x402 Data Utilities (wallet-signed, no chain)

End-to-end data utility service (FastAPI backend + Next.js frontend) gated by a local x402-style invoice/signature flow. No blockchain calls or real payments.

Endpoints & Prices

• POST /validate/csv ($0.01)
• POST /clean/dataframe ($0.05)
• POST /extract/pdf ($0.05) — now text-only (tables removed)
• POST /summarize/logs ($0.02)

Wallet Flow (local-only)

• First call to a protected route returns HTTP 402 with an invoice.
• Canonical message: x402-local-wallet|invoice_id=<id>|path=<path>|price=<price>|pay_to=<pay_to>|nonce=<nonce>|expires_at=<expires_at>
• Client signs with a local EVM wallet (eth_account) and retries with X-X402-Proof (base64 JSON: {invoice, payer, signature}).
• Success returns 200 + headers X-X402-Receipt, X-X402-Payer (plus price/path/pay_to).

Env Vars

• PAY_TO_ADDRESS (required)
• INVOICE_TTL_SECONDS (optional, default 300)
• REDIS_URL (optional; if absent, in-memory store is used)
• NEXT_PUBLIC_API_BASE (frontend) — API base URL (e.g., http://localhost:8000 or your Render URL)

Backend (FastAPI, in backend/)

python -m venv .venv
source .venv/bin/activate  # Windows: .venv\Scripts\activate
pip install -r backend/requirements.txt
export PAY_TO_ADDRESS=0x1111111111111111111111111111111111111111
uvicorn backend.main:app --reload
# Docs: http://127.0.0.1:8000/docs

Render deploy: use Procfile (web: uvicorn backend.main:app --host 0.0.0.0 --port ${PORT}) and set PAY_TO_ADDRESS (and REDIS_URL if desired).

Frontend (Next.js in website/)

cd website
npm install
export NEXT_PUBLIC_API_BASE=http://127.0.0.1:8000  # or your Render backend URL
npm run dev

Vercel deploy: set project root to website/, build npm run build, and set NEXT_PUBLIC_API_BASE to your backend URL. Base path/asset prefix are /x402 for path-based hosting.

Live Preview

Current frontend + wallet-signed flow is hosted at https://www.devank.cv/x402 (path-based, mock local wallet signing).

Demo Script (terminal)

python backend/demo_wallet_client.py

Shows 402 invoice -> signed proof -> 200 receipt -> replay rejected.

Testing

pytest

(Requires PAY_TO_ADDRESS set; tests use in-memory store.)

Invoice Example (402 response body)

{
  "invoice_id": "<uuid>",
  "path": "/summarize/logs",
  "price": "0.03",
  "pay_to": "<pay_to_address>",
  "nonce": "<random>",
  "issued_at": "<iso>",
  "expires_at": "<iso>",
  "asset": "local-usdc",
  "chain": "local",
  "domain": "x402-local-wallet"
}