Cross-Chain MEV Validates the Need for Shared Sequencing

Arbitrageurs exploit price differences across chains, extracting $100M+ annually in value that should flow to users and protocols. This is a direct tax on interoperability, with bots racing to front-run cross-chain messages from LayerZero and Wormhole.

• Value Leakage: Profits siphoned from LPs and swappers.
• Latency Arms Race: Bots optimize for ~500ms message finality, not user experience.
• Security Risk: Creates incentives for time-bandit attacks on individual chains.

A single, decentralized sequencer (like Espresso, Astria, Radius) orders transactions for multiple rollups before they hit their respective L1s. This creates a unified mempool, enabling atomic cross-chain bundles.

• Atomic Composability: Guarantee execution of actions across chains or revert all.
• MEV Redistribution: Capture and redistribute cross-chain arbitrage value via mechanisms like MEV-Share.
• User Experience: Enables secure, intent-based cross-chain swaps (see UniswapX, CowSwap) without front-running risk.

The shift from transaction-based to intent-based systems (e.g., Anoma, Across, UniswapX) is the killer app for shared sequencing. Users submit what they want, solvers compete to fulfill it optimally across chains.

• Solver Efficiency: A shared sequencer provides solvers a global view of liquidity and state, enabling better pricing.
• Prover Unbundling: Separates transaction ordering from proof generation, a core tenet of modular design.
• Economic Finality: Faster, economically secured cross-chain settlement without waiting for L1 finality.

Espresso provides a decentralized sequencing layer that rollups can outsource to, using a HotStuff-based PoS consensus. Its core thesis is that sequencing must be a public good, not a rollup-specific profit center.

• Key Benefit: Enables cross-rollup atomic composability via its shared mempool.
• Key Benefit: Timeboost mechanism auctions block space for fair ordering, capturing MEV for the protocol and users.

Astria builds a decentralized shared sequencer network that provides raw, ordered blockspace to multiple rollups. It decouples execution from ordering, allowing rollups to retain sovereignty over execution and settlement.

• Key Benefit: No forking required—rollups plug in via a simple block builder API.
• Key Benefit: Native cross-rollup liquidity as transactions from different rollups are ordered in a single, shared sequence.

Without shared sequencing, arbitrage between Ethereum L2s like Arbitrum and Optimism is slow and risky. Searchers must post collateral and execute transactions sequentially across chains, losing atomicity.

• Result: Value leaks to external bridging protocols like Across and LayerZero.
• Result: Inefficient markets with wider spreads and delayed price convergence.

Radius tackles MEV at the source by using threshold encryption for the shared mempool. Transactions are encrypted until they are ordered, preventing frontrunning and sandwich attacks.

• Key Benefit: PBS for rollups—builders commit to blocks without seeing transaction content.
• Key Benefit: Enables credible neutrality and fair ordering, similar to ideas from CowSwap and Flashbots SUAVE.

A shared sequencer's mempool allows a searcher to submit a single bundle containing dependent transactions across multiple rollups. The sequencer guarantees atomic inclusion and ordering.

• Result: Eliminates bridge risk and unlocks complex DeFi strategies.
• Result: Captures MEV value for the shared sequencer ecosystem and its stakers, not external parties.

Madara, a Starknet sequencer using Substrate, exemplifies the sovereign rollup model. It highlights the spectrum of sequencing choices: fully sovereign, outsourced to a shared network like Astria, or a hybrid model.

• Key Benefit: Maximum flexibility for rollups to choose their security, decentralization, and interoperability trade-offs.
• Key Benefit: Creates a competitive market for sequencing services, driving innovation beyond monolithic stacks.

A shared sequencer must be decentralized enough to be trusted with billions in cross-chain value, yet fast enough to finalize blocks in ~500ms. Achieving both simultaneously is an unsolved engineering problem.\n- Security Risk: A cartel of sequencers could censor or reorder transactions for profit.\n- Liveness Risk: Over-decentralization introduces latency, making the system unusable for high-frequency arbitrage.

Rollups like Arbitrum and Optimism adopted their own stacks for control. Ceding transaction ordering to a third-party sequencer (e.g., Espresso, Astria) is a major political and technical concession.\n- Economic Risk: Shared sequencers capture the MEV revenue that L2s currently keep.\n- Technical Risk: Forces L2s into a one-size-fits-all execution environment, stifling innovation.

LayerZero and Axelar have established $10B+ in secured value with a validated, application-specific security model. A shared sequencer must prove its cross-chain security is superior, not just different.\n- Adoption Risk: DApps are entrenched in existing messaging layers; migration cost is high.\n- Security Risk: A new shared sequencer creates a single, larger attack surface compared to fragmented, app-chain security.

The business model is unproven. MEV revenue is volatile and may not cover the high fixed costs of running a decentralized sequencer network with sub-second latency.\n- Subsidy Risk: Requires continuous VC funding or L2 subsidies to remain operational.\n- Extraction Risk: To be profitable, the sequencer may be forced to maximize MEV extraction, harming end-users.

The ~12-second finality gap between Ethereum and faster L2s like Arbitrum creates a persistent attack surface. This isn't a bug; it's a fundamental property of a multi-chain world where state updates are not atomic.

• $100M+ in value has been extracted via cross-domain MEV.
• Creates toxic order flow and degrades execution for end-users.
• Turns every fast chain into a potential oracle for slower ones.

A shared sequencer network like Astria or Espresso enables atomic inclusion across rollups, making cross-chain MEV impossible by construction. This is the only way to guarantee composability without trust.

• Eliminates the latency race between sequencers.
• Enables native cross-rollup arbitrage as a public good.
• Unlocks new primitives like single-block DEX aggregation across chains.

The rise of UniswapX, CowSwap, and Across proves users and developers will route around MEV risk. These systems abstract away execution by expressing intent, which a shared sequencer is uniquely positioned to solve optimally.

• UniswapX volume shows demand for MEV-protected swaps.
• A shared sequencer becomes the natural settlement layer for intents.
• Turns cross-chain MEV from an extractive force into an optimized routing problem.

A rollup's security is only as strong as its weakest link—its sequencer. Isolated sequencing creates single points of failure and censorship. A decentralized, shared sequencer network provides credibly neutral ordering as a base-layer service.

• Mitigates liveness failures from individual sequencer downtime.
• Provides censorship resistance at the network level.
• Reduces the trust surface from N sequencers to 1 network.

Cross-chain MEV is value that leaks out of the ecosystem. A shared sequencer allows rollups to capture and redistribute this value via fees or protocol incentives, realigning economic security.

• Transforms MEV from a negative externality into a protocol revenue stream.
• Enables sustainable funding for public goods like block building.
• Aligns sequencer incentives with the long-term health of the rollup ecosystem.

The debate is over. Sequencing is not an application-layer concern—it's critical blockchain infrastructure, akin to bandwidth or compute. The future is a shared, decentralized sequencing layer that rollups opt into for security and interoperability.

• Follows the historical playbook of AWS, Cloudflare.
• Enables specialization: Rollups focus on execution, sequencers focus on ordering.
• Creates a virtuous cycle of shared security and liquidity.