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Permissions and PoolKey

The 14 Uniswap v4 hook flag bits and which ones GeneHook's address sets, what each implemented callback does, and how the PoolKey and poolId are formed.

In Uniswap v4, a hook's permissions are encoded in the low 14 bits of its address, and the PoolManager calls only the callbacks whose bits are set (Uniswap v4: Hooks). GeneHook's address must have those 14 bits equal to exactly 0x2AC0. The constructor enforces this, so no GeneHook can exist at any other address shape (GeneHook.sol:225-226).

#Hook flag bits

Bit positions and names are from the vendored v4-core Hooks.sol (Hooks.sol:27-47). 0x2AC0 sets bits 13, 11, 9, 7 and 6.

Notes:

• Self-calls are skipped. v4 does not call a hook's initialize and liquidity callbacks when the hook is the caller (noSelfCall, Hooks.sol:171-175), and returns early from the swap callbacks for the hook's own swaps (Hooks.sol:253, Hooks.sol:293). This is what lets the always-reverting callbacks coexist with launch(), metabolize() and REGENERATION's buyback (GeneHook.sol:40-43).
• Donations are not blocked. With the donate bits clear, v4's donate works on the pool; a donated amount accrues as fees to in-range positions, which are the hook's, and is collected when a later metabolize() pokes or tops up that position (GeneHook.sol:554-559, GeneHook.sol:671-689).
• No dynamic fee and no hook fee. The fee is static in the PoolKey, nothing in GeneHook calls updateDynamicLPFee, and beforeSwap returns fee override 0 (GeneHook.sol:26-27, GeneHook.sol:365; invariants FEE1 and FEE2).
• REQUIRED_FLAGS() returns 0x2AC0 on chain (GeneHook.sol:148-149). GeneHook has no getHookPermissions() function; the tests assert address & ALL_HOOK_MASK == 0x2AC0, the prefix rule and REQUIRED_FLAGS() == 0x2AC0 (SecurityGates.t.sol:272-273, SecurityGates.t.sol:292; invariant ADDR).

#Address prefix rule

The constructor also reverts if the address's top byte is 0x91 (GeneHook.sol:227-228). The source states the reason: the Uniswap routing auto-allowlist excludes addresses starting with 0x91 (GeneHook.sol:227; GeneSaltMiner.sol:6-9). Routing policy is an off-chain rule outside GENE's control. The deploy script mines a CREATE2 salt through the Arachnid deterministic deployer to satisfy both rules (Deploy.s.sol:31-33; GeneSaltMiner.sol:6-11).

#PoolKey

The constructor builds the key once and poolKey() rebuilds the same value (GeneHook.sol:236-242, GeneHook.sol:965-973). Field definitions are Uniswap's (Uniswap v4: create a pool; PoolKey.sol:11-22).

currency0 < currency1 always holds because currency0 is address(0).

Price orientation. currency0 is ETH, so the pool price is GENE per ETH: a higher tick means cheaper GENE, and a buy of GENE (zeroForOne = true) moves the tick down (GeneHook.sol:103-104).

#poolId derivation

poolId = keccak256(abi.encode(poolKey)): the keccak-256 of the five 32-byte words of the key (PoolId.sol:9-16). GeneHook computes it in the constructor and stores it as the immutable poolId() (GeneHook.sol:243-244).

To recompute it after deployment:

HOOK=0x...   # from /docs/reference/addresses/ after deployment
# poolKey() returns a static struct, so its raw return data is exactly abi.encode(poolKey)
KEY=$(cast call $HOOK "poolKey()" --rpc-url $RPC)
cast keccak $KEY
cast call $HOOK "poolId()(bytes32)" --rpc-url $RPC   # must match

The full verification procedure is on Verify the deployment.