Overview

1 A batch every few seconds

Orders gather in a batch for 2 rounds of the drand beacon, about 6 seconds by default. Each batch is named by the round at which it opens.

While a batch is open, it holds seals: commitments whose contents nobody can read, the venue included. When the beacon publishes the batch's round, every order in it becomes readable to everyone at the same moment.

Opposite orders on a pair cross at one price. Solvers bid for what is left over, the net, and route it. The program checks the clearing before a token moves, and every fill on the pair gets the same batch price.

2 Why a batch

On Solana today a swap's place in the block decides its price, so that place can be bought. Inside a batch there is no first and no last: the contents are sealed until the whole batch opens, and the price is set by the batch, not by where an order fell.

This is the call auction, the structure equity markets use for their closing price, run every few seconds and sealed with cryptography instead of trust in whoever holds the book.

3 The steps

• Seal — the order is encrypted in the browser to the batch's opening round and committed with one signature.
• Close — the batch stops taking seals a margin ahead of the round.
• Open — the beacon publishes the round; an opener posts every plaintext, and the program checks each against its seal.
• Bid — solvers cross each pair, price the net and bid, backed by a bond.
• Clear — the bid that leaves the orders the most surplus wins and clears in one transaction.
• Settle — a permissionless crank credits every fill at the batch price.

4 Where it comes from

Vitalik Buterin's essay “The cryptographic world computer” (2026-09-27) argues for a stronger decentralized layer in the middle between users and a chain: work sealed, opened together, cleared by open parties and verified. Unison builds that layer as an exchange.