> ## Content Index > Fetch the complete content index at: https://stablecoininsider.org/llms.txt > Use this file to discover other available public pages before exploring further. # How to Enable Circle x402 Facilitator for USDC (2026) - URL: https://stablecoininsider.org/how-to-enable-circle-x402-facilitator-for-usdc/ - Published: 2026-09-21T12:33:55.000Z - Updated: 2026-09-21T12:33:55.000Z - Description: Enable Circle x402 Facilitator Service for USDC: seller verify/settle on Arc, Base, and Polygon PoS with EIP-3009, address screening, gas sponsorship, and idempotent retries. - Author: Alexandra - Tags: AI, Stablecoins Sellers that want x402 USDC acceptance without running a relayer, funding a gas wallet, or building sanctions screening can point their HTTP API at Circle's hosted Facilitator Service. Circle announced Facilitator Service availability around **September 19, 2026** for USDC settlement on **Arc, Base, and Polygon PoS** via the EIP-3009 **exact** scheme. This guide is the seller-side verify and settle how-to for that named product, not a CDP-centric facilitator picker and not Gateway nanopayments. 📌 Stablecoin Insider's framing: Circle Facilitator Service is the managed x402 facilitator for sellers. Buyers sign EIP-3009 authorizations. Circle verifies, screens addresses, records durable payment state, pays settlement gas, and broadcasts the USDC transfer. Differentiate from Circle Agent Wallet (buyer spend), Circle Gateway nanopayments (batched gas-free path), and CDP / Coinbase facilitator choice guides. Facts below come from Circle's [Facilitator Service docs](https://developers.circle.com/facilitator-service) and the [Arc testnet quickstart](https://developers.circle.com/facilitator-service/quickstart). No invented fees, SLA numbers, or unpublished chain IDs. ### Key Takeaways - Circle Facilitator Service is a hosted x402 facilitator that settles USDC on Arc, Base, and Polygon PoS through EIP-3009 exact transfers. - Circle verifies buyer signatures, screens buyer and seller addresses, records payment state before broadcast, pays settlement gas, and submits the onchain transfer. - Sellers authenticate each verify, settle, and status call with a Facilitator-Seller-Proof (EIP-712 seller proof bound to payTo). - Production settle uses a Circle API key; Circle also documents a keyless trial on Arc testnet without a Circle account. - Named downside: Base and Polygon PoS settlements carry reorg risk and Circle does not guarantee fund receipt there; Arc settlements are described as final. ⚠️ Named downside: On Base and Polygon PoS, Circle states settlements are subject to blockchain reorganization risk and that Circle does not guarantee fund receipt. Arc settlements are described as final. Design fulfill-on-terminal-evidence, not on HTTP 200 alone. ## Who this is for Use Facilitator Service if you sell metered APIs, agent tasks, datasets, or marketplace settlement and want one Circle-hosted facilitator across Arc, Base, and Polygon PoS. Skip this path if you only need buyer-side agent wallets (see [Circle Agent Wallet](https://stablecoininsider.org/how-to-create-a-circle-agent-wallet-for-usdc/)) or Gateway batched nanopayments (see [Circle agent nanopayments](https://stablecoininsider.org/how-to-make-a-circle-agent-nanopayment-in-usdc/)). For facilitator shopping across vendors, start with [how to choose an x402 facilitator](https://stablecoininsider.org/how-to-choose-an-x402-facilitator-for-usdc/). ## What Circle Facilitator Service is Per Circle docs, Facilitator Service is Circle's hosted x402 facilitator for sellers. Point your HTTP API at it and accept x402 payments in USDC without operating a relayer, funding a gas wallet, or building your own sanctions screening. Circle verifies each buyer-signed EIP-3009 authorization and submits the USDC transfer onchain. Circle broadcasts every transfer, pays settlement gas, and screens both parties before any money state is created. Disclaimer from Circle: Facilitator Service is offered by Circle Technology Services, LLC as a software provider. It verifies buyer-signed EIP-3009 USDC authorizations under x402 only. It does not hold, control, or transmit user funds, verify transaction purpose, or confirm agent authority scope. ## How the money path works x402 remains HTTP-native: the seller returns 402 with payment requirements; the buyer (wallet or agent) signs and retries with a payment payload. On Facilitator Service, **/settle** is the authoritative money path. It validates the authorization, screens buyer and seller, records durable payment state, submits the USDC transfer, and