Circle CEO Jeremy Allaire said USDC accounted for 99.3% of payment volume processed through the x402 protocol during the second quarter of 2026, highlighting the growing role of stablecoins in automated machine-to-machine commerce. The figure, however, covers x402 activity specifically and does not represent the entire AI payments market.

USDC Gains Ground in AI Agent Payments

Allaire discussed the opportunity during Circle's Aug. 19 earnings AMA, arguing that AI agents require reliable settlement assets that support fast, inexpensive, and predictable transactions.

The x402 protocol enables autonomous software agents to pay for digital services without continuous human approval. As a result, agents can automatically purchase data, computing resources, application access, and digital content. The protocol is an open standard built around the HTTP 402 "Payment Required" status code, which was introduced by Coinbase in 2025 as an internet-native way for software to request and settle payments programmatically.

USDC's dollar denomination makes it well suited to these transactions because agents can operate with a consistent unit of account, while its blockchain-based settlement allows payments to move without relying on traditional banking processes for each transaction.

Circle CEO: Where Is the Biggest Opportunity for USDC in Global Payments? On August 19, 2026, Circle CEO Jeremy Allaire @jerallaire stated during a earnings live AMA that over 99% of AI agent payments made through agent payment protocols are completed using USDC. He… pic.twitter.com/jpuruXL5gT — Wu Blockchain (@WuBlockchain) August 25, 2026

Circle's Agent Stack further supports this emerging market. The platform launched globally in May and had more than 900 paid services by the end of the second quarter.

Circle reported that USDC circulation reached $73.3 billion at quarter-end, representing 19% annual growth. Quarterly USDC transaction volume rose 151% year over year to $14.8 trillion. Those figures include broader blockchain activity rather than AI payments alone, so they should not be interpreted as direct measures of machine-driven commerce.

Circle Targets Broader Payment Adoption

Beyond AI agents, Allaire identified cross-border settlement, capital markets, and retail payments as important growth opportunities for USDC. Circle has continued developing payment infrastructure for financial institutions while testing applications involving merchants and international transactions. The company also expects instant payment methods, including QR codes, to support further digital payment adoption.

Circle is additionally preparing for the public launch of Arc's mainnet on Sept. 16. The network is expected to include programmable tools designed for agent-based financial activity.

The developments come as stablecoins take on a larger role in digital payments and tokenized financial markets, a trend reinforced in the United States by the GENIUS Act, the federal stablecoin legislation signed into law in July 2025 that established a regulatory framework for payment stablecoin issuers. Adoption nonetheless will depend on infrastructure, regulation, merchant acceptance, and developer activity. For now, USDC's strong share of x402 payments offers evidence that stablecoins could become an important settlement layer for autonomous software, though broader AI payment adoption remains an emerging market.