Order lifecycle - Endl API

An order and each of its items report one of six states. Internal detail is deliberately not exposed — these six are the contract.

UNDER_REVIEW means the outcome is not yet known with certainty. It resolves to FULFILLED, FAILED or a refund without you doing anything. Re-ordering while an order sits in UNDER_REVIEW risks paying for the same card twice.

Polling

Question	Answer
How often?	Every few seconds while `PENDING`. The group limit is 300/min per key.
How long?	Most orders settle in seconds; some take minutes.
Are there webhooks?	Not in v1. Polling is the only mechanism.
When do I stop?	At `FULFILLED`, `FAILED` or `REFUNDED`. `REFUND_PENDING` still moves.

`state_reason`

Present on items, null unless one of exactly four values applies.

Value	Meaning	Your remedy
`AMOUNT_MISMATCH`	`amount_minor` did not equal the sum of the items.	Fix your total calculation; re-place the order.
`CURRENCY_COUNTRY_MISMATCH`	The requested currency does not match the product.	Use the product’s own currency from the catalogue.
`VALIDATION_ERROR`	Rejected during asynchronous validation.	Inspect the order; correct and re-place.
`NO_OFFER_AVAILABLE`	Nothing could serve this item.	Retry later, or choose a different denomination.

AMOUNT_MISMATCH is the cheapest error in the system to avoid and one of the more expensive to resolve — the order is accepted, then fails, and raises a refund obligation. Compute Σ(denomination_minor × qty) yourself before sending.