1. The Modular Crisis: Fragmentation and the Centralization Trap
The evolution of the Ethereum ecosystem over the last half-decade has been defined by a decisive shift from a monolithic architecture—where execution, settlement, consensus, and data availability are handled by a single network of nodes—to a modular paradigm. This transition, codified in the “Rollup-Centric Roadmap,” was driven by the inescapable physics of blockchain scalability: to support global adoption, the execution of transactions must be decoupled from the security of the base layer. The success of this roadmap is evident in the proliferation of Layer 2 (L2) solutions, which now process transaction volumes significantly outstripping the Ethereum mainnet.1 However, this architectural splintering has introduced a new, critical vulnerability: the isolation of state and the re-centralization of the sequencing function.
As rollups have matured, a stark reality has emerged. The vast majority of active rollups—ranging from industry giants like Optimism and Arbitrum to newer entrants—rely on a single, centralized sequencer operated by the core development team.2 This “training wheels” phase, initially justified as a temporary measure to ensure safety during the early stages of protocol development, has ossified into a permanent structural risk. The centralized sequencer has become the singular traffic controller for the L2, possessing absolute authority over the ordering of transactions. While this centralization affords certain user experience (UX) benefits, primarily low latency and instant “soft” confirmations, it reintroduces the very trust assumptions that blockchain technology seeks to eliminate.4
The current landscape of L2 infrastructure is thus characterized by a dangerous dichotomy: decentralized security at the settlement layer (Ethereum L1) but centralized control at the transaction ingestion layer (the L2 Sequencer). This creates a bottleneck where the censorship resistance and liveness of the entire system are capped by the integrity of a single server. Furthermore, because each rollup operates its own isolated sequencer, the ecosystem has fractured into synchronous silos. A transaction on one rollup is invisible to another until it settles on L1, breaking the synchronous composability that fueled the innovation of Ethereum’s DeFi ecosystem.5 The industry’s answer to these twin crises of centralization and fragmentation is the concept of Shared Sequencing—a coordination layer that aggregates transaction ordering across multiple domains, promising to restore decentralization and unlock cross-chain atomic composability.
1.1 The Sequencer’s Role: Traffic Controller of the Modular Stack
To understand the necessity of shared sequencing, one must first dissect the anatomy of a rollup transaction. In the typical Optimistic or Zero-Knowledge (ZK) rollup architecture, the sequencer performs three distinct but interrelated functions:
- Transaction Ordering: The sequencer receives raw transactions from the user mempool and determines their specific order within a block. This step is the primary source of Maximal Extractable Value (MEV), as the ordering determines the outcome of arbitrage and liquidation opportunities.7
- Execution (Soft Finality): In most current implementations, the sequencer also executes the transactions against the L2 state, providing the user with an immediate receipt. This “soft confirmation” allows for the snappy UX users expect from modern web applications, even though “hard” finality on Ethereum L1 may take minutes or hours.8
- Batch Submission: Finally, the sequencer compresses the ordered transactions into batches and submits them to the Data Availability (DA) layer (typically Ethereum L1, though increasingly alternatives like Celestia are used).2
Without the sequencer, the rollup effectively halts. It is the heartbeat of the L2. In the current centralized model, if the sequencer goes offline—whether due to a software bug, a targeted Distributed Denial of Service (DDoS) attack, or legal coercion—the L2 loses liveness.4 Users can no longer transact comfortably. While most rollups implement an “escape hatch” that allows users to force-include transactions via the L1, these mechanisms are cumbersome, expensive, and often take up to 24 hours to activate, rendering them useless for time-sensitive financial operations.4
1.2 The Centralization Trilemma
The reliance on centralized sequencers creates a “Centralization Trilemma” that plagues the current L2 ecosystem:
1.2.1 Censorship and Regulatory Fragility
A centralized sequencer possesses the technical capability to censor transactions arbitrarily. It can blacklist specific addresses, block interactions with privacy protocols, or filter out transactions based on geographic origin.3 This creates a single point of coercion. In a geopolitical environment where regulatory scrutiny on crypto infrastructure is intensifying, a centralized sequencer operated by a known legal entity is a vulnerable choke point. A court order in a single jurisdiction could effectively force a rollup to implement KYC/AML screening at the sequencer level, fundamentally altering the permissionless nature of the chain.4
1.2.2 The Single Point of Failure (SPOF)
The engineering risks are as potent as the political ones. A single sequencer represents a classic Single Point of Failure (SPOF). History is replete with examples of centralized services suffering outages due to infrastructure failures. When a centralized sequencer goes down, the entire ecosystem built on top of it grinds to a halt. The capital locked in the rollup remains secure (thanks to the L1 settlement guarantees), but it becomes illiquid and unusable.1 This brittleness is unacceptable for a financial system aspiring to process trillions of dollars in global value.