returns terminal evidence or a pending response. Buyers authorize with EIP-3009 **TransferWithAuthorization** fields: from, to, value, validAfter, validBefore, and nonce. USDC uses 6 decimals (1 USDC = 1000000 base units in Circle's examples). | Surface | What operators get from Circle docs | | ----------- | ----------------------------------------------------------------------------------------------------- | | Networks | Arc, Base, and Polygon PoS (one seller integration) | | Scheme | EIP-3009 exact USDC transfers | | Gas | Circle pays settlement gas and broadcasts the transfer | | Screening | Buyer and seller addresses screened before money state | | Idempotency | payment-identifier extension (16–128 chars \[A-Za-z0-9\_-\]) or exact same signed auth on retry | | Auth | Facilitator-Seller-Proof header; production settle needs Circle API key; keyless trial on Arc testnet | | Endpoints | api.circle.com/v1/facilitator/x402/settle and /status/{paymentId} | ### Step 1\. Confirm Facilitator Service is the right product Read Circle's [Facilitator Service overview](https://developers.circle.com/facilitator-service) and confirm you need seller-side verify/settle, not Gateway nanopayment batching and not Agent Wallet issuance. Stablecoin Insider's take: if the job is "accept x402 USDC and let Circle run the relayer," Facilitator Service is the named object. If the job is sub-cent gas-free batching into a Gateway balance, stay on the nanopayments docs instead. ### Step 2\. Stand up a seller payTo wallet Create an EVM wallet that will receive USDC. That address is **payTo** in payment requirements and in every seller proof. You need the private key (or signing path) that controls **payTo**, because Facilitator Service requires an EIP-712 seller proof proving control of that address for verify, settle, and status. ### Step 3\. Start on Arc testnet with the keyless trial Circle's quickstart accepts a signed x402 authorization on Arc testnet through Facilitator Service without a Circle account or API key (keyless trial). Documented prerequisites: Node.js v22.6+, viem, a **payTo** wallet plus its private key, and a buyer wallet funded with Arc testnet USDC from the Circle Faucet. Quickstart examples sign against Arc testnet chainId **5042002** and USDC verifyingContract **0x3600000000000000000000000000000000000000** with domain name USDC / version 2. ### Step 4\. Capture the buyer EIP-3009 authorization In production, the buyer's wallet or agent signs **TransferWithAuthorization** and sends it in the x402 retry. Keep signature plus authorization fields (from, to, value, validAfter, validBefore, nonce) for **/settle**. Match **to** to your **payTo**, and set **value** in USDC base units. Circle's sample uses 1000000 for 1 USDC. ### Step 5\. Build Facilitator-Seller-Proof for each call The seller proof is a base64url-encoded envelope with an EIP-712 signature. Domain name in Circle's sample: **Circle Facilitator Seller Request** version 1. Sign with **purpose** matching the route (**verify**, **settle**, or **status**), plus method, bodyHash, network (for example **eip155:5042002** on Arc testnet), payTo, nonce, issuedAt, and expiresAt (sample uses a 5-minute window). Pass the proof in the **Facilitator-Seller-Proof** HTTP header on every Facilitator Service call. ### Step 6\. Call /settle (and reconcile pending) POST to **https://api.circle.com/v1/facilitator/x402/settle** with the x402 payment payload and payment requirements. Include a **payment-identifier** extension when you can: Circle requires id length 16 to 128 from \[A-Za-z0-9\_-\]. Circle documents that **/settle** always answers HTTP 200\. Terminal success returns **success: true** with payer, transaction hash, network, and amount. Pending returns **success: false** with **errorReason: settlement\_pending** and a **paymentId** for **/status**. Do not fulfill the paid resource on pending. A timeout is not evidence of failure. To retry, reuse the same payment-identifier, or the exact same signed buyer authorization if you omitted one. Never re-sign a fresh authorization for the same charge. [Open Circle Facilitator quickstart](https://developers.circle.com/facilitator-service/quickstart) ### Step 7\. Confirm with /status before fulfillment Sign a fresh seller proof with purpose **status**, then GET **https://api.circle.com/v1/facilitator/x402/status/{paymentId}** until status is **completed** or **failed**. Only after **completed** should your API return the paid resource. That is the same fulfill-on-settlement discipline Stablecoin Insider uses in [accepting x402 USDC from AI