Checkout flows involve multiple steps (cart → shipping → payment → confirmation) with async validation, error recovery, and complex branching based on user choices.

• Nested states for checkout steps

• Parallel states for simultaneous validations

• Guards for conditional step skipping

• Context for order data accumulation

• Pattern: Forms — Multi-step forms

• Pattern: Data Fetching — Async payment processing

• Pattern: Navigation — Step routing

• Add full checkout machine definition

• Add payment error handling flow

• Add abandoned cart recovery