Why does Optimistic Rollup need to introduce ZK proofs? The technical approach and strategic logic of Base

For a Layer 2 network holding billions of dollars in assets, the speed of final transaction confirmation not only impacts user experience but also directly determines the efficiency of capital flow. Currently, Base has a locked staking value of approximately $4.64B, with 24-hour DEX trading volume reaching $862 million, making it one of the most active Layer 2 networks in the Ethereum ecosystem. In its initial optimistic rollup design, a withdrawal transaction from Base back to the Ethereum mainnet required a challenge period of up to 7 days—during which anyone could dispute the validity of the transaction. While this mechanism ensures security through game-theoretic assumptions, it also means funds are locked for a maximum of one week before they can be freely moved. To achieve predictable and rapid final confirmation, the network must fundamentally change its validation approach. Zero-knowledge proofs offer a viable path: replacing time windows with cryptographic proofs, shifting trust from “waiting for disputes” to “mathematical verification,” thereby significantly shortening the waiting time for funds.

How does a multi-proof system reshape the final confirmation mechanism of Layer 2?

The core of Azul’s upgrade is not simply replacing optimistic proofs with ZK proofs, but building a multi-proof system. The new system runs two verification channels simultaneously: zero-knowledge proofs generated by SP1, and TEE proofs generated by trusted execution environments. Both mechanisms can independently confirm transaction proposals, and when their results agree, withdrawal settlement time can be drastically reduced to 1 day. This design directly addresses the long-standing conflict between efficiency and security in optimistic rollups—long challenge periods reduce capital efficiency, while shorter periods concentrate attack windows. The multi-proof system provides redundant security through dual verification: errors or attacks in one mechanism are difficult to breach through the other. Additionally, when the two proofs conflict, an unpermissioned ZK proof can override the permitted TEE proof, providing on-chain fault detection and handling capabilities—an important step toward Stage 2 decentralization as defined by L2Beat.

Architectural independence beyond the OP stack: strategic value of a unified codebase

In February this year, Base announced a shift from the Optimism OP stack to its own unified codebase. This is not just a simple technical tool replacement. Under the OP Stack framework, Base’s node software versions, upgrade cadence, and data packaging are constrained by external dependencies. Independence means the Base engineering team gains full control over technical decisions—from the frequency of hard forks to consensus layer optimizations—all can be internally coordinated. The benefits of a unified codebase are already evident in the Azul upgrade: the number of empty blocks dropped from about 200 daily to around 2—a nearly 99% reduction; during testing, the network handled bursts of up to 5,000 TPS. More importantly, this architecture allows Base to prioritize integrating ZK proofs on its own timeline, without waiting for the OP ecosystem’s unified roadmap. This concentration of control and the multi-proof security model are not contradictory—centralized management of underlying infrastructure provides reliable engineering support for the multi-proof system’s goals.

How does a leading TVL Layer 2 make validation mechanism decisions?

Based on staked value, Base is currently the largest Ethereum Layer 2 network, with approximately 46.36% market share. For networks of similar size, adjusting the verification mechanism is not just a technical upgrade but a cautious migration involving hundreds of protocols and tens of millions of user assets. This upgrade adopts a hybrid approach—retaining the basic optimistic rollup framework while adding a ZK proof channel, allowing both systems to coexist long-term. This pragmatic evolution strategy avoids rushing to dismantle existing infrastructure, instead gradually shifting the system through layered security enhancements. As the largest security-scale zkVM, SP1 has generated millions of proofs for over 35 clients, covering assets worth about $4 billion. Base’s choice of SP1, which has extensive security validation experience, to prove its approximately $7.4 billion in deposits, reflects a robust upgrade path based on proven infrastructure.

Performance and security: how does SP1’s zero-knowledge VM achieve real-time proofs?

From a technical perspective, whether ZK proofs can truly integrate into daily Layer 2 operations depends on the efficiency and cost of proof generation. SP1 Hypercube has already demonstrated the ability to generate zero-knowledge proofs for 99.7% of Ethereum mainnet blocks within 12 seconds in testing environments. This performance provides a mathematical foundation for real-time validation of Layer 2 blocks. Compared to traditional ZK solutions that require custom circuit design and hours-long proof generation, SP1 allows developers to write programs in standard Rust, compile to RISC-V, and directly generate ZK proofs—greatly lowering the adoption barrier for ZK technology. More importantly, all 62 core RISC-V opcodes of SP1 have been formally verified by Nethermind Security and the Ethereum Foundation, providing a mathematically verifiable basis for its security. For a network managing over $4 billion in assets, the proof scheme’s security must meet the highest standards of auditing, and SP1 offers industry-leading assurance in this regard.

