Aztec Fee Payment Contracts

A collection of Fee Payment Contracts (FPCs) for Aztec that enable transaction fee sponsorship strategies.

Overview

This repository provides a production-ready Metered FPC implementation:

Contract	Description
Metered	Tracks internal balances and deducts max gas cost

Project Structure

├── src/
│   ├── nr/                          # Noir smart contracts
│   │   ├── counter_contract/        # Test utility contract
│   │   └── metered_contract/        # Metered FPC
│   └── ts/                          # TypeScript package
│       ├── artifacts/               # Generated contract bindings
│       ├── fee-payment-methods/     # Fee payment method classes
│       ├── utils/                   # Utilities (gas, deploy)
│       └── test/                    # Integration tests
├── target/                          # Compiled contract artifacts
└── benchmarks/                      # Performance benchmarks

Setup

Prerequisites

• Aztec Sandbox v3.0.0 or later
• Node.js 22+
• Yarn 1.22+

Installation

yarn install

Compile Contracts

# Compile Noir contracts
nargo compile --silence-warnings

# Post-process with Aztec tooling
aztec compile

# Generate TypeScript bindings
aztec codegen target --outdir src/ts/artifacts

Testing

Start the Aztec sandbox:

yarn start:sandbox

Run tests:

yarn test

The Metered FPC test file validates:

• ✅ SUCCESS: Transaction succeeds, FPC pays fees
• ❌ Private revert: Transaction is invalid (not included)
• ⚠️ Public revert: FPC still pays fees (APP_LOGIC_REVERTED)

External Usage

See src/ts/README.md for detailed documentation on using the published NPM package.

yarn add @defi-wonderland/aztec-fee-payment

Quick example:

import {
  MeteredContract,
  MeteredFeePaymentMethod,
  deployMeteredContract,
} from '@defi-wonderland/aztec-fee-payment';

// Deploy and fund the FPC
const fpc = await deployMeteredContract(wallet);

// Mint balance for user
await fpc.methods.mint(userAddress, 1_000_000_000_000n).send().wait();

// Use it for transactions
await myContract.methods.doSomething()
  .send({ fee: { paymentMethod: new MeteredFeePaymentMethod(fpc.address) } })
  .wait();

Benchmarks

yarn benchmark

License

MIT