Sierra launched fleming-1 on October 7, 2026, a model designed to detect when the caller on a phone call is another AI agent. The company described the release as an update to the constellation of models behind agents built on its platform. Sierra said the question companies face when the phone rings has shifted from who is calling to what is calling. The company first encountered the issue in 2025, when agents built on Sierra started calling agents built on Sierra in healthcare. With personal…