SAFe encourages Suppliers-even those using traditional methodologies-to collaborate closely with ARTs (Agile Release Trains) and the Solution Train. This is accomplished by participating in key Value Stream events such as PI Planning, Solution Demos, and Inspect and Adapt. This helps synchronize work, ensures alignment, and enables the Supplier's deliverables to integrate with the ART's outputs.
"Suppliers-regardless of their methods-are encouraged to participate in key Solution Train and ART events to ensure alignment and synchronization across the Value Stream." (Source: SAFe 6.0 Framework: Suppliers; SPC 6.0 Guide, "Building Solutions with Agile Product Delivery")