The "technical file" is a compilation of all the documentation that confirms that you designed a safe and effective device, and that you can routinely manufacture that safe and effective device.
Part of that documentation will be a description of the manufacturing flowpath, including how the supply of raw materials is determined and routinely controlled, additionally how any subcontracted and/or outsourced activities are controlled.
Part of that control might include establishing a technical agreement with critical suppliers. That is a different emphasis from the financial agreement you might have with them. For example, a key element would be insisting that the supplier couldn't make a significant change to the material without getting your agreement in advance...even if the price remained exactly the same!