1. Providers
  2. Builder Modifications (~5 minutes)


Builder Modifications (~5 minutes)

Below is a general overview of the minor changes needed to an Ethereum Execution Client like geth to enable Primev. We will walk through the changes needed using a standard fork of the Flashbots builder. We also detail changes needed with commit references in case your geth instance has custom modifications.

Please reach out to us if you need any assistance.


Builder-boost sits as a sidecar module to your execution client. The builder will consistently spin up lightweight go-routines to POST new block templates.

block template generation

Quickstart (5 mins)

You can follow the steps below to use our reference implementation:

  1. Clone the repository from https://github.com/primevprotocol/builder-reference-primev.
  2. Build the instance and add the flag -builder.remote_primev_endpoint <your-builder-boost-url> --builder.primev_token <your-selected-private-token>.

[optional] Advanced Instructions

General Overview of Changes Needed

The idea behind the builder changes is to enable a new local “relay” to publish blocks to, in a fashion similar to how blocks are sent to relays like flashbots, blocknative, or agnostic today.

Below is a more detailed perspective of the standard flow in the Flashbots builder. We add a command of go SubmitBlockPrimev(&blockData) in the SubmitBlock section.

Geth instances have the concept of an IRelay. You simply need to add a SubmitBlockPrimev to such a relay that is in use and configure any necessary configurations via modifications similar to this commit: https://github.com/primevprotocol/builder-reference-primev/commit/9f160e8934fef1aadd21e095c432db41538b93af.

Step by Step Walkthrough

Step 1. Registering the Builder Boost environment variables

Step 1a. Primev Endpoint

You can view the entire commit for this section below.

Commit: 9f160e8934fef1aadd21e095c432db41538b93af

You can build Geth and you will see the following output by the end of this:

        **WARN [timestamp] Remote Primev Endpoint is not Set, payloads will not be sent to Primev Network**


If you set the correct environment variable BUILDER_REMOTE_PRIMEV_ENDPOINT or pass in the flag builder.remote_primev_endpoint while running Geth, you'll see the following successful message:

        **INFO [timestamp] Remote Primev Endpoint is Set, payloads will be sent to Primev Network endpoint=<Your builder boost URL>**


Step 1b. Primev Auth Token

The primev auth token is used to authorize and authenticate the builder instance. This is to ensure only your block builders can post payloads to builder-boost.

The following link showcases the necessary modifications to set up the Primev Auth Token:

Commit: d9b8addd1fdeea8c841a43ff7653e7c9345e7e0d

We will describe below in Step 3 how to submit the request. Ensure you make the modification to add the X-Builder-Token: <primev-token> header to the POST request that is made to Boost.

Step 2. Updating the Relay Interface to Support Block Submission to Primev/Builder Boost

In this commit, we simply add all the required function details to support updating the Relay interface to publish to builder-boost.

Commit: 6d8ae9aae17a1b966ac0f682ba9843bd8746dc4f

Step 2a. Update interface needs for Unit Tests

Follow the commit to add a stub for the testRelay to ensure it adheres to the new interface.

Commit: 122e82ee6072ff2cda94ed8e75fdd861befccd19

Step 3. Start Submitting Blocks to builder-boost

Finally, we submit the block details via a go-routine to ensure we don't block for the response:

Commit: 04d81efdf499ada3cee303316665edf0d5945a27

Voila, your Block builder is now a bleeding edge builder that can share execution data! Not some off the shelf Block builder 😉