Calls Gemini through an API key the customer owns, created in Google AI Studio on their own Google account and billing. One variable: the key, injected server-side at deploy time, so it never reaches a repository or a browser. This is also where an app built against a hosted AI gateway lands: point the same calls at the Gemini API with a key the customer holds, and the feature keeps working with no platform in the middle. Usage is billed by Google on the customer’s account, so set a spend limit in the console before the first deploy, not after the first invoice.
Google Gemini's own documentation →GEMINI_API_KEY