USDC — one balance, two interfaces:

• ERC-20 view: 6 decimals (use for balances/transfers/UI display)
• Native/gas view: 18 decimals (msg.value, gas math)
• USDC token address (both nets): 0x3600000000000000000000000000000000000000
• CCTP domain: 26

This contract moves value via msg.value, which is the 18-decimal native view. To split $10, send value = parseEther("10") (= 10 × 10¹⁸), not 10 × 10⁶. viem's built-in arc / arcTestnet chain configs already define the native currency as 18 decimals, so parseEther is correct. Only drop to 6 decimals when displaying USDC balances or calling the ERC-20 interface.

Install Foundry (Windows: use Git Bash or WSL):

curl -L https://foundry.paradigm.xyz | bash
foundryup

Install deps and configure env:

forge install foundry-rs/forge-std
cp .env.example .env       # then fill in PRIVATE_KEY

forge build
forge test -vvv

The test suite covers: even splits, dust conservation, bps/array/zero-value validation, escrow release after lock, refund before lock, and all the unauthorized / double-finalize revert paths.

Testnet first (free — fund the deployer at https://faucet.circle.com):

forge script script/Deploy.s.sol:Deploy --rpc-url arc_testnet --broadcast

Mainnet (spends REAL USDC gas — only when ready to submit):

forge script script/Deploy.s.sol:Deploy --rpc-url arc_mainnet --broadcast

To fund the mainnet deployer, bridge a few dollars of USDC to Arc via Circle CCTP: https://developers.circle.com/cctp/quickstarts/transfer-usdc-ethereum-to-arc

• Push payments: executeSplit sends to each recipient directly, so a recipient contract that reverts on receive would block the whole split. Fine for wallet recipients; a v2 would use a pull-withdraw pattern.
• Vault is time-based only: no work-verification or dispute resolution — the recipient is guaranteed payment after the lock expires, and the sender can cancel before it.