A window manufacturer begins making the glass it formerly purchased. Which strategy is this?

Vendor-managed inventory (VMI) involves the supplier taking responsibility for managing the inventory levels at the customer's location. This strategy does not apply here, as it pertains to inventory management rather than the production of materials, which is not what the window manufacturer is doing.

Forward vertical integration occurs when a company expands its operations to include distribution or retailing of its products rather than focusing on production. In this scenario, the manufacturer is not moving forward in the supply chain but rather backward by making its own glass.

An agile supply chain emphasizes flexibility and the ability to respond quickly to market changes. While this is a valuable strategy, it does not directly relate to the decision of the window manufacturer to produce its glass. The focus here is specifically on the integration of production processes rather than supply chain agility.