1.2.3 The MEV Monopoly
In the current paradigm, the centralized operator enjoys a monopoly on MEV extraction. By controlling the ordering of transactions, the sequencer can extract value through front-running, back-running, and sandwich attacks, or they can sell this right to a privileged set of builders. While some projects, like Optimism, direct this revenue toward public goods funding (Retrospective Public Goods Funding), the structural reality is an economic monopoly.12 This lack of competition can lead to poor execution quality for users and stifles the development of a sophisticated, decentralized supply chain for block building.
1.3 The Fragmentation Problem: Synchronous Silos
Beyond the issues of control, the “one sequencer per rollup” model has shattered the Ethereum ecosystem into fragmented islands of liquidity. In the monolithic Ethereum L1 era, all applications lived on the same state machine. A user could perform a complex transaction that swapped tokens on Uniswap, lent them on Aave, and staked the receipt tokens in a yield aggregator—all in a single atomic transaction. If any part of the sequence failed, the entire transaction reverted.6
In the modular world, this synchronous composability is lost. Assets on Arbitrum cannot interact atomically with contracts on Optimism. Cross-chain interaction requires asynchronous bridging, which introduces latency and new trust assumptions. A user must lock assets on Chain A, wait for finality, and then mint assets on Chain B. This breaks the “money lego” composability that is unique to crypto finance.3 Shared sequencers aim to bridge this divide by allowing multiple rollups to share a single ordering mechanism, thereby enabling transactions that span across chain boundaries within the same block—a capability known as atomic inclusion.13
2. Theoretical Framework: The Mechanics of Shared Sequencing
Shared sequencing proposes a radical restructuring of the L2 stack. Instead of each rollup operating its own proprietary sequencer, multiple rollups outsource the ordering function to a decentralized network of nodes. This middleware layer sits between the execution environments (the rollups) and the settlement layer (Ethereum L1), acting as a unified coordination engine.14
2.1 Decoupling Ordering from Execution: The “Lazy” Paradigm
The foundational architectural shift in shared sequencing is the decoupling of transaction ordering from transaction execution. In the traditional centralized model, the sequencer does both: it orders the transactions and then executes them to update the state. In the shared sequencer model—often referred to as Lazy Sequencing—the shared network is responsible only for ordering.9
The shared sequencer receives transactions for Rollup A, Rollup B, and Rollup C. It aggregates these into a single “global” block, establishing a canonical order for all transactions across all participating chains. It then publishes this data to the Data Availability layer. The rollup nodes (the execution layer) then fetch this ordered data and execute the transactions valid for their specific Virtual Machine (VM). If a user submits an invalid transaction (e.g., trying to spend funds they don’t have), the shared sequencer will still order and include it, but the rollup’s execution engine will simply revert it when processing the block.16
This “lazy” approach has profound implications for scalability and flexibility. The shared sequencer does not need to run a full node for every rollup it serves. It is agnostic to the execution logic, allowing it to service EVM rollups, SVM (Solana VM) rollups, and MoveVM rollups simultaneously without the computational overhead of execution.15
2.2 The Holy Grail: Synchronous Composability
The most transformative promise of shared sequencing is the restoration of synchronous composability to the modular stack. By having a single entity (the shared sequencer network) control the ordering for multiple chains, it becomes possible to guarantee atomic inclusion.17
2.2.1 Atomic Inclusion vs. Atomic Execution
It is vital to distinguish between two levels of atomicity in this context:
| Feature | Atomic Inclusion | Atomic Execution |
| Definition | Guarantee that a bundle of transactions (Tx A on Chain 1, Tx B on Chain 2) are both included in the same block height, or neither is. | Guarantee that the outcome of the transactions is linked; if Tx A fails (reverts) during execution, Tx B also reverts. |
| Provider | Shared Sequencer Network (e.g., Espresso, Astria). | Superbuilders (e.g., NodeKit Javelin) or Shared State Machines (e.g., Rome Protocol). |
| Mechanism | The sequencer commits to an order containing both transactions. | Requires a builder that simulates execution on both chains or a shared execution environment. |
| Use Case | Simple arbitrage, synchronized state updates. | Complex cross-chain DeFi, flash loans across chains. |
Shared sequencers primarily provide Atomic Inclusion.8 This allows for new types of cross-chain coordination. For instance, an arbitrageur can submit a bundle that buys an asset on Rollup A and sells it on Rollup B, knowing that both transactions will land in the same block. This reduces the execution risk compared to asynchronous bridging, where market prices could move in the time between the two transactions.19
However, Atomic Execution is significantly harder to achieve because the state of Rollup A is independent of Rollup B. If the transaction on Rollup A reverts during execution (e.g., due to slippage), the shared sequencer has already committed the transaction on Rollup B. Achieving true atomic execution requires advanced architectures like Superbuilders (discussed in Section 3.2) or shared validity sequencing where proofs are aggregated.20
2.3 Economic Redesign: Democratizing MEV and PBS
Shared sequencing also fundamentally alters the economic landscape of Layer 2. By aggregating transaction flow from multiple chains, the shared sequencer becomes a nexus for Cross-Domain MEV.
