Spree Checkout

Before writing code

Fetch live docs:

1. Fetch https://spreecommerce.org/docs/developer/core-concepts/orders for the canonical state machine.
2. Fetch https://spreecommerce.org/docs/developer/core-concepts/payments for the Payment + PaymentSession (v5.4+) flow.
3. Check the live Spree::Order source on GitHub for the state_machine block — transitions and callbacks change.
4. For headless checkout, fetch the v3 Store API docs at https://spreecommerce.org/docs/api-reference.
5. Verify any custom-step pattern against the latest examples in spree-starter.

Conceptual Architecture

The Order State Machine