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FiberBoost is a service that broadcasts ("boosts") blocks through the Fiber Network for faster global propagation, resulting in a reduced probability of missed slots due to proposer boost & honest reorgs. FiberBoost provides multiple interfaces to boost blocks:


The most straightforward and performant way to publish a block to Fiber is through the gRPC API. The PublishBlock endpoint is a bi-directional gRPC stream that accepts SSZ encoded, signed beacon blocks. The blocks can optionally be compressed with gzip.

Both fiber-go >= v1.8.0 and fiber-rs >= v0.5.1 provide an implementation of this method with gzip compression:

import (

fiber ""

func main() {
// Connection process omitted

// SSZ encoded, signed beacon block
beaconBlock := []byte{...}

ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
defer cancel()

// Returns the slot, root, and timestamp of the block, or a potential error
slot, root, timestamp, err := client.SubmitBlock(ctx, beaconBlock)
if err != nil {

fmt.Println("Submitted block", slot, root, timestamp)


Chainbound maintains an open-source, modified version of the MEV-Boost validator sidecar at this repository. The fork has a very minimal diff with the upstream Flashbots repository and follows the same release schedule. Track the diff here.

How it works

The following interaction diagram depicts the block proposal process using the modified MEV-Boost: The main difference with normal MEV-Boost is that when it receives a Payload from the relay, it will reconstruct the full signed beacon block, SSZ encode it and publish it to Fiber.

If you're a validator running MEV-Boost, this is the easiest way to start using FiberBoost.

Running it

Coming soon!

Direct Peering

Just like with FiberGuard, we offer a direct peering connection on the consensus layer for boosting blocks. This means that all blocks we receive on said connection will be boosted on our network.

The requirements and setup procedure are the same as with FiberGuard, you can read them here.