In a fragmented system, MEV is local. An arbitrage opportunity on Optimism is captured by an Optimism searcher. In a shared system, opportunities that span across chains (e.g., price discrepancies between a token on Arbitrum and Optimism) become capturable.21 While this theoretically increases the total extractable value, it also changes the distribution model.
Most shared sequencer protocols implement Proposer-Builder Separation (PBS).22 In this model:
- Users submit transactions to the network.
- Builders (sophisticated actors) bundle these transactions to maximize revenue (MEV) and bid for the right to have their bundle included.
- Proposers (the shared sequencer nodes) accept the highest bid and propose the block.
This market mechanism ensures that the value of the block space is captured efficiently. Crucially, shared sequencing protocols are designing mechanisms to redistribute this revenue back to the participating rollups. Instead of a centralized operator keeping all the fees, the shared network can programmatically split the MEV revenue among the rollups based on their contribution to the block’s value.21 This creates a more equitable and sustainable economic model for the modular ecosystem.
3. The Middleware Ecosystem: Protocol Architectures
The shared sequencing sector has blossomed into a diverse ecosystem of protocols, each taking a unique architectural approach to solving the coordination problem. We can categorize these solutions into three primary archetypes: the Full Stack Consensus approach (Espresso), the Superbuilder approach (NodeKit), and the Cryptographic approach (Radius), alongside unique hybrid models like Rome Protocol.
3.1 Espresso Systems: The Full Stack Approach
Espresso Systems has established itself as a heavyweight in the shared sequencing arena, offering a vertically integrated stack designed to replace the centralized sequencer entirely while maintaining high performance. The Espresso architecture rests on three pillars: the HotShot consensus mechanism, the Tiramisu data availability layer, and a marketplace for sequencing rights.23
3.1.1 HotShot Consensus: Optimistic Responsiveness
At the heart of Espresso is HotShot, a proof-of-stake (PoS) consensus protocol designed for optimistic responsiveness. Unlike Ethereum’s Gasper, which has fixed 12-second slots, HotShot allows the network to confirm blocks as fast as the network latency allows. If the network is healthy, blocks can be finalized in under a second.25
HotShot achieves this scalability by utilizing a Web2-style Content Delivery Network (CDN) architecture for data dissemination. In traditional consensus, every node must broadcast the full block data to every other node, creating a bandwidth bottleneck (O(n²) complexity). HotShot decouples the data transmission from the consensus voting. Nodes vote on a small metadata commitment (the block header), while the CDN ensures the actual transaction data is propagated efficiently. This allows HotShot to scale to thousands of validators—potentially leveraging Ethereum’s validator set via restaking (EigenLayer)—without sacrificing performance.27
3.1.2 Tiramisu Data Availability
Recognizing that data availability (DA) is often the bottleneck for sequencing throughput, Espresso developed Tiramisu. Tiramisu employs a tiered approach to DA:
- Web2 Speed: It uses a Data Availability Committee (DAC)—a small set of nodes—to optimistically verify data availability. This allows for extremely fast confirmations.
