The old “vertical slice” status in this file described the original ZIP and is no longer current. Mercado Pago now runs through the canonical plugin/payment/ledger architecture with capture, cancellation, partial refunds, holds, settlement, provider-shaped errors and signed webhook validation.
Use Fidelity — Mercado Pago for the confirmed routes, state mapping, emulated behaviour and explicit gaps. Use Adding a provider for the provider architecture rather than copying Mercado Pago as a template for core behaviour.