Ethereum Foundation and Open Anonymity launch zkAPI on Ethereum mainnet for unlinkable AI API payments
The Ethereum Foundation and the Open Anonymity Project launched zkAPI on Ethereum mainnet, letting users prepay in ETH or USDC and spend it on AI APIs with zero-knowledge proofs that hide the payer from the payment server.
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Why it matters
zkAPI puts a zero-knowledge payment layer in front of metered web services, which is the pattern every AI billing relationship runs on today. No token was launched and no fund moved, so the near-term effect is on infrastructure and privacy design rather than on trading: the project's own repository calls it experimental, and the provider still receives the prompt in the clear, so the anonymity covers billing identity, not the content or the user's IP address.
Where the sources disagree
Launch date
announced October 1, 2026
Decrypt, Bitcoin.com News, Crypto News (CryptoNews.net)
foundation promoted it October 2, 2026
CryptoPotato
The foundation announced the launch on October 1 according to Decrypt, Bitcoin.com News and the Ethereum Foundation tweet quoted by Crypto News, while CryptoPotato dates the foundation's promotion of zkAPI to October 2.
Key facts
The Ethereum Foundation and the Open Anonymity Project launched zkAPI on Ethereum mainnet.
Reported by The Block
The design was published in February by Ethereum Foundation dAI lead Davide Crapis and Ethereum co-founder Vitalik Buterin, and Open Anonymity built the client, server and smart contracts.
Reported by The Block
Users make one deposit into a vault contract and the balance becomes a private note on their device, from which zero-knowledge proofs authorize spending without identifying the payer.
Reported by Crypto News Flash
The live system runs under the ZkApiVault contract and uses the Groth16 proof system over the BN254 curve with Poseidon hashes and 32-level Merkle trees.
Reported by Crypto News (CryptoNews.net)
A zkAPI server verifies the proof and issues a temporary API key with a dollar cap, and the private balance is charged for actual usage once the key expires.
Reported by Unchained
The project's repository labels the protocol experimental, and its documentation points to OpenRouter as the AI provider behind the keys.
Reported by Decrypt
OA Chat, a browser-based private chatbot, launched alongside zkAPI and needs no installation.
Reported by Bankless
The AI provider still receives the prompt and users can be identified through IP data, so the system separates payment from identity without hiding network activity or prompt content.
Reported by Bitcoin.com News
What happened
The Ethereum Foundation and the Open Anonymity Project launched zkAPI on Ethereum mainnet, a system that lets users prepay for AI models and other metered APIs without the payment server or the API provider tying requests back to the person who paid. The foundation said in a blog post published on October 1 that zkAPI implements a design Ethereum researcher Davide Crapis and co-founder Vitalik Buterin posted on Ethereum Research in February, and Unchained and Bankless described it as the first working build of that proposal, with Open Anonymity writing the client, server and smart contracts. The mechanism is the same across every account: a user makes one deposit into a vault contract, the balance becomes a private note held on the user's device, and local software generates a zero-knowledge proof that a funded, unspent note covers the cost without revealing which note it is, after which a server issues a temporary API key with a dollar cap and charges the private balance once the key expires. Crypto News Flash specified that the live vault is the ZkApiVault contract and that it uses the Groth16 proof system over the BN254 curve, Poseidon hashes and 32-level Merkle trees; Crypto News Flash and Bankless both describe deposits in ETH and USDC, and Crypto News Flash says prepaid credits are converted into private notes. Decrypt reported that the repository labels the protocol 'experimental' and that its documentation points to OpenRouter as the AI provider behind the keys, and Unchained reported the same 'experimental' label from the code repository. Alongside the launch the foundation and Open Anonymity released OA Chat, a browser-based private chatbot, and Bankless said the local client speaks the standard OpenAI and Ollama interfaces so existing apps can point at it; Bankless also said a user's balance stays withdrawable from the vault onchain if zkAPI's servers go dark. The limits are stated plainly: Bitcoin.com News noted that the AI provider still sees the prompt and that IP data can leak identity, and CryptoPotato said the protocol separates payment records from prompts but does not hide all network activity or the content users submit.
How the story developed
- Official statement
Open Anonymity Project announces its collaboration with the Ethereum Foundation
A post introducing Open Anonymity's public AI chat services, OA-chat.
- Official statement
Ethereum Foundation announces zkAPI on Ethereum mainnet
The foundation's blog post 'Introducing zkAPI: private usage credits for any API' sets out the vault, private note and zero-knowledge spending flow.
- Update
Open Anonymity ships the client, server and smart contracts
OA built the implementation now running on mainnet, and the foundation separately promoted zkAPI on October 2.
- First report
First report by The Block
Ethereum Foundation launches zkAPI to let users pay for AI models without revealing identity
- Update
Buterin and Crapis publish the zkAPI design on Ethereum Research
The February proposal that zkAPI implements.
- Independent corroboration
Independently corroborated by Crypto News Flash
Ethereum zkAPI Brings Unlinkable AI Payments to Mainnet
- Official statement
Official statement from Bitcoin.com News
Ethereum’s zkAPI Gives AI Payments a Privacy Cloak With a Catch
- Update
Coverage notes the protocol's own 'experimental' label and its limits
Decrypt and Unchained cite the repository's experimental label, while Bitcoin.com News and CryptoPotato report that prompts reach the AI provider in the clear and IP data can leak identity.
How coverage built up
Independent sources over time, counted the way the consensus panel counts them: a republication of a wire story does not move the line.
- 2 Oct 2026, 00:22 UTC: The Block — 1 independent source, 1 reports
- 2 Oct 2026, 01:37 UTC: Crypto News (CryptoNews.net) — 2 independent sources, 2 reports
- 2 Oct 2026, 06:45 UTC: Crypto News Flash — 3 independent sources, 4 reports
- 2 Oct 2026, 09:40 UTC: Unchained — 4 independent sources, 5 reports
- 2 Oct 2026, 17:08 UTC: Bankless — 5 independent sources, 6 reports
- 2 Oct 2026, 20:16 UTC: Decrypt — 6 independent sources, 7 reports
- 2 Oct 2026, 20:16 UTC: CryptoPotato — 7 independent sources, 8 reports
- 5 Oct 2026, 03:20 UTC: Bitcoin.com News, official — 8 independent sources, 9 reports
Affected entities
Also mentioned: Coinbase, Bitcoin, Base
Original sources
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