github.com/vbuterin/zkapi You deposit once into a vault. After that, every AI request you send carries a zero knowledge proof that it is paid for. The server checks the proof and lets the request through, but it cannot tell which deposit it came from. Two requests from the same person look like two strangers. Your prompt goes from your browser straight to the AI provider. The zkAPI server only decides who is allowed to spend and how much, then settles the bill. When you are done, the unused part of your deposit comes back to you. Under the hood it uses Groth16 proofs, Poseidon hashes and a Merkle tree of deposits, and it ships an OpenAI compatible client, so existing apps can point at it. Built by the Open Anonymity Project with the Ethereum Foundation, from a design Vitalik and Davide Crapis published in February. We liked it enough to build the Solana version. PARANOID. paranoid.red