Ethereum co-founder Vitalik Buterin has unveiled a sweeping plan to overhaul the network's block construction process, targeting the Glamsterdam upgrade scheduled for the first half of 2026. The proposal follows recent discussions on execution changes and quantum resistance, explaining why structural reform is needed now.
ePBS: Proposer-Builder Separation
Buterin said Glamsterdam will introduce enshrined Proposer-Builder Separation (ePBS), allowing validators to outsource block building to a permissionless builder market. This prevents builder dominance from spilling into staking power. However, he noted that block building itself may still concentrate among advanced actors who optimize ordering to extract value, making ePBS necessary but incomplete.
FOCIL and 'Big FOCIL': Censorship Resistance
To address censorship, Buterin highlighted Forward Obligatory Commitment to Inclusion Lists (FOCIL), where 16 randomly selected attesters force transaction inclusion. Missing required transactions cause the network to reject the block. He also described an expansion called 'Big FOCIL,' where participants include most transactions themselves, leaving builders to focus on MEV and state execution. This limits censorship even under high builder concentration.
Encrypted Mempools and Anonymized Routing
Buterin also tackled risks before transactions reach blocks, citing sandwiching, frontrunning, and transaction griefing as persistent issues. Encrypted mempools can prevent these by hiding details until inclusion. Beyond mempools, he emphasized the ingress layer: routing through public RPCs exposes users to surveillance. He cited growing research into anonymized routing using Tor and Ethereum-focused mixnets like Flashnet, calling it an open design space tied to Ethereum Foundation work.