Eco Routes: Settlement Modularity for the Best Cross-Chain UX

We built Eco Routes because of our prior experience developing Bend, an early account abstraction wallet optimized for fast onboarding and easy stablecoin use. We introduced chain-abstracted stablecoin balances, paid gas fees in USDC, and even implemented private-key abstraction through Shamir’s Secret Sharing. But existing cross-chain settlement systems couldn’t deliver the product experience we wanted for our users — true chain abstraction, with the ability to execute any onchain action by sending a stablecoin with a single signature.

We built Eco Routes — the first component of the upcoming Eco protocol — with this goal in mind. We realized early on that intent-based architecture offered the best UX for this goal, but that existing intent protocols were often not flexible enough for developers to configure to their use case — just as everyday payments rely on different rails, cross-chain actions may require varying security, settlement, and cost assumptions. We came to believe that modularity would be one crucial design factor in building the best cross-chain settlement system.

This post summarizes the various proof systems available (or soon to be available), the Native, Hyperlane, Polymer, T1, and Syndicate Routes, for validating and settling transactions across Eco Routes — some of their technical considerations and relative advantages, and how they fit into the broader architecture.

The Native Route: A Storage Prover with No Added Trust Assumptions

Eco’s first method prioritized trust minimization and focused on transfers across Ethereum L2s, considering how finality constraints impacted pricing for transfers across rollups. We started here because we knew this method would always be available among Ethereum rollups and could serve as an effective fallback method if any service-based prover suffered an outage or a vulnerability. 

The Ethereum state root can be used to settle transactions via proofs that verify the contract storage root of a destination rollup. We productionized the storage proof method when we released Cross-L2 Actions (RIP-7755 standardized the same approach). This storage prover is also known as the Native Route in the Eco Routes suite. 

As mentioned, this prover relies on a convenient property: Many Layer 2 rollups expose the L1 block hash inside their execution environment. Because L2s regularly post their state roots to L1, we can likewise prove any L2 state root on Ethereum and, from there, any L2 contract storage slot. 

That, in a nutshell, is how the Native Route operates. It pulls the L1 State Root, proves the L1 contract storage slot that stores the destination chain’s state root, and that the state root is finalized (beyond the 7-day finalization window). It then performs a storage proof to validate that a given intent was executed on the destination chain. 

An example flow of an intent originated on Optimism for Base, then works like this:

1. The user/app locks up funds in the intentSource contract on Optimism, indicating they have an action they want to take on Base.
2. The solver enters the Inbox and solves the intent, which stores the intent in storage as solved. 
3. The solver then enters the Native Route prover and proves the status of the intent. After the proof is verified, they can claim their funds. 

The diagram below illustrates the proof path in the Native Route on Optimism.  

Because the Native Route only uses information exposed within the given Rollup Environment, it inherits no additional trust assumptions beyond those of the rollup and Ethereum. This makes it an ideal proving mechanism for transactions requiring absolute security and guaranteed resolution. 

This approach does come with obvious and significant drawbacks, most notably that the solver must wait the whole seven-day rollup challenge period before reclaiming collateral, which imposes a considerable opportunity cost. This means the Native Route is not very capital efficient; in the most optimal case, the solver can only recycle capital once a week. In addition, the storage proof process incurs considerable calldata and execution cost, making it cost-prohibitive on most rollups, especially for smaller payments.

Consequently, we expect intents settled through the Native Route to be costly compared with other Eco Routes and other intent protocols that utilize optimistic settlement methods. That premium is worthwhile for actions that may be less frequent and require absolute finality, such as governance messages or very large transfers. Still, it is not ideal for everyday payments until finality times improve (🙏).

The Hyperlane Route: Message-Based Permissionless Prover

In response to the long settlement times inherent to the storage-based Native Route, we introduced a new option that enables fast, inexpensive, and permissionless settlement across any chain we currently support: the Hyperlane Route. It relies on Hyperlane’s underlying message-passing system to relay the status of proven intents back to the origin chain.

Hyperlane’s flow mirrors the storage proof approach, but without the seven-day delay:

1. A user initiates an intent on the origin chain, selecting the Hyperlane Route as the settlement mechanism.
2. A solver moves to the destination chain and fulfills the intent.
3. During (or immediately after) fulfillment, the solver sends a Hyperlane message to the origin chain, marking the intent as proven.
4. The solver then reclaims its collateral.

