Hooks

The protocol uses two kinds of hook: transfer-restriction hooks consulted on token transfers, and a Uniswap v4 hook used by LiquiLeX pools.

Transfer-restriction hooks

ITransferRestrictionHook

interface ITransferRestrictionHook {
    function checkTransferRestriction(
        address from,
        address to,
        uint256 tokenId,   // token id for cyberCERTs; amount for cyberSCRIP
        bytes memory data
    ) external view returns (bool allowed, string memory reason);
}

Both LedgerEntryToken (the cert printer, formerly CyberCertPrinter) and CyberScrip consult these hooks on transfer:

• CyberScrip holds an array of hooks (setRestrictionHook); every hook must allow the transfer or it reverts RestrictedTransfer(reason).
• LedgerEntryToken holds per-id hooks (setRestrictionHook(id, hook)) and a globalRestrictionHook (setGlobalRestrictionHook).

Implementations

In src/hooks/transfer/:

Hook	Purpose
BaseTransferHook	Common base for transfer-restriction hooks.
WhitelistTransferHook	Allows transfers only between whitelisted addresses.
ToggleTransferHook	Per-token transfer on/off switch, with a configurable default.

These three implement ITransferRestrictionHook. Consult each contract's source for its admin functions (whitelist management, toggle setters).

Uniswap v4 hook

MetalexIssuerFeeHook

In src/hooks/uniswap/. A Uniswap v4 hook for LiquiLeX AMM pools that splits swap fees between MetaLeX and the issuer, so a cyberSCRIP / stablecoin pool pays the issuer onchain on every trade.

• Per-pool configuration via setPoolConfig (onlyAdmin): a PoolFeeConfig with the MetaLeX and issuer recipients, metalexFeeBps / issuerFeeBps (their sum capped at 10 000 bps), and an enabled flag.
• Registers beforeSwap/afterSwap permissions with return deltas and handles all four swap flows: exact-input swaps are charged in beforeSwap, exact-output swaps in afterSwap, in both directions (zeroForOne and oneForZero).

See the source for the hook-address requirements Uniswap v4 imposes.