Ethereum co-founder Vitalik Buterin has detailed the technical roadmap for the upcoming Glamsterdam upgrade, placing enshrined Proposer-Builder Separation (ePBS) at the core. The mechanism formally splits block proposing from block building, allowing proposers to delegate construction to a decentralized marketplace of builders. Buterin argues this separation is essential to curb the concentration of block-building power and prevent it from bleeding into validator centralization.
Beyond ePBS: FOCIL and Big FOCIL as Safeguards
Buterin stressed that ePBS alone cannot eliminate centralization risks in block building; its main contribution is to clarify role boundaries. To further strengthen decentralization, the Fork-Choice Enforced Inclusion Lists (FOCIL) model is being considered. Under FOCIL, a random set of 16 validators per block can mandate that specific transactions must be included; omitting them could result in the block being rejected by the network.
Buterin also floated 'Big FOCIL' as an extension that would enforce inclusion for all transactions. In this model, participants would be assigned responsibility for different sender addresses to avoid collisions, paving the way for fully distributed inclusion.
Toxic MEV, Encrypted Pools, and Relay Layer Vulnerabilities
Buterin turned attention to 'toxic MEV'—practices like front-running and sandwich attacks that harm ordinary users. He endorsed encrypted transaction pools, where transactions remain hidden until inclusion, as a countermeasure against premature information leaks. However, he admitted that infrastructure for timely decryption and validation is still immature.
The transaction relay layer, bridging wallets and blockchain nodes, drew special scrutiny. Although operating off-chain, it is vulnerable to surveillance and manipulation. Buterin cited Tor-based routing, Ethereum-specific anonymizing mixers, low-latency options like Flashnet, and the Kohaku initiative—which supports both network-level and on-chain privacy protocols—as potential mitigants.
Long-Term Vision: Block Production Modeled on BitTorrent
Buterin envisions Ethereum's block production eventually resembling BitTorrent's peer-to-peer architecture, where no single node manages all data and operations are broadly dispersed. The main technical hurdle lies in Ethereum's highly synchronized global state, where each transaction can depend on any other, complicating truly distributed block production. Still, Buterin noted that many transactions could be transitioned to limited-scope types that avoid full state interaction, reducing cost and complexity.
He emphasized that these ideas remain drafts without a concrete timeline or roadmap. The ultimate goal is to minimize the influence of any single participant and move toward a modular, distributed block architecture as Ethereum matures.