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Alto

Alto is an open-source TypeScript implementation of the ERC-4337 bundler specification that can be built and run as an Ethereum bundler instance, with a stated focus on transaction-inclusion reliability.

Explore the practical guide ↓

Independent OpenViST project profile, based on linked sources.

Alto — OpenViST project profile in Infrastructure.
OpenViST project illustration. See the linked sources for product details.
Understand the project

Practical overview

When it fits

Use Alto when you need to build or self-host an ERC-4337 bundler for an account-abstraction application, or when setting up a local bundler development environment.

Who it is for

  • Teams building Ethereum applications that use account abstraction and need bundler infrastructure.
  • Developers setting up a local bundler environment or working with ERC-4337 bundler tests.

Documented uses

  • Build and start a bundler instance with configured entry points, keys, RPC URL and network name.
  • Run Alto locally with an Anvil node using the repository's helper script.
  • Build the project and invoke its test suite.
Before you choose

Requirements & limits

The repository is public and specifies the GPL-3.0 license. Its listed prerequisites are Node.js LTS and pnpm.

  • Alto is a bundler implementation, not an account-abstraction application interface.
  • The startup configuration requires an RPC URL, network name, entry points and private-key settings.
  • The supplied run example targets a local RPC endpoint; it does not verify a specific production network.
  • Running the documented test suite requires Foundry.

Check current requirements in the official documentation. Source-based guidance does not mean OpenViST has run or independently tested this project.

Source-based practical guide

Build and start Alto against a local RPC endpoint

Build Alto and configure a bundler instance with a local RPC URL and network name.

Before you start

  • Node.js LTS
  • pnpm
  • A reachable RPC endpoint; the example uses http://localhost:8545
  • Entry-point addresses and the executor and utility private-key configuration required by the startup command

Steps

  1. Install dependencies with pnpm install.

  2. Build the project with pnpm build:all.

  3. Start ./alto with the required entry points, key settings and minimum balance, setting --rpc-url to the local endpoint and --network-name to local.

Expected outcome

A configured Alto bundler instance targeting the specified local RPC endpoint.

Guide limitations

  • The example documents a local network configuration and does not establish compatibility with a particular production network.
  • The private-key values in the README are placeholders; configure actual values for the intended environment.
Documentation 1 ↗
Source-based practical guide

Build and run the documented test suite

Build Alto and run its test suite.

Before you start

  • Node.js LTS
  • pnpm
  • Foundry installed on the machine

Steps

  1. Run pnpm build.

  2. Run pnpm test.

Expected outcome

The repository's test suite is invoked after the build.

Guide limitations

  • The instructions state that Foundry must be installed for the test command to work.
Documentation 1 ↗
Evidence and transparency

Sources & review

Official repository ↗
Source record details
Source availability
Active
Sources checked
9 October 2026
Original website title
pimlicolabs/alto · Official homepage title · retained in its source language
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