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Circle’s x402 Facilitator Service goes live on Arc, supports Base and Polygon PoS
The new service lets sellers accept USDC payments without managing their own relayers or gas wallets, launching alongside Circle's Arc mainnet with BlackRock, DTCC, and Visa as founding validators.
Circle just made it a lot easier for API providers, data services, and AI agents to get paid in USDC. The company’s x402 Facilitator Service is now live, processing payments across three networks: Circle’s own Arc blockchain, Coinbase’s Base, and Polygon PoS.
The service launched on September 16, 2026, the same day Circle’s Arc mainnet went public.
What the x402 Facilitator Service actually does
The HTTP 402 status code has existed since the early days of the web. It was originally reserved for “Payment Required” but never saw real adoption because the internet didn’t have native money rails. The x402 protocol changes that by embedding USDC payments directly into HTTP request-response flows.
Circle’s Facilitator Service handles the messy middle part. Sellers don’t need to spin up their own relayer infrastructure, fund gas wallets, or run sanctions screenings. Circle verifies the buyer’s signed EIP-3009 authorization and settles the transaction on-chain. All the seller needs is a Circle API key to get started, with a keyless trial option available for those who want to test the waters.
The service uses what Circle calls the “exact” scheme for processing payments across the three supported networks.
Arc’s mainnet arrives with heavyweight validators
Circle built an EVM-compatible Layer 1 blockchain where USDC serves as the gas token. The validator set includes BlackRock, DTCC, and Visa as founding validators securing the network.
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More than 100 partners and applications were operational on Arc at launch. The testnet processed between 500 million and 700 million transactions before the public launch.
Circle minted the full supply of 10 billion ARC tokens, though the company has made no commitment to a public token launch.
USDC’s quiet dominance in agent payments
Circle launched its Agent Stack in May 2026, a toolkit designed for AI agents that need to transact autonomously. The early data from that initiative is striking: 98.8% of volume in agent-to-agent x402 payments used USDC.
An AI agent needs to pull data from another agent’s API without a credit card or bank account. USDC via x402 fits that requirement, and Circle is now making it trivially easy for the receiving side to accept those payments. By extending the Facilitator Service to Base and Polygon PoS, Circle ensures that sellers across different ecosystems can tap into the same payment flow without being locked into Circle’s own chain.
What this means for the broader payments landscape
The risk is concentration. If Circle controls the facilitator service, the primary blockchain (Arc), and the stablecoin (USDC), that’s a lot of critical infrastructure sitting under one corporate umbrella.