Aztec v5 Alpha Goes Live: Client-Side ZK Brings Privacy-Native Smart Contracts Closer on Ethereum

Aztec Labs has released an alpha version of Aztec v5 on Ethereum mainnet, positioning it as an execution layer where applications can combine confidential and public state within the same Layer 2 environment. At the center of v5 is a client-side zero-knowledge execution engine built with Noir, Aztec's domain-specific language for private smart contracts. Rather than distributing confidential transaction execution across validators, private computation runs on users' devices. The client generates the transaction, produces recursive SNARK proofs locally, and submits only those proofs for onchain verification. Inputs, amounts, and identities stay hidden while Ethereum's security model is retained. Aztec v5 also introduces a hybrid state design aimed at reducing a common bottleneck in privacy-focused chains: contention over shared public state. Private data is maintained in UTXO-like note trees, while public state is stored in key-value trees. Private functions can queue deferred public calls that are executed later in the same transaction lifecycle, allowing confidential and public actions to interoperate deterministically and avoiding race conditions. For developers, the model opens a path to dApps that blend confidential user data with Ethereum's public DeFi rails. Potential use cases include confidential order matching, private liquidity provisioning, and selective-compliance applications that reveal only what is necessary through viewing keys. By keeping transaction details hidden until state is committed, the design also reduces the visibility adversaries rely on for frontrunning and many MEV tactics. Aztec has framed programmable privacy as broader than private transfers, emphasizing verifiable, fine-grained disclosure workflows with privacy as the default. In an April 2025 interview, CEO Zac Williamson said onchain privacy requires three pillars—user privacy, confidential transaction data, and private smart contract execution—and argued privacy will become a standard feature across crypto. In May 2026, Aztec acquired ZKPassport and said it would remain open source. The ZKPassport tooling adds zero-knowledge identity capabilities to Aztec's stack, supporting selective disclosure such as proving age or nationality without exposing raw identity data. Aztec said the tooling has already been used to reduce Sybil attacks and to run sanctions screening during an AZTEC token sale. Aztec expects applications to begin rolling out over the coming week, starting with Nyx, which will launch invite-only and then briefly open to all users for a 24-hour window. The team is also pitching the release as delivering the "fastest private transactions" it has shipped to date. The v5 alpha launch follows Aztec's disclosure of two recent incidents involving deprecated legacy contracts. Earlier this month, Aztec reported that about $2 million was moved from an immutable payments contract deployed in 2021 and discontinued in 2022; the team said it had no admin keys to pause or upgrade the contract. Separately, an older RollupProcessorV3 contract linked to Aztec Connect lost around $2.1 million. Aztec Labs and the Aztec Foundation said both incidents involved sunset products that remained live on Ethereum and are not related to the active Aztec network or the AZTEC ERC20 token. Aztec v5's alpha release puts a more practical developer path in place for privacy-native smart contracts on Ethereum, combining local ZK execution, recursive SNARK verification, and a hybrid private/public state model designed to preserve composability with public DeFi. If the system proves resilient in alpha, it could influence how privacy and compliance are implemented across onchain applications.