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Introducing Voltaire - ERC-4337 Python Bundler

· 3 min read

Voltaire is a modular and lightning-fast Python Bundler for Ethereum EIP-4337 Account Abstraction. It is designed to operate within the peer-to-peer mempool of user operations, facilitating the inclusion of transactions on-chain more quickly, at the frontier of efficiency. A good way to think about Voltaire is as software that delivers User Operations and cannot change them, similar to those expected of block-builders. It is incentivized to participate in the network through priority fees and MEV.

Voltaire presently has complete coverage of the compatibility test suites written by ERC-4337 team. These test suites ensure that different bundlers can communicate effectively and defend against DDoS attack vectors. While the specification is still under development, all upcoming updates will aim to sustain full compliance coverage.

Voltaire is open-source, meaning that anyone can launch Voltaire and capture User Operation profits. By participating in the network, the mempool becomes more robust when facing censorship attacks.

Getting Started using Voltaire

Bundler Endpoints


Get started by getting bundler endpoints for your developement here

ERC-4337 developers can get started sending user operations requests for Sepolia, Goerli, and Optimism-Goerli testnet. Stay tuned for more networks coming soon.

We partnered with BlockPi, Chainbase, and LlamaNodes to offer low latency and resilience ERC-4337 compliant public hosted bundlers using Voltaire


The docker image is a single command line to get starting running an instance of Voltaire, locally or on a private server. A bundler needs access to a full node. Run your own, or get one from a node provider.


Running from the source is intended for developers who wish to develop on top of Voltaire or contribute to the project. Check out the readme on Github

Voltaire Architecture


Python is a powerful programming language that, due to its simplicity, versatility, and wide range of libraries and frameworks, is a suitable language for a Bundler. One of the key features that makes Python suitable is the ability to write concurrent programs. The asyncio library primitives allow for writing simple and pure asyncio implementations.

A bundler needs to perform and handle multiple User Operations requests at a time. Asyncio is ideal for handling multiple concurrent tasks efficiently. This enables the server to handle multiple client requests simultaneously without blocking other requests.

A big of part of our inspiration for Voltaire is Trinity, a previous open-source Ethereum client implementation written in Python. We would like to thank the Trinity team, as well as all Python community members for their open-source contributors.

If you are building on account abstraction, reach out on Twitter, Discord or come say hello at