Sierra launches fleming-1 to detect AI agents calling by phone

Sierra released fleming-1 on October 7, 2026, a model that analyzes a caller's speech in real time to determine whether the caller is an AI agent rather than a human. The model works with any voice agent built on Sierra and is turned on by the business; it is tuned to be conservative by default so real people are not flagged.

• fleming-1 analyzes audio in real time to score whether a voice is synthetic
• The model works with any voice agent built on Sierra and requires only turning it on
• It is tuned to be conservative by default so real people are not flagged
• Launched October 7, 2026, a day after the Personal Agent Protocol announcement