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GPv2VaultRelayer Contract

The GPv2VaultRelayer contract serves as an intermediary between the settlement contract and Balancer Vault, enabling secure token transfers and batch swaps while maintaining strict access controls.

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Overview

The relayer acts as an intermediary between the settlement contract and Balancer Vault with specialized functions for handling user fund interactions safely. Only the settlement contract can initiate transfers.

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State Variables

VariableTypeDescription
creatoraddress (immutable)The settlement contract address with exclusive privileges
vaultIVault (immutable)The Balancer Vault instance

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Access Control

All external functions use the onlyCreator modifier, restricting operations to the settlement contract that deployed the relayer: 
modifier onlyCreator {
    require(msg.sender == creator, "GPv2: not creator");
    _;
}

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Main Functions

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transferFromAccounts()

Moves sell token amounts from user accounts to the settlement contract, supporting three balance types: 
function transferFromAccounts(
    GPv2Transfer.Data[] calldata transfers
) external onlyCreator;
Supported balance types:
  • ERC20 - Standard ERC20 token transfers
  • External - Balancer Vault external balances
  • Internal - Balancer Vault internal balances

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batchSwapWithFee()

Executes Balancer batch swaps on behalf of users while simultaneously collecting protocol fees: 
function batchSwapWithFee(
    IVault.BatchSwapStep[] calldata swaps,
    IERC20[] calldata tokens,
    IVault.FundManagement calldata funds,
    int256[] calldata limits,
    uint256 deadline,
    GPv2Transfer.Data calldata feeTransfer
) external onlyCreator returns (int256[] memory tokenDeltas);
The function returns token deltas indicating amounts sent and received.

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Security Architecture

The contract implements layered protection:
  • Creator-only access prevents unauthorized vault interactions
  • Immutable references prevent state tampering post-deployment
  • User approvals remain isolated since only the settlement contract can trigger transfers
  • No direct user interaction pathway exists — users never call this contract directly

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Integration Point

The vault relayer operates within the settlement workflow, handling token transfers before and after batch swaps. It is automatically instantiated by the settlement contract during deployment.
Users approve the Balancer Vault, not the VaultRelayer directly. The relayer leverages existing vault approvals to move tokens.
Last modified on March 4, 2026