Qian is a multichain exchange and payments layer for every asset. This repo holds what Qian runs on Arc, Circle's stablecoin-native L1, during its public testnet: QianPay, the payment-settlement contract behind qian.ag/pay. MIT licensed. No proxies, and no admin key over user funds.

Gas on Arc is USDC, so a payment settles without the payer ever holding a separate gas token. The rest of the Qian stack follows when Arc reaches mainnet.

Deployed addresses

Contract	Address
QianPay	`0x73Da198D58fFD43B5754a2d72D989cab1c9aF0ce`

Source-verified on https://testnet.arcscan.app.

How it works

QianPay settles payment links: pay a fixed USDC amount straight to a wallet. Stateless, no admin functions, 0.5% platform fee on the USDC side. On chains with Uniswap V3 it also accepts any token a V3 path can turn into USDC; Arc testnet has no canonical Uniswap deployment yet, so the swapRouter02 constructor slot holds an inert placeholder and only payUSDC is active. Same source as the Base deployment.

Layout

dtm-v4/contracts: QianPay and the interfaces it calls
chains/: chain config and the deployed address

Build

Solidity 0.8.24 with the optimizer on (1 run, viaIR enabled). The exact verified build lives on https://testnet.arcscan.app; this repo is the plain-source mirror.

Dependencies

OpenZeppelin (SafeERC20, ReentrancyGuard) and the Uniswap V3 router interface, kept in-tree under dtm-v4/contracts/interfaces. No forked or vendored AMM code.

Security

See SECURITY.md for the security model, the design tradeoffs, and how to report a vulnerability.

License

MIT. Contact: [email protected]