A performant, reliable, and type-safe ERC-4337 Bundler written in Typescript
Last updated Jul 3, 2026
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README
⛰️ Alto ⛰️
Alto is a Typescript implementation of the ERC-4337 bundler specification developed by Pimlico, focused on transaction inclusion reliability.
Getting started
For a full explanation of Alto, please visit our docs page
Run an instance of Alto with the following commands:
pnpm install
pnpm build:all
./alto --entrypoints "0x5ff1...2789,0x0000...a032" --executor-private-keys "..." --utility-private-key "..." --min-balance "0" --rpc-url "http://localhost:8545" --network-name "local"
To find a list of all options, run:
./alto help
A helper script for running Alto locally with an Anvil node can be found at scripts/run-local-instance.sh.
A comprehensive guide for self-hosting Alto can be found here.
Run the test suite with the following commands:
pnpm build
pnpm test # note: foundry must be installed on the machine for this to work
Prerequisites
How to run E2E tests
- pnpm run test
How to test bundler specs
- Run Geth node or any other node that support debug_traceCall
- Clone bundler-spec-tests repo.
- build & run bundler with
--environment development --bundleMode manual --safeMode true
License
Distributed under the GPL-3.0 License. See LICENSE for more information.
Contact
Feel free to ask any questions in our Telegram group
Acknowledgements
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