The Evolution of Cross-Chain Engineering: From "Aggregation Bridge" to "Atomic Interoperability", what kind of future are we heading towards?

Author: imToken

If you are an on-chain Degen, you are probably familiar with the following scenario:

Transfer ETH from the mainnet to Arbitrum to interact with DeFi at lower Gas fees; exchange USDT on Polygon for USDC on Base; or, for optimal strategy, diversify assets across different chains to connect with specific applications.

These operations point to one of the core propositions of the blockchain world—cross-chain interoperability. This article also plans to outline the evolution of cross-chain technology and shed light on how Web3 moves from a single “cross-chain bridge” to the final goal of “seamless interoperability.”

1. Rollup and the Fragmentation of Multi-Chain Ecosystem

If you are an old player in the Ethereum ecosystem, how many L2s have you used at most? 5, 10, or 20 or more?

In fact, compared to the total amount, the vast majority of players may have only explored a small part of the L2 landscape. According to incomplete statistics from L2BEAT, there are nearly a hundred L2s in the Ethereum ecosystem today, not including other independent L1 public chains. We are in an unprecedentedly prosperous multi-chain era.

However, this has also led to a new dilemma where liquidity and yield opportunities are increasingly fragmented — the traffic that was originally concentrated on Ethereum is gradually being divided, creating isolated value islands, while it is destined that with the increase in the number of public chains and L2s, the degree of liquidity fragmentation will further intensify.

So what does this mean for the average user? When you need to perform a cross-chain operation from Chain A to Chain B, it's like planning a complex international trip, full of difficulties.

After all, from Chain A to Chain B, each route has different travel times (bridging time), tolls (cross-chain costs), and fuel consumption (Gas), and each time the travel time, tolls, and fuel consumed may vary, making it difficult to find the optimal route:

• Some routes may only support specific tokens;
• The tolls for certain routes may vary based on the amount of tokens, so it may not be ideal for large transactions;
• Alternatively, contract interactions on certain routes may incur high costs, leading to increased travel time and fuel consumption;

This process is not only cumbersome, but each step may also incur additional slippage and fees. Therefore, just as DEX aggregators like 1inch became a necessity after the flourishing of DEXs like Uniswap and SushiSwap, in the context of an increasing number of bridges in the market, cross-chain bridge aggregators have also become the first wave of evolution.

The idea of cross-chain (layer) aggregation not only achieves direct aggregation and transfer of assets between different blockchain networks, but also includes the aggregation of DEXs and DEX aggregators, such as Uniswap, 1inch, etc. This allows users to directly exchange different assets while transferring assets across chains (layers).

This means that you only need to input the starting point (DAI on Arbitrum) and the endpoint (ETH on Optimism), and the system will instantly calculate the optimal solution under the current market conditions for you. The user only needs to confirm once, and the backend will complete the entire process of cross-chain + exchange operations.

This marks the evolution of cross-chain experience from “manual mode” to “automatic mode,” greatly lowering the user threshold.

II. Evolution from “Cross-chain” to “Aggregation”

In short, the core value of a cross-chain aggregator lies in becoming an intelligent navigation system for users, simplifying complex multi-step operations into a single click.

This is also the focus of development in the direction of cross-chain aggregators and similar ideas over the past few years. In this process, the system will automatically find all available routes and sort them based on the following three criteria - maximum asset output on the target chain, lowest Gas fees, and shortest time. Users only need to choose from the paths provided by the aggregator to complete the optimal cross-chain exchange operation.

We can intuitively feel the advantages of this cross-chain (layer) aggregation exchange by comparing it with traditional cross-chain exchange paths. Suppose a user has DAI on Arbitrum and wants to exchange it for ETH on Optimism. Under traditional cross-chain (layer) projects, multiple paths can be used to achieve this:

• First, use 1inch on Arbitrum to swap DAI for ETH, then use a cross-chain bridge to transfer ETH from Arbitrum to Optimism;
• Alternatively, first transfer DAI from Arbitrum to Optimism via a cross-chain bridge, and then use Uniswap on Optimism to exchange DAI for ETH;

Although different paths have their own advantages in terms of cost and experience, the underlying logic is largely similar. They all involve the same two logical processes: cross-chain (layer) transfers of the same asset and exchanges of different assets, followed by optimal selection operations. This requires a comprehensive evaluation based on factors such as the size of the exchange funds, the degree of slippage, whether the corresponding network has sufficient liquidity, and the speed of transactions.

However, in the approach of cross-chain (layer) aggregation, the aforementioned trade-offs and considerations do not need to be made by the user. It automatically finds all available routes and helps users move funds between different blockchains in the most optimal way based on factors such as the maximum output on the destination chain, the minimum Gas fees for transactions and transfers, and the shortest bridging time.

