Uniswap Labs has launched StablePair Hook with two Ethereum pools after stablecoin swaps on Uniswap reached $43.4 billion during the second quarter.

Uniswap Labs said on Sept. 10 that the Uniswap v4 tool replaces a static liquidity provider fee with a fee calculated for every swap. The first pools pair USDC with USDT and Global Dollar, or USDG.

Both pools use a reference rate of 1:1. The system measures how far the pool price has moved from that rate and whether a proposed transaction pushes the price closer to or farther from it.

The company says the mechanism gives liquidity providers a larger share of the value generated when traders correct price differences. StablePair Hook does not guarantee better returns, since results still depend on trading activity, liquidity depth, asset prices and the parameters approved for each pool.

StablePair Hook changes fees with pool conditions

Stablecoin pools usually contain assets designed to maintain the same dollar value. Market activity can still move a pool away from parity, creating an opportunity for arbitrageurs to trade against the price difference.

With a fixed fee, Uniswap Labs says pool operators face a trade-off. A low fee may allow arbitrage bots to retain more of the available price difference, while a high fee may discourage ordinary transactions.

StablePair Hook changes the fee according to the pool’s position relative to a configured reference price. Inside a narrow band around that price, the mechanism adjusts fees to maintain a fixed spread between quoted buying and selling prices.

Once the pool leaves the band, the treatment depends on the direction of the next swap. A transaction that moves the pool farther from the reference rate pays no liquidity provider fee because it gives the pool what Uniswap describes as a favorable price.

A swap bringing the pool back toward parity enters a Dutch auction. Its fee begins at a high level and falls with each Ethereum block until a trader accepts the available price.

“LPs keep the difference,” Uniswap Labs said when describing the auction system. The statement expresses the developer’s expected outcome for liquidity providers, not a guaranteed level of fee income.

Two Uniswap stablecoin pools are operating on Ethereum

Uniswap’s public code repository records the USDC/USDT and USDC/USDG pools as initialized on Ethereum on Sept. 10. Both use the dynamic-fee flag and a tick spacing of one.

The USDC/USDT pool has an onchain identifier ending in e39f634, while the USDC/USDG pool identifier ends in b7edb. Uniswap’s developer materials advise applications to derive pool identifiers from their pool keys instead of hard-coding them.

At the contract level, StablePair Hook operates through an ERC-1967 proxy. Its permanent Ethereum hook address encodes the permissions available to the contract, while governance can replace the implementation behind the proxy.

Pool fee configurations and future implementation upgrades are controlled by the Uniswap Governance Timelock, according to the project’s repository. A separate Uniswap Labs multisignature wallet can create pools and assign their initial fee parameters but cannot upgrade the contract or modify existing configurations.

StablePair pools cannot be created permissionlessly. Uniswap Labs controls their initial creation, distinguishing the product from v4 pools that any user can initialize without prior approval.

The launch extends Uniswap v4’s use of custom hooks, which attach external contracts to pools and change their behavior at defined points in a transaction. Hooks can control fees, pricing logic and access rules without changing the v4 core contracts.

In related coverage, Uniswap v4 became the largest DeFi venue for tokenized-stock deposits after its measured total reached $59.1 million in early September. StablePair Hook applies the same customizable pool architecture to assets expected to trade near an established exchange rate.

An OpenZeppelin review found and fixed a fee issue

OpenZeppelin reviewed the core StablePair fee mechanism from Feb. 9 through Feb. 13, according to Uniswap’s security documentation. The assessment covered a non-upgradeable predecessor that uses the same main fee calculations.

During the review, OpenZeppelin identified one high-severity issue involving corrective swaps. A trader could obtain a cheaper combined price by dividing one corrective transaction into several smaller swaps.

Uniswap says it addressed the finding by caching the pool price once per block. Every swap within the same block uses the cached starting price when calculating its fee, removing the fee advantage previously available from splitting a transaction.

The review did not cover the current upgrade system or its role structure because those components were introduced later. Uniswap’s published security page identifies the scope difference, meaning the cited audit should not be treated as a full assessment of every component in the live version.

Price caching creates two documented limitations. Later swaps during a busy block may use a starting price that no longer matches the pool’s latest price, while a swap crossing the reference rate can invert fee directions for the rest of the block.

Uniswap says both conditions last for one block and correct themselves when the next cached price is recorded. The documentation states that removing either limitation would restore the transaction-splitting opportunity addressed after the OpenZeppelin review.

Governance controls future StablePair Hook upgrades

Uniswap Governance can modify pool fee settings and replace the hook’s implementation without moving liquidity into a different pool. A configuration change resets the fee-decay process, causing the following swap to use a fresh pool-price reading.

Permissions embedded in the permanent hook address limit what an upgrade can do. Uniswap says the contract cannot prevent liquidity providers from withdrawing assets or change swap amounts to collect unapproved fees because the required callback permissions are disabled.

Quote calculations carry separate limits. The hook’s getFee function returns the current liquidity provider fee using the same start-of-block price that the next transaction will receive. It excludes protocol fees, ignores the size of the trade and does not calculate the price effect caused by moving through available liquidity.

Large trades may therefore execute at a different average price from the initial quote. The difference depends on the depth and distribution of liquidity in the pool, according to the project’s technical documentation.

StablePair Hook joins other custom tools developed for Uniswap v4, including DualPool, LitePSM and Permissioned Pools. As previously reported, Uniswap’s work on correlated tokenized-asset pools processed $33 million across 10 stock-to-SPY markets during their first 12 days.

Uniswap Labs has released the hook’s contracts and tests through its public GitHub repository under an MIT license. Its developer documentation lists the mainnet proxy address, current implementation address, two pool identifiers and a security contact for reporting contract issues.