The execution layer for Robinhood Chain. A protected JSON-RPC gateway, a sealed-bid second-price backrun auction with signed and anchored outcomes, trust-minimised on-chain settlement, a sequencer feed relay, and the measurement that makes the numbers checkable. Overview# Robinhood Chain is an Arbitrum Nitro rollup with a single, first-come-first-served sequencer and no public mempool. Blocks arrive every ~100 ms. That combination changes what MEV looks like: nobody can front-run a pending transaction, because there is no pending set to read. What exists instead is a latency race to backrun: the sequencer feed reveals each transaction the instant it is ordered, and bots compete to trade immediately after anything that moves a pool. OrdoFi sits between the user and the sequencer and does three things with that fact: Protect the submission Every raw transaction is simulated from its recovered sender before it is forwarded. A transaction that would revert is refused and never pays gas. Nothing is broadcast to a third-party provider on the way; sends go to the sequencer operator's endpoint. Auction the backrun If a transaction touches a pool, the right to trade right after it is sold in a sealed-bid, second-price auction that closes in 200 ms. The user's transaction is dispatched first, then the winner's. The clearing price is charged on-chain and 90% returns as rebates. Make it checkable Bids are acknowledged and rounds are receipted under EIP-712 signatures from the auctioneer; receipts are Merkle-anchored to OrdoReceiptLog. An independent watcher measures backrun extraction across every venue and publishes it.