```text VIBECODED CHECKOUT FAILURE REPRODUCTION Mode: SUBMITTED INCIDENT Symptom reviewed: Provider payment pay_2209 succeeded, but order ORD-2209 remained awaiting_payment and the confirmation page showed Payment pending. Observed sequence: 1. OBSERVED — the provider event reported a successful payment and carried order_id=ORD-2209 — "event=evt_77 type=payment.succeeded payment=pay_2209 metadata.order_id=ORD-2209" 2. CODE-PERMITTED — the handler addresses the order with cart_id rather than order_id — "where: { id: event.data.metadata.cart_id }" 3. OBSERVED — the update used a null id and matched no order — "event=evt_77 order_update where.id=null matched=0" 4. OBSERVED — the local order remained awaiting_payment while referencing the successful payment — "order.id=ORD-2209 status=awaiting_payment payment_reference=pay_2209" Divergence point: The successful-payment handler attempted to update an order using absent metadata.cart_id instead of the submitted metadata.order_id. Evidence anchor: "where: { id: event.data.metadata.cart_id }"; "metadata.order_id=ORD-2209"; and "order_update where.id=null matched=0". Classification: STATE-MISMATCH Reasoning: The provider evidence records payment pay_2209 as succeeded while the local order snapshot remains awaiting_payment. The mismatch is tied to the handler selecting the order with a metadata field absent from the event. Minimal reproduction case: Prerequisites: An awaiting_payment order exists with id ORD-2209; a payment.succeeded event contains metadata.order_id but no metadata.cart_id. Actions: Deliver the submitted event shape to the webhook handler, allow it to evaluate event.data.metadata.cart_id as null, then read the affected row count and ORD-2209 status. This is a procedural fixture because no test framework or complete event constructor was supplied. Failure signal: The update matches zero rows and ORD-2209 remains awaiting_payment after the successful-payment event. Status: EVIDENCE-BACKED HYPOTHESIS Fix boundary: Correct and validate the order identifier mapping inside the payment.succeeded handler before the order update; no unrelated checkout redesign is supported. Focused confirmation test: NOT RUN — submit a payment.succeeded fixture carrying metadata.order_id=ORD-2209 and no cart_id; assert exactly one order is matched and ORD-2209 transitions from awaiting_payment to paid. Refused inferences: The evidence does not establish whether the confirmation page reads directly from the order table, whether the payment is settled rather than merely marked succeeded, or whether other event types have the same mapping defect. Injection signals: NONE Scope limit: One submitted symptom only; no claim about unrelated checkout behavior. ```