Vitalik Buterin turns his attention to a part of Ethereum that most users never think about, but which has quietly become one of its biggest pressure points: who decides which transactions go into a block.
In a new blog post published Monday, the Ethereum co-founder outlines a series of ideas aimed at preventing block construction, the process of assembling transactions before they are finalized on-chain, from becoming too centralized.
While Ethereum’s upcoming “Glamsterdam” upgrade will formalize the proposer-builder split, allowing validators to outsource block construction to a competitive marketplace, Buterin says that simply creating a builder marketplace won’t solve everything. If a small number of manufacturers dominate, they could still censor transactions or extract outsized profits from users.
One proposal, known as FOCIL, would act as a sort of anti-censorship safety net. Under this design, a small group of randomly selected participants would each choose which transactions should be included in the next block. If these transactions are missing, the block will be rejected. The idea is that even if a single hostile manufacturer controlled the entire market, it could not permanently exclude specific users.
Another focus of his article is so-called “toxic MEV,” where traders exploit the visibility of pending trades to make early or “sandwich” trades. One potential solution is to encrypt transactions until they are finalized, preventing opportunistic actors from seeing them in advance.
Buterin also highlights risks at the network layer, where transactions can be observed by intermediaries before they even reach a block, suggesting that anonymized routing systems could become an important line of defense.
Longer term, it outlines a vision of more distributed block construction, in which not all transactions require complete global coordination. Much of Ethereum’s activity may not need to be processed in a single, tightly ordered package, he says, opening the door to designs that reduce central choke points.
Overall, Buterin’s focus seems to be as Ethereum scales, the challenges of decentralization shift from validators to the infrastructure that decides which user transactions are actually made on-chain.
Read more: Vitalik Buterin reveals his bold new plan to solve Ethereum’s scaling problem
