PBS

Essence

Proposer-Builder Separation, or PBS, is a fundamental re-architecture of blockchain transaction processing. It divides the block creation process into two distinct roles: the proposer, who suggests the order of transactions and signs the final block, and the builder, who constructs the optimal block payload from available transactions. This mechanism was introduced to mitigate the negative externalities of Maximal Extractable Value (MEV) by decentralizing the power to dictate transaction order.

In traditional blockchain models, a single entity ⎊ the miner in Proof-of-Work or the validator in early Proof-of-Stake ⎊ controlled both the inclusion and ordering of transactions. This single point of control created a powerful incentive for front-running, sandwich attacks, and other forms of value extraction, leading to higher execution risk for all market participants.

The core design goal of PBS is to externalize the complex, computationally intensive task of finding the most profitable transaction order. By separating these concerns, the protocol aims to reduce the centralization pressure on validators, as they no longer need specialized hardware or proprietary algorithms to compete for MEV. The proposer’s role becomes simpler: select the most valuable block from a set of submissions provided by competing builders.

This system introduces a market for block space itself, where builders bid for the right to have their block included, creating a more efficient and potentially fairer distribution of MEV. The impact on crypto options is significant because it fundamentally alters the assumptions about execution risk and transaction finality, which are critical inputs for derivatives pricing models.

PBS fundamentally re-architects value capture by separating transaction ordering from block finalization, creating a market for block space itself.

Origin

The concept of PBS emerged directly from the challenges presented by MEV in Proof-of-Work (PoW) systems, and its necessity became undeniable during the transition to Proof-of-Stake (PoS) for Ethereum. In PoW, miners observed that certain transactions offered opportunities for profit beyond standard fees, primarily through front-running. This led to the “dark forest” phenomenon, where sophisticated bots constantly monitored the public mempool to execute profitable arbitrage strategies against standard users.

The value extracted became substantial, leading to a race for specialized hardware and private communication channels to gain an advantage in block inclusion.

As Ethereum transitioned to PoS, the problem of MEV became even more pronounced. A validator’s stake in the network made them a powerful central point for value extraction. The community recognized that if a single validator controlled both block creation and proposal, it would lead to an immense concentration of wealth and power, potentially compromising the network’s decentralization goals.

The initial solution, spearheaded by Flashbots, introduced a private communication channel where searchers could bid directly to builders (initially miners, then validators) to have their transactions included in a specific order. PBS formalizes this ad-hoc system at the protocol level. It institutionalizes the separation of concerns, moving from a temporary mitigation strategy to a core architectural design choice.

The origin story of PBS is a direct reflection of the adversarial nature of open-source financial systems, where a new source of value (MEV) necessitates a re-design of the system’s core consensus mechanism to maintain equilibrium.

Theory

The theoretical underpinnings of PBS are rooted in auction theory, game theory, and market microstructure analysis. From a quantitative perspective, PBS introduces a new set of variables that must be accounted for when modeling execution risk and options pricing. The most immediate impact is on the calculation of execution cost.

Before PBS, execution risk for large options hedges involved the probability of being front-run by a validator. With PBS, this risk transforms into a new calculation: the cost of securing private order flow through a builder versus the risk of using the public mempool.

The builder’s optimization problem is a complex knapsack problem. Builders must select a subset of transactions from the mempool to maximize their profit, which involves balancing transaction fees against MEV opportunities. This creates a highly competitive, dynamic environment where the value of a transaction can change based on the builder’s specific optimization strategy.

For options market makers, this means the price of hedging a large position is no longer a static fee but a variable cost determined by the current state of the builder market. The market maker must decide whether to pay a premium for priority inclusion via a builder or risk a lower-cost, but less certain, execution via the public mempool. This dynamic directly impacts the pricing of options, particularly for large notional values where execution certainty is paramount.

The second theoretical implication lies in the volatility skew. In options pricing, volatility skew refers to the difference in implied volatility between options with different strike prices. The introduction of PBS changes the underlying probability distribution of future asset prices by reducing certain forms of short-term volatility (like large price movements caused by sandwich attacks).

By mitigating these specific risks, PBS could theoretically flatten the skew for short-term options, reflecting a more efficient market. However, a new type of systemic risk emerges from the centralization of builders. If a small number of builders dominate the market, they could collude or engage in strategic behavior that reintroduces new forms of price manipulation.

The system’s stability becomes dependent on the competitive dynamics of the builder market, rather than the validators alone. The theoretical elegance of PBS lies in its ability to convert a systemic problem (MEV extraction) into an economic opportunity (the builder auction), but this conversion introduces new, complex dependencies that require careful analysis.

From a game-theoretic standpoint, PBS introduces a principal-agent problem between the proposer and the builder. The proposer wants to maximize their revenue, while the builder wants to maximize their profit from transaction ordering. The system relies on a credible commitment from the proposer to select the highest-bidding block, creating a mechanism design challenge to ensure both parties act in good faith.

