Why Interoperability Is the Modular Stack's Achilles' Heel

Separate settlement and execution layers create predictable latency gaps. Searchers exploit this to front-run transactions across domains like Ethereum → Arbitrum, extracting value and degrading user experience.\n- Attack Vector: Time-bandit attacks between proposer/sequencer and finality.\n- Impact: User slippage increases, trust in cross-chain fairness erodes.

Rollups inherit security from their settlement layer (e.g., Ethereum), but app-chains and validiums opt for their own validator sets. This creates a security mosaic where the weakest chain compromises the entire ecosystem's composability.\n- Trust Assumption: Users must audit each chain's consensus.\n- Systemic Risk: A bridge hack on a smaller chain can drain liquidity from connected majors.

Frameworks like UniswapX and CowSwap abstract routing via intents, while shared sequencers (e.g., Espresso, Astria) provide atomic cross-rollup execution. This moves the interoperability burden from users to the infrastructure layer.\n- Key Benefit: Atomic composability across domains without new trust assumptions.\n- Key Benefit: MEV capture is socialized and can be redistributed.

Centralizing transaction ordering across rollups (like Espresso, Astria) creates a single point of failure and latency. It's a trade-off: atomic composability for re-centralized control.\n- Risk: Censorship and MEV extraction at the network level.\n- Reality: Most implementations today are permissioned or federated.

Rollups that settle to Celestia or EigenLayer instead of Ethereum L1 create new security and bridging layers. Each settlement layer becomes a new silo.\n- Problem: Bridging between two Celestia-based rollups requires a separate bridge from Ethereum-based ones.\n- Result: Liquidity fractures across multiple trust-minimized but isolated clusters.

Protocols like UniswapX and CowSwap abstract the complexity by using solvers, but this outsources trust. It's an economic fix, not a cryptographic one.\n- Solution: Users specify what they want, not how to get it.\n- Caveat: Relies on solver competition and reputation, reintroducing off-chain trust.

Projects like Polygon AggLayer and LayerZero's Omnichain promise a unified state, but they rely on external attestation committees or multi-sigs. The security is only as strong as its weakest validator set.\n- Architecture: Adds a new consensus layer above the execution layers.\n- Trade-off: Faster native bridging vs. new, often opaque, trust assumptions.

Using EigenDA, Celestia, or Avail creates protocol-level lock-in. Rollups on different DA layers cannot easily verify each other's data, breaking light client bridges.\n- Consequence: Interoperability becomes a function of shared DA, not just shared settlement.\n- Future: Forces a consolidation around 2-3 dominant DA providers.

A rollup secured by Ethereum's $50B+ staked ETH cannot port that security to another chain. Bridges like Across and Chainlink CCIP must bootstrap their own validator stake, creating weaker, duplicated capital pools.\n- Root Cause: Security is siloed at the base layer.\n- Metric: Total Value Secured (TVS) for a bridge is often <1% of the chains it connects.