Powered by Circle: USDC, RefundProtocol, and Nanopayments

StableFi's payment network runs on USDC — the dollar-backed stablecoin issued by Circle with over $75 billion in circulation. We chose USDC because it is the most trusted stablecoin in the market, fully reserved and regularly audited, and accepted by institutions ranging from BlackRock to Visa. When an AI agent holds USDC, it holds real dollars.

But using USDC as a currency is only the beginning. StableFi leverages two additional Circle technologies that make agent commerce practical: RefundProtocol for on-chain escrow and dispute resolution, and Nanopayments for sub-cent transfers with zero gas fees.

USDC: The Native Currency of Agent Commerce

Every AI agent on StableFi holds USDC in a Coinbase-backed wallet on Base. USDC is the unit of account for all transactions — agent-to-agent, agent-to-merchant, escrow deposits, and refunds. We do not support volatile cryptocurrencies because price instability is incompatible with commerce. An agent that purchases a $50 SaaS subscription should pay $50, not $50 plus or minus 10% depending on market conditions.

USDC on Base settles in seconds and costs fractions of a cent in gas — and with StableFi's gasless transfers via Coinbase CDP, even that tiny cost is abstracted away. The agent pays the exact amount owed, nothing more.

RefundProtocol: On-Chain Escrow

When an agent makes a purchase, the funds do not go directly to the merchant. Instead, they are deposited into an on-chain escrow contract powered by Circle's RefundProtocol, deployed on Base. The escrow holds the USDC for a configurable settlement period — typically 24 to 72 hours — during which either party can raise a dispute.

If no dispute is raised, the funds automatically release to the merchant at the end of the settlement period. If a dispute is raised, StableFi acts as the designated arbiter. Our dispute resolution team reviews the evidence — transaction logs, delivery confirmations, API response codes — and directs the escrow contract to release funds to the appropriate party. Everything happens on-chain, fully transparent and auditable.

Nanopayments: Sub-Cent Transfers

Traditional payment systems have minimum transaction amounts — typically $0.50 or higher — because processing fees make smaller amounts uneconomical. But agent commerce generates enormous volumes of tiny transactions: a fraction of a cent for an API call, a few thousandths of a cent for a data query, millionths of a dollar for a compute cycle.

Circle's Nanopayments protocol solves this by batching sub-cent transfers off-chain and settling them on-chain periodically. An agent might make 10,000 API calls at $0.000001 each throughout the day. Instead of 10,000 on-chain transactions, Nanopayments batches them into a single settlement of $0.01. The result is zero-gas, sub-cent transfers that make micropayment business models viable for the first time.

The Full Stack

Together, USDC, RefundProtocol, and Nanopayments form the financial backbone of StableFi. Agents hold dollars. Escrow protects both parties. Micropayments enable any pricing model. And because everything runs on Circle's infrastructure, merchants and developers get the security and compliance guarantees that come with the most regulated stablecoin issuer in the world.

Learn more about building on StableFi's payment infrastructure in our developer documentation.