Ethereum block builder Titan Builder briefly out-earned Tether — the stablecoin issuer behind USDT, the largest stablecoin by market value — in daily revenue, a development that underscores the growing economic significance of block construction within the Ethereum network. According to data from stake.fish, Titan and Quasar together accounted for 73% of MEV-Boost blocks in October 2026, rekindling concerns about competition, censorship resistance, and potential protocol changes.

According to the report, Titan constructed 52.4% of MEV-Boost blocks during the period, while Quasar was responsible for 20.6%. BuilderNet held 15%, Eureka made up 6.5%, and all other builders were left with a combined 5.5%. Two providers thus now control almost 73% of outsourced blocks, compared with roughly 60% a year earlier.

The revenue readings differ by source. While the report states that Titan generated $22.83 million, TokenPost separately estimated that the builder's fees over 24 hours on October 30 were worth $24.7 million. The two datasets may measure different things and cannot be compared directly as pure revenue figures.

The spike drew attention on X, where the account AllThingsEVM.eth noted that the 24-hour fee total was so far above normal that DefiLlama, a widely used analytics dashboard, flagged it as a data error:

Panic is a tax, and the bots collect it 👀 – TitanBuilder took $24.7M in fees in 24h – So far above normal, DefiLlama's systems flagged it as a data error – Hack flows plus panic selling = huge arb Grok @bot how can I get in on this action?

— AllThingsEVM.eth (@AllThingsETH) October 30, 2026 (source)

The issue with concentration lies in the builder's core function: selecting which transactions are included in the next block and in what order they appear. Access to the transaction stream can influence the outcome of the auction, the fee levels users pay, and whether certain transactions are included at all. When only a handful of companies produce most blocks, the network becomes vulnerable to operational and governance failures at those firms.

MEV-Boost and the Shift in Builder Market Share

Through MEV-Boost, validators delegate block-building duties to external specialists. Builders gather transactions, arrange them in ways that maximize extractable value — a practice known as maximal extractable value, or MEV, the value that can be captured through the selection, ordering, and placement of transactions in a block — and submit bids through relays. The system has fostered competition in block building since the Merge, Ethereum's 2022 transition to proof-of-stake, but it also concentrates significant power outside the core protocol. Because most validators outsource this work, the small set of competing builders effectively shapes how a large share of Ethereum's blocks are assembled.

Stake.fish's year-over-year comparison reveals considerable reshuffling behind the headline numbers. Quasar climbed from 9.6% in October 2025 to its current 20.6%. BuilderNet dropped from 29.8% to 15%, while Titan gained 1.6 percentage points to reach 52.4%. The top three builders continue to dominate block creation.

Relay Concentration Risks

The relay layer connects builders and validators, verifying blocks and submitting bids without revealing transactions until the proposer has committed to a block. In statistics covering October 22–28, Ultra Sound relayed 92.2% of transactions, while Titan relayed 89.1%. The percentages can overlap because blocks can be delivered to validators through multiple relay options.

Several relay options can protect validators if one service provider fails. However, dependence on a small group of major providers creates opportunities for influence. The relay layer can affect which transactions are included in a block, including transactions subject to sanctions screening, giving operators a sensitive role in what ultimately reaches the chain. The closure of bloXroute's Max Profit service in August also altered the landscape.

ePBS Offers a Protocol-Level Response

Ethereum's enshrined proposer-builder separation (ePBS), detailed in EIP-7732, is slated for implementation through the Glamsterdam upgrade. ePBS seeks to bring the builder auction into the protocol itself, reducing validators' dependence on external relays. Under the proposed framework, builders would submit signed bids, with block contents revealed at a later stage.

The proposal also calls for a Payload Timeliness Committee that would determine the timeliness of block contents delivered by builders. Adoption timing, however, remains unresolved: the fork on the Hoodi testnet — the public network where Ethereum rehearses protocol upgrades before mainnet deployment — initially scheduled for October 26, was postponed to an indefinite date on October 22.

What the Fee Figures Represent

Titan's fee collection illustrates how much value can be captured during periods of heavy blockchain activity. Fees from liquidations, arbitrage, and transaction reordering all add to the cost of blockspace. Fees, however, do not equate to the total value extractable within the network, and even a strong single day does not establish a trend. For builders, a spike of this kind reflects short-lived market conditions rather than a steady income stream.

Builder centralization affects Ethereum validator operators, DeFi users, and application developers alike. Users may have to adapt to inclusion or execution pricing, while validators rely on the bidding system. Application developers and researchers are watching closely to see whether ePBS would open the field to more participants without creating additional barriers for smaller builders.

MEV-Boost remains widely used, and a mainnet launch date for ePBS has yet to be announced. Upcoming milestones include the delayed Hoodi testnet schedule, the EIP-7732 review period, and further decisions around Glamsterdam implementation. Until protocol changes arrive, builder and relay centralization will remain live issues in the network's governance, with the October data offering a snapshot of a market still in flux.