BlockBatchClearing

How it works

Almost all of what is called MEV is the value of being first. A continuous market prices each order at the state the one before it left behind, so the right to arrive earlier is worth money, and that right is sold. Batch auctions were proposed for exactly this in the equities literature, and the answer they give is not to police the ordering but to abolish it: collect every order in an interval and clear them all at one uniform price.

Being first in a batch is worth nothing, because there is no first. CoW Protocol runs that design with a network of solvers off-chain. Doing it on-chain has needed a solver too, since a uniform price for a batch against a bonded curve looks like a fixed point: the price depends on the net trade, and the net trade depends on the price.

For a constant-product pool it is not a fixed point. Requiring that both sides clear at one price `p` and that the invariant hold gives a quadratic in `p` with an exact solution, and this hook solves it in closed form. There is no solver, no auction, no bond and nobody to trust with the ordering.

What falls out of it is the part traders will notice. Orders in opposite directions settle against each other before the curve is touched at all, so matched flow pays no slippage whatsoever; only the imbalance moves the price. A block where buyers and sellers are evenly matched clears at the spot price for everybody, which is a thing a continuous AMM cannot do at any size.

The cost is that a swap does not return tokens. It returns a claim on a batch that has not cleared yet, and the trader collects afterwards. That is the honest price of not having an ordering to sell.

Using it

Uniswap v4 removed hookData from initialize, so per-pool parameters arrive out of band. Fix them for a pool key whose pool does not exist yet, then initialize. Nobody can change them afterwards, including you.

poolManager.initialize(key, startingSqrtPriceX96);

Parameters

This hook takes no per-pool configuration.

From TypeScript

npm i @hookforge/sdk

import {getHook, hookAddress, poolKeyFor} from "@hookforge/sdk";

const hook = getHook("block-batch-clearing");
const key  = poolKeyFor({
  hook: hookAddress("block-batch-clearing", 8453),   // Base
  currencyA: USDC, currencyB: WETH,
  tickSpacing: 60,
});

What it reverts with

The callbacks it claims

Uniswap v4 reads a hook's permissions from the low fourteen bits of its own address, which is why deploying one means mining a CREATE2 salt. This hook claims 5, so every deployment of it has an address ending in 0x2a88.

• beforeInitialize
• afterInitialize
• beforeAddLiquidity
• afterAddLiquidity
• beforeRemoveLiquidity
• afterRemoveLiquidity
• beforeSwap
• afterSwap
• beforeDonate
• afterDonate
• beforeSwapReturnsDelta
• afterSwapReturnsDelta
• afterAddLiquidityReturnsDelta
• afterRemoveLiquidityReturnsDelta

It says what it is, on-chain

Nothing about a hook's address tells an indexer, a wallet, a router or an agent what the pool does, which is why hook discovery today is a curated list. This hook answers for itself, in one eth_call, with no registry in the loop.

cast call $HOOK "hookName()(string)"    # BlockBatchClearing
cast call $HOOK "specURI()(string)"     # https://block-batch-clearing.pages.dev/hook.json
cast call $HOOK "hookTags()(string[])"  # mev, batch-auction, uniform-price, order-flow, no-admin

Build, test and deploy

git clone --recurse-submodules https://github.com/nirholas/block-batch-clearing
cd block-batch-clearing
forge build && forge test

# Dry run: mines the salt, prints the address, sends nothing.
forge script script/Deploy.s.sol --rpc-url $RPC_URL

# For real.
forge script script/Deploy.s.sol --rpc-url $RPC_URL --broadcast --verify

Try it

This is the hook running, not a picture of it. Connect a wallet on a chain it is deployed to, or bring the whole stack up locally in one command and use it with no funds and no wallet risk at all.

git clone --recurse-submodules https://github.com/nirholas/block-batch-clearing
cd block-batch-clearing

anvil &
forge script script/DeployLocal.s.sol --rpc-url http://127.0.0.1:8545 --broadcast \
  --private-key 0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80

node web/build.mjs && npx serve web/dist