createOAuthBackend
fun createOAuthBackend(tokens: TokenSource, tools: List<AgentTool> = BuiltinTools, approver: ToolApprover = ToolApprover.AlwaysApprove, instructions: String = ""): ChatBackend(source)
The backend for a signed-in profile: every turn takes a fresh access token from tokens (refreshing as needed) and adds the provider's account headers.