You become a provider when you turn a system into a high-risk one.
Modify the intended purpose of an AI system already on the market, a general-purpose model included, so that it becomes high-risk under Article 6, and Article 25(1)(c) makes you the provider. Substantially modify an already-high-risk system and Article 25(1)(b) does the same, and building your own system on top of a model can make you an Article 3 provider outright. Provider obligations are heavy: technical documentation, conformity assessment, the Articles 9 to 15 stack.
