Fee Delegation

Overview

FeeDelegatedDynamicFeeTx is a specialized transaction type that extends the existing DynamicFeeTx by introducing the concept of a “fee payer,” allowing a party other than the sender to cover the network transaction fees. The SenderTx field holds standard DynamicFeeTx data, while specifying a FeePayer address and its signature values (FV, FR, FS) implements the logic for a third party to pay the gas fees on behalf of the original sender.

In addition, during the transaction hashing process (Transaction.Hash()), if a transaction is identified as FeeDelegatedDynamicFeeTxType, the prefix is switched to DynamicFeeTxType, and the actual object being hashed (x) is replaced with the SenderTx. This ensures that the hash is calculated in the same manner as a standard dynamic fee transaction. As a result, the original sender’s signature applies to the standard DynamicFeeTx data, while the fee payer’s signature is managed separately—enabling both signatures to be independently verified.

This document provides example code demonstrating how to implement the FeeDelegatedDynamicFeeTx structure, hashing logic, signing flow, and actual transaction submission process in a go-cross environment. By adapting your existing DynamicFeeTx-based logic, you can seamlessly incorporate a flexible “fee delegation” capability that suits the needs of applications or services requiring a third party to pay transaction fees.

Supported Transaction Types

A Fee Delegation Transaction only supports previously signed transactions by the sender if they are of DynamicFeeTxType. It does not support LegacyTxType, AccessListTxType, or BlobTxType.