Ethereum Foundation Launches zkAPI Mainnet Implementation for AI Payments

The Ethereum Foundation announced that zkAPI is now live on the Ethereum mainnet. The system, which was coauthored by Vitalik Buterin and Davide Crapis, provides a framework for private AI-payment billing. It introduces a mechanism for users to withdraw unspent funds even if a billing server becomes unresponsive.

The implementation, developed by Open Anonymity in collaboration with the Ethereum Foundation, allows for two primary withdrawal methods. A mutual close requires server clearance, while an escape withdrawal allows a user to initiate a payout independently. The escape route involves a 24-hour challenge period, during which the system can verify if the state used for the withdrawal has already authorized service.

If a valid challenge is submitted before the deadline, the pending payout is canceled and the note is restored to the active set. This process is designed to prevent users from withdrawing funds from a state that has already been used to authorize an API request. The system does not resolve disputed bills, meaning that if a user attempts to exit using a state that has already authorized usage, the provider's accounting remains a factor in the recovery process.

The vault includes a pause function that can block new exits, though it does not affect pending finalizations, challenges, or expiry claims. Additionally, notes have a 30-day lifetime, after which they become eligible for a treasury claim. Once a note expires, the full deposit is sent to the treasury rather than being returned to the user.

The system uses ETH for deposits, with balances accounted for in whole gwei. While dollar-denominated inference is charged based on a pinned Chainlink ETH/USD price quote, the underlying balance remains in ETH, meaning the dollar value of the user's remaining funds fluctuates with the price of ETH.

The current mainnet configuration is labeled as experimental and has not undergone a production audit. The setup relies on Groth16 circuit artifacts generated by a single party, rather than a multiparty ceremony. Users remain dependent on their own wallet data, compatible proof software, and the availability of the vault to successfully execute an exit.