EIP-7702 Implementation Guide

Overview

EIP-7702 enables Externally Owned Accounts (EOAs) to temporarily delegate their code to a smart contract during a transaction. This allows EOAs to function as smart contracts, enabling features like:

• Sponsored Transactions: A relayer pays gas for the EOA.
• Batching: Multiple operations in one atomic transaction.
• Key Rotation/Recovery: Programmable access control.

1. Smart Contract Development

To use EIP-7702, you need an implementation contract. This contract will be the code that the EOA "borrows".

Key Requirement: The contract must handle authentication (ensure the EOA signed the intent) and replay protection (nonce), as the EIP-7702 authorization only delegates code, it doesn't inherently validate the payload of the function call if anyone can call it.

Reference Implementation

A robust example supporting Batching and Sponsorship is available in assets/BatchCallAndSponsor.sol.

Features:

• execute(calls, signature): For sponsored transactions. Requires an inner signature from the EOA verifying the batch and nonce.
• execute(calls): For direct execution (when msg.sender == address(this)).

2. Testing with Foundry

Foundry supports EIP-7702 via the prague EVM version and specific cheatcodes.

Key Cheatcodes:

• signDelegation: Creates the EIP-7702 authorization signature.
• attachDelegation: Attaches the authorization to the next transaction.

See Foundry Guide for detailed test patterns and configuration. See assets/test/BatchCallAndSponsor.t.sol for a complete test suite.

3. Client Interaction (Viem v2)

Viem v2 provides first-class support for EIP-7702 via signAuthorization and sendTransaction/writeContract with authorizationList.

Best Practices:

• Use writeContract with strongly typed ABIs (as const) for safer interactions.
• Ensure correct signing of raw hashes using signMessage({ message: { raw: ... } }).
• No experimental extensions are required in modern Viem versions.

See Viem Guide for code snippets and TypeScript patterns.