Integrate Laso Finance into your agent wallet

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What your users get

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How identity works

• The paying wallet is the account. Laso reads the payer from each x402 or MPP payment. The first paid request from a new wallet creates a Laso account for it, and the response includes that account’s credentials (auth.id_token, auth.refresh_token).
• Free sign-in without paying. GET /auth with a SIGN-IN-WITH-X header proves ownership of the wallet and returns the same credentials. Use it for read-only calls before a first purchase.
• Bearer tokens for everything else. Card details, balances, status checks, and webhooks use Authorization: Bearer <id_token>. Tokens last about an hour; POST /auth with the refresh_token renews them for free. See authentication.

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Choose an integration path

curl "https://laso.finance/discovery/resources?network=eip155:8453"

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Reference integration

npm install @x402/fetch @x402/evm @x402/extensions viem

import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { wrapFetchWithSIWx } from "@x402/extensions/sign-in-with-x";
import { privateKeyToAccount } from "viem/accounts";

const LASO = "https://laso.finance";

// One signer per end user. This wallet is the user's Laso identity.
const signer = privateKeyToAccount(process.env.USER_WALLET_PRIVATE_KEY);

const client = new x402Client();
registerExactEvmScheme(client, { signer });
const payFetch = wrapFetchWithPayment(fetch, client);
const siwxFetch = wrapFetchWithSIWx(fetch, signer);

// Free sign-in. Proves wallet ownership and returns API credentials.
async function signIn() {
  const res = await siwxFetch(`${LASO}/auth`);
  const { auth, user_id } = await res.json();
  return {
    idToken: auth.id_token,
    refreshToken: auth.refresh_token,
    userId: user_id,
  };
}

// Paid route. The x402 client settles the 402 challenge and replays the request.
async function orderUsaCard(amount: number, idToken: string) {
  const res = await payFetch(`${LASO}/get-card?amount=${amount}`);
  if (!res.ok) {
    throw new Error(`get-card failed: ${res.status} ${await res.text()}`);
  }
  const { card } = await res.json();

  // Card details are issued asynchronously, usually in 7 to 10 seconds.
  for (let attempt = 0; attempt < 20; attempt++) {
    const poll = await fetch(`${LASO}/get-card-data?card_id=${card.card_id}`, {
      headers: { Authorization: `Bearer ${idToken}` },
    });
    const data = await poll.json();
    if (data.status === "ready") {
      return data.card_details;
    }
    await new Promise((r) => setTimeout(r, 3000));
  }
  throw new Error(`card ${card.card_id} still pending`);
}

import { registerExactSvmScheme } from "@x402/svm/exact/client";
import { createKeyPairSignerFromBytes } from "@solana/kit";

const solanaSigner = await createKeyPairSignerFromBytes(userSecretKeyBytes);
registerExactSvmScheme(client, { signer: solanaSigner });

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Behaviors your integration should handle

• Budget for the fee-inclusive total. The amount you pass is face value. Most routes charge face value plus a fee, so a request for the user’s entire balance as face value will fail. Read limits from GET /get-pricing and the exact total from the 402 challenge.
• Asynchronous fulfillment. USA cards need a short poll of /get-card-data. International cards stay queued for up to about a day, so report the state instead of polling every few seconds. Register a webhook with POST /register-webhook to get signed delivery events instead of polling.
• Identity verification belongs to the human. Venmo and PayPal payouts and the bank account flow need the account owner to verify their identity first. Instead of failing, they return a verification link (kyc_url on /send-payment, kycUrl in the banking calls). Show the link to your user; never let the agent fill in the form for them. GET /get-kyc-status reports when they are done.
• Nothing is lost when fulfillment fails. A payment that settles but cannot be fulfilled (verification needed, a provider outage, a validation error) is credited to the user’s Laso account balance. The agent can retry, or return the funds to a Solana address with POST /withdraw.
• Retry a refused payment with a fresh challenge. A rejected signature or payment comes back as another 402 with a new challenge. Sign the new one; never resend the same payload. See error handling.

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Launch checklist

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