zkAPI Withdrawals Pending During 24-Hour Challenge Period

An escape withdrawal from the zkAPI system remains pending during a default 24-hour challenge period, creating a deadline for users attempting to recover deposits from the Ethereum-based payment platform. The zkAPI system, developed by Open Anonymity in collaboration with the Ethereum Foundation, officially launched on the Ethereum mainnet on Oct. 1, 2026. It is designed to facilitate metered API services, including AI applications, through secure, anonymous transactions.

Users deposit funds into an Ethereum vault and authorize metered API usage with cryptographic proofs. The payment server verifies spending without linking the request to a specific deposit. In the escape process, the vault removes a note from its active set and records a pending withdrawal. A challenger can cancel this withdrawal by proving that the same spending state had already authorized usage, returning the note to the active set.

Additionally, an active note that expires without being closed can be claimed by the treasury, covering the full deposit recorded in that note. Users can also close deposits cooperatively with server clearance. The experimental design was published by Davide Crapis and Vitalik Buterin, with the implementation noted as single-party using the Groth16 setup.