How Modular MEV Infrastructure Works in 2026

The modular shift in MEV

The transition from monolithic to modular MEV is not just an architectural upgrade; it is a fundamental change in how value is captured and distributed across the blockchain stack. In the legacy monolithic model, block builders held a monopoly on both sequencing and execution. They determined the order of transactions and then executed them, capturing the majority of the profit. This created a bottleneck where the builder’s primary incentive was to maximize extraction from the limited space within a single block.

Modular MEV breaks this monopoly by separating sequencing from execution. In this new landscape, a dedicated sequencer orders transactions, often using optimistic or verifiable methods to ensure fairness and efficiency. These ordered transactions are then sent to separate execution layers—such as rollups or specialized execution environments—where the actual computation and state changes occur. This separation allows for parallelization and specialization, enabling different parts of the network to optimize for their specific roles.

This shift significantly alters the profit landscape. Builders no longer need to be generalists who can handle everything from ordering to smart contract execution. Instead, specialized actors can emerge: sequencers focused on high-throughput ordering, and executors focused on complex MEV strategies like arbitrage or liquidations. Platforms like RBuilder have begun to facilitate this by providing infrastructure that connects searchers with builders in a more flexible, modular environment, allowing for more granular competition and potentially higher returns for specialized actors.

The result is a more dynamic and competitive MEV ecosystem. By decoupling sequencing from execution, the modular approach reduces the barriers to entry for specialized MEV strategies and allows for more efficient use of network resources. This is not just about efficiency; it is about creating a more robust and diverse MEV market where value is distributed based on specific capabilities rather than brute-force block space control.

Sequencing layers and order flow

In a modular MEV stack, the job of ordering transactions is pulled out of the execution layer and given to a shared sequencer. This separation changes how value is captured. Instead of a single builder managing the entire pipeline, the sequencer acts as a neutral gatekeeper, accepting order flow from multiple builders and relaying it to the consensus layer. The result is a system where ordering is a distinct service, rather than a byproduct of block production.

Shared sequencers like Celestia handle this by receiving transaction bundles and producing ordered data blobs. Builders then compete to propose blocks based on that ordered data. This creates a new extraction point. MEV is no longer just about what happens inside a block; it is also about who controls the sequence that feeds the block. If a sequencer can reorder transactions before they reach the builder, it captures value that would otherwise go to the proposer.

The implications are significant for transparency. In monolithic chains, the builder’s internal ordering logic is often opaque. In modular setups, the sequencer’s role is more visible, but it also introduces new risks. A malicious or compromised sequencer could front-run transactions or prioritize specific builders. The separation of duties means that security assumptions shift. You must trust the sequencer’s ordering integrity, not just the proposer’s block construction.

This dynamic is similar to how a factory assembly line works. The sequencer is the conveyor belt, moving parts in a specific order. The builder is the worker who assembles the final product. If the conveyor belt speeds up or slows down arbitrarily, the worker cannot predict the outcome. In MEV terms, that unpredictability is where value leaks or gets captured. The key is ensuring the conveyor belt runs at a consistent speed, regardless of who is assembling the product.

Component	Role in MEV	Primary Risk
Shared Sequencer	Orders transactions into a stream	Reordering or censoring flow
Builder	Assembles blocks from ordered stream	Extracting value from ordered data
Proposer	Publishes final block	Colluding with builder or sequencer

What is a shared sequencer?

How does modular MEV differ from monolithic MEV?

Can a sequencer censor transactions?

Execution Layer Extraction Strategies

The execution layer is where modular MEV actually happens. While the consensus layer orders blocks, the execution layer is where builders and proposers extract value by optimizing transaction inclusion. This process relies on specialized infrastructure that separates the sorting of transactions from the final block production. Builders construct blocks by selecting the most profitable transactions, while proposers verify and broadcast them. The modular approach allows each participant to focus on their specific role without needing to run the entire stack.

Builders use tools like RBuilder to aggregate and sort transactions before they reach the proposer. RBuilder, developed by Paradigm, is a MEV builder built on the Reth client. It allows builders to construct blocks by searching for profitable opportunities across the mempool. This separation of duties means that builders don't need to validate every transaction themselves; they only need to ensure the final block is valid when sent to the proposer. This efficiency is critical for handling the high volume of transactions in a modular ecosystem.

