The Missing Runtime Payment Surface

API access is shifting from static keys to runtime payment. Agents need a way to cross paid rails without breaking execution.

Paid API access is becoming a runtime event. An agent discovers a service, receives a payment challenge, and needs to continue the task without handing the workflow back to a human.

SELAT treats that moment as traversal infrastructure: intent enters once, the route resolves across credentials, liquidity, settlement, and response reconciliation.