Uniswap Labs announced on September 10 that its StablePair Hook was live on Ethereum mainnet, initially serving USDC/USDG and USDC/USDT pools. The Uniswap v4 add-on changes trading fees according to a pool's price relative to a reference rate. blog.uniswap.org
Within a narrow band around that rate, fees adjust to quote a fixed bid-ask spread. Outside the band, swaps that move the price farther away pay no liquidity-provider fee. Swaps that bring it back face a fee that starts high and falls each block until someone trades, leaving more of the adjustment value for liquidity providers under the design. blog.uniswap.org
Uniswap Governance controls upgrades to the implementation and changes to pool fee settings. The security documentation says the hook's fixed permissions prevent upgrades from blocking liquidity withdrawals or altering swap amounts to skim additional fees. developers.uniswap.org
That documentation also limits what the cited security review establishes. OpenZeppelin's February review covered the fee mechanism in a non-upgradeable predecessor. The upgradeability and role model came afterward, so that review does not establish coverage of the current governance arrangement. developers.uniswap.org
Quotes also have limits. The hook uses a cached start-of-block price, which can lag later trades in the same block. Its getFee quote excludes protocol fees and price impact, so a larger trade's execution price can differ. developers.uniswap.org