Cost as a first-class fact

Every request is metered: the frontend action that triggered it, the operation it hit, and the third-party resources it consumed.

How a cost becomes a fact

• the action tags the request (x-suluk-action)
• the operation declares its cost model (x-suluk-cost)
• the events stream to a durable ledger at /cost

When the cost is a fact instead of a guess, usage-based pricing stops being spreadsheet math — you charge the metered cost plus your margin, metered straight to Stripe Billing.