@4o2/sdk

x402 helper for paid endpoints — drop in front of your existing handler, or mount as a standalone /warmup route.

→ 4o2.dev — get an API key, manage your listing, see live activity.

Install

pnpm add @4o2/sdk

Quick start

Wrap any existing paid handler. Unsigned traffic falls through to your handler unchanged; signed warming traffic gets the SDK's challenge.

// app/api/predict/route.ts
import { wrap } from "@4o2/sdk/next";

async function realPOST(req: Request) {
  // your existing paid handler
}

export const POST = wrap(realPOST);

Or mount as a standalone route:

// app/api/warmup/route.ts
export { POST } from "@4o2/sdk/next";

Other runtimes

// Hono
import { wrap } from "@4o2/sdk/hono";
app.post("/predict", wrap(async (c) => { /* ... */ }));

// Express
import { wrap } from "@4o2/sdk/express";
app.post("/predict", wrap(async (req, res) => { /* ... */ }));

// Bun / Cloudflare Workers / any fetch runtime
import { wrap } from "@4o2/sdk/fetch";
const handler = wrap(async (req) => { /* ... */ });

Configuration

Set one env var:

FOUR_O_TWO_API_KEY=4o2_<slug>_<secret>

Get the key from your dashboard at 4o2.dev. The SDK fetches the rest of its config (splitter address, network, asset) at first request and caches it.

Verify

curl -X POST https://your-domain.com/api/predict

Expected: HTTP/1.1 402 Payment Required with an x402 v2 challenge body. That confirms the wrap is wired correctly.

License

MIT.