Uniswap v4 hooks on Robinhood Chain, explained

Uniswap v4 is now where most of Robinhood Chain’s DEX volume trades: at time of writing, about $301 million of a roughly $604 million 24-hour DEX volume ran through v4 pools, slightly more than Uniswap v3. Many of those pools have a hook attached. Hooks are what make v4 flexible (launch taxes, dynamic fees, anti-snipe rules), and also what make some v4 pools dangerous. This article explains how they work and how to check one.

What a hook is

In Uniswap v4 every pool lives inside one contract, the PoolManager. When a pool is created it can name a hook contract, which the PoolManager calls at fixed points:

before and after a pool is initialized;
before and after liquidity is added or removed;
before and after every swap;
before and after donations.

A hook can also return deltas: it can change how many tokens a swap or liquidity change actually moves. That is how hook-based taxes work.

Permissions live in the address

A hook can’t decide at runtime which callbacks it uses. The permissions are encoded in the lowest 14 bits of the hook’s address, and the PoolManager only calls the callbacks whose bit is set. Deployers mine an address with the right bits.

That has a useful consequence: you can read a hook’s capabilities from its address alone, without trusting its source code or even seeing it.

The permissions that matter

Permission	What the hook can do	Risk flag
`beforeSwap`	Run code before every swap, including reverting it	`can_block_or_reprice_swaps`
`beforeSwapReturnDelta`, `afterSwapReturnDelta`	Change the amounts a swap moves (taxes, fees, or worse)	`can_modify_swap_amounts`
`beforeRemoveLiquidity`	Run code before liquidity leaves, including blocking it	`can_gate_liquidity_removal`
`beforeAddLiquidity`	Run code before liquidity is added, including blocking it	`can_gate_liquidity_add`
`afterAddLiquidityReturnDelta`, `afterRemoveLiquidityReturnDelta`	Change the amounts a liquidity change moves	`can_modify_liquidity_amounts`

None of these is bad on its own: launchpads use beforeSwap to enforce launch rules, and dynamic-fee hooks use it to set the fee. But a hook that can block swaps and is unverified deserves caution, because you can’t see what conditions it blocks on.

Checking a hook

The Crius API decodes every v4 hook on Robinhood Chain. List them with /hooks:

curl "https://api.crius.sh/v1/robinhood/hooks?sort=pools&limit=20" -H "x-api-key: $CRIUS_API_KEY"

and inspect one with /hook/{address}:

curl "https://api.crius.sh/v1/robinhood/hook/0x4e3468951d49f2eea976ed0d6e75ffcb44a9a544" -H "x-api-key: $CRIUS_API_KEY"

You get the decoded permissions, risk flags, whether the source is verified, the events the hook actually emits on chain and the pools that use it. Filter the list with verified=false or risk=can_block_or_reprice_swaps to find the hooks worth a closer look.

Hooks in token security checks

You rarely care about a hook in the abstract; you care whether the token you want to trade is safe. The /security endpoint includes the token’s pool hook (permissions and risk) and the hook tax measured from real trades: what the pool sent versus what the trader received. Because it’s measured from actual swaps, it catches taxes that a simple contract scan would miss, including taxes that only apply to some wallets.

What to look for

Verified, widely used hooks (launchpad hooks, well-known fee hooks) are generally fine; their behaviour is visible.
Unverified hooks with beforeSwap and return deltas can change or block your trade. Check the realized tax and whether people have successfully sold recently.
beforeRemoveLiquidity on an unverified hook can stop liquidity providers from withdrawing.
A hook’s behaviour can depend on who you are. Compare buy and sell tax across many real trades rather than trusting one simulation.

Read more in the Uniswap concepts guide and the pools and hooks reference.

To catch new hooked pools as they are created, see the hands-on guide How to Detect New Uniswap v4 Pools on Robinhood Chain, and the Uniswap v4 API for every endpoint in one place.