What Is the Role of a ‘Block Builder’ in the Context of MEV Mitigation?

In Proof-of-Stake systems with Proposer-Builder Separation (PBS), the block builder is a specialized entity responsible for aggregating transactions from the mempool and private relays, optimizing their order, and constructing the final block body. In MEV mitigation, builders are key because they can be incentivized to accept private bundles and create 'MEV-aware' blocks that minimize predatory extraction.

They compete to create the most profitable block, which is then proposed by a validator.