Author: imToken

In previous articles of the Interop series, we explored 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 (allowing funds to run in a standardized manner).

However, to achieve a perfect "single-chain experience," we still face 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," we need a foundational capability across the Ethereum interoperability roadmap: "Acceleration" and finality brought by ZK technology's "real-time proof" (see further reading "Ethereum Interop Roadmap: How to Unlock the 'Last Mile' of Large-Scale Adoption").

In the recently activated Fusaka upgrade, the unassuming EIP-7825 has cleared the biggest engineering obstacle for achieving L1 zkEVM and real-time proof on Ethereum.

1. The Underestimated EIP-7825 Behind the Fusaka Upgrade

On December 4, the Ethereum Fusaka upgrade was officially activated on the mainnet, but it did not have the same grandiosity as the Dencun upgrade from years past. The market's spotlight was mostly on Blob expansion and PeerDAS, with much discussion about the further reduction of L2 data costs.

However, beyond this commotion, there is an unassuming proposal, EIP-7825, which has cleared the largest obstacle for Ethereum to achieve L1 zkEVM and real-time proof, and can even be said to be quietly paving the way for the endgame of Interop.

In this Fusaka upgrade, the focus of attention was almost entirely on scalability: Blob capacity was expanded by 8 times, and with PeerDAS's random sampling verification, the cost narrative of the DA (Data Availability) track has become a thing of the past.

Indeed, cheaper L2 is 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 (approximately 16.78 million gas).

As is well known, this year, the gas limit for Ethereum blocks has been raised to 60 million, but even with the limit continually increasing, theoretically, if someone is willing to pay an extremely high gas price, they can still send a super complex "Mega-Transaction" that fills the entire block's 60 million gas capacity, thereby clogging the entire block.

This was previously allowed, but EIP-7825 introduced a new restriction: regardless of the block size, the gas consumption of a single transaction cannot exceed 16.78 million gas.

So why limit the size of a single transaction? In fact, this change has no impact on ordinary users' transfers, but for ZK Provers (proof generators), it makes a life-and-death difference, which is 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 sequentially process this extremely complex transaction, unable to split or parallelize it. This is like a single-lane highway where a very slow giant truck in front causes all the smaller cars (other transactions) behind to be stuck waiting for it to finish.

This undoubtedly sentenced "real-time proof" to death—because the time to generate the proof would be completely uncontrollable, potentially taking dozens of minutes or even longer.

However, after EIP-7825, even if future block capacity expands to 100 million gas, 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 transformed from a tricky "logical problem" into a pure "computational power problem (Money Problem)":

As long as we can invest enough parallel computing power, we can process these split small tasks simultaneously in a very short time, thus generating ZK proofs for large blocks.

As Brevis co-founder and CEO Michael stated, EIP-7825 is the most underestimated upgrade on the path to future ZK and 100x scalability for Ethereum. It transforms "real-time proof" from "theoretically impossible" to "engineerably schedulable." As long as we can solve the computational power problem through parallel computing, even a 200 million gas block could achieve second-level proof, which is not only a breakthrough for ZK technology but also the physical foundation for the Ethereum Interoperability Layer (EIL) to achieve second-level cross-chain settlement.

So while this upgrade may not seem like the main event, it is actually a significant breakthrough for the ZK roadmap and the future of Ethereum's scalability in 2026.

2. L1 zkEVM: The "Trust Anchor" of Ethereum Interoperability

However, while EIP-7825 has paved the physical road for real-time proof (parallelizable) by limiting the size of a single transaction, this is only one side of the coin. The other side concerns how the Ethereum mainnet itself can utilize this capability.

This leads us to the most hardcore narrative in the Ethereum roadmap—L1 zkEVM.

For a long time, zkEVM has been seen 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, with the core idea being to enable the Ethereum mainnet to generate and verify ZK proofs.