- Web3 Security: To prevent the DAC from withholding data (a classic attack vector), Tiramisu backs this up with Verifiable Information Dispersal (VID). This uses erasure coding to split the data into chunks, ensuring that as long as a sufficient fraction of the network is honest, the data can always be reconstructed. This hybrid model offers the speed of a centralized server with the security guarantees of a decentralized network.28
3.1.3 The Marketplace and Roadmap
Espresso does not just order transactions; it creates a marketplace for them. It allows rollups to sell sequencing slots to builders. This is fully compatible with PBS, allowing specialized builders to construct cross-chain bundles and bid for their inclusion.
- Current Status: Espresso launched its Mainnet 0 in November 2024 with a permissioned validator set.
- Future Outlook: The roadmap targets a transition to a fully permissionless Proof-of-Stake model in late 2025. This gradual decentralization strategy allows them to stress-test the HotShot consensus in a live environment before opening the gates to thousands of restaked validators.30
3.2 NodeKit: The Superbuilder Paradigm
While Espresso focuses on consensus, NodeKit attacks the problem from the block-building layer. NodeKit identifies that ordering alone is insufficient for true composability; you need an entity that can construct valid blocks across multiple chains simultaneously. They call this entity the Superbuilder, powered by their Javelin technology.32
3.2.1 The SEQ Chain and Javelin
NodeKit operates on a custom Layer 1 blockchain called SEQ, which serves as the coordination hub. However, the core innovation is Javelin.
- The Superbuilder Concept: In a standard shared sequencer, the sequencer might order a batch for Chain A and a batch for Chain B, but it doesn’t necessarily know if the transactions inside are valid or how they interact. Javelin acts as a builder that constructs a “superblock” containing atomic bundles for multiple rollups.
- Atomic Execution Mechanism: Because the Javelin builder sees the state of multiple rollups during the building process, it can enforce atomic constraints. For example, it can construct a bundle where a transaction on Rollup A is only included if the paired transaction on Rollup B is also valid. If one fails during the simulation, the builder discards the entire bundle before it is even proposed to the chain.20
This approach is distinct because it moves the complexity of cross-chain atomicity from the consensus layer (which is slow and dumb) to the builder layer (which is fast and smart). Javelin is designed to be agnostic, capable of plugging into rollups with centralized sequencers, shared sequencers, or based preconfs, effectively acting as a universal adapter for atomic execution.32
3.3 Radius: Cryptographic Fairness via Encrypted Mempools
Radius takes a different angle, focusing heavily on the fairness and censorship resistance of the sequencing process. They identify that even a decentralized shared sequencer can be toxic if the validators collude to extract MEV or censor users. To solve this, Radius introduces the Encrypted Mempool.34
3.3.1 Practical Verifiable Delay Encryption (PVDE)
The core technology behind Radius is a cryptographic scheme known as Practical Verifiable Delay Encryption (PVDE) (and its successor, Single Key Delay Encryption or SKDE). The workflow is as follows:
- Encryption: When a user submits a transaction, it is encrypted using a time-lock puzzle or a threshold encryption key. The sequencer cannot see the contents of the transaction (e.g., “Swap 100 ETH for USDC”).
- Ordering: The sequencer orders these encrypted blobs. Because it cannot see the content, it cannot front-run the trade or censor the user based on their activity. It must order blindly.
- Commitment: The sequencer cryptographically commits to this order. This is the point of no return.
- Decryption & Execution: Once the order is committed, the encryption is unlocked (the puzzle is solved or the key is revealed), and the transactions are executed in the sequence that was locked in.35
This “blind sequencing” effectively eliminates toxic MEV. It allows for a shared sequencer network that is trustless not just in terms of liveness, but in terms of neutrality. Radius positions itself as a modular layer that can sit on top of other sequencing solutions (like Madara for StarkNet), enhancing their security profile with cryptographic fairness.34
3.4 Rome Protocol: The Solana Bridge
Rome Protocol offers perhaps the most unconventional architecture in the shared sequencing landscape. Rather than building a new blockchain, Rome leverages the Solana network as a shared sequencer for Ethereum rollups.37
3.4.1 Architecture: Rollups as Smart Contracts
In the Rome architecture, Ethereum rollups are deployed as Neon EVM smart contracts directly on the Solana blockchain.
- The Workflow: Users submit transactions to the Rome sequencer (Rhea). Rhea aggregates these transactions and submits them to Solana.