The interaction between builders and proposers is a continuous auction. Builders submit their constructed blocks to proposers, who then choose the one that offers the highest bid or best alignment with their own interests. This competition drives the efficiency of the network, as builders are incentivized to find the most valuable transaction sets. However, it also means that proposers have significant power in deciding which transactions get included. This dynamic creates a complex landscape where value extraction is not just about finding profitable trades, but about managing the relationship between builders and proposers.

Finality and MEV Timing

In modular MEV, the gap between transaction inclusion and final state is where the profit margin lives. Unlike monolithic chains where blocks are final in seconds, modular stacks often rely on data availability layers like Celestia. This introduces a distinct two-step process: first, the sequencer bundles transactions and posts the blob to the data layer; second, the rollup verifies the data and commits the state. For modular MEV operators, this delay creates a specific extraction window that requires different risk management strategies than traditional block-building.

The core challenge is that finality is no longer a single event but a sequence. A proposer might secure a block on the execution layer, but if the data availability layer experiences congestion or delays, the block’s value can evaporate before it is truly finalized. This is why modern modular MEV strategies, such as those built on RBuilder, focus heavily on data availability guarantees. They treat data posting not as a backend task, but as a critical part of the bidding process. If the data doesn’t make it onto Celestia within a tight timeframe, the bid is worthless.

This timing mismatch forces operators to price in the risk of "data unavailability." In practice, this means modular MEV bots must monitor data layer latency in real-time. If the cost of posting to Celestia spikes or the queue lengthens, the operator must either adjust their bid or exit the block entirely. The result is a more dynamic, albeit riskier, MEV landscape where the speed of data propagation is just as important as the speed of transaction execution.

Build a modular MEV stack

Constructing a modular MEV infrastructure requires separating the sequencing, building, and execution layers. This approach lets you swap components like Celestia for data availability or RBuilder for block construction without rewriting the entire system. The goal is to isolate risks and optimize each layer independently.

Select your sequencer

The sequencer orders transactions before they hit the execution layer. In a modular setup, you might use a shared sequencer like Celestia’s to handle ordering while keeping data availability separate. This reduces the attack surface for reordering attacks compared to monolithic chains. Ensure your sequencer supports the specific ordering guarantees your MEV strategy requires.

Configure the builder

Once transactions are sequenced, the builder constructs the block. Tools like RBuilder allow you to run a builder on top of Reth, giving you granular control over bundle inclusion and profit extraction. This layer is where you implement your specific MEV logic, such as sandwich protection or arbitrage strategies. Make sure your builder can communicate efficiently with your sequencer and executor.

Monitor mempool and execute

The final step is monitoring the mempool for profitable opportunities and executing bundles through your executor. This requires low-latency connections to your builder and sequencer. Use real-time monitoring tools to detect opportunities and submit bundles before they are included in a block. Regularly audit your execution latency to ensure you remain competitive in the MEV landscape.

Common modular MEV pitfalls

Even with a robust modular MEV stack, execution errors can erase profits. The separation of sequencing, execution, and data availability creates new failure points that monolithic chains do not face. Builders often assume that the modularity itself guarantees efficiency, but the latency between layers introduces significant risks.

One major error is ignoring sequencer censorship. Shared sequencers are not always neutral; they may prioritize certain transactions or filter out others based on political or economic pressure. If your builder does not account for this, your extracted value disappears before it ever reaches the execution layer. You must verify the censorship resistance of your chosen sequencer.

Another frequent mistake is misjudging finality times. In modular setups, data availability finality often lags behind execution finality. If your builder assumes immediate finality, it may include transactions that are later reverted or invalidated when the data is published to the chain. This leads to wasted gas and failed arbitrage opportunities. Always build in a buffer for data availability confirmation.

Finally, ensure your builder integrates properly with the modular data layer. Tools like RBuilder demonstrate how specialized builders can handle these complexities, but generic builders may fail to optimize for the specific constraints of modular data submission. Test your stack against real-world latency and censorship scenarios before going live.