Ethereum is engaged in the most consequential infrastructure battle since The Merge. On March 2, 2026, Vitalik Buterin published a sweeping roadmap to dismantle the growing centralization of the block-building pipeline — a problem that now sees a single entity, Titan Builder, producing over 50% o...
"When you create an EIP to solve the problem of filtering out transactions with sanctioned addresses and your solution is to allow validators to impose constraints on builders... that's either naive or reckless." — Ameen Soleimani, Privacy Pools Founder
Ethereum is engaged in the most consequential infrastructure battle since The Merge. On March 2, 2026, Vitalik Buterin published a sweeping roadmap to dismantle the growing centralization of the block-building pipeline — a problem that now sees a single entity, Titan Builder, producing over 50% of all Ethereum blocks. The weapons: enshrined Proposer-Builder Separation (ePBS) in the forthcoming Glamsterdam upgrade, Forward Obligatory Commitment to Inclusion Lists (FOCIL) in the Hegota upgrade, encrypted mempools, and network-layer anonymization.
The stakes are existential. If block building remains concentrated in the hands of two or three sophisticated actors, Ethereum's core promise — censorship resistance — becomes a theoretical property rather than a practical guarantee. Between December 2025 and January 2026, MEV searchers extracted approximately $24 million in profit from Ethereum users. Annualized across the broader ecosystem, MEV extraction runs to roughly $1 billion per year. The question is no longer whether Ethereum has a centralization problem. It's whether the protocol can engineer its way out before institutional adoption locks in the current power structure.
Ethereum's block production has consolidated at a pace that should alarm anyone who takes decentralization seriously. As of February 27, 2026, the market share breakdown for Ethereum block builders stands at:
| Builder | Market Share | |---------|-------------| | Titan Builder | 50.15% | | BuilderNet | 27.94% | | Quasar | 16.22% | | Others | ~5.69% |
This represents a notable shift from 2024, when Beaverbuild and Titan collectively built approximately 86% of all mainnet blocks over rolling two-week periods, forming a de facto duopoly. The emergence of BuilderNet — a joint initiative between Flashbots, Beaverbuild, and Nethermind — has partially fractured this concentration. But partial isn't sufficient. Three entities still control over 94% of Ethereum's block production.
The root cause is economic. Block building is an MEV extraction game. Builders with superior access to exclusive order flow, more sophisticated arbitrage algorithms, and better latency infrastructure consistently win the block auction. Advantages compound: more winning blocks attract more order flow, which attracts more MEV, which funds better infrastructure. It is a natural monopoly dynamic playing out in real time.
Buterin's March 2 blog post laid out a phased roadmap that amounts to the most ambitious structural intervention Ethereum has attempted since the transition to Proof of Stake:
Phase 1: ePBS (Glamsterdam, H1 2026) — Enshrining Proposer-Builder Separation directly into the protocol eliminates the need for third-party relay infrastructure like MEV-Boost. Proposers (validators) auction off the right to build blocks to specialized builders through an in-protocol mechanism. This prevents block builder centralization from contaminating staking centralization — but it explicitly does not solve builder centralization itself.
Phase 2: FOCIL (Hegota, H2 2026) — The first real offensive move. Sixteen randomly selected attesters create mandatory inclusion lists. If a block builder ignores these lists, the block is rejected by the fork-choice rule. Censorship becomes protocol-impossible, not just protocol-discouraged.
Phase 3: Big FOCIL (Post-Hegota) — Expands inclusion lists to cover nearly all transactions in a block, effectively reducing the builder's role to state computation and marginal MEV optimization. The builder becomes a utility, not a power center.
Phase 4: Encrypted Mempools — Transactions are encrypted until inclusion in a block, eliminating the information asymmetry that makes front-running and sandwich attacks profitable. This is the kill shot for toxic MEV.
Each phase builds on the previous one. ePBS contains the damage. FOCIL prevents censorship. Big FOCIL commoditizes building. Encrypted mempools eliminate the economic incentive for centralization.
FOCIL is the centerpiece of Ethereum's censorship-resistance strategy, and it is already confirmed for the Hegota upgrade in the second half of 2026. Alex Stokes, an Ethereum Foundation researcher, confirmed its inclusion during a recent All Core Devs meeting.
The mechanism works as follows: at the start of each slot, a committee of 16 randomly selected validators creates inclusion lists — sets of transactions that must appear in the next block. The block builder retains the freedom to order transactions and include additional ones, but the FOCIL transactions are non-negotiable. If the builder produces a block that excludes any FOCIL-listed transaction, the network's fork-choice rule rejects the block entirely.
The design has a profound implication. Even if 100% of block building were captured by a single hostile entity, that entity could not censor transactions. The 16 FOCIL committee members — randomly selected from the entire validator set — serve as a decentralized check on builder power.
As Buterin wrote: transactions "must be included somewhere in the block (the block gets rejected otherwise)." This is censorship resistance enforced at the consensus layer, not dependent on builder goodwill.
FOCIL is also the most controversial proposal on Ethereum's 2026 roadmap. Privacy Pools founder Ameen Soleimani has mounted a public critique that strikes at the intersection of protocol design and regulatory reality.
