99.3% of x402 agent-payment volume settled in USDC during Circle’s second quarter, company figures showed.USDC circulation reached $73.3 billion at quarter-end, increasing 19% from the previous year, Circle reported.Circle recorded $14.8 trillion in quarterly USDC transaction volume, representing 151% year-over-year growth during Q2.Circle’s Agent Stack hosted more than 900 paid services following its May 2026 launch globally.Arc’s public mainnet launch remains scheduled for September 16, with programmable agent-finance tools included there.