// the find
flashbots/mev-boost
MEV-Boost allows Ethereum validators to source high-MEV blocks from a competitive builder marketplace
mev-boost is middleware that sits between an Ethereum validator's beacon client and a marketplace of block builders, implementing proposer-builder separation (PBS) outside the protocol. Validators run it to get higher rewards than they'd earn building blocks locally. It's production infrastructure used by a large fraction of Ethereum validators today.
The timing games feature is genuinely thoughtful — delaying getHeader requests to catch later, higher-value bids is the kind of detail that only comes from running this in production at scale. The mock relay in server/mock is properly structured for testing the full proposer flow without a live relay, which makes contributing to this without Ethereum node access actually viable. The -min-bid fallback mechanism is a clean escape hatch: if no builder beats your threshold, you build locally, so validators aren't forced into bad blocks. Multi-relay fan-out with best-bid selection is correct by default and the config supports hot-reloading, which matters for operators who can't restart during a slot.
The single audit from 2022 is showing its age — the codebase has evolved through multiple Ethereum hard forks since then and the relay API surface has grown. The timing games feature is explicitly flagged as 'advanced users only' with a docs page but no guardrails in the config, so misconfiguring it can get validators slashed or miss proposals entirely. Relay trust is entirely the operator's problem: mev-boost will happily forward validator registrations to any relay you hand it, and there's no built-in list hygiene or reputation tracking. The OFAC/censorship implications of relay choice are documented elsewhere but not surfaced in the tool itself, which is a gap for operators who don't follow flashbots research closely.