agents](https://stablecoininsider.org/how-to-accept-x402-usdc-payments-from-ai-agents/). ### Step 8\. Move to production settle with a Circle API key Circle states Facilitator Service requires a Circle API key to settle in production, while the keyless trial lets teams start on Arc testnet without an account. Point the same seller integration at Arc, Base, and Polygon PoS once production credentials and network parameters are confirmed from Circle's supported-networks reference. ## How this differs from nearby Circle and x402 posts | Guide | Job to be done | | ----------------------------------- | ------------------------------------------------------- | | This post (Facilitator Service) | Seller verify/settle via Circle-hosted x402 facilitator | | How to choose an x402 facilitator | Compare facilitator options (often CDP-centric) | | Circle Agent Wallet | Issue/control agent spend wallets | | Circle agent nanopayment | Gateway batched gas-free nanopayments | | Accept x402 from AI agents | Generic seller HTTP 402 pattern | | Fireblocks Agentic Payments Gateway | PSP hosted facilitator into Fireblocks Vaults | For protocol basics, see [x402 protocol explained](https://stablecoininsider.org/x402-protocol/). For another managed facilitator stack, see [Fireblocks Agentic Payments Gateway](https://stablecoininsider.org/how-to-enable-fireblocks-agentic-payments-gateway/). [How to Choose an x402 Facilitator for USDC (2026)Compare x402 facilitator options for USDC settlement so sellers pick verify/settle infrastructure that matches chain coverage, compliance, and ops load.![](https://stablecoininsider.org/favicon.ico)Stablecoin Insider](https://stablecoininsider.org/how-to-choose-an-x402-facilitator-for-usdc/) ## Stablecoin Insider's take Stablecoin Insider's take: Circle is productizing the boring half of x402, verification, screening, gas, and broadcast, so sellers can stay focused on 402 surfaces and fulfillment. Treat Arc as the finality-friendly path Circle documents most clearly in the quickstart, and treat Base/Polygon PoS reorg language as a hard product constraint in risk reviews. Comparing facilitators before wiring Circle? [Read how to choose an x402 facilitator ](https://stablecoininsider.org/how-to-choose-an-x402-facilitator-for-usdc/) --- ## FAQ #### What is Circle Facilitator Service? It is Circle's hosted x402 facilitator for sellers. It verifies buyer-signed EIP-3009 USDC authorizations, screens addresses, records payment state, pays settlement gas, and submits the onchain transfer on Arc, Base, and Polygon PoS. #### Which networks does Facilitator Service support? Circle documents USDC settlement on Arc, Base, and Polygon PoS through the EIP-3009 exact scheme from one seller integration. #### Do sellers need a gas wallet? No for settlement gas on Facilitator Service. Circle broadcasts each transfer and pays settlement gas. Sellers still need a payTo address that can receive USDC and a signing path for Facilitator-Seller-Proof. #### What is Facilitator-Seller-Proof? A base64url envelope carrying an EIP-712 signature that proves control of payTo and binds purpose (verify, settle, or status), method, body hash, network, and time window. Pass it in the Facilitator-Seller-Proof header. #### How should sellers handle settlement\_pending? Do not fulfill. Poll /status with the paymentId until completed or failed. Retry with the same payment-identifier or the exact same signed buyer authorization. Never re-sign a new authorization for the same charge. #### Is the keyless trial the same as production? No. Circle documents a keyless trial on Arc testnet without a Circle account. Production settle requires a Circle API key. #### How is this different from Circle Gateway nanopayments? Facilitator Service settles individual EIP-3009 exact transfers with Circle as the hosted facilitator. Gateway nanopayments batch authorizations into gas-free Gateway balances. Use the product that matches your settlement model. #### What risks does Circle call out on Base and Polygon PoS? Circle states settlements on Base and Polygon PoS are subject to blockchain reorganization risk and that Circle does not guarantee fund receipt on those networks. Arc settlements are described as final. --- This content is provided for informational and educational purposes only and does not constitute financial, investment, legal, or tax advice; no material herein should be interpreted as a recommendation, endorsement, or solicitation to buy or sell any financial instrument, and readers should conduct their own independent research or consult a qualified professional.