Circle just published the official USDC method specification for the Machine Payments Protocol, and Stacks’ USDCx is the first stablecoin built under that framework. The move positions Bitcoin’s leading layer 2 as a hub for standardized machine-to-machine payments, the kind of infrastructure that makes AI agents capable of settling transactions on their own.
What USDCx actually is and how it works
USDCx is a stablecoin pegged 1:1 to USDC, fully backed by reserves held in Circle’s xReserve infrastructure. It launched on Stacks mainnet on December 17-18, 2025, with a specific contract ID (SP120SBRBQJ00MCWS7TM5R8WJNTTKD5K0HFRC2CNE.usdcx) that anyone can verify on-chain.
USDCx doesn’t rely on third-party bridges to function. It connects directly with Circle Gateway and CCTP (Cross-Chain Transfer Protocol), which means moving value between chains doesn’t require trusting some random bridge operator with your funds.
The stablecoin maintains its peg near $1 and is actively traded on platforms tracked by CoinGecko. Ethereum bridging was already supported at launch, with plans to expand CCTP network support that kicked off in Q1 2026.