- Leveraging Solana: Solana’s validators use Proof of History (PoH) to order these transactions. Because Solana supports parallel execution and has extremely low block times (400ms), it can process thousands of transactions for multiple rollups simultaneously and cheaply.38
- Shared State Machine: Because all the participating rollups effectively live as contracts on the same Solana state machine, Rome achieves Atomic Composability natively. A transaction can interact with the state of Rollup A (a Neon contract) and Rollup B (another Neon contract) in a single atomic Solana transaction. If any part fails, the whole Solana transaction reverts.39
This approach allows Ethereum rollups to inherit the massive security budget of Solana (~$50B staked) without having to bootstrap their own validator sets. It also creates a unique bridge between the two largest DeFi ecosystems, potentially allowing for atomic arbitrage between Solana and Ethereum L2s.38
4. The “Based” Counter-Narrative: Returning to Layer 1
While middleware solutions like Espresso and NodeKit build external infrastructure to solve the sequencing problem, a powerful counter-narrative has emerged from within the Ethereum Foundation research community: Based Rollups. Spearheaded by researcher Justin Drake, this thesis argues that the most robust, censorship-resistant, and economically aligned sequencer for Ethereum rollups is Ethereum itself.41
4.1 The Thesis: Superpowers from L1 Sequencing
A Based Rollup (or L1-sequenced rollup) is an L2 that does not have a separate sequencer. Instead, it utilizes the existing Ethereum L1 proposers (validators) to order its transactions.
- Mechanism: L2 transactions are submitted directly to the Ethereum L1 mempool (or a specialized L1 builder). The L1 block proposer includes these L2 transactions in the L1 block. The order of the L2 transactions is determined by their order in the L1 block.42
- Advantages:
- Maximal Liveness: A based rollup inherits 100% of Ethereum’s liveness. As long as Ethereum is producing blocks, the rollup is running. It cannot be shut down by a centralized sequencer failure.
- Simplicity: It eliminates the need for complex “escape hatch” code, as the “happy path” (normal sequencing) is effectively the same as the escape hatch (L1 sequencing).43
- Economic Alignment: In a middleware model, MEV leaks to the external sequencer network. In a based model, MEV flows naturally to the Ethereum L1 validators, strengthening the economic security of the base layer and accruing value to ETH.43
4.2 The Trade-off and the Solution: Based Preconfirmations
The primary criticism of the Based Rollup model is latency. Ethereum has a 12-second block time. Users accustomed to the 250ms confirmations of centralized L2s find a 12-second wait unacceptable for interactive applications.
To bridge this gap, the Based Rollup roadmap has adopted Based Preconfirmations (Preconfs).
- The Mechanism: Ethereum L1 proposers can opt-in to become “Preconfirmers.” They issue a cryptographic promise (signed message) to a user that their transaction will be included in the next block. This promise is backed by collateral. If the proposer fails to include the transaction after promising it, they are slashed.44
- The Result: This allows Based Rollups to offer <1 second “soft” finality (the preconfirmation) to the user, providing the snappy UX of a centralized sequencer, while still ultimately being settled and sequenced by the decentralized L1.45
Taiko, a prominent ZK-rollup, has pioneered this approach. In August 2025, Taiko launched Phase 1 of its preconfirmation system on mainnet, achieving transaction times of approximately 2 seconds while maintaining a fully decentralized, based architecture.46 This proves that the latency trade-off of based rollups is solvable.
4.3 The “Fabric” Initiative
To ensure that Based Rollups do not fragment into incompatible standards, the community has proposed Fabric—a coordination effort to standardize the infrastructure for based rollups. Fabric aims to define common standards for how L1 proposers issue preconfirmations and how users discover these preconfirmers. This standardization is crucial for ensuring that “Based” rollups can interoperate, allowing a single L1 block to sequence transactions for dozens of L2s atomically.47
4.4 Comparison: Middleware vs. Based
| Feature | Middleware Shared Sequencer (e.g., Espresso) | Based Rollup (L1 Sequencing) |
| Liveness Source | External Validator Set (Middleware) | Ethereum L1 Validators |
| Latency | Low (HotShot < 2s) | High (12s) without Preconfs; Low with Preconfs |
| Sovereignty | High (Rollup can swap sequencers easily) | Tied to L1 architecture and block times |
| Implementation | Requires external integration/SDK | Native to L1 interaction |
| Economics | Revenue stays with Sequencer/Rollup | Revenue/MEV flows significantly to L1 |
| Composability | Atomic across rollups on the same sequencer | Atomic across all Based Rollups sharing L1 sequencing |
| Complexity | High (New consensus, new tokenomics) | Low (Reuses L1 infrastructure) |
5. Market Dynamics and The Astria Post-Mortem
The shared sequencing market is not just a theoretical playground; it is a live environment with winners and losers. The most significant event in the sector’s recent history was the shutdown of Astria in late 2025, which serves as a critical case study for the viability of middleware chains.
