Smart Contracts

SellPolia runs on three purpose-built contracts, one per role, deployed across the sell chain (Sepolia) and the payment/payout chains.

Contract	Chain(s)	Role
SethVault	Sepolia	Holds seller deposits + house reserve; delivers sold SETH to buyers.
PaymentCollector	Payment chains (Base, …)	Takes and prices buyer payments; emits the purchase event.
Payout	Base	Pays sellers in ETH from their USD-owed balances.

Deployed addresses are on the Deployed Addresses page.

Shared design

All three contracts share a common structure:

Upgradeable via proxy. Each is deployed behind a minimal EIP-1967 transparent proxy (Proxy.sol). The implementation is initialized with an initialize(...) call rather than a constructor (the constructor only locks the implementation). The proxy admin (who can upgrade) and the owner (who operates the contract) are always distinct addresses.
Simple ownership. Privileged actions are guarded by onlyOwner, and ownership can be transferred with changeOwner(newOwner) (emits OwnerChanged). A version() getter returns the implementation version.
Chainlink pricing. The PaymentCollector and Payout contracts read USD prices from Chainlink feeds and require the feed to report 8 decimals, with staleness and sanity checks on every read.

Units

SETH and ETH use 18 decimals (1e18 raw = 1 coin).
USD values use 8 decimals (1e8 raw = $1.00), matching Chainlink.
Stablecoin decimals vary by token/chain (USDC/USDT are usually 6; DAI is 18) — the collector stores each token’s decimals so amounts convert correctly.

Source

The Solidity sources live in the repo under contracts/contracts/: SethVault.sol, PaymentCollector.sol, Payout.sol, Proxy.sol, and IEthUsdPriceFeed.sol.