Plumb

Plumb is an onchain escrow for rent withheld over housing violations. When a NYC tenant's apartment has an open HPD (Housing Preservation & Development) violation, their rent is locked in a USDC escrow on Arc instead of flowing to the landlord. A Chainlink CRE oracle checks the violation's real status against NYC's official open-data feed and posts the verified outcome onchain, which settles the escrow automatically: if the landlord fixes the issue (violation Closed), the contractor who did the repair is paid their fee and the landlord receives the remaining rent; if the violation is Dismissed, the landlord is made whole. Any yield earned on the locked funds always goes to the tenant. No party can release the money unilaterally — settlement is driven only by the city's own verified data.

The core is a Solidity EscrowVault on Arc testnet (chain 5042002) holding USDC — Arc's native gas token, 6 decimals — which it deposits into a yield source for the lock period and settles per-escrow through an oracle-gated updateStatus(). The real-world data comes from a Chainlink CRE (Chainlink Runtime Environment) workflow in TypeScript: a cron job polls NYC's HPD Housing Maintenance Code Violations dataset (Socrata wvxf-dwi5) by violationId, maps violationstatus/currentstatus to an onchain Status enum (Open/Closed/Dismissed), and delivers a signed report through the Chainlink Keystone forwarder to an EscrowVaultReceiver that inherits Chainlink's ReceiverTemplate and is registered as the vault's authorized oracle. The frontend is Next.js + Privy (embedded wallets) + viem. Two things worth noting: we vendored Chainlink's ReceiverTemplate/IReceiver verbatim from the official docs rather than reconstructing them, so the auth and interface match upstream exactly; and we proved the full loop end-to-end in CRE simulation against live HPD data — using the Arc MockForwarder, a real corrected violation (ID 18100032) drove escrow #1 to settle onchain, with the contractor/landlord/tenant payouts verified by reading contract state, not logs. The production path swaps the MockForwarder for the live KeystoneForwarder (DON-signed reports).