Vitalik Buterin is zeroing in on a part of Ethereum that most users rarely think about but that plays a critical role in decentralization: who decides which transactions make it into a block.
In a post on X, Vitalik outlined concerns that Ethereum’s upcoming Glamsterdam upgrade, which introduces enshrined Proposer Builder Separation, could unintentionally concentrate power among a small group of sophisticated block builders. While the upgrade is designed to prevent staking centralization, Vitalik argues it does not automatically solve the risk of builder dominance.
One proposed safeguard is FOCIL, short for Forward Obligatory Commitment to Inclusion Lists. Under this design, a randomly selected group of participants would ensure certain transactions must be included in a block or the block would be rejected. The goal is to preserve censorship resistance even if a single builder gains outsized influence.
Vitalik also addressed so-called toxic MEV, suggesting encrypted mempools to prevent frontrunning and sandwich attacks. As Ethereum scales, he argues, decentralization challenges are shifting from validators to the infrastructure that determines what actually lands onchain.