The success of PBS hinges on the economic incentives being aligned to prevent collusion and ensure a fair auction. If a proposer and builder collude, they can circumvent the auction mechanism, undermining the very purpose of the separation.

Approach

For a derivative systems architect, implementing a strategy in a PBS environment requires a complete re-evaluation of execution logic. The approach shifts from simply managing market risk to managing systemic execution risk. The core decision for a market maker is how to route their orders to ensure minimal slippage and optimal hedging.

There are generally two approaches to execution in a PBS environment: utilizing a private relay or using the public mempool. A market maker operating on a decentralized options protocol must decide whether the cost of private order flow is justified by the reduction in execution risk. The private relay system, where orders are sent directly to a builder, ensures that the market maker’s large hedge orders are not visible to front-running bots in the public mempool.

This certainty comes at a cost, as builders extract a portion of the value. The decision process for a large institutional options trader might involve the following steps:

• Liquidity Assessment: Determine if the required hedge size exceeds a certain threshold where public mempool execution becomes prohibitively risky.
• Builder Selection: Choose a builder based on their historical performance, reliability, and fee structure. This selection process involves evaluating the builder’s reputation for honesty and their commitment to censorship resistance.
• Cost-Benefit Analysis: Calculate the expected cost savings from avoiding front-running against the premium paid to the builder for private inclusion.
• Order Routing Logic: Implement a smart order router that dynamically switches between private relays and public mempools based on real-time market conditions and the size of the order.

The practical application of PBS in crypto options trading also impacts the design of automated market makers (AMMs) and options vaults. AMMs must now consider the MEV generated by their own operations as a potential source of profit for external searchers. By integrating with PBS, AMMs can potentially capture this MEV internally, increasing capital efficiency for liquidity providers.

The approach for a new protocol design would involve creating a system where the protocol itself acts as a searcher or builder, ensuring that the value created by options trading stays within the protocol rather than being extracted by external parties.

The most effective approach for options market makers in a PBS environment is to integrate private order flow strategies directly into their execution logic to mitigate execution risk.

Evolution

The evolution of PBS from its theoretical inception to its current implementation has revealed a critical paradox: solving one form of centralization (validators extracting MEV) has led to another (centralization of builders and relays). The current implementation of PBS relies heavily on a small number of centralized relays and builders. These entities act as trusted intermediaries, creating new points of failure and potential censorship vectors.

If a relay decides to censor certain transactions, it can effectively block specific types of options trading or prevent users from accessing liquidity.

The current state of PBS is characterized by the tension between efficiency and decentralization. The market for builders has become highly competitive, but the infrastructure that supports it remains concentrated. The next phase of evolution aims to address this by moving toward a fully decentralized system.

This involves developing Decentralized Builder Networks (DBNs) where a multitude of builders compete, and the proposer selects from a large, diverse pool of blocks. This aims to distribute power more widely and increase censorship resistance. Another area of evolution is Encrypted Mempools , which protect transactions from being read by builders before they are included in a block.

This removes the ability for builders to front-run transactions, further reducing execution risk for options traders.

The future of PBS will likely involve a move toward a more robust, decentralized infrastructure. The goal is to create a system where the value of block space is efficiently captured and distributed without relying on centralized entities. The development of new protocols that integrate DBNs directly into their consensus mechanism will be key.

This evolution is driven by the realization that a truly resilient financial system requires not only a decentralized settlement layer but also a decentralized execution layer.

Horizon

Looking ahead, the long-term impact of PBS on crypto options markets will be defined by its success in creating a fair and efficient execution layer. If PBS fully delivers on its promise of decentralized block building, it could significantly lower execution risk for institutional market makers. A reduction in execution risk directly translates to tighter options spreads and more competitive pricing.

This creates a more attractive environment for large-scale, institutional options trading.

The horizon also presents the possibility of new derivative products built around MEV itself. If block space becomes a truly tradable commodity, we could see the creation of “MEV futures” or “block space derivatives.” These products would allow market participants to hedge against the volatility of MEV extraction, creating a new layer of financial engineering. The integration of options protocols with DBNs will also become a critical design choice.

Protocols could allow users to sell their right to block space directly to options market makers, creating a new form of value accrual. This future involves a complete re-imagining of how execution risk is priced and traded, moving from an implicit cost to an explicit, tradable asset.

The ultimate goal is to move beyond the current state of PBS to achieve execution-aware pricing. This means that options pricing models will no longer rely solely on market volatility but will also incorporate the specific cost of execution, which varies depending on the current state of the builder market. This level of precision allows for more sophisticated risk management and capital deployment.

The future of crypto derivatives is intertwined with the evolution of PBS; the success of one depends on the other.

The future of options pricing will be execution-aware, incorporating the variable cost of block space and private order flow into pricing models.