Strategic outlook: does Azul mean Base will fully transition to ZK Rollup?

The current multi-proof system is not the end goal. Azul is explicitly defined as an intermediate step toward fully ZK proofs, with the long-term aim of near-instant final withdrawal confirmation. The roadmap includes key milestones: further integrating more ZKVM solutions to increase proof diversity, continuously optimizing real-time proof performance, and gradually reducing final confirmation times as technological trustworthiness improves. It’s important to note that the architecture of coexistence between TEE and ZK proofs during the multi-proof phase is itself a progressive security strategy—attackers would need to compromise both independent security systems simultaneously to disrupt fast withdrawal channels. This security model not only provides redundancy for the current upgrade but also accumulates engineering experience and real-time data for a future complete transition to ZK verification.

From ecosystem debates to technical implementation: a verifiable architectural evolution

Base’s decision to introduce zero-knowledge proofs is not isolated but builds on its previous architectural independence from the OP stack. Market discussions initially focused on economic interests—Base, as the largest contributor of nearly 96.5% of Gas fees within the OP ecosystem, was seen as potentially impacting Optimism’s revenue model. However, from Azul’s technical path, the value of independence lies not only in economic autonomy but also in the ability to control the tech stack and dynamically incorporate deep infrastructure-dependent upgrades like ZK proofs. As security and compatibility needs grow, a unified codebase empowers the engineering team to directly integrate at the protocol level rather than waiting for third-party dependency synchronization. This is a trade-off—centralizing infrastructure control to enable rapid deployment of complex security features—and Azul’s upgrade is a practical validation of this approach.

Potential trade-offs and long-term challenges of a hybrid verification system

Any security architecture adjustment introduces new risks. Unlike most ZK rollups, Base’s current TEE proofs rely on hardware trusted execution environments, which depend on hardware manufacturers’ trust assumptions. Although the design specifies that ZK proofs have final authority when conflicting with TEE proofs, the security of the TEE channel still depends on the trustworthiness of the hardware supply chain. Additionally, generating ZK proofs requires significantly more computational resources than optimistic challenge mechanisms; whether the proof generation costs can be maintained within acceptable limits depends on continuous optimization of SP1 in real-world deployment. Azul’s upgrade also involves a large-scale overhaul of the core client stack, moving away from supporting multiple consensus and execution clients to a unified base-reth-node and base-consensus client. While this simplifies node operation and coordination, it also introduces single-client centralization risks. Balancing operational simplicity with multi-client coordination remains an ongoing challenge as the system moves toward Stage 2 decentralization.

Summary

Through the Azul upgrade and collaboration with Succinct, Base introduces a multi-proof architecture that retains the optimistic rollup framework while adding a ZK proof channel, reducing transaction finality from 7 days to 1 day. This hybrid model centralizes infrastructure control to enable rapid deployment of complex security features, while laying an engineering-verified bridge toward full ZK rollup transition. The unified codebase independent of the OP stack, formally verified SP1 zkVM, and redundant multi-proof design together form a practical path to optimize Layer 2 architecture across efficiency, security, and scalability.

FAQs

When will the Base Azul upgrade be deployed?

The Base Azul upgrade went live on the testnet on April 22, 2026, with the mainnet activation targeted for May 13, 2026. The collaboration with Succinct will be fully integrated as part of the Azul mainnet launch.

How is the 1-day final confirmation achieved?

When the zero-knowledge proof generated by SP1 and the trusted execution environment proof from TEE support the same transaction proposal, Base can settle withdrawals to the Ethereum mainnet within 1 day. If the two proofs conflict, an unpermissioned ZK proof overrides the TEE proof, ensuring system security and finality.

Has Base fully transitioned to ZK Rollup?

Not yet. The current Azul upgrade employs a hybrid multi-proof system—TEE proofs and ZK proofs run in parallel. This is an intermediate step toward full ZK proof transition, with the long-term goal of near-instant final withdrawal confirmation once the technology matures.

What is SP1?

SP1 (Succinct Processor 1) is an open-source zero-knowledge virtual machine developed by Succinct Labs. It allows developers to write programs in standard Rust and generate verifiable ZK proofs without custom circuit development. As of May 2026, over 35 clients have used SP1 to generate millions of proofs, covering assets worth approximately $4 billion.

How much assets are involved in this upgrade?

SP1 will be used to prove approximately $7.4 billion in deposits on Base. The current total locked value of the Base network is about $4.64B.

What other performance optimizations are included in the Azul upgrade?

Besides the proof system updates, Azul also unifies Base’s execution client into base-reth-node, adds a new base-consensus client, reduces empty blocks from about 200 daily to around 2, and has handled bursts of up to 5,000 TPS during testing.