No subscription, no per-call rounding. An agent opens a stream, pays one tiny USDC tick per second of compute, and stops the instant it has enough. The provider only gives away what was paid for.
The first request gets an HTTP 402 Payment Required with the terms (asset = USDC, network = Arc, price for this tick). The agent signs a USDC authorization from its Circle Gateway balance and retries; the node verifies, settles, and serves. No API key, no account. Money is the key.
Each "pull" buys one tick (~one second) of streaming. The model is held server-side with backpressure so it can't run ahead of payment. The moment the agent stops pulling, generation halts and the node frees the GPU, so you only ever pay for the seconds you actually consumed.
A provider pricing agent quotes a per-second price that surges under load and discounts when the machine is idle. A buyer agent discovers providers, walks away if the price is over its limit, streams, and judges the answer each second, stopping on its own when it's good enough or the budget is hit. Both narrate their reasoning.
Sub-cent ticks are economical because Circle Gateway batches them off-chain and settles as a single transaction on Arc (sub-second finality, USDC-native gas). Operators withdraw their accrued balance to chain whenever they like.