Interop Roadmap Accelerates: After Fusaka Upgrade, Ethereum Interoperability May Reach a Critical Leap

Author: imToken

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In previous articles of the Interop series, we discussed the OIF (Intent Framework) and EIL (Interoperability Layer), which address cross-chain intent standardization (making the entire network understand what you want to do) and execution channel issues (standardizing the transfer of funds).

However, to achieve a perfect “single-chain experience,” there are still trade-offs between speed and trust. After all, in the current interoperability experience, one either endures slowness (such as Optimistic Rollup requiring a 7-day challenge period to confirm finality) or sacrifices decentralization (relying on multi-signature bridges’ trust assumptions).

Breaking this “impossible triangle” relies on a foundational capability in Ethereum’s interoperability roadmap: “Acceleration” and “Finalization,” enabled by ZK technology bringing “real-time proofs” (Extended reading: “Ethereum Interop Roadmap: How to Unlock the ‘Last Mile’ of Large-Scale Adoption”).

Recently activated in the Fusaka upgrade, an apparently inconspicuous EIP-7825 has cleared the biggest engineering obstacle toward this final goal.

I. Behind Fusaka Upgrade: The underrated EIP-7825

On December 4th, the Ethereum Fusaka upgrade was officially activated on the mainnet. Unlike the Dencun upgrade back then, which was highly anticipated, the market spotlight mainly focused on Blob scalability and PeerDAS, with continued enthusiasm for reducing L2 data costs.

But behind this clamor, there is an unassuming proposal—EIP-7825—that clears the biggest obstacle for Ethereum to achieve L1 zkEVM and real-time proofs, and can even be said to be quietly paving the way for the Interop’s ultimate goal.

In this Fusaka upgrade, the focus was almost entirely on scaling: Blob capacity increased eightfold, combined with PeerDAS random sampling verification, making the cost narrative for the DA (Data Availability) track a thing of the past.

Indeed, cheaper L2 solutions are good, but for Ethereum’s long-term ZK roadmap, EIP-7825 is the real game-changer, as it sets a Gas limit (about 16.78 million Gas) for individual transactions.

It is well known that this year, the Gas Limit of Ethereum blocks has been raised to 60 million. But even with this increasing ceiling, theoretically, if someone is willing to pay an extremely high Gas Price, they could still send a “Mega-Transaction” consuming the entire 60 million Gas, directly clogging the entire block.

This was permitted before, but EIP-7825 introduces a new restriction: regardless of block size, a single transaction cannot consume more than 16.78 million Gas.

Why place such a limit on transaction size? In fact, this change has no impact on regular users transferring assets. However, for ZK Provers (proof generators), this is a matter of life and death, closely related to how ZK systems generate proofs.

For example, before EIP-7825, if a block contained a Mega-Transaction consuming 60 million Gas, the ZK Prover would have to process this extremely complex transaction sequentially, without splitting or parallelization. It’s like a single-lane highway with a slow-moving giant truck ahead, causing all following cars (other transactions) to be stuck waiting for it to pass.

This effectively spells doom for “real-time proofs”—since the proof generation time becomes uncontrollable, potentially taking dozens of minutes or longer.

After EIP-7825, even if future block capacity expands to 100 million Gas, because each transaction is forcibly limited to 16.78 million Gas, each block is broken down into predictable, bounded, parallelizable “small task units.” This turns Ethereum’s proof generation from a difficult “logical puzzle” into a straightforward “computational problem” (Money Problem):

As long as sufficient parallel computing power is invested, these split small tasks can be processed simultaneously in a very short time, enabling ZK proofs for huge blocks.

As Brevis co-founder and CEO Michael stated, EIP-7825 is the most underrated upgrade on the path to 100x ZK and Ethereum scalability. It transforms “real-time proof” from “theoretically impossible” to “engineeringly schedulable.” As long as we can solve the compute problem through parallel processing, even blocks of 200 million Gas could potentially generate proofs within seconds. This is not only a breakthrough for ZK technology but also a fundamental enabler for the interoperability layer (EIL) to achieve second-level cross-chain settlements.

Therefore, this upgrade might seem not to be the main event, but in fact, it marks a huge breakthrough for the ZK roadmap and Ethereum’s scalability future in 2026.

II. L1 zkEVM: The “trust anchor” of Ethereum interoperability

However, while EIP-7825 paves the physical path for real-time proofs (parallelizable by limiting transaction size), the other side of the coin is: how will Ethereum mainnet itself utilize this capability?

This involves the most core narrative in Ethereum’s roadmap—L1 zkEVM.

