A stateful, multi-chain spending session for AI agents. One session enforces a hard USDC budget cap across every tool call, with a verifiable receipt and running ledger for each payment — not a one-shot budget check, but persistent spend governance with a full audit trail. The gateway enforces the cap for the paying wallet on Stacks and Base. USDC on Base (standard x402) or Stellar (via the AgentPay SDK); sBTC on Stacks (any Stacks x402 client).