Hyperlane’s message system is designed to be very flexible for the applications running it. Hyperlane does not enshrine any specific validation method, relayer, or message behavior, which makes it ideal for Eco Routes. By default, the Hyperlane Route uses Hyperlane’s default Interchain Security Module (ISM) and validators, but can introduce new provers with new security assumptions to match better applications that demand a different security model. 

Another advantage of the Hyperlane Route is permissionless deployment: Hyperlane can be deployed on demand to any EVM-compatible chain without waiting for central approval. If Eco Routes wants to add a new chain, we can deploy the necessary infrastructure ourselves and fold that chain into the existing Hyperlane network. 

The Hyperlane Route can settle almost instantaneously when compared to the Native Route. This means capital can be recycled very quickly, requiring solvers to hold much less inventory on their balance sheet to service a large volume of intents. For example, even with a conservative 15-minute recycle time — in reality, it’s most often 5 minutes or less — a solver could theoretically service a weekly volume of over $600 million with only $1 million of underlying collateral.

The Hyperlane Route is also designed with the option to batch intents, which further improves the unit economics of each intent fulfillment. Obviously, like any message bridge, this means that users and solvers utilizing the Hyperlane Route incur additional trust assumptions of the Hyperlane default ISM. Still, those assumptions are configurable and modifiable for future iterations of the Hyperlane Route, providing users and solvers fine-grained control over the trust assumptions of this method.  

The Polymer Route: Pull-Based Prover from the Origin Chain

Eco has already prototyped and is nearing release of a Polymer Route that leverages Polymer’s cross-chain proving system to confirm the status of intents on supported destination chains. To understand how the prover works, it’s instructive first to outline how Polymer works. Polymer consumes local confirmations produced by validator networks on various source chains and relays them to destination blockchains using an efficient data structure.  

Anyone can then request proof from the Polymer API for a given log on any source chain. When a cross-chain proof is requested from Polymer, the following steps occur:

1. Polymer runs a full node for each supported L2. Once it receives a sequencer-signed blockhash with the information for the given log, it ingests that block into its own rollup. 
2. Within the Polymer Rollup, the validity of the blockhash is confirmed by checking the signature, and the relevant log (or storage in the future) information is extracted from the blockhash. 
3. The information is then ingested into an IAVL apphash (the state root of Cosmos-based systems) that is very efficient to conduct inclusion proofs against. 
4. Polymer then returns to the proof submitter the IAVL apphash that is signed by the Polymer sequencer.
5. This proof is submitted to the destination chain for the message, and its validity is verified via signature. The log data can then be used for any application on that chain. 

Below is an example of how Polymer works in the Eco intent flow: 

This process makes it straightforward to prove any log or storage value on the origin chain. In effect, Polymer delivers many of the benefits of the storage proof system, but with significantly faster messaging times and far lower proof execution costs. Because Polymer uses an IAVL apphash for proofs, which are very efficient to prove against, it uses 13 times less gas than the storage proof system. 

Polymer is essentially a “pull-based” proof mechanism. This means that solvers can simply solve intents on the destination chain without needing to execute a relay or message on top of the fill, which lowers the cost of fills. Polymer simply queries the destination rollup for the fulfillment log when needed. This enables a whole host of new features, such as same-chain cancellations, proofs with atomic claims and solves, and very efficient proving methods (shown below). 

Finally, we are exploring a mechanism where Polymer can broadcast a Merkle root of all intent fulfillments on a given rollup, with each leaf of the tree representing a specific set of intents for a given destination chain. Because all the destination chains can consume this single root, it makes it easy to efficiently synchronize the status of intents on a specific chain with all the other intents in the system. If you'd like to learn more about the Polymer Route, please see our talk from ETHDenver.

The T1 Route: A Prototype Prover for Seamless Cross-Chain Reads

Another proof method currently in development is a T1 Route built on T1’s real-time, cross-chain proof system. T1 operates a Trusted Execution Environment (TEE) for every supported rollup or L1 that runs a full node of that rollup. Using the data from the full node, the TEE can perform cross-chain reads, sign the results cryptographically, and return them to the caller. This lets a multi-chain application feel like a single-chain experience.

