x402 Mesh Inference — integration in three steps
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# 1. See what each model costs. Free, no wallet, no key.
curl -s https://x402-mesh-gateway.fly.dev/v1/pricing

# 2. See the payment challenge for a request you have not paid for.
curl -si -X POST https://x402-mesh-gateway.fly.dev/v1/chat/completions \
  -H "content-type: application/json" \
  -d '{"model":"llama-3.3-70b-versatile","messages":[{"role":"user","content":"hi"}]}' \
  | grep -i payment-required

# 3. Install the client and pay it.
npm i @x402/core @x402/avm

------------------------------------------------

// pay.mjs — a complete paid request against https://x402-mesh-gateway.fly.dev
// Run: AVM_PRIVATE_KEY=<base64 64-byte Algorand secret key> node pay.mjs
//
// The paying account needs a little ALGO for its minimum balance and must be OPTED IN to the
// USDC ASA. The facilitator sponsors the transaction fee, so you only sign the asset transfer.

import { toClientAvmSigner } from "@x402/avm";
import { ExactAvmScheme } from "@x402/avm/exact/client";
import { x402Client, x402HTTPClient } from "@x402/core/client";
import { decodePaymentRequiredHeader } from "@x402/core/http";

const ENDPOINT = "https://x402-mesh-gateway.fly.dev/v1/chat/completions";
const body = {
  // Any model a healthy node advertises at https://x402-mesh-gateway.fly.dev/v1/nodes.
  model: "llama-3.3-70b-versatile",
  messages: [{ role: "user", content: "Reply with one word." }],
};

// Register the WILDCARD, not a concrete network id. A client matches the challenge's network
// verbatim, and this server advertises the facilitator's full-genesis-hash form rather than
// the truncated constant `@x402/avm` exports. Registering the constant here fails with
// "No network/scheme registered for x402 version: 2".
const signer = toClientAvmSigner(process.env.AVM_PRIVATE_KEY);
const http = new x402HTTPClient(
  new x402Client().register("algorand:*", new ExactAvmScheme(signer)),
);

const post = (headers) =>
  fetch(ENDPOINT, {
    method: "POST",
    headers: { "content-type": "application/json", ...headers },
    body: JSON.stringify(body),
  });

const unpaid = await post({});
if (unpaid.status !== 402) throw new Error(`expected 402, got ${unpaid.status}`);

// The challenge is in the HEADER. The JSON body is a human-readable preview with no
// `accepts[]` — decoding that instead yields a challenge with nothing to pay against.
const challenge = decodePaymentRequiredHeader(unpaid.headers.get("payment-required"));
console.log("price:", challenge.accepts[0].amount, "atomic USDC");

// Spread the header MAP the SDK returns. The name is part of the protocol: x402 v2 expects
// `PAYMENT-SIGNATURE`, and renaming it to `X-PAYMENT` makes the server answer 402 again.
const paid = await post(http.encodePaymentSignatureHeader(await http.createPaymentPayload(challenge)));
if (!paid.ok) throw new Error(`${paid.status}: ${await paid.text()}`);

const completion = await paid.json();
console.log(completion.choices[0].message.content);
console.log("settled:", paid.headers.get("payment-response") ? "yes" : "pending");


------------------------------------------------

Prices:     https://x402-mesh-gateway.fly.dev/v1/pricing
Models:     https://x402-mesh-gateway.fly.dev/v1/nodes
Manifest:   https://x402-mesh-gateway.fly.dev/.well-known/x402
Agent docs: https://x402-mesh-gateway.fly.dev/llms.txt