Installation

Install

Install the SDK alongside viem, its one peer dependency.

npm install @ctrl-arcz/sdk viem

pnpm add @ctrl-arcz/sdk viem

yarn add @ctrl-arcz/sdk viem

The SDK is viem-based and ships ESM + CJS + types. viem is a peer dependency, so you control its version. Arc Testnet is a built-in viem chain, which requires viem >= 2.38.

Set up clients

Every SDK call takes a ClientPair: a viem public client for reads and a wallet client for writes. Both run on arcTestnet, and the chain plus RPC are exported from the SDK so you never transcribe them.

import { createPublicClient, createWalletClient, http } from 'viem';
import { privateKeyToAccount } from 'viem/accounts';
import { arcTestnet, RPC_URL } from '@ctrl-arcz/sdk';

const account = privateKeyToAccount('0x...'); // or a browser wallet account

const publicClient = createPublicClient({ chain: arcTestnet, transport: http(RPC_URL) });
const walletClient = createWalletClient({ account, chain: arcTestnet, transport: http(RPC_URL) });

const clients = { publicClient, walletClient };

Pass the account object (not just its address) to the wallet client. That is what tells viem to sign locally and submit via eth_sendRawTransaction. A bare address string makes viem call wallet_sendTransaction, which Arc’s RPC does not support.

Arc’s public RPC is rate-limited. For a multi-transaction flow, wrap the transport to back off on the JSON-RPC error -32011 (“request limit reached”), which viem does not retry by default, and enable Multicall3 batching on the public client (batch: { multicall: true }) to collapse concurrent reads into one request.

Addresses and chain constants

Contract addresses, the chain, and endpoints live in one place and are exported from the SDK, so you never hardcode them:

import {
  arcTestnet,                    // viem chain
  ARC_TESTNET_CHAIN_ID,          // 5042002
  RPC_URL,                       // https://rpc.testnet.arc.network
  ADDRESSES,                     // USDC, Memo, Permit2, CCTP, Gateway, ...
  CTRL_ARCZ_ADDRESS,             // protected-transfer contract
  CODE_CLAIM_VERIFIER_ADDRESS,   // the code-claim verifier behind it
  SPEND_POLICY_FACTORY_ADDRESS,  // payer-shield account factory
  STEALTH_ANNOUNCER_ADDRESS,     // ERC-5564 announcement registry
  SHIELD_VAULT_ADDRESS,          // demo vault contract
} from '@ctrl-arcz/sdk';

Contract	Arc Testnet address
CtrlArcZ (protected transfer)	`0x8dAb7148cdc31DAcad6d7e12161AA3DEDb572Dca`
CodeClaimVerifier	`0x2C0f268DE2Aa8BB2ab27F2Ea5Ae8a0f9a0E068c4`
SpendPolicyFactory	`0x9B3b30573D7f1d65d1cFeeb52E3a6E69a5792161`
SpendPolicyAccount (implementation)	`0x047870050bA2a20665F053797140044C004970c5`
StealthAnnouncer (ERC-5564)	`0x9b9F9F8b98Dd7a74889725e79591B3E69BdC991D`
Vault (demo)	`0xc8185AF46b882368b771E8E8a1C8abe1C8e4127f`
USDC (native gas token)	`0x3600000000000000000000000000000000000000`

Read these from the SDK rather than copying them. SPEND_POLICY_FACTORY_ADDRESS was redeployed on 2026-08-24 and the superseded factory is still live on chain, so a hardcoded address keeps working while pointing at the wrong contract. SPEND_POLICY_FACTORY_PRIOR_ADDRESSES lists the retired ones, which is how the co-signer still recognises a box created under an older factory.

About Arc Testnet

Chain id 5042002, exported as ARC_TESTNET_CHAIN_ID.
RPC https://rpc.testnet.arc.network (RPC_URL). The explorer is ArcScan at https://testnet.arcscan.app, which exposes a Blockscout-compatible REST API the firewall reads from.
USDC is the native gas token, exposed as an ERC-20 interface at 0x3600000000000000000000000000000000000000 with 6 decimals. Because it is native, an ERC-20 transfer moves native balance, so contracts that receive it implement receive(). The SDK only ever touches the ERC-20 interface.
Faucet. Fund a test wallet with USDC from https://faucet.circle.com.

Send your first protected transfer in the quickstart.

Get started

Integrate the SDK

Concepts

Reference

Clients

Install

Set up clients

Addresses and chain constants

About Arc Testnet

Next

​Install

​Set up clients

​Addresses and chain constants

​About Arc Testnet

​Next

Install

Set up clients

Addresses and chain constants

About Arc Testnet

Next