In other words, in the future, after executing each block on Ethereum, it will output a verifiable mathematical proof, allowing other nodes (especially light nodes and L2) to confirm the correctness of the results without needing to recompute—if the ability to generate ZK proofs is directly written into the Ethereum protocol layer (L1), then for every block packaged by the proposer and the ZK proof generated, the validating nodes will no longer need to rerun transactions but only verify this extremely small mathematical proof.

What does this mean for interoperability?

In the context of Interop, the significance of L1 zkEVM goes far beyond scalability 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 that all L2s can read L1's final state in real-time and without trust, which will bring about two qualitative changes:

• Elimination of Challenge Period: The confirmation time between chains will be compressed from "7 days (OP mechanism)" to "seconds (ZK mechanism)";
• Decentralized Interconnection: Cross-chain interactions will no longer require trusting third-party multi-signature bridges but rather trust the mathematical truth of the Ethereum mainnet;

This is also the physical foundation for the EIL (Interoperability Layer) to truly operate—without L1's real-time finality, interoperability between L2s will forever be shadowed by "latency."

With the goal set (L1 zkEVM) and physical limitations removed (EIP-7825), what about the specific implementation tools?

This leads us to the subtle evolution occurring in the ZK technology stack: from zkEVM to zkVM.

3. Fusaka & EIP-7825: The Liberation of the Interoperability Roadmap

If EIP-7825 provides a "parallelizable hardware environment" for ZK by limiting the size of a single transaction, then the evolution of the ZK technology stack is aimed at finding a "more efficient software architecture." While this may sound like a tongue twister, the distinction is significant and represents two stages of ZK development.

The first stage is naturally zkEVM, which can be seen as the compatible or reformist faction.

The logic is to closely mimic every instruction of the Ethereum EVM, allowing developers to deploy Solidity code directly and reduce migration costs and barriers.

In other words, the greatest advantage of zkEVM is its compatibility with existing Ethereum applications, significantly reducing the workload for Ethereum ecosystem developers, who can reuse most of the existing infrastructure and tools (including execution clients, block explorers, debugging tools, etc.).

However, because the EVM was not originally designed with ZK friendliness in mind, to maintain compatibility, zkEVM's proof efficiency often has a ceiling, and proof times can be much slower, carrying a heavy historical burden.

On the other hand, zkVM 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 accelerate proof times and achieve better execution speed and performance.

However, it also loses compatibility with many EVM features and the ability to use existing tools (such as low-level debuggers). Nevertheless, a clear trend is that more and more L2 projects are beginning to shed their burdens, optimizing proof speed and cost to explore architectures based on zkVM.

So why is the Fusaka upgrade a liberator?

After all, before EIP-7825, whether zkEVM or zkVM, once faced with a giant transaction on Ethereum, they would experience a dramatic increase in proof generation time due to the inability to split tasks.

Now, EIP-7825 forces transactions to be broken down into predictable small units, and with a parallel environment, the efficient architecture of zkVM can unleash its maximum power. Even with complex Ethereum blocks, when placed into zkVM and combined with parallel computing, real-time proof can be achieved.

What does this mean for interoperability? The proliferation of zkVM combined with EIP-7825 means that the cost of generating proofs will significantly decrease. When the cost of generating a cross-chain proof becomes negligible and the speed is as fast as sending an email, traditional "cross-chain bridges" will completely disappear, replaced by a universal messaging protocol at the underlying layer.

Final Thoughts

As repeatedly mentioned in previous articles of the Interop series, the ultimate goal of Interop is not just asset "cross-chain" but has long transcended the concept of "asset bridges." It encompasses a complete 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 among future Ethereum ecosystem protocols. Its significance lies not only in transmitting value but also in sharing logic, with ZK playing a role in ensuring execution correctness, supporting real-time state verification, and making cross-domain calls "daring and doable." It can even be said that without real-time ZK, it is difficult to have a truly usable Interop UX.

Therefore, as EIP-7825 quietly activates in the Fusaka upgrade and L1 zkEVM gradually becomes a reality, we are infinitely closer to that endgame: execution, settlement, and proof are completely abstracted in the background, and users are unaware of the existence of chains throughout the process.

This is also the Interop endgame that each of us looks forward to in the future.

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