> ## Documentation Index
> Fetch the complete documentation index at: https://kleros-mintlify-6ebc7975.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Gateway Contracts

> Home and Foreign Gateway contract reference for cross-chain Kleros V2 arbitration between KlerosCore on Arbitrum and arbitrables on foreign chains.

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

<Warning>
  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.
</Warning>

## Vea Bridge

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

See [Vea Bridge Architecture](/reference/architecture/vea-overview) for details.

[Foreign Gateway Source](https://github.com/kleros/kleros-v2/blob/master/contracts/src/gateway/ForeignGateway.sol) | [Home Gateway Source](https://github.com/kleros/kleros-v2/blob/master/contracts/src/gateway/HomeGateway.sol)