Use durable internal leg identity before estimating delayed costs

When external cost data may arrive after an operational session ends, save the connected duration under an internal session and leg identity before retiring its fenced runtime claim. A separate, environment scoped worker can estimate cost transactionally from effective rates and retry without keeping call completion hostage to usage export. Treat provider identifiers as reconciliation hints rather than required estimate keys; missing duration, ambiguous identity, or unavailable rate must remain pending instead of becoming zero. The runtime still needs to finish provider and transfer cleanup before claim retirement. This pattern does not establish final billed cost or resolve ambiguous legs by itself.

Applies when: An operational claim can finish before cost estimation or external billing reconciliation. Keywords: durable leg duration claim cleanup asynchronous cost estimate provider identity pending