A property where re-running the same operation produces the same result.
An idempotent bulk edit can be safely retried after a failure without applying the change twice. Shopify's mutations are naturally idempotent when they set an absolute value (`price = 19.99`) and dangerously non-idempotent when they apply a delta (`price = price * 0.9` in a loop). Every well-designed bulk operation records which record IDs it has already touched so a mid-job crash resumes rather than double-applies.