5.1 The Rise of Astria
Astria was a pioneer in the shared sequencing space. It built its thesis on modularity, utilizing Celestia for data availability and building a dedicated Proof-of-Stake network for sequencing. Astria advocated heavily for “Lazy Sequencing” and planned to launch its own “Flame” EVM to demonstrate the power of its network. It raised $18 million from top-tier investors like 1kx, Delphi Ventures, and Placeholder.16
5.2 The Fall: A Reality Check for App-Chains
Despite its strong backing and technical innovation, Astria ceased operations in December 2025, halting its network at block 15,360,577.49 The shutdown offers vital lessons:
- The Economic Viability of Middleware: Bootstrapping a decentralized validator set is incredibly capital-intensive. To be secure, a sequencing network needs billions of dollars in economic stake. Astria struggled to generate enough revenue from sequencing fees to justify the cost of this security, especially when competing against the massive sunk capital of Ethereum (Based Rollups) and EigenLayer-backed competitors (Espresso).50
- Competitive Squeeze: Astria found itself squeezed between two dominant narratives. On one side, Based Rollups offered decentralization for “free” by leveraging L1. On the other, Espresso leveraged Ethereum’s existing validator set via restaking, lowering the barrier to bootstrapping security. Astria’s reliance on the Celestia ecosystem, while innovative, limited its total addressable market compared to Ethereum-aligned solutions.
- Technical Complexity: Building a high-performance BFT network that interfaces seamlessly with disparate rollup VMs proved to be a formidable engineering challenge. The “lazy sequencing” model, while elegant in theory, faced hurdles in practical implementation regarding how rollups handled invalid transactions included in the shared block.50
Implication: The failure of Astria suggests that the market for “pure” middleware sequencing chains is thin. To survive, shared sequencing protocols must likely align deeply with existing liquidity hubs—either by being “Based” (Ethereum) or by leveraging massive existing security pools (Solana/Rome, EigenLayer/Espresso).
6. The Convergence: Future Outlook
As we look toward 2026 and beyond, the “Coordination Layer” is poised for a period of convergence. The binary distinction between “Based” and “Shared” is likely to blur as protocols adopt hybrid models.
6.1 Middleware vs. Based: A Spectrum, Not a Binary
We will likely see a spectrum of solutions. High-value DeFi rollups that prioritize censorship resistance and alignment with Ethereum liquidity will gravitate toward the Based Rollup model, utilizing Fabric standards and preconfirmations to solve latency.51 Conversely, high-performance app-chains (e.g., gaming, social) that require throughput exceeding Ethereum’s limits will utilize middleware solutions like Espresso or NodeKit. These middleware layers may eventually settle on Ethereum, acting as “Based” L3s, creating a fractal scaling architecture.
6.2 The Role of Flashbots SUAVE
Any discussion of the future coordination layer must include Flashbots SUAVE (Single Unified Auction for Value Expression). While technically distinct from a shared sequencer, SUAVE acts as a “global mempool” and “preference environment.” It allows users to express intents (e.g., “I want to swap Token X for Token Y across these chains”) and utilizes a decentralized network of executors to build the optimal transaction bundles. SUAVE is likely to sit upstream of shared sequencers. SUAVE builders will construct the cross-chain bundles, and shared sequencers (or L1 proposers) will be the entities that finalize them.52
6.3 Conclusion
The era of the centralized sequencer is drawing to a close. The industry has recognized that the fragmentation and centralization risks of the early rollup era are existential threats to the promise of crypto. Whether through the direct usage of L1 validators via Based Sequencing or through specialized, high-performance middleware like Espresso and Rome, the next generation of rollups will be coordinated.
This coordination layer is the missing link in the modular stack. It is the infrastructure that will finally allow the ecosystem to deliver on the promise of “Money Legos” at scale, enabling a user experience where the boundaries between chains dissolve, leaving only a unified, secure, and permissionless global computer. For infrastructure architects and rollup developers, the choice is no longer if they will decentralize sequencing, but which coordination network they will join to secure their future.