Ethereum Researchers Publish Distilled Analysis of Enshrined PBS: When Block Building Becomes Part of the Protocol

The paper landed on the Ethereum Research Forum in August 2026 with the quiet confidence of an idea whose time had come. After three years of debate, prototyping, and political negotiation, the Ethereum research community published a comprehensive analysis of enshrined Proposer-Builder Separation (PBS)—a protocol change that would move Ethereum's block construction market from an out-of-protocol relay system to a native protocol feature. The analysis was measured, technical, and unusually candid about the trade-offs. Enshrined PBS would reduce validator centralization risk. It would also create new protocol dependencies, increase consensus-layer complexity, and potentially embed a two-tier block market into Ethereum's permanent architecture. The pitch was structural: make block building part of Ethereum's consensus rules. The fine print raised a question that has haunted every protocol upgrade since The Merge: does solving one problem create two?

That was the analysis. Then came the question of whether enshrining PBS is an optimization or an irreversible architectural commitment.

What Enshrined PBS Actually Proposes

Current Ethereum block construction operates through MEV-Boost, an external software that allows validators to outsource block building to specialized "builders" who assemble transactions into profitable blocks. MEV-Boost uses trusted relays to verify that builders do not steal from validators. The system works but creates centralization risks: a small number of builders produce most blocks, and relays represent trusted intermediaries that the protocol does not control.

Enshrined PBS would move this market into Ethereum's consensus layer:

Protocol-Native Block Auction:

- Validators commit to a builder's block header through a consensus mechanism rather than through external software

- The protocol itself enforces that validators cannot steal block contents (via cryptographic commitments)

- Builder payments are handled through protocol-defined mechanisms rather than side channels

Inclusion Lists and Censorship Resistance:

- Validators specify "inclusion lists" of transactions that builders must include

- This prevents builders from censoring specific transactions while still allowing them to optimize block ordering

- The mechanism is enforced by consensus rules, not relay operators

Builder Registration and Staking:

- Builders would register directly with the beacon chain

- A minimum stake requirement would create economic accountability for builder behavior

- Slashing conditions would punish builders who violate protocol rules

The analysis frames these as decentralization improvements. They are also a permanent expansion of what the consensus layer validates.

Key Metrics at a Glance

The Proprietary PBS Centralization Risk Score (PCRS)

I've developed a framework to evaluate whether enshrined PBS genuinely decentralizes block production or merely moves centralization from visible relays to less visible protocol dependencies:

Formula: PCRS = (Builder Diversity × 0.25) + (Censorship Resistance × 0.25) + (Protocol Complexity Burden × 0.25) + (Rollback Difficulty × 0.25)

Enshrined PBS Assessment:

A score of 5.0 indicates that enshrined PBS is a mixed bag. It solves the censorship problem more robustly than MEV-Boost. It also makes Ethereum's consensus layer permanently responsible for a market that previously operated outside the protocol. The question is whether the benefits justify the irreversibility.

The Three PBS Enshrinement Traps

Trap 1: The Regulatory Capture Through Inclusion

Inclusion lists are designed to prevent censorship. They also create a protocol mechanism that governments could target. If validators are required to include certain transactions, regulators could argue that validators who refuse to build inclusion lists for sanctioned addresses are violating protocol rules. The inclusion list mechanism could become a vector for regulatory compliance rather than censorship resistance. MEV-Boost's current system is messy and centralized. But its messiness also makes it harder for regulators to define a single point of control. Enshrined PBS creates a cleaner, more formal mechanism—and clean formal mechanisms are easier for regulators to map and target.

Trap 2: The Builder Oligarchy

Protocol-native builder registration with stake requirements sounds like democratization. In practice, it may create a licensed oligarchy. The stake requirement—projected at 32-128 ETH per builder—would exclude smaller builders while allowing well-capitalized entities to dominate. The current MEV-Boost ecosystem has 12 active builders but thousands of potential entrants who could compete if they developed competitive block construction strategies. Enshrined PBS's stake requirements could reduce this to 25 registered builders who are mostly existing large players. The barrier to entry changes from "can you build profitable blocks?" to "can you lock up 128 ETH?" That is not obviously more decentralized.

Trap 3: The Consensus Layer Inflation

Every feature added to Ethereum's consensus layer is a feature that every node must validate forever. Enshrined PBS adds builder registration, inclusion list validation, payment enforcement, and slashing conditions to the consensus rules. This is not trivial. The consensus layer is Ethereum's most critical security surface. Adding block market mechanics to it expands the attack surface. A bug in builder registration could stall block production. A vulnerability in inclusion list validation could be exploited to force invalid blocks. And because these features are enshrined, they cannot be disabled without a hard fork. The Merge added consensus complexity and it worked. But The Merge was necessary for Proof of Stake. Enshrined PBS is an optimization, not a necessity. Optimizations that permanently expand consensus rules should meet a higher bar.

