Decentralized Sequencers as Cross-Chain MEV Hubs

Rollup sequencers like Arbitrum and Optimism capture MEV locally, but miss the $500M+ annual cross-chain arbitrage opportunity. This creates inefficiency and leaves value on the table for users and validators.\n- Fragmented Liquidity: Arb opportunities exist between Uniswap on Arbitrum and Curve on Base, but no sequencer sees both.\n- Suboptimal Execution: Users get worse rates on cross-chain swaps via bridges like Stargate or LayerZero without a global view.

A cross-chain sequencer acts as a unified mempool, running a continuous auction for bundles spanning multiple chains (e.g., Ethereum → Arbitrum → Polygon). This mirrors the intent-based model of UniswapX and CowSwap, but for chain-level settlement.\n- Maximal Extractable Value (MEV): Auction revenue is shared back to the source rollups and their stakeholders.\n- Better User Outcomes: Cross-chain swaps via Across or Socket can be routed through the optimal path with embedded liquidity.

Infrastructure like Espresso, Astria, and Shared Sequencer from the OP Stack provide the neutral coordination layer required. They don't solve cross-chain MEV by themselves but create the substrate for it by decentralizing block building across rollups.\n- Atomic Composability: Enables transactions that conditionally execute on Chain B only if they succeed on Chain A.\n- Credible Neutrality: Prevents a single L1 or L2 from monopolizing cross-chain flow, critical for adoption by protocols like Aave or Compound.

Espresso is building a horizontally scalable, shared sequencer network designed for rollups. It aims to be the neutral, high-throughput foundation for cross-chain MEV.

• Key Benefit: Enables cross-rollup atomic composability, allowing transactions across different chains to be bundled and settled atomically.
• Key Benefit: Uses HotShot consensus for high throughput (~10k TPS) and fast finality (~2 seconds).
• Key Benefit: Provides a censorship-resistant ordering layer that rollups can outsource to, separating execution from sequencing.

Astria is constructing a decentralized sequencer network that provides shared, permissionless block building for multiple rollups, directly competing with centralized RPC providers.

• Key Benefit: Decouples block building from proposing, creating a competitive marketplace for builders and enabling MEV redistribution.
• Key Benefit: Offers instant, soft-confirmations to users by leveraging a fast data availability layer.
• Key Benefit: No protocol token required for rollup integration, lowering adoption friction compared to validator-stake models.

Today, most rollups rely on a single, centralized sequencer operated by the founding team. This creates a critical point of failure and captures all MEV value.

• Key Risk: Censorship & Downtime: A single operator can censor transactions or go offline, halting the chain.
• Key Risk: MEV Centralization: All transaction ordering power and its associated profits are captured by one entity, stifling competition.
• Key Risk: Trust Assumption: Users must trust the sequencer to order transactions fairly, violating blockchain's core value proposition.

A decentralized sequencer hub enables a global, permissionless market for cross-chain MEV. Builders compete to create the most valuable bundles across chains.

• Key Benefit: MEV Redistribution: Auction revenue can be shared with rollups and their users via mechanisms like EIP-1559 burns or direct redistribution.
• Key Benefit: Atomic Arbitrage: Enables seamless, risk-free arbitrage between DEXs on Ethereum, Arbitrum, and Optimism in a single bundle.
• Key Benefit: Enhanced Liquidity: Creates a unified liquidity landscape, reducing fragmentation and improving capital efficiency for protocols like Uniswap and Aave.

Radius solves the frontrunning problem inherent in public mempools by implementing a practical verifiable delay encryption (VDE) scheme for decentralized sequencers.

• Key Benefit: Censorship-Resistant Ordering: Validators commit to blocks without seeing transaction content, preventing transaction censorship.
• Key Benefit: MEV Prevention: By hiding transaction intent until after ordering, it eliminates frontrunning and sandwich attacks at the sequencer level.
• Key Benefit: Universal Plug-in: Designed as a module that can be integrated into any Tendermint-based or similar consensus layer.

The winning model will treat sequencing infrastructure like a utility—neutral, reliable, and credibly decentralized. This shifts value from infrastructure capture to application layer innovation.

• Key Shift: Commoditized Sequencing: Sequencing becomes a low-margin, high-reliability service, similar to AWS for web2.
• Key Shift: Application-Layer MEV: Innovation moves to sophisticated cross-chain searchers and builders, creating a new ecosystem akin to Flashbots on a multi-chain scale.
• Key Shift: Protocol Revenue: Rollups capture sustainable revenue through sequencer fee sharing, reducing reliance on token emissions.

A decentralized sequencer must be both resilient to downtime and resistant to transaction censorship. Achieving one often weakens the other.\n- Liveness Attack: A malicious coalition stalls the sequencer, halting cross-chain settlement for hours or days.\n- Censorship Vector: Validators collude to exclude transactions, enabling targeted Denial-of-Service (DoS) against protocols like UniswapX or Across.

A sequencer's ability to reorder transactions on its native chain creates arbitrage opportunities on connected chains like Ethereum or Arbitrum.\n- Time-Bandit Attack: An attacker withholds a block, observes price movements on DEXs across chains, then reorgs to insert profitable trades.\n- Amplified Impact: A single reorg on a $1B+ TVL rollup can trigger $10M+ in extracted value across all connected liquidity pools.

Sequencers often provide data to cross-chain oracle networks like Chainlink. Compromising the sequencer corrupts the primary data source for billions in DeFi.\n- Data Integrity Failure: A malicious sequencer feeds false price data or timestamps to oracles.\n- Domino Effect: Triggers incorrect liquidations and broken stablecoin pegs on every chain consuming the corrupted feed, exploiting protocols like Aave and Compound.

Major cross-chain bridges (LayerZero, Wormhole) rely on external attestation committees. A captured sequencer can forge fraudulent state proofs.\n- Fake Deposit Proofs: The sequencer attests to non-existent deposits on the source chain, minting unbacked assets on the destination.\n- Sybil-Resistance Failure: If the sequencer set overlaps heavily with the bridge committee, a ~$500M+ exploit becomes trivial.

Decentralized sequencers that auction block-building rights (via MEV-Boost++ models) create a centralized profit hub.\n- Builder Cartels: A few dominant builders (<5 entities) win most auctions, controlling cross-chain flow and extracting >80% of MEV.\n- Regulatory Target: This centralized profit conduit becomes a clear target for financial regulators, jeopardizing the network's legal neutrality.

Cross-chain transactions have inherent latency. An attacker can frontrun the settlement message after it's committed on the source chain but before it's executed on the destination.\n- Widow's Window: The ~10-30 minute delay for optimistic rollup challenges or bridge finality is exploited.\n- Solution Race: Protocols like Across use optimistic verification; others like Chainlink CCIP use off-chain committees. Both have delay-based attack vectors.