Building Uniswap V4 hooks and navigating the Balancer wind-down

Uniswap v4 Hook Implementation

Uniswap v4 uses a singleton architecture where the PoolManager contract manages all pool state. Hooks are independent smart contracts that execute custom logic during pool actions. Developers use the IHook interface to implement functions like afterSwap or afterAddLiquidity. This design allows for custom fee structures or limit orders. I find the security requirements for these hooks demanding. A developer must verify every caller and ensure custom accounting matches the PoolManager settlement. Errors in this logic cause significant losses. The Bunni exploit was $8.4M in September 2025 due to a rounding bug in idle-balance accounting. The Cork exploit was $12M in losses in May 2025 because untrusted data reached hook logic. A developer can build a points hook using the afterSwap and afterAddLiquidity functions to reward users. This hook awards points to users when they swap ETH for a token or add liquidity in a 1:1 ratio. The hook uses hookData to encode the user address because the PositionManager does not pass it directly to the hook. Aggregator hooks wrap external liquidity sources to turn them into v4 pools. Seven sources are available at launch to cover 90% of DEX activity on Ethereum mainnet, Base, and Robinhood Chain. These aggregator hooks allow the router to build efficient routes across both Uniswap pools and outside sources in a single transaction.

The Balancer Exit Strategy

The DeFi market shifts as Balancer initiates its phased wind-down. BAL holders approved Proposal BIP-928 to close the protocol because V3 failed to generate enough revenue to replace V2 income. On October 30, 2026, pools with pause functionality transition to withdrawal-only mode. Users must withdraw funds before the V3 Vault pauses in November. The DAO treasury holds at least $9 million. This money goes to BAL holders through a distribution starting in May 2027. I believe the November 2025 exploit that drained $128 million from V2 pools effectively ended the protocol’s growth. The transition team manages a minimal withdrawal system. The plan excludes BAL from distributable assets except for the share owed to tetuBAL holders. The wind-down budget is $400,000. It allocates $150,000 for use until May 2027 and $30,000 for the final phase. The remaining $220,000 stays in reserve for unforeseen needs. The plan follows a vote held between September 25 and September 29, 2026. How will users navigate the final treasury distribution?

Technical Development and Security

Developers start by cloning the v4-template repository and installing dependencies with Foundry. They use bit flags to tell the PoolManager which hook functions to trigger.

The implementation requires inheriting from BaseHook to keep the getHookPermissions function in sync with the active callbacks. The developer must check the permission bits carefully to avoid reverting transactions when the PoolManager calls a missing function, or they must ensure the getHookPermissions function remains in sync with the active callbacks and declared permissions. I suggest you use the BaseHook entrypoints to enforce caller checks. The developer must label every balance and delta to prevent value leaks. One must ensure that no user receives output that the accounting did not charge for. The developer must keep LP funds, fees, and incentives in separate buckets. The developer must also keep non-essential code out of the main user flow. If the reward distribution fails, the entire swap reverts. The developer must also verify that the address bits match the declared permissions. Developers implement a SwapLimiterHook to restrict users to a maximum of five swaps per hour. This hook uses a mapping to track the swap count and a timestamp to reset the count every hour. You must use the BaseHook contract to implement the internal _beforeSwap function. This ensures the PoolManager remains the only caller. The developer can implement a function like getRemainingSwaps to let users check their remaining limits.