Arcus
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Getting started

Networks

Arcus settles on Arc mainnet and Arc testnet only. Requirements that name any other network are rejected with unsupported_network.

Supported networks

Arc MainnetMainnet
CAIP-2
eip155:5042
Chain ID
5042
USDC
0x3600000000000000000000000000000000000000
Decimals
6
EIP-712 domain
name "USDC", version "2"
Explorer
www.arcexplorer.org
Arc TestnetTestnet
CAIP-2
eip155:5042002
Chain ID
5042002
USDC
0x3600000000000000000000000000000000000000
Decimals
6
EIP-712 domain
name "USDC", version "2"
Explorer
testnet.arcscan.app

USDC on Arc

USDC is the native gas token on Arc and is also exposed as an ERC-20 at the predeploy address 0x3600000000000000000000000000000000000000. The two are one balance. The ERC-20 interface uses 6 decimals, which is what x402 amounts use; the native balance reports 18.

The contract implements EIP-3009, so a payer signs a transferWithAuthorization message off-chain and the Arcus relayer submits it. Sign with the domain name USDC and version 2; the SDK reads these from the extra field of the payment requirements.

Same address on both networks
Mainnet and testnet share the USDC address and domain. The only thing that changes between them is the CAIP-2 network identifier in your requirements and client config.

RPC and explorers

Arcus uses the public RPC endpoints for both networks. Mainnet transactions are visible on arcexplorer.org and testnet on testnet.arcscan.app. RPC reachability for each network is published at /health and on the status page.