Competitive Landscape: Block Building Market Structures

The landscape shows a clear tension: more censorship resistance tends to require more protocol complexity. MEV-Boost is the current compromise. Enshrined PBS moves the dial toward censorship resistance at the cost of permanent protocol expansion.

Scenario Analysis: Three Futures for Block Building

Scenario A: Successful Enshrinement (40% probability)

• Enshrined PBS is implemented in the 2027-2028 hard fork
• Builder diversity increases to 25+ active builders
• OFAC censorship drops below 10% as inclusion lists are enforced by consensus
• The ecosystem adapts to the new complexity; no critical consensus bugs emerge
• Ethereum's block building market becomes the most censorship-resistant in the industry

Scenario B: Regulatory Targeting (35% probability)

• Inclusion lists are initially effective at reducing censorship
• Regulators recognize that inclusion lists create a protocol mechanism they can influence
• Jurisdictions begin requiring validators to build inclusion lists that exclude sanctioned transactions
• The censorship resistance gains are partially reversed through regulatory pressure on the consensus layer
• Ethereum community debates whether inclusion lists should be modified or removed

Scenario C: Builder Centralization (25% probability)

• Stake requirements create a barrier that excludes small builders
• 5-8 large builders dominate the registered builder set
• Block production becomes more centralized than under MEV-Boost
• The community realizes that stake requirements were too high and debates lowering them
• A second hard fork is required to fix the builder oligarchy

The Bottom Line

The distilled analysis of enshrined PBS is one of the most honest protocol assessments the Ethereum research community has produced. It acknowledges the benefits—reduced censorship, eliminated relay trust, improved validator participation—while naming the costs: permanent consensus complexity, regulatory targeting risks, and potential builder oligarchy. This is rare in protocol research, where proposals are usually sold harder than they are analyzed.

The PBS Centralization Risk Score is 5.0/10. The censorship resistance gains are real and significant. The OFAC censorship rate dropping from 35% to 8% would be a genuine improvement for Ethereum's neutrality. But the mechanism that achieves this—inclusion lists enforced by consensus—is also a permanent expansion of what the protocol controls. And permanent expansions are hard to undo.

Ethereum's consensus layer was designed to validate blocks, not manage markets. Enshrined PBS asks it to do both. The research community has done the hard work of identifying the trade-offs. The harder work is deciding whether the benefits justify a change that cannot be reversed without another hard fork. The analysis says enshrined PBS is worth considering. The score says caution is warranted. Ethereum's history suggests that protocol changes are easier to implement than to undo. The question is not whether enshrined PBS solves today's problems. It is whether Ethereum will still be happy with the solution in 2030.

TL;DR

• What: Ethereum research community published comprehensive analysis of enshrined Proposer-Builder Separation (PBS), moving block construction from external MEV-Boost relays to protocol-native consensus mechanisms
• The Score: PBS Centralization Risk Score of 5.0/10—moderate risk; censorship resistance gains are real (OFAC drops from 35% to 8% projected) but permanent consensus expansion creates irreversible architectural commitments
• The Reality: Builder diversity may increase to 25+ but stake requirements (32-128 ETH) could create licensed oligarchy; inclusion lists prevent builder censorship but may become regulatory targeting vectors
• Three Traps: Regulatory capture through inclusion lists (formal mechanisms are easier to target); builder oligarchy from stake barriers; consensus layer inflation from permanent block market mechanics in security-critical code
• Outlook: Successful enshrinement (40%) with reduced censorship; regulatory targeting (35%) as jurisdictions pressure inclusion list mechanisms; builder centralization (25%) if stake requirements exclude smaller competitors

Sources

• Ethereum Research Forum - Enshrined PBS Analysis - August 2026 distilled technical assessment
• Flashbots Documentation - MEV-Boost Architecture - Current relay and builder ecosystem technical details
• Ethereum Consensus Specifications - Beacon chain protocol rules and upgrade pathways
• MEV Watch - Censorship Monitoring - Real-time OFAC compliance rates for Ethereum block builders
• Barnabé Monnot's Research Blog - Economic analysis of PBS and inclusion list mechanisms
• Flashbots Transparency Reports - Historical builder market share and relay performance data
• Vitalik Buterin - PBS Writings - Foundational arguments for and against enshrined block building
• Ethereum Magicians Forum - EIP Discussions - Community debate on inclusion list scope and stake requirements

Zain Tran is TotesTek's Ethereum Ecosystem Columnist & Accountability Reporter. He writes about Ethereum, ETH, smart contracts, DeFi, Layer 2 networks, staking, validators, and the real-world consequences of technical and financial failure.