Circle launches hosted x402 USDC facilitator for sellers

Circle announced a hosted x402 Facilitator Service, generally available around Sept. 19, 2026, that lets sellers accept USDC on Arc, Base and Polygon PoS using the EIP‑3009 TransferWithAuthorization exact transfer scheme. The service verifies buyer-signed authorizations, screens buyer and seller addresses, records durable payment state, pays settlement gas and broadcasts the onchain transfer.

Sellers integrate by pointing their HTTP API at Circle’s hosted endpoints. The x402 flow remains HTTP-native: a seller returns an HTTP 402 with payment requirements, the buyer or buyer agent signs an EIP‑3009 TransferWithAuthorization containing from, to, value, validAfter, validBefore and nonce, and retries the request with the payment payload. Circle’s /settle endpoint is the authoritative money path; it validates the authorization, runs screening checks, records money state, submits the USDC transfer and returns terminal evidence or a pending response. Circle documents endpoints at api.circle.com/v1/facilitator/x402/settle and /status/{paymentId}.

Each call to the Facilitator Service must include a Facilitator‑Seller‑Proof header: a base64url envelope carrying an EIP‑712 signature that proves control of the payTo address and binds a purpose (verify, settle or status), HTTP method, a body hash, a network identifier and a short time window. Sellers must create and control a payTo EVM wallet that will receive USDC and hold the private key or signing path for seller proofs.

Circle’s /settle always returns HTTP 200. A terminal successful response contains success: true with payer, transaction hash, network and settled amount. A pending response returns success: false with errorReason: settlement_pending and a paymentId. Sellers are instructed not to deliver paid resources while a settlement is pending and to confirm completion by signing a fresh seller proof with purpose status and polling /status/{paymentId} until the status is completed or failed.

For idempotency, Circle accepts either a payment identifier extension (16–128 characters from [A‑Za‑z0‑9_-]) or the exact same signed buyer authorization on retry. Circle warns against re‑signing a fresh authorization for the same charge. USDC transfers use six decimals in Circle’s examples (1 USDC = 1,000,000 base units).

Circle states the Facilitator Service pays settlement gas and broadcasts each transfer but does not hold, control or transmit user funds. The service screens addresses before creating money state and does not verify transaction purpose or confirm agent authority scope. The company documents that Arc settlements are final in its materials. For Base and Polygon PoS, settlements are subject to blockchain reorganization risk and Circle does not guarantee receipt of funds on those networks.

Teams can start on Arc testnet with a keyless trial, following Circle’s quickstart that references chainId 5042002 and a testnet USDC verifying contract. The quickstart lists Node.js v22.6+ and viem as example tooling. Production settlement requires a Circle API key and confirmation of supported network parameters before moving an integration live. The Facilitator Service targets sellers that need a hosted, seller‑side verify‑and‑settle solution for metered APIs, agent services, datasets and marketplaces across the three supported networks.