🚧 UNDER CONSTRUCTION 🚧

Router Rebates

A gas subsidy program, sponsored by Uniswap Foundation and Brevis, to encourage routing and solving integration with Uniswap v4 Hooks

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Program Specs

For any transaction that touches a Uniswap v4 pool, with a hook, authors of the swap router (sender address in the Swap event), will be able to claim a rebate against the gas spent

Rebates will be available on the 12 initial chains with Uniswap v4, with claims faciliated on Unichain. The rebate is paid out in native Ether.

Rebate Size

For a given transaction hash, with swap events coming from a hook'ed pool, the rebate is calculated according to:

gasUsageToRebate = 80,000 * number_of_swap_events + 80,000
ethToRebate = gasUsageToRebate * txnReceipt.baseFee

As a safety precaution against hyper-optimized swaps, the minimum of the above calculation or 80% of transaction gas usage is taken

Glossary

swap router / beneficiary - the onchain contract, that implements IUnlockCallback, and is the caller for poolManager.swap(). Can also be thought of as the sender address in the Swap() event

claimer - the address which is claiming the rebate on behalf of the swap router / beneficiary

recipient - the recipient address that is receiving the rebate

Router Integrations

Because rebates are claimed on Unichain for trades happening on other networks, beneficiaries need to specify the authorized claimer.

The swap router contract (the contract calling poolManager.swap()) should implement this function selector:

function rebateClaimer() external view returns (address);

See IRebateClaimer for the full interface.

The wallet which claims the rebate is specified by this address, rebateClaimer. The backend system performs verification against this address, to prevent griefing scenarios where malicious attackers are claiming rebates they are not entitled to.

Claim Process: Signatures

The Router Rebates initiative offers two flows for claiming rebates. In the signature flow, an API service operated by Uniswap Foundation, verifies transactions to produce the rebate size and an authorization signature. The authorization signature, along with its corresponding data, is provided to a smart contract on Unichain to claim the rebate.

To prevent signature replays and/or duplicate claiming, rebate claims operate on a block range. Once a block number has been claimed against, transactions occuring prior to the block number are inelligible for rebates.

1. Gather a list of transaction hashes, for a single chain. Note the sender of the first Swap event of first tx is treated as the beneficiary. Swap events with non-beneficiary sender are ignored.

   txnHashList = ["0xABC", "0xDEF"]
   

2. Provide the chainId and transaction list to the API

   curl -G 'https://router-rebates-testnet.up.railway.app/sign' \
     --data-urlencode 'chainId=1' \
     --data-urlencode 'txnHashes=0xABC,0xDEF'

3. Example response:

   {
     // rebateClaimer address set by the beneficiary
     "claimer": "0x7024cc7e60D6560f0B5877DA2bb921FCbF1f4375",
   
     // authorization signature to provide to RouterRebates
     "signature": "0xaac2124f1f581cd5e0e9d743250d01d23972a620caadb9df223650be2b5e057862bb8436fb0be03bdd345067e2766d41a10ed2fb42d61d4729283bfd19fd79a71b",
   
     // amount of rebate determined, wei units of native Ether tokens
     "amount": "26907876080000",
   
     "startBlockNumber": "7839623",
     "endBlockNumber": "7839623"
   }

4. Claim the rebate, from the authorized claimer address

   	RouterRebates
   Sepolia	0x6bec6dff20730840266a2434bcc4c3aa0b139482
   Unichain	TBD

   ---

   function claimWithSignature(
       uint256 chainId,
       address beneficiary,
       address recipient,
       uint256 amount,
       BlockNumberRange calldata blockRange,
       bytes calldata signature
   ) external;

   Name	Type	Description	Notes
   chainId	uint256	The chainId of the transaction hashes	The same chainId provided to the GET /sign request
   beneficiary	address	The address of contract that interacted with PoolManager	The swap router contract, should expose a rebateClaimer() external view returns (address)
   recipient	address	The recipient of the rebate	The address should be able to safely recieve native Ether tokens
   amount	uint256	The amount of rebate being claimed	The amount returned the GET /sign request
   blockRange	BlockNumberRange	A struct of (uint128,uint128) containing the start and end block numbers of the transaction hashes	Start and end block numbers are returned the GET /sign request
   signature	bytes	A signature authorizing rebate claims	Returned by the GET /sign request. Internally derived from abi.encodePacked(r, s, v)

Claim Process: Brevis ZK Proof

Router projects can also claim gas rebates using Brevis ZK proof in a trust-free manner. High level flow is similar to signature-based above except that a ZK proof is returned from Brevis backend and sent to onchain contract by the claimer.

1. Brevis system recognizes claimer address from router contract's rebateClaimer
2. Provide the chainId and transaction list to Brevis backend xxxx(tbd).brevis.network/zk/new in the same format as signature-based flow, and receives reqid in response as generating ZK proof is async
3. Query xxxx(tbd).brevis.network/zk/get/{reqid} to get ZK proof and data to submit onchain. See full response object definition here
4. Claimer sends onchain tx to the same RouterRebates contract's claimWithZkProof function

function claimWithZkProof(
    uint64 chainid, // swaps happened on this chainid, ie. 1 for eth mainnet
    address recipient, // eth will be sent to this address
    bytes calldata _proof,
    bytes[] calldata _appCircuitOutputs,
    bytes32[] calldata _proofIds,
    IBrevisProof.ProofData[] calldata _proofDataArray
)

Name	Type	Description	Notes
chainId	uint64	The chainId of the transaction hashes	The same chainId provided to the GET /zk/new request
recipient	address	The recipient of the rebate	The address should be able to safely recieve native Ether tokens
_proof	bytes	ZK proof received from Brevis backend	Included in zk/get/ response object
_appCircuitOutputs	bytes[]	ZK circuit output data	Included in zk/get/ response object
_proofIds	bytes32[]	IDs identifiying each ZK proof	Included in zk/get/ response object
_proofDataArray	IBrevisProof.ProofData[]	Data required by ZK verification	Included in zk/get/ response object