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PromptPay is a pay-per-prompt AI marketplace that replaces subscriptions and API keys with a single wallet connection.

Users grant a one-time ERC-7715 spend permission, then send prompts that are paid for automatically via x402 on-chain micro-payments settling fractions of a cent per request in the background, with no transaction to sign each time.

Prompts run on Venice AI for privacy-first inference, and payments are relayed gaslessly through the 1Shot permissionless relayer on Base. The result is a frictionless, usage-based way to access AI: pay only for what you actually use, no commitments, no key management, no recurring fees.

We designed and built PromptPay end-to-end during the hackathon, going from concept to a working pay-per-prompt AI marketplace.

• Architecture & planning: Mapped the full system: wallet, ERC-7715 spend permission, x402 micro-payment , Venice AI inference, with the 1Shot relayer handling gasless settlement on Base Sepolia.

• Frontend: Built the Next.js 14 app: landing page, prompt interface, wallet connect, a permission gate for granting the one-time spend allowance, result panel, and transaction history.

• Payments; Implemented the x402 client/server flow so a protected API returns 402 Payment Required, the client auto-settles the micro-payment, and the prompt proceeds, no per-prompt signing.

• Permissions: Integrated ERC-7715 spend permissions via wagmi + MetaMask SDK so users grant a budget once.

• AI integration: Wired up the Venice AI API for privacy-first, OpenAI-compatible inference behind the paid endpoint.

• Relayer: Connected the 1Shot permissionless relayer (EIP-7710) for gasless, USDC-paid transactions.

By the end we had a functional flow: connect wallet, grant permission once, prompt and auto-pay per request.

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