Calls Claude with an API key the customer owns, created in the Anthropic Console on their own account and billing. One variable, injected server-side at deploy time, so the key never reaches a repository or a browser. Claude may also be the model behind the coding agent that built the application, but this key is a different thing: it is the application’s own runtime access, spending the customer’s budget, so it belongs in a workspace of its own with a spend limit of its own. Usage is billed by Anthropic on the customer’s account.
Anthropic Claude's own documentation →ANTHROPIC_API_KEY