Why Proposer Commitments Are a Flawed MEV Solution

Commitments create a winner-take-all market for the most sophisticated proposers, accelerating stake centralization.\n- Economic Advantage: Entities with the best MEV extraction tooling can pay the highest commitment premiums, outbidding smaller validators.\n- Stake Skew: This creates a feedback loop where >33% of stake can be controlled by a few actors, threatening network liveness and censorship resistance.

On-chain commitments are only as good as their verification, which is either impossible or prohibitively expensive.\n- Verification Gap: Proving a proposer violated a complex rule (e.g., 'no sandwich attacks') requires a full state simulation, which is ~O(n²) computational overhead.\n- Slashing Complexity: This leads to weak or non-existent slashing conditions, making commitments cheap talk rather than credible threats. Projects like EigenLayer face similar cryptographic verification limits.

Commitments are a band-aid on a broken user flow. The real solution is removing the proposer's discretionary power entirely.\n- Architectural Shift: Systems like UniswapX, CowSwap, and Across use fillers competing on a user's signed intent, bypassing the block builder's MEV monopoly.\n- Inevitability: As SUAVE and intents mature, the value of controlling block space diminishes, making proposer commitments obsolete.

Commitments concentrate power in the hands of a few large builders who can afford the infrastructure and capital to honor them. This recreates the centralization PBS was meant to solve.

• Top 3 builders control >80% of Ethereum blocks.
• Small validators are priced out, relying on external relays.
• Creates a cartel-like market where builders, not proposers, dictate terms.

Commitments rely on cryptographic proofs that a builder intended to include a transaction. This fails against dynamic, real-time MEV extraction.

• Frontrunning and time-bandit attacks can invalidate commitments after they are signed.
• Builders can simply ignore commitments if a more profitable opportunity arises, with proposers having no recourse.
• This makes commitments soft social promises, not hard cryptographic guarantees.

The network latency between proposers, builders, and relays creates a race condition that breaks commitment logic. Faster builders can always outmaneuver slower ones.

• A ~500ms advantage allows a competing builder to snipe profitable bundles.
• Forces an arms race in low-latency infrastructure, further centralizing the builder market.
• Commitments become stale before they can be included, rendering them useless for high-frequency MEV.

Ethereum's current PBS implementation via MEV-Boost is a prime example of commitments failing in practice. It outsources trust to a relay cartel.

• Validators must trust relays to honestly forward the winning block and payment.
• Relay censorship (e.g., OFAC compliance) becomes a systemic risk.
• The proposer payment is a separate, off-chain transaction, creating a fragile economic link.

Commitments create a principal-agent problem. The builder's profit motive is directly opposed to the proposer's commitment goals.

• Builder profit is maximized by breaking commitments for higher-value MEV.
• Proposer rewards are a fixed bid, creating no incentive to police builder behavior.
• This leads to a race to the bottom on commitment integrity as builders compete on profitability, not reliability.

To make a commitment, transaction flow must be revealed to builders early, destroying user privacy and creating new MEV opportunities.

• Transaction pre-revelation allows builders to frontrun their own commitments.
• Privacy solutions like SUAVE or encrypted mempools are incompatible with the commitment model.
• Forces a trade-off: enforce commitments or protect users, but not both.

Proposer commitments create misaligned incentives between validators (agents) and users (principals). Validators maximize their own revenue, not user outcomes, leading to predictable failures.

• Economic Capture: Validators are rational; they will defect from commitments for higher MEV rewards.
• Enforcement Gap: No on-chain mechanism can force a validator to honor a commitment without sacrificing liveness.
• User Harm: The illusion of protection is worse than no protection, creating systemic risk.

Commitments require proposers to pre-declare block-building rules, turning block production into a high-frequency, off-chain competition that centralizes infrastructure.

• Speed Wins: Builders with ~100ms latency advantages dominate, creating a winner-take-most market.
• Infrastructure Tax: Validators become rent-seekers, outsourcing to a few elite builders like Flashbots SUAVE or Jito.
• Network Fragility: The system's security depends on a handful of ultra-low-latency data centers.

The solution is to move the complexity upstream. Let users express desired outcomes (intents) via solvers, bypassing the proposer's discretion entirely.

• User Sovereignty: Protocols like UniswapX and CowSwap aggregate and fill intents off-chain, guaranteeing optimal execution.
• Proposer Irrelevance: The block builder's role is reduced to ordering pre-settled bundles, neutralizing their extractive power.
• Architectural Shift: This moves the competition to solver networks, a more competitive and user-aligned layer.

Commitments attempt to create 'fair' ordering, a concept regulators are scrutinizing. This creates legal risk without solving the core economic problem.

• SEC Target: Promising 'fair' sequencing could classify the activity as a securities-based swap or other regulated action.
• Unenforceable Promise: A commitment is a marketing term, not a legal contract, offering zero recourse for users.
• Distraction: Focus should be on credibly neutral, protocol-level solutions, not regulatory appeasement.

The economic and technical demands of honoring commitments will consolidate block production into a few vertically integrated entities.

• Staking Pools Dominate: Only large pools like Lido or Coinbase can afford the infrastructure to compete, replicating traditional finance.
• Cartel Formation: Top builders and proposers will form exclusive relationships, creating de-facto ordering cartels.
• Protocol Capture: The entities controlling ordering will eventually capture the governance and roadmap of the underlying chain.

Flashbots' SUAVE demonstrates the logical conclusion: a dedicated chain for preference expression and block building. This makes proposer commitments on L1s obsolete.

• Specialization: SUAVE separates the expression of demand (intents) from the supply of blockspace (execution).
• Commitment Redundancy: With a neutral auction platform, L1 proposers have no special information to commit against.
• Build Here, Not There: The innovation battle shifts to intent infrastructure, not L1 consensus tweaks.