The Sushi declaration signed between Azerbaijan and Turkey includes the concept of common defense act. In other words, if one of these states feels threatened, the other country is obliged to defend it. The technical content of the agreement is quite comprehensive in this respect, and frankly, there are not many examples in the world. For example, if any country declares war on Azerbaijan, Turkey can get the parliament to decide on full mobilization or declare a state of emergency. The two countries now have a common red book. If you follow the Armenia-Azerbaijan dispute closely, you will see that this is the main discomfort of Armenia in recent months. Armenia's dreams of Karabakh have completely destroyed.
Another issue is that Turkey is the guarantor country of Nakhchivan according to international law. If Armenia undertakes a de facto military action on Nakhchivan, Turkey's right to intervene is reserved.
In short, Turkey and Azerbaijan are two countries that gradually harmonize their defense doctrines with each other and tend to act with a common strategy in the field, which keeps the relationship between the two countries far beyond a simple weapon-military standard purchase and sale relationship. Of course, there is a huge cultural and historical depth that keeps this bond strong.