zkAPI Keeps Escape Withdrawals Pending During Default 24-Hour Challenge

An escape withdrawal from zkAPI remains pending during a default 24-hour challenge period, while active notes that expire before closure can be claimed for the treasury, setting a deadline for users seeking to recover deposits from the Ethereum-based payment system.

zkAPI went live on Ethereum mainnet on Oct. 1, 2026. Open Anonymity developed the system with the Ethereum Foundation for metered API services, including AI applications.

Users deposit funds into an Ethereum vault and authorize metered API use with proofs. The payment server checks whether spending is covered without linking a request to a deposit.

In the escape process, the vault removes a note from its active set and records a pending withdrawal. A challenger can cancel it by proving that the same spending state had already authorized usage, returning the note to the active set.

Separately, an active note that expires without being closed can be claimed for the treasury. The claim covers the full deposit recorded in that note. Users can also close deposits cooperatively with server clearance.

The design was published by Davide Crapis and Vitalik Buterin. The implementation is experimental, and its Groth16 setup is single-party.