Like Polymer, T1 is pull-based: solvers need to do nothing on the origin chain beyond fulfilling the intent. In practice, a solver can (1) prove an intent’s status, (2) reclaim collateral, and (3) redeploy that collateral to solve a new intent all in one transaction. This prototype also allows a solver to batch-prove any number of intents at once, enabling them to accumulate fulfillments on a destination chain and submit a single, large proof when convenient.

More broadly, T1 represents a class of TEE-backed routes, including platforms such as Lit, that enable large-batch settlements, early cancellations from the origin chain, and rapid, low-cost execution across multiple rollups. 

The Syndicate Route: A Speculative Prover Enabling Atomicity

Finally, Eco is also experimenting with a Syndicate Route, which would rely on Syndicate’s atomic, programmable on-chain sequencing logic.

Syndicate enables the enforcement of sequencing rules through programmable constraints. Developers can use these constraints to craft custom transaction ordering, enshrine protocol logic, and embed economic incentives that dictate how the sequencer behaves and what it is permitted to include in a block.

Any rollup that supports Syndicate’s atomic sequencing modules could enable cross-chain intents that atomically settle collateral the moment an intent is fulfilled. In other words, collateral release and intent execution would be bundled into a single, indivisible operation, which would eliminate delayed settlement and ensure end-to-end atomicity across chains.

Conclusion & Next Steps

Eco Routes already runs two production-grade routes today: the Native Route and the Hyperlane Route. In early Q3, we will release the Polymer Route and debut a fully featured demo of the T1 Route, providing builders with four distinct settlement paths that span the cost, speed, and trust spectrum.

But the story doesn’t end just with new Routes. Each prover presents a unique opportunity to add new features that improve user experience and the system’s tradeoff space: 

• Composable fallback paths. We’ve already prototyped a Unity Route that defaults to Polymer’s fast path but automatically falls back to the Native Route if Polymer is unavailable or its trust assumptions are no longer acceptable. Similar hybrid designs can pair any fast prover with a slower, fully trust-minimized backup.
• Early cancellations. Pull-based systems such as Polymer and T1 make it easy to introduce cancellations on the origin chain. If an intent remains unfilled after a specified fill deadline, the user can cancel it instantly as long as it hasn’t been fulfilled already, with no relay round-trip required. For message-based provers, ping-pong-based cancellation can provide a similar experience, similar to Aori; it just requires an extra message to be passed, adding some cost.
• Efficient Batch Settlement. Although the system already supports batch settlement, new proving systems make it easy to support a host of very efficient and convenient settlement mechanisms that drastically improve the unit economics of fills. 

We view modular settlement as more than a convenience; it’s a strategic prerequisite for a cross-chain future:

• Cost, speed, and trust on demand. With multiple provers, solvers, and users can pick the exact trade-off their use case demands, from five-second settlement times to Ethereum-level security.
• Resilience through redundancy. If a proving system set goes offline or is compromised, intents can still settle via an alternate route.
• Broader chain reach. Some chains lack native proofs, others cannot host a TEE, and still others sit outside the EVM universe entirely. Route diversity enables Eco to expand into each environment without compromising the user experience (UX).

As Routes scales to new EVM rollups and non-EVM chains, settlement flexibility and prover diversity will remain pillars of Eco’s architecture, ensuring that every intent finds the optimal path home.

Special thanks to Christian Angelopoulos from Uniswap Labs for contributions, feedback, and review.

About Eco

Eco enables any onchain action to be a simple, one-click stablesend. With Eco, apps can easily accept anyone’s preferred stablecoin, regardless of the network — unlocking stablecoin liquidity from any connected chain and giving users the simplest onchain experience. To make this possible, the Eco Protocol brings together Routes, Accounts, and Crowd Liquidity (coming soon) to give app developers the ultimate flexibility while prioritizing speed, cost, and security. 

Website | Eco Docs | Twitter | LinkedIn | Discord | Forum

About Eco Inc.

Eco Inc. is a blockchain company building software that maximizes money’s value. The company is a founding contributor to the Eco Protocol and the builder of Bend. We expect better from our money, and we want you to as well. That’s what drives us every day. 

Twitter | LinkedIn