Sierra launched fleming-1 on October 7, 2026, a mannequin designed to detect when the caller on a telephone name is one other AI agent. The corporate described the discharge as an replace to the constellation of fashions behind brokers constructed on its platform.
Sierra mentioned the query corporations face when the telephone rings has shifted from who is asking to what’s calling. The corporate first encountered the problem in 2025, when brokers constructed on Sierra began calling brokers constructed on Sierra in healthcare. With private brokers comparable to Muse and Intuition taking off, Sierra mentioned, a big share of the calls corporations obtain may come from AI appearing on behalf of customers.
How Fleming-1 Detects Agent Callers
In keeping with Sierra, fleming-1 analyzes a caller’s speech in actual time, scoring the audio for indicators that it was generated by AI. The mannequin seems to be past how a voice sounds to a human listener, assessing whether or not the voice on the opposite finish is artificial whereas the decision continues to be occurring.
Sierra mentioned telling an artificial voice from a human one over the telephone is getting more durable. Background noise, muffled audio, and a nasty connection can obscure the clues, whereas AI voices hold bettering.
Sierra flags the calls fleming-1 identifies as possible AI. The corporate mentioned the mannequin is tuned to be conservative by default in order that actual folks don’t inadvertently get flagged, and the enterprise decides what occurs subsequent.
The Caller ID Comparability
Sierra framed the mannequin via the historical past of Caller ID, which BellSouth launched in Memphis, Tennessee, in 1988. Caller ID by no means instructed you whether or not to select up, and Sierra mentioned fleming-1 works the identical means: it’s for corporations to resolve how they wish to deal with such calls.
The corporate mentioned its beginning precept is that corporations ought to know what is asking. As examples of what companies would possibly do with that info, Sierra mentioned a financial institution would possibly wish to add a verification step when the caller is an agent, and an organization with excessive name quantity would possibly begin by measuring how usually it occurs.
Sierra mentioned some automated callers might be fraudsters testing account safety at scale, whereas others might be prospects who handed off a chore to an agent, or individuals who depend on text-to-speech.
Sierra mentioned Caller ID ended up on each telephone as a result of folks discovered it helpful, and that it believes the identical might be true of understanding when an agent is asking.
Relationship to Private Agent Protocol
The launch got here sooner or later after Sierra introduced Private Agent Protocol on October 6, 2026, an open customary Sierra and Meta are creating with trade companions Genesys, Intuition, Rocket, Shopify, Stripe, and Walmart that defines how private brokers work together with companies. When an agent makes use of the protocol, the corporate is aware of it’s an agent and who it’s appearing for. Sierra famous that some brokers might not respect the protocol.
Sierra described the very best case as an agent that claims who it’s, which is what the protocol is for, with fleming-1 overlaying the calls the place that doesn’t occur. Sierra plans to publish the protocol’s v0.1 specification later in October 2026, host design workshops with events, and publish a reference implementation to assist builders get began.
Voice and the Constellation Structure
fleming-1 applies to a voice channel Sierra introduced on October 9, 2024, when the corporate mentioned its AI brokers can choose up the telephone. Sierra mentioned these brokers combine with present call-center platforms, can sit in entrance of or behind conventional IVR techniques, and escalate to human groups with AI-generated summaries when a state of affairs requires an individual to intervene. Sierra’s Agent OS permits an organization to construct an agent as soon as and deploy it throughout channels, together with chat and telephone.
The mannequin additionally joins an structure Sierra detailed in a December 3, 2025 put up: brokers constructed on Sierra are assembled from 15+ frontier, open-weight, and proprietary fashions, every chosen for the job to be executed. Sierra mentioned it runs task-specific evaluations and invests in fine-tuned fashions the place off-the-shelf fashions fail to satisfy its constraints.
Sierra mentioned fleming-1 works with any voice agent constructed on Sierra and requires solely that the enterprise flip it on.
