What is the ruling on taking compensation for the deterioration in the value of the local currency in contracting agreements, and is that considered usury (riba)?

If the contracting party is the one that allows the submission of the letter, then there is no harm in accepting the awarded compensation. There is also no harm for the contractor, in the event of unusual losses due to circumstances beyond their control and not due to their negligence, to present their case to the judge and demand an equitable settlement. The judge may grant the obligated party a grace period if the unforeseen circumstance is likely to disappear soon and the other party will not suffer significant harm. This solution achieves justice and prevents severe damage to either party due to circumstances beyond their control.