The core argument: FOCIL forces validators to include transactions from OFAC-sanctioned addresses. When Tornado Cash was sanctioned in August 2022, approximately 80% of Ethereum blocks voluntarily excluded Tornado Cash transactions. By late 2023, OFAC-compliant blocks had fallen to roughly 27% as non-censoring relays gained adoption. But critically, US-based validators were never forced to include sanctioned transactions — they chose to exclude them, and the system still worked because non-US validators picked up the slack.
FOCIL changes this dynamic. If a US-based validator is randomly selected for the FOCIL committee, they must include sanctioned transactions in their inclusion list or the protocol breaks. Soleimani warns that US regulators could target validators, attesters, or even the developers who designed the forced inclusion system.
The counterargument from Ethereum researchers is that FOCIL committee members don't process or relay transactions in the traditional sense — they simply attest that valid transactions should be includable. Whether this legal distinction holds under existing sanctions law remains untested. This tension — between protocol-level censorship resistance and real-world regulatory compliance — is perhaps the defining governance question for Ethereum in 2026.
While Ethereum's core developers work on protocol-level solutions, the private sector isn't waiting. Flashbots launched BuilderNet in late 2025 with an approach that tackles centralization from the supply side.
BuilderNet's architecture runs on Trusted Execution Environments (TEEs) — encrypted secure enclaves that process transactions without revealing order flow data. This neutralizes the exclusive order flow advantage that has driven builder centralization. Key design principles include:
The early results are significant. BuilderNet has captured 27.94% of Ethereum block production as of late February 2026, making it the second-largest builder behind Titan. This is a meaningful dent in what was a two-player market just twelve months ago.
However, BuilderNet is a market-based solution, not a protocol guarantee. It works as long as participants voluntarily use it. FOCIL and ePBS operate at the consensus layer — they cannot be opted out of.
The final piece of Buterin's roadmap — encrypted mempools — targets the economic root of the problem. Today, transactions sit in a public mempool visible to anyone before they're included in a block. This transparency creates a multi-billion-dollar extraction opportunity:
Encrypted mempools would make transaction contents invisible until block inclusion. Without visibility, front-running becomes impossible. Sandwich attacks cannot be constructed. The information asymmetry that makes MEV extraction profitable simply vanishes.
The Ethereum Foundation is exploring integration with network-layer anonymization tools including Tor and Ethereum-focused mixnets like Flashnet. These would anonymize not just transaction contents but also the identity of the submitter, closing the final information leakage vector.
The timeline for encrypted mempools extends beyond 2026, but the research trajectory is clear. Combined with FOCIL, this creates a world where block building is both uncensorable and unprofitable to monopolize.
The economic value redistribution implied by this roadmap is significant:
For MEV searchers and builders: The current ~$1 billion annual MEV extraction economy faces structural compression. FOCIL limits builder discretion. Encrypted mempools eliminate toxic MEV entirely. The surviving MEV opportunities — benign arbitrage that improves market efficiency — become commoditized. Builder margins collapse toward zero.
For validators: ePBS creates a clean auction mechanism for builder payments to proposers. Validators benefit from a transparent, protocol-enshrined payment channel rather than relying on off-protocol relay infrastructure. The value captured by validators may actually increase as MEV auctions become more competitive.
For users: The primary beneficiary. Reduced MEV extraction means better execution prices on DeFi trades. Censorship resistance guarantees that no transaction can be permanently excluded. The "invisible tax" that MEV imposes on every Ethereum user — estimated at basis points on every swap — gradually approaches zero.
For institutions: The FOCIL legal question is the key variable. If US-based validators face prosecution risk for participating in FOCIL committees, institutional staking operations may need to restructure. Conversely, strong censorship resistance may be exactly what institutional adopters need — the guarantee that their transactions cannot be blocked by competitors or hostile actors.
Ethereum is attempting something no major blockchain has done: retroactively dismantling a natural monopoly at the infrastructure layer while the network processes billions in daily value. The block builder centralization problem is not a bug in Ethereum's design — it is an emergent economic outcome of MEV-driven competition. Buterin's phased roadmap acknowledges this reality and attacks it from multiple vectors simultaneously.
The technical solutions are elegant. FOCIL is a minimal, high-impact mechanism that transforms censorship from a builder choice to a protocol impossibility. Encrypted mempools eliminate the economic incentive for centralization at the source. BuilderNet provides a market-based bridge during the transition.
But the unresolved tension — between protocol-level censorship resistance and real-world regulatory regimes — cannot be engineered away. If FOCIL forces US validators into legal jeopardy, the most likely outcome is geographic fragmentation of the validator set, with US-based operators either exiting or seeking legal safe harbors. This is not necessarily a bad outcome for decentralization, but it is a messy one.
What is clear is that Ethereum's leadership recognizes the threat. A network where three entities control 94% of block production is not decentralized in any meaningful sense. The next twelve months will determine whether Ethereum can bend this curve — or whether centralization, once entrenched, proves irreversible.