Author: imToken
In previous articles of the Interop series, we discussed OIF (Intent Framework) and EIL (Interoperability Layer), which respectively address the standardization of cross-chain intents (making the entire network understand what you want to do) and the execution channel problem (enabling funds to move in a standardized manner).
However, achieving a perfect "single-chain experience" still involves a trade-off between speed and trust. After all, in the current interoperability experience, one must either endure slowness (such as Optimistic Rollup requiring a 7-day challenge period to confirm finality) or sacrifice decentralization (relying on the trust assumptions of multi-signature bridges).
To break this "impossible triangle," it is essential to have a foundational capability that spans the "acceleration" and finalization of Ethereum's interoperability roadmap—the "real-time proof" brought by ZK technology (extended reading: "Ethereum Interop Roadmap: How to Unlock the 'Last Mile' of Mass Adoption").
And the recently activated Fusaka upgrade, with its inconspicuous EIP-7825, has cleared the biggest engineering obstacle for this ultimate goal.
I. Behind the Fusaka Upgrade: The Underestimated EIP-7825
On December 4, the Ethereum Fusaka upgrade was officially activated on the mainnet. Unlike the fanfare of the Dencun upgrade, the market spotlight was largely focused on Blob scaling and PeerDAS, with much discussion about the further reduction of L2 data costs.
But beyond this buzz, there was actually a low-profile proposal, EIP-7825, which removed the biggest obstacle to achieving L1 zkEVM and real-time proof for Ethereum, and can even be said to be quietly paving the way for the ultimate goal of Interop.
In this Fusaka upgrade, the focus was almost entirely on scaling: Blob capacity expanded by 8 times, combined with PeerDAS random sampling verification, making the cost narrative of the DA (Data Availability) track a thing of the past.
Indeed, cheaper L2s are a good thing, but for Ethereum's long-term ZK roadmap, EIP-7825 is the real game-changer because it sets a Gas limit for a single transaction on Ethereum (about 16.78 million Gas).
As we all know, Ethereum's block Gas Limit was increased to 60 million this year. But even as the upper limit continues to rise, theoretically, if they were willing to pay an extremely high Gas Price, someone could send a super-complex "Mega-Transaction" that directly occupies the entire block's 60 million Gas capacity, thereby clogging the entire block.
This was allowed before, but EIP-7825 introduces a new restriction: no single transaction can consume more than 16.78 million Gas, regardless of the block size.
So why limit the size of a single transaction? This change actually has no impact on ordinary user transfers, but for ZK Provers (proof generators), it is a matter of life and death, and it is also closely related to how ZK systems generate proofs.
To give a simple example, before EIP-7825, if a block contained a "Mega-Transaction" consuming 60 million Gas, the ZK Prover had to run this extremely complex transaction sequentially—it couldn't be split or parallelized. This is like a single-lane highway where a giant, extremely slow truck is in front, and all the cars behind (other transactions) have to wait for it to pass.
This would undoubtedly sentence "real-time proof" to death—because the time to generate the proof would be completely unpredictable, potentially taking dozens of minutes or even longer.
After EIP-7825, even if the block capacity expands to 100 million Gas in the future, since each transaction is forcibly limited to within 16.78 million Gas, each block is broken down into predictable, bounded, and parallelizable "small task units." This means that Ethereum's proof generation has changed from a tricky "logical puzzle" to a pure "money problem":
As long as enough parallel computing power is invested, we can process these split small tasks simultaneously in an extremely short time, thereby generating ZK proofs for huge blocks.
As Michael, co-founder and CEO of Brevis, said, EIP-7825 is the most underestimated upgrade on the future path of ZK and 100x scaling for Ethereum. It turns "real-time proof" from "theoretically impossible" to "engineerably schedulable." As long as we can solve the computing power problem through parallel computation, even a 200 million Gas block could achieve second-level proof. This is not only a breakthrough for ZK technology but also the physical foundation for Ethereum's Interoperability Layer (EIL) to achieve second-level cross-chain settlement.
So this upgrade might not seem like the main event, but it is actually a huge breakthrough for the ZK roadmap and Ethereum's scaling future in 2026.
II. L1 zkEVM: The "Trust Anchor" for Ethereum Interoperability
However, although EIP-7825 paves the physical path (parallelizability) for real-time proof by limiting single transaction size, this is only one side of the coin. The other side is how the Ethereum mainnet itself utilizes this capability?
This involves the most hardcore narrative in Ethereum's roadmap—L1 zkEVM.
For a long time, zkEVM has been regarded as the "holy grail" for scaling Ethereum, not only because it can solve performance bottlenecks but also because it redefines the trust mechanism of blockchain. Its core idea is to enable the Ethereum mainnet to generate and verify ZK proofs.
