Gateway Contracts

Cross-chain Foreign and Home Gateway contracts for multi-chain arbitration

Gateways enable cross-chain arbitration between Kleros Court on Arbitrum and Arbitrable contracts on foreign chains.

Home Gateway (Arbitrum)

Located on Arbitrum, the Home Gateway:

• Receives dispute creation messages from the Vea bridge
• Creates disputes on KlerosCore
• Sends rulings back through the bridge

From KlerosCore’s perspective, the Home Gateway behaves as an Arbitrable contract.

Foreign Gateway (Foreign Chain)

Located on Ethereum mainnet, Gnosis Chain, etc., the Foreign Gateway:

• Accepts createDispute() calls from Arbitrable contracts
• Relays dispute creation through the Vea bridge to the Home Gateway
• Receives rulings from the bridge and calls rule() on the Arbitrable

From the Arbitrable’s perspective, the Foreign Gateway behaves as an Arbitrator.

Key Methods

createDispute(uint256 _choices, bytes _extraData) payable → uint256

Creates a cross-chain dispute. Caller must send ETH equal to the arbitration cost.

arbitrationCost(bytes _extraData) view → uint256

Returns feeForJuror[courtID] × minJurors in ETH.

relayRule(address _messageSender, bytes32 _disputeHash, uint256 _ruling, address _relayer)

Called by the Vea outbox once a ruling is relayed from Arbitrum. Forwards the ruling to the Arbitrable.

withdrawFees(bytes32 _disputeHash)

Pays the relayer’s fee after a ruling has been delivered.

Governance Methods (Governor Only)

changeCourtJurorFee(uint96 _courtID, uint256 _feeForJuror)

Updates the per-juror fee stored in the ForeignGateway for a specific court. This must be called to keep gateway fees in sync when KlerosCore court fees change on Arbitrum. Fee drift is a known operational risk — if this is not updated after a governance change to feeForJuror on Arbitrum, arbitration cost on the foreign chain will be incorrect.

changeVea(address _veaOutbox, uint256 _gracePeriod)

Updates the Vea outbox address. Supports a grace period for deprecated bridge transitions.

ERC-20 Fee Limitation

The ForeignGateway does not support ERC-20 arbitration fees. Calling the ERC-20 overload of createDispute on the ForeignGateway will revert with "Not supported".

ERC-20 fee payments (WETH, DAI, etc.) are only available when integrating directly with KlerosCore on Arbitrum. Cross-chain arbitrables using the gateway must always pay fees in ETH.

Vea Bridge

The underlying message transport. Uses optimistic verification with claim/challenge mechanics for security.

See Vea Bridge Architecture for details.

Foreign Gateway Source | Home Gateway Source