Vitalik Buterin Proposes ePBS, FOCIL and Encrypted Mempools to Reshape Ethereum Block Building by 2026

Vitalik Buterin outlined a roadmap on Monday to overhaul Ethereum's block building process ahead of the Glamsterdam upgrade planned for the first half of 2026, focusing on reducing block builder centralization and strengthening censorship resistance. Glamsterdam will introduce enshrined Proposer-Builder Separation (ePBS), allowing validators to outsource block construction to a permissionless builder market so that block builder dominance does not spill over into staking power, though he warned that block building itself could still concentrate among advanced actors optimizing transaction ordering for value extraction. To counter censorship risks, Buterin proposed Forward Obligatory Commitment to Inclusion Lists (FOCIL), where 16 randomly chosen attesters can enforce transaction inclusion by causing the network to reject blocks that omit required transactions, and described a "Big FOCIL" model in which participants directly include most transactions so builders mainly handle MEV-related activity and state execution. He also addressed pre-block risks such as sandwiching, frontrunning, transaction griefing and RPC-level surveillance, arguing that encrypted mempools and anonymized routing via tools like Tor and Ethereum-focused mixnets such as Flashnet are an active design area linked to ongoing work by the Ethereum Foundation.