Arc Mainnet opened on September 16, and by the evening A-Identity had an agent on its identity registry, a spend vault holding real USDC and trust checks settling through Circle Gateway. Here is what we shipped, what it cost, and what is still on testnet.
The Network Opened, So We Moved In
Circle opened Arc Mainnet to the public on September 16. Arc is a chain where the gas token is USDC itself, finality is deterministic and under a second, and Circle Gateway, CCTP and nanopayments are there from the first block. For a product whose whole job is to answer one question before an agent pays, should it pay this counterparty, that is the most natural home it could have.
Arc was where A-Identity started, on testnet. The same day mainnet opened, we moved the parts that handle real money onto it, and every step below has a transaction you can open at a-identity.xyz/proof/arc.
Funding a Chain That Had No Gas of Ours
A new network has a chicken and egg problem: every write needs gas, and on Arc the gas is USDC we did not hold there yet. We burned native USDC on Base through CCTP V2 with Circle's Forwarding Service attached. Circle attested the burn and broadcast the mint on Arc for us, paying the destination gas out of the transfer. 1.012 USDC left Base and 0.945 arrived on Arc sixteen seconds after the burn receipt, with nothing of ours signing on the Arc side.
Agent Number Zero
Arc Mainnet carries the canonical ERC-8004 identity and reputation registries, the same family Base and Arbitrum One share. We checked that the hard way, by reading each proxy's implementation slot and matching the implementation code against Base, because a small proxy at a familiar address proves nothing on its own. Then we registered, and our agent became token #0, the first mint on that registry. Our oracle anchored its reputation right after.
A Budget the Contract Enforces
The AgentSpendPolicy vault is the contract that gives an agent a budget it cannot exceed. On Arc Mainnet it holds real USDC under a 1 USDC daily cap and a 0.25 USDC auto-approve line. It paid 0.01 inside its policy, and when we asked it to pay 0.50 the contract refused with its own typed error before anything was broadcast.
Two Ways to Get Paid, Both in USDC
Trust checks now sell on Arc Mainnet through two x402 rails. With Circle Gateway nanopayments the buyer signs against its Gateway balance, Circle credits the call at once and settles on-chain in a batch, and nobody pays gas. With our own EIP-3009 facilitator the buyer signs a transfer and we broadcast it. That settlement measured 87165 gas, and because the gas is USDC that is an exact 0.0148 dollars with no price feed involved, which is where the 0.03 settlement fee comes from.
One thing broke on the way, and it was ours. Our gas ceiling was a single number sized for ether, and on a chain whose gas is a dollar it refused the first settlement before broadcasting. Nothing moved. The ceiling now follows the unit of the chain it guards.
What Is Still on Testnet
Escrow and KYA anchoring still run on Arc testnet: the ValidationRegistry and Arc's reference escrow contract are not on mainnet yet. The first payments on mainnet were our own and the ledger labels them internal, and Arc's mainnet explorer is permissioned for now, so a receipt link may ask you to sign in. Start at a-identity.xyz/arc and click anything.