In other words, in the future, after each Ethereum block is executed, it can output a verifiable mathematical proof, allowing other nodes (especially light nodes and L2s) to confirm the correctness of the result without repeating the calculation—if the ability to generate ZK proofs is directly written into the Ethereum protocol layer (L1), the proposer packs a block and generates a ZK proof, and validating nodes no longer need to rerun the transactions; they only need to verify this tiny mathematical proof.
What does this mean for interoperability?
In the context of Interop, the significance of L1 zkEVM far exceeds scaling itself. It can be said to be the "trust anchor" for all L2s. After all, if Ethereum L1 can generate proofs in real time, it means all L2s can read L1's final state in real time and trustlessly. This will bring about two qualitative changes:
- Eliminate the Challenge Period: The confirmation time between chains will be compressed from "7 days (OP mechanism)" to "seconds (ZK mechanism)";
- Decentralized Interconnection: Cross-chain will no longer require trust in third-party multi-signature bridges but will trust the mathematical truth of the Ethereum mainnet;
This is also the physical foundation we mentioned in the previous article for EIL (Interoperability Layer) to truly work—without real-time finality from L1, interoperability between L2s will never escape the shadow of "delay."
The goal is set (L1 zkEVM), and the physical limitation is removed (EIP-7825). So what about the specific implementation tools?
This leads to the subtle evolution happening in the ZK technology stack: from zkEVM to zkVM.
III. Fusaka & EIP-7825: The Interoperability Roadmap is Liberated
If EIP-7825 provides a "parallelizable hardware environment" for ZK by limiting single transaction size, then the evolution of the ZK technology stack is to find a "more efficient software architecture." This might sound like a tongue twister, but the difference is significant and represents two stages of ZK development.
The first stage is naturally zkEVM, which can be seen as the compatibility faction or the reformist faction.
The logic is to strive to imitate every instruction of the Ethereum EVM, allowing developers to deploy Solidity code directly, reducing migration costs and barriers.
In other words, the biggest advantage of zkEVM is its compatibility with existing Ethereum applications, greatly reducing the workload for Ethereum ecosystem developers. They can reuse most of the existing infrastructure and tools (including execution clients, block explorers, debugging tools, etc.).
However, precisely because of this, since the EVM was not designed with ZK-friendliness in mind, for the sake of compatibility, zkEVM's proof efficiency often has a ceiling, and proof times are much slower, burdened by historical baggage.
zkVM, on the other hand, belongs to the radical revolutionary faction, directly building a virtual machine that is extremely friendly to ZK proofs (such as based on RISC-V or WASM) to speed up proof time and achieve better execution speed and performance.
But it also loses compatibility with many EVM features and the ability to use existing tools (like low-level debuggers). However, a clear trend is that more and more L2 projects are shedding their baggage,极致 optimizing proof speed and cost, and exploring architectures based on zkVM.
So why is the Fusaka upgrade the unlocker?
After all, before EIP-7825, whether zkEVM or zkVM, once they encountered a Mega-Transaction on Ethereum, the proof generation time would skyrocket due to the inability to split the task.
Now, EIP-7825 forcibly breaks down transactions into predictable small units. With a parallelizable environment, an efficient architecture like zkVM can exert its maximum power. Even complex Ethereum blocks, when placed in a zkVM and combined with parallel computing power, can achieve real-time proof.
What does this mean for interoperability? The proliferation of zkVM combined with EIP-7825 means the cost of generating proofs will drop significantly. When the cost of generating a cross-chain proof is low enough to be negligible, and the speed is as fast as sending an email, traditional "cross-chain bridges" will completely disappear, replaced by underlying universal message protocols.
In Conclusion
As repeatedly mentioned in previous articles of the Interop series, the ultimate goal of Interop is not just asset "cross-chain," nor is it limited to the concept of "asset bridges" anymore. It is a comprehensive set of system-level capabilities, including cross-chain data communication, cross-chain logic execution, cross-chain user experience, cross-chain security, and consensus.
From this perspective, Interop can be understood as the universal language between future Ethereum ecosystem protocols. Its significance lies not only in transferring value but also in sharing logic. ZK's role in this is to guarantee execution correctness and support real-time state verification, making cross-domain calls "dare to do, able to do." It can even be said that without real-time ZK, there can hardly be truly usable Interop UX.
So when EIP-7825 was quietly activated in the Fusaka upgrade, and as L1 zkEVM gradually becomes a reality, we are getting closer to that ultimate goal: execution, settlement, and proof are completely abstracted in the background, and users are completely unaware of the chain's existence throughout the process.
This is the Interop endgame we all look forward to in the future.
