Soft-deletes a line item — it leaves the invoice and its derived total immediately, but the row is retired for audit history, never removed. expected_updated_at is required: the line's updated_at from your read (invoice_item_read); without it the removal is refused and the refusal names the current value. Refuses when the parent invoice is 'paid' (ledger-locked: retire the payment first) or 'cancelled' (terminal: its lines stay as issued), and with CONFLICT when the line changed since that read (read it again). If retiring the line settles the remaining balance on a partially-paid invoice, the parent re-derives to 'paid' by itself. NEXT: invoice_read to see the updated total.