@aifinpay/agent (Node / TypeScript)

Non-custodial x402 payment client for autonomous AI agents on AiFinPay — canonical domain aifinpay.io (the legacy aifinpay.company host is retired). SDK settlement: since 1.3.0, direct fee-on-top splitter settlement (AiFinPayAgent.call()) works on Polygon (default), Base, Optimism, Unichain, BOT Chain and XRPL EVM (native-token path only — no ERC-20/USDC settlement yet), plus Solana; the backend-quoted invoice flow (/api/b2b/pay-with-split) remains Polygon + Solana. The protocol is live across 13 networks — see aifinpay.io/llms.txt.

The Ed25519 keypair is generated locally with tweetnacl and never leaves your process. The SDK only sends a one-time SHA-256 + Ed25519 signature in the x-signature header to authenticate against AiFinPay-protected endpoints.

Install

# install (latest)
npm install @aifinpay/agent
# or pnpm add @aifinpay/agent
# or yarn add @aifinpay/agent

# stable (when 1.0 ships)
npm install @aifinpay/agent

Quick start

import { Agent } from "@aifinpay/agent";

// Generate a fresh keypair locally — never transmitted
const agent = Agent.new();
console.log("Fund this address:", agent.address);
console.log("Save this secret:", agent.secretB58); // store securely!

// Wait until the wallet has at least $0.01 worth on-chain
await agent.waitForFunding({ minUsdCents: 1 });

// Request an invoice for a Seat (USDC on Solana)
const invoice = await agent.reserveSeatInvoice({
  amountUsd: 1.0,
  asset: "USDC",
});
// Build + sign + submit the on-chain tx with @solana/web3.js or viem.
// `invoice.raw` has program_id, treasury_vault, mints, nonce, etc.

// Once the Seat is on-chain, gated endpoints just work:
const res = await agent.get("https://aifinpay.io/api/stats");
console.log(await res.json());

Loading an existing keypair

// from solana-keygen JSON file (Node only)
const agent = await Agent.fromKeypairFile("./agent-wallet.json");

// from base58 secret string (works in browser too)
const agent2 = Agent.fromSecretB58("3RvZm7Gw...");

How x402 auth works under the hood

For every gated request the SDK:

1. GET /nonce → receives a one-time UUID with 60s TTL.
2. computes SHA-256("AiFinPay-x402:{nonce}:{pubkey}").
3. signs with Ed25519, base58-encodes the signature.
4. retries the original request with headers:
   • x-agent-pubkey: <base58 pubkey>
   • x-nonce: <uuid>
   • x-signature: <base58 sig>

The server verifies the signature, checks the agent has a live Seat PDA on-chain, and serves the resource.

Privacy

• The server never sees your private key. Period.
• Nonces are consumed on use; replay-resistant.
• All transactions are public and on-chain — Solana + Polygon mainnet.

License

MIT.