How do you work with you CMs who work with component suppliers in a multi-echelon envirom

Summary:

Hello All,

One of my customer has a turn key solution with their Contract Manufacturer (CM). They place a PO with the CM for supplying the finished good (chips). CMs source components from multiple vendors. For example, if my customer wants 5000 qty for a FG. The CMs commit only 3000, because they are not able to get commits for the components from their component suppliers.

Business process wise, how do you work with CMs such a way that you still get 5000 qty from the CM. The customer uses only one CM. I would like to know if there is a business process you follow to handle scenarios like this.