Long regarded as the “Holy Grail” for scaling Ethereum, zkEVM not only addresses performance bottlenecks but also redefines blockchain trust mechanisms. Its core idea is to enable Ethereum mainnet to generate and verify ZK proofs.

In other words, after future blocks are executed, they can output a verifiable mathematical proof, allowing other nodes (especially light nodes and L2s) to confirm correctness without re-executing transactions—if the capability to generate ZK proofs is embedded in the Ethereum protocol layer (L1), proposers (block packers) generate a block and produce a ZK proof, then verification nodes no longer need to re-run transactions, just verify this tiny mathematical proof.

What does this mean for interoperability?

In the context of Interop, L1 zkEVM’s significance surpasses mere scaling; it can be seen as the “trust anchor” for all L2s. If Ethereum L1 can generate proofs in real-time, then all L2s can verify L1’s final state instantly and trustlessly—bringing two major transformations:

• Eliminating challenge periods: confirmation time between chains from “7 days (OP mechanism)” to “seconds (ZK mechanism)”;

• Decentralized interconnection: cross-chain trust no longer relies on third-party multi-sig bridges, but on the mathematical truth of Ethereum mainnet.

This is also the physical foundation for the effectiveness of our previous article’s EIL (Interoperability Layer)—without L1’s real-time finality, interoperation among L2s will forever be shadowed by “delay.”

With the goal (L1 zkEVM) achieved and the physical limit (EIP-7825) removed, what about the specific tools for realization?

This leads to a subtle evolution in the ZK tech stack: from zkEVM to zkVM.

III. Fusaka & EIP-7825: The roadmap of interoperability enters liberation

If EIP-7825 provides the “parallel hardware environment” for ZK by limiting transaction size, then the evolution of the ZK tech stack aims to find a “more efficient software architecture.” While this might sound like a tongue-twister, the difference is substantial and represents two stages of ZK development (Extended reading: “ZK Roadmap ‘Dawn’: Is Ethereum’s Endgame Accelerating?”).

The first stage is naturally zkEVM, which can be seen as the compatibility or “improvement” camp.

Its logic is to mimic every instruction of Ethereum’s EVM, enabling developers to deploy Solidity code directly, minimizing migration costs and barriers.

In other words, zkEVM’s biggest advantage is compatibility with existing Ethereum applications, greatly reducing the workload for Ethereum ecosystem developers—they can reuse most existing infrastructure and tools (including execution clients, block explorers, debugging tools, etc.).

However, because EVM was not originally designed with ZK friendliness in mind, zkEVM proof efficiency often hits a ceiling: proof times are much slower, and historical baggage remains.

In contrast, zkVM belongs to the radical revolutionary camp, building a virtual machine (such as RISC-V or WASM-based) that is highly ZK-proof friendly, to accelerate proof times and achieve better execution speed and performance.

But this may come at the cost of losing compatibility with many EVM features and utilizing existing tools (like low-level debuggers). Currently, a clear trend is that more L2 projects are shedding these limitations, heavily optimizing proof speed and cost, and exploring zkVM-based architectures.

Why say Fusaka upgrade is an unlocker?

Because before EIP-7825, whether zkEVM or zkVM, encountering mega-transactions on Ethereum would cause proof generation time to skyrocket due to inability to split tasks.

Now, with EIP-7825 forcing transactions into predictable small units and enabling parallel environments, high-efficiency architectures like zkVM can realize maximum potential. Even with complex Ethereum blocks, placing them into zkVM and leveraging parallel compute can achieve real-time proofs.

What does this mean for interoperability? The widespread adoption of zkVM combined with EIP-7825 implies that the cost of generating proofs will be drastically reduced. When the cost of generating cross-chain proofs becomes negligible and speed is as fast as sending an email, traditional “cross-chain bridges” will vanish, replaced by underlying universal messaging protocols.

In conclusion

As repeatedly emphasized in previous Interop articles, the ultimate goal of interoperability is not merely asset “cross-chain,” but a comprehensive system-level capability—including cross-chain data communication, cross-chain logic execution, cross-chain user experience, cross-chain security, and consensus.

From this perspective, interoperability can be understood as a universal language among future Ethereum ecosystem protocols. Its significance lies not only in value transfer but also in sharing logic. ZK plays a role in guaranteeing execution correctness, supporting real-time state verification, making cross-domain calls “dare to do, capable of do.” In fact, without real-time ZK, truly usable interoperability UX would be difficult.

Therefore, with EIP-7825 quietly activated in Fusaka and L1 zkEVM gradually becoming a reality, we are infinitely approaching that ultimate goal: execution, settlement, and proofing are fully abstracted in the background, completely invisible to users.

This is the interoperability future we all look forward to.