GasX is a professional suite of ERC-4337 Paymasters designed to eliminate gas fee friction for any dApp. Sponsor transactions completely with our Whitelist Paymaster, or empower users to pay gas with tokens like USDC using our ERC20 Fee Paymaster. GasX is the flagship protocol of Builder-Hub.
On-chain adoption stalls when new users must first acquire a native gas token (like ETH) before they can perform any action. The GasX Suite directly solves this by offering two powerful solutions that dApps can integrate:
-
Complete Sponsorship (
GasXWhitelistPaymaster):- Problem: You want to offer a truly free "first mint" or "create profile" experience to onboard new users.
- Solution: The protocol uses the
GasXWhitelistPaymasterto pay 100% of the gas fees for specific, pre-approved actions, creating a frictionless, Web2-like experience.
-
Convenient Payments (
GasXERC20FeePaymaster):- Problem: Your users hold stablecoins like USDC but don't have ETH on the right network to pay for gas.
- Solution: The
GasXERC20FeePaymasterallows users to pay for their own transactions using USDC. The protocol handles the on-chain price conversion and pays the network in ETH, abstracting away the native gas token entirely.
The GasX Suite is currently deployed and tested on Arbitrum Sepolia and Scroll Sepolia and is fully compatible with EntryPoint v0.8.
The GasX Protocol has achieved a feature-complete MVP (Minimum Viable Product) state. The core contracts, tooling, and documentation have been professionally architected, providing a stable foundation for rigorous testnet validation and future expansion.
| Category | Deliverable | Status |
|---|---|---|
| Smart Contracts | GasXWhitelistPaymaster deployed and verified on-chain. |
✅ |
GasXConfig and MultiOracleAggregator deployed and verified. |
✅ | |
GasXERC20FeePaymaster deployed and verified. |
✅ | |
GasXSubscriptions subscription & credit payment system. |
✅ | |
| Tooling | Professional, multi-chain Hardhat deployment and testing suite. | ✅ |
| Frontend | Functional Next.js demo app for gasless transactions. | ✅ |
| Testing | Unit, Integration, E2E, Fuzz, and Invariant tests with 100% coverage on core. | ✅ |
| Security | Pausable contracts, emergency withdrawals, events for monitoring. | ✅ |
| Documentation | Complete /docs suite, including architecture, guides, and references. |
✅ |
| Open Source | MIT License, CONTRIBUTING.md, and SECURITY.md in place. |
✅ |
The project is fully prepared for deployment and E2E testing on the Arbitrum network.
The GasX Protocol is rigorously tested using a multi-layered approach to ensure reliability and security. Our test suite includes unit tests, integration tests, fuzz tests, and invariant tests.
| Test Type | Contract / System Tested | Key Verifications |
|---|---|---|
| Unit & Integration | GasXWhitelistPaymaster |
Owner-only access, selector whitelisting, gas limit enforcement, oracle signature logic, pausable, emergency withdrawal. |
GasXERC20FeePaymaster |
Token fee payments, price oracle integration, pausable functionality. | |
GasXSubscriptions |
Plan management, credit system, ETH/token payments, CEI pattern. | |
GasXConfig |
Correct deployment, access control, and parameter updates. | |
MultiOracleAggregator |
Oracle management, average/median price calculation, and deviation checks. | |
| Fuzz Testing | GasXWhitelistPaymaster |
9 fuzz tests with 1,000 runs each. |
GasXSubscriptions |
9 fuzz tests with 1,000 runs each. | |
| Invariant Testing | GasXWhitelistPaymaster |
9 invariant properties verified via Echidna. |
GasXSubscriptions |
7 invariant properties verified via Echidna. | |
| End-to-End (E2E) | Full AA Stack (Local) | Simulates a complete, sponsored UserOperation on a local Hardhat network. |
| Full AA Stack (Public) | Verifies the entire flow on live testnets (e.g., Arbitrum Sepolia) using a real bundler. |
| Contract | Statements | Branches | Functions | Lines |
|---|---|---|---|---|
GasXWhitelistPaymaster |
100% | 88.1% | 100% | 100% |
GasXERC20FeePaymaster |
100% | 96.88% | 100% | 100% |
GasXSubscriptions |
93.18% | 68.82% | 88.57% | 95.57% |
GasXConfig |
100% | 91.67% | 100% | 100% |
The entire test suite is run automatically on every commit via our Continuous Integration pipeline.
- Security-First Design: V1 contracts are deployed as immutable for maximum trust. The protocol uses a strict separation of concerns and includes on-chain protections like gas ceilings and selector whitelists.
- Pausable Contracts: All paymasters can be paused by the owner in case of emergency, using OpenZeppelin's
PausablewithwhenNotPausedmodifier. - Emergency Recovery:
emergencyWithdrawEth()allows recovery of accidentally sent ETH. - Comprehensive Events: All admin actions emit events for monitoring:
LimitsUpdated,SelectorUpdated,DevModeChanged,Paused,Unpaused,EmergencyWithdraw. - Multi-Paymaster Suite: A suite of specialized paymasters allows dApps to choose the exact tool for their needs.
- Resilient On-Chain Oracles: A robust
MultiOracleAggregatorprovides reliable price data with built-in deviation checks. - Chain-Agnostic Architecture: Professional deployment scripts and a centralized configuration allow for seamless multi-chain support.
- Off-Chain Extensibility: Paymasters support time-bound signatures from off-chain services for powerful, real-time validation logic.
- Analytics & Monitoring: Paymasters emit detailed events like
GasSponsoredon every successful transaction.
| Quarter | Phase | Key Deliverables |
|---|---|---|
| Q3 2025 | Foundation & Launch | - GasXWhitelistPaymaster: Deploy the immutable contract on Arbitrum & other L2s.- Professional Tooling: Finalize the multi-chain deployment and testing suite. - Complete Documentation: Publish the full /docs suite. |
| Q4 2025 | USDC & Partner Onboarding | - GasXERC20FeePaymaster: Develop, test, and deploy the USDC fee paymaster.- Off-Chain Service: Launch the secure Oracle Signer service. - First Partner Integrations: Onboard the first wave of dApps. |
| Q1 2026 | SDK & Scalability | - Developer SDK: Release a public NPM package to simplify dApp integration. - Admin Dashboard v1: Launch a UI for partners to manage paymaster configurations. |
Comprehensive technical documentation for the GasX protocol is maintained in the /docs directory. The best place to start is the Documentation Hub (/docs/index.md).
- Architecture Overview: A deep dive into the smart contract system.
- Deployment Guide: Step-by-step instructions for deploying the protocol.
- Node.js:
20.19.3(Exact version recommended) - Yarn: v3.x or higher
# Clone the repo and install dependencies
git clone [https://github.com/edsphinx/builder-hub.git](https://github.com/edsphinx/builder-hub.git)
cd builder-hub
yarn install
# In one terminal, run the local blockchain & deploy contracts
cd packages/hardhat
yarn deploy
# In a second terminal, start the frontend demo
cd packages/nextjs
yarn startThe frontend is now available at
http://localhost:3000.
The GasX Protocol is an open-source project. We welcome contributions and take security very seriously. Please see our Contributing Guide and our Security Policy.
| Name | Role | GitHub / X |
|---|---|---|
| edsphinx | Lead Solidity / ZK | @edsphinx / @oFonCK |
MIT – see LICENSE.
Made with ♥ in Honduras. Coming soon to Arbitrum, Base, Scroll, and more.