A quick guide to self-hosting an ERC-4337 bundler for handling UserOperations.

The bundler package is implemented in Go and is open source at


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Via go install

Make sure to have your environment variables configured before running the client. See the configuration page for details.


To get the latest version:

go install

Alternatively, if you're looking for an older version:

# See for version releases
go install[email protected]

Running the bundler


Full access to a node is required.

A bundler should be considered as an extension, or a side-car, to a full node. It requires full access to the node's debug API for custom JS tracing. Most RPC providers do not support this.

For maximum performance, it is also recommended to run the bundler in the same machine as the node.

Run an instance in private mode:

stackup-bundler start --mode private

For a description on the CLI commands and other supported modes:

stackup-bundler start --help