Accepts a complete UCP checkout response envelope negotiated at either 2026-04-08 or 2026-08-25. The seven UCP top-level checkout fields are required and extension members remain open. August responses must also carry ucp.payment_handlers; line items retain their official required fields and quantity floor; checkout totals contain exactly one subtotal and one total. Historical April callers retain the original adapter's optional payment-handler compatibility. Missing, ambiguous, or unsupported material fails before policy evaluation.

Decionis authorizes; the connected merchant system remains responsible for execution. An ALLOW decision is not itself an execution grant. An authoritative response may carry an exact-action grant that must be claimed immediately before the merchant commits the checkout, then finalized as COMMITTED, FAILED, or INDETERMINATE.