x402 pay per request

HTTP/1.1 402 Payment Required
Content-Type: application/json
PAYMENT-REQUIRED: eyJ4NDAyVmVyc2lvbiI6Mi... (base64 JSON, x402 v2)
Link: <https://inference.dagon.so/terms>; rel="terms-of-service"

{
  "x402Version": 1,
  "accepts": [{
    "scheme": "exact",
    "network": "solana",
    "maxAmountRequired": "500000",
    "resource": "https://inference.dagon.so/v1/chat/completions",
    "mimeType": "application/json",
    "payTo": "9rMdbu4KdLWH2nPXbzhm9HTKaibGZ2ckakQbW1wPh6KK",
    "maxTimeoutSeconds": 60,
    "asset": "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v",
    "extra": { "feePayer": "4UZVmNWoetLmDeQnfFFCYrFuN7epN6WgchiDxJ6VVA52" }
  }],
  "error": { "message": "...", "type": "billing_error", "param": null, "code": "payment_required" }
}

// npm install @x402/fetch @x402/svm @solana/kit
import { readFileSync } from "node:fs";
import { wrapFetchWithPaymentFromConfig } from "@x402/fetch";
import { ExactSvmScheme, toClientSvmSigner } from "@x402/svm";
import { createKeyPairSignerFromBytes } from "@solana/kit";

// A solana-keygen JSON keypair for a wallet holding USDC (no SOL needed).
const secret = Uint8Array.from(JSON.parse(readFileSync(process.env.SOLANA_KEYPAIR ?? "", "utf8")));
const signer = toClientSvmSigner(await createKeyPairSignerFromBytes(secret));
const pay = wrapFetchWithPaymentFromConfig(fetch, {
  schemes: [{ network: "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp", client: new ExactSvmScheme(signer) }],
});

const res = await pay("https://inference.dagon.so/v1/chat/completions", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({ model: "abliterated-model-large-flash", messages: [{ role: "user", content: "Hi" }], max_tokens: 200 }),
});
console.log(await res.json());
// Keep this key: it holds what the request did not spend.
const key = res.headers.get("x-dagon-key");

# pip install "x402[httpx,svm]"
import asyncio, os
from x402 import x402Client
from x402.http.clients import x402HttpxClient
from x402.mechanisms.svm import KeypairSigner
from x402.mechanisms.svm.exact.register import register_exact_svm_client


async def main():
    # Refuse any single payment above $1; raise it for large requests.
    client = x402Client().set_spend_controls({"max_amount_per_payment": "$1"})
    register_exact_svm_client(client, KeypairSigner.from_base58(os.environ["SOLANA_PRIVATE_KEY"]))
    async with x402HttpxClient(client, timeout=120) as http:
        r = await http.post("https://inference.dagon.so/v1/chat/completions", json={
            "model": "abliterated-model-large-flash",
            "messages": [{"role": "user", "content": "Hi"}],
            "max_tokens": 200,
        })
        await r.aread()
        print(r.status_code, r.json())
        print("x-dagon-key:", r.headers.get("x-dagon-key"))

asyncio.run(main())