Beyond the intuitive “aggregation” evolutionary path perceived from the user experience side, on a technical level, in order to break down barriers, the cross-chain track has been exploring various more diverse technical solutions for many years.

• Message Layer Interoperability: For example, LayerZero and IBC (Cosmos), achieve data interoperability through cross-chain message verification.
• State layer synchronization: Allows different chains to directly share state without the need for intermediaries.
• Zero-Knowledge (ZK) Cross-Chain: Utilizing zero-knowledge proofs to make cross-chain verification more efficient and secure.

These solutions point to a common goal of making the blockchain world truly “seamlessly interconnected,” allowing users to feel no boundaries of the chain.

On August 29, the Ethereum Foundation also released “Protocol Update 003 - Improve UX,” focusing on improving user experience (Improve UX) as one of the three major strategies after restructuring the development team (Scale L1, Scale Blobs, Improve UX).

The article emphasizes that interoperability (interop) is at the core of EF, aiming for a seamless, secure, and permissionless Ethereum ecosystem experience.

3. The Latest Cross-Chain Thoughts on Ethereum

Against this background, there are two new paths worth noting in the academic and developer communities that may determine the future form of cross-chain in the Ethereum ecosystem.

1. SCOPE: Rebuilding the “synchronous composability” of Ethereum

First of all, the SCOPE (Synchronous Composability Protocol) concept recently proposed by Ethereum researcher jvranek aims to achieve synchronous composability between Ethereum L1 and L2, as well as between L2 and L2, supporting atomic execution of cross-domain contracts.

In simple terms, it means allowing different Rollups and interactions between Rollups and the Ethereum mainnet to be executed in an “atomic” manner, as if on the same chain—all operations within a single transaction must either succeed entirely or fail entirely, without any intermediate state. However, this has been difficult to achieve due to the barriers of cross-chain interoperability, making it challenging to implement once cross-chain operations are involved.

For example, with SCOPE, you will be able to simultaneously call the Aave protocol on Arbitrum and the Uniswap protocol on Optimism in a comprehensive strategy trade involving Swap and Lend, where either both succeed or both fail, without getting stuck in between, wasting Gas and opportunity costs.

The potential value is also evident, as it will unlock complex DeFi strategy combinations such as cross-L2 flash loans and one-click liquidations. Although SCOPE is still in the PoC stage, it is widely regarded as a key piece to solve the fragmentation of L2 composability.

Once mature, the aggregation experience at the application layer will complement the atomic interoperability at the underlying layer: the former lowers the threshold, while the latter ensures security and consistency.

2. ZK Accelerated Interoperability: Replacing 'Trust' with Mathematics

Another direction is to use zero-knowledge proofs (ZK Proof) to make cross-chain verification no longer rely on a group of trusted intermediaries (verification nodes), but purely depend on mathematics.

The state changes on the source chain can generate a concise ZK proof. The target chain verifies the events on the source chain through mathematical proof, thereby confirming them as true within the security model. The representative solutions include the native Interop mechanism proposed by ZKsync, among others.

There are also some routes with a stronger engineering orientation, attempting to achieve a dynamic balance between “speed” and “security cost.” Taking the concept of the t1 Protocol as an example, the aim is to find a middle ground between the two extremes of “pure ZK trust minimization” and “highly trusted intermediaries,” achieving asynchronous, rapid, and cryptoeconomic guarantees.

It uses TEE + AVS to prove events/states of other chains, and when the risk amount exceeds the crypto economic budget, ZK proofs are introduced on demand as a safeguard (saving daily costs); in terms of the specific security architecture, it separates ordering from execution, allowing TEE outputs to be reproducible for fraud detection and punishment, achieving accountability in the crypto economy through deterministic outputs.

In short, this type of approach emphasizes “enhancing 80% of user needs to a 10x experience” first, and then leveraging a cost-flexible proof system at critical moments. From the perspective of engineering implementation, if it can be combined with the wallet's intention routing, risk control, and limit mechanisms, it would be a very pragmatic implementation direction.

Overall, whether it's cross-chain aggregation at the application layer or atomic interoperability / ZK acceleration at the protocol layer, the common trend is gradually diminishing the presence of “chain” and the perception of “cross”:

For ordinary users, you may not need to remember names like SCOPE or ZK Interop; what truly matters is that cross-chain operations are becoming faster (in seconds), more secure (with mathematical guarantees), and more seamless (completed in one go).

This is also how the cross-chain ultimate goal should be achieved: allowing users to focus on the flow of value itself, rather than the barriers between chains.