import { VelumXClient } from '@velumx/sdk';

const velumx = new VelumXClient({
  paymasterUrl: '/api/velumx',
  network: 'testnet',  // <-- switch here
});

const unsignedTx = await buildSponsoredContractCall({
  contractAddress: 'ST...',
  contractName: 'my-contract',
  functionName: 'my-function',
  functionArgs: [...],
  publicKey: userPublicKey,
  network: 'testnet',  // <-- and here
});

import { VelumXClient, buildSponsoredContractCall, RelayerError } from '@velumx/sdk';
import { uintCV, contractPrincipalCV } from '@stacks/transactions';
import { request } from '@stacks/connect';

const velumx = new VelumXClient({ paymasterUrl: '/api/velumx', network: 'testnet' });

// Get public key from connected testnet wallet
const addrResult = await request('stx_getAddresses') as {
  addresses: Array<{ address: string; publicKey: string }>;
};
const publicKey = addrResult.addresses[0].publicKey;

// Build a sponsored call against a testnet contract
const unsignedTx = await buildSponsoredContractCall({
  contractAddress: 'ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM',
  contractName: 'my-testnet-contract',
  functionName: 'my-function',
  functionArgs: [uintCV(1_000_000n)],
  publicKey,
  network: 'testnet',
});

const signResult = await request('stx_signTransaction', {
  transaction: unsignedTx instanceof Uint8Array
    ? Buffer.from(unsignedTx).toString('hex')
    : unsignedTx,
  broadcast: false,
});

try {
  const { txid } = await velumx.sponsor(signResult.transaction);
  console.log('Testnet txid:', txid);
  // Verify on: https://explorer.hiro.so/txid/<txid>?chain=testnet
} catch (err) {
  if (err instanceof RelayerError) {
    console.error('Relayer rejected:', err.reason);
  } else {
    throw err;
  }
}

https://explorer.hiro.so/txid/<txid>?chain=testnet