Running a Builder

Information about running a builder for Espresso.


Participants in the Espresso Sequencer Marketplace must run a builder, a piece of software which tracks the state of HotShot consensus so that it is able to make bids and propose blocks at the correct time. Espresso provides a simple builder implementation, which participants can run out of the box or build their own software on top of. This document describes how to run the basic builder software. The builder functions to create a block filled with transactions, drawing from transactions accessible in Espresso's public mempool as well as its own private mempool. For comprehensive guidance on the design of a builder tailored for Espresso, it is recommended to refer to the hotshot-builder-core repository. Furthermore, to gain insight into the process of enabling builder services for a sequencer, pertinent information can be found at espresso-sequencer-builder. For access to the most recent builder docker images, please visit here.


# Clone the espresso sequencer repository
git clone

# Build the executable in release mode
cargo build --release

# Run a builder natively
target/release/permissionless-builder [options]

# To understand more about the available builder options
target/release/permissionless-builder -h

# Run a node with the builder docker image
docker run -it \
  [-e ENV=VALUE...] \

For a quick start, we recommend referring to the sequencer docker compose file, and looking particularly at permissionless-builder.

Parameters & options

Env VariableCLI FlagDescription



URL of hotshot events API running on Espresso Sequencer DA committee node. A builder will subscribe to this server to receive hotshot events. (e.g. http://localhost:8081)



Mnemonic phrase for builder account (e.g. "test test test test test test test test test test test junk")



Index of a funded account. Note: This account must be funded in Espresso, meaning ETH must be bridged from the L1



A Url builder will use for RPC communication with L1 (e.g. http://demo-l1-network:8545)



Peer nodes use to fetch missing state



Unique identifier for an instance of the sequencer network



Maximum allowed size (in bytes) for a block



Minimum fee in WEI per byte of payload



Port to run builder server on through which sequencer node can query builder provided APIs (e.g 41003)



Bootstrapping View number (e.g. 0)



The most outstanding hotshot events a builder wants at a point in time (e.g. 1024)



The amount of time a builder can wait before timing out a request to the API (e.g 1s)



The number of views to buffer before a builder garbage collects its state (e.g. 15)

Hardware Requirements

Hardware requirements are still in flux as we refine our testnets and add new features, but for now we recommend the following:

RAM: 4-8 GB

CPU: 2-4 Cores

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