[Updated] Highlights of MEV Space 4: Searcher-Builder Integration, Jaredfromsubway.eth and BuilderNet

Insights on Private Order Flow, MetaMask's Smart Transaction, and Protecting Against Sandwich Attack

Update on 10:02 AM EDT, 2025.03.28

Shea of flash bots provided more details on BuilderNet to avoid misunderstanding.

Thing 1: The fact that one node in the network has different profitability than others does not contradict any of the stated properties of the network. This can happen for a variety of reasons

- Different blocklists

- Different configs (eg subsidies)

- Different location

-> proximity to orderflow (while all flow is shared, one node will inherently see it first)

-> proximity to relays

Thing 2: Generally, indexing on individual node “profitability” doesn’t really make much sense in the context of BuilderNet. I understand this is something people are accustomed to in the current market, but that mental model doesn’t entirely apply the same way in BuilderNet. Node operators currently have 0 right to the profit generated by their machine. Most of it is refunded and any remaining amount is currently shared as an R&D budget (the initial operator set is not being paid by BuilderNet at all). So the fact that one operator is temporarily more profitable doesn’t really have an impact on the overall incentives / decentralization the way the post implies.

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On Mar 24, we held a 30-minute Twitter Space, MEV Space #4, with Benjamin Hunter, VP of Engineering from BTCS, as our speaker. Here are the highlights from this compact session.

MEV Space brings together the sharpest minds in crypto to dissect the evolving MEV landscape.

1. BTCS Reaching 1% Market Share and CoWSwap Access

BTCS has achieved a significant milestone by reaching 1% market share in the block builder market, a position that Benjamin Hunter describes as hard-won through substantial investment and persistent effort. This growth has qualified them for a coveted partnership with CoWSwap, which Hunter revealed was just approved the morning of the Twitter Space. Starting the following week, BTCS will begin processing CoWSwap's private order flow, representing a major advancement for this publicly traded US-based company. Hunter noted the achievement came after considerable struggle, emphasizing they've been "fighting for every fraction of percentage" in a highly competitive builder landscape where market share translates directly to access to valuable order flow sources.

2. Surge in Searcher-Integrated Builders

The Ethereum builder ecosystem has undergone a significant transformation over the past 6-12 months, with Hunter highlighting "a huge growth in searcher-integrated builders" coinciding with many smaller independent builders exiting the space. These departing builders typically pivoted toward proprietary trading or general DeFi activities rather than continuing block building development. The trend has created a challenging competitive environment where even small builders with exclusive order flow can generate outsized profits while building blocks with surprisingly few transactions. Hunter explained that BTCS can analyze blocks to identify unknown transactions, revealing that searcher-integrated builders often have exclusive access to highly profitable order flow that allows them to outbid larger builders despite processing fewer transactions overall.

3. Jaredfromsubway.eth's Dynamic Strategies

EigenPhi's research has uncovered increasingly sophisticated sandwich attack strategies deployed by Jaredfromsubway.eth, who has developed techniques to make sandwiching retail traders easier and more profitable. Traditional sandwich attacks typically require victim transactions to reach a certain volume threshold to be profitable, but Jared’s innovation involves adding liquidity to pools to reduce his own transaction fee requirements, thereby expanding the range of smaller user transactions that become viable sandwich targets.

4. MetaMask Smart Transactions

According to Benjamin Hunter, MetaMask's Smart Transactions feature has become the default pathway for an overwhelming majority of user transactions, with "85 or 95 percent" now flowing through this system. This closed-access mechanism functions as an auction platform where builders and searchers compete to provide either optimal execution or maximum refunds for users, significantly reducing the exploitation risk compared to public mempool transactions. As a protective measure, Smart Transactions requires participating builders to provide refunds back to MetaMask, though Hunter was uncertain whether these refunds flow entirely to users or if MetaMask retains a portion. The system effectively provides "protection by default" for average users who might otherwise be vulnerable to sandwich attacks and other MEV extraction techniques, representing a significant shift in how retail transactions are handled.

5. Beaver Leading BuilderNet

Within BuilderNet, Ethereum's initiative to decentralize block building, Beaver has consistently emerged as the top-earning builder despite weekly fluctuations in performance metrics across the network. Hunter expressed surprise at this pattern, noting it contradicts BuilderNet's documentation, suggesting all participants run identical builder software with the same order flow access. This unexpected performance differential raises questions about BuilderNet's implementation and the factors determining builder success within the system. Hunter and EigenPhi expressed eagerness to join BuilderNet, with BTCS waiting since November for the opportunity to participate. This situation highlights the growing interest in decentralized building solutions and the current limited access to this evolving ecosystem.

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Below are the highlights from previous MEV Spaces.

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