Why does our AI phone agent talk over callers or cut them off mid-sentence?

Endpointing is a guess, not a fact

A voice agent does not know when you have finished a thought. It watches the audio stream, detects when speech energy stops, and starts a timer. When that timer expires without new speech, it treats your turn as complete and hands the transcript to the model. That timer is the single most consequential setting in a phone agent, and it is usually left at whatever the vendor shipped.

Better systems add semantic endpointing: they also look at whether the words so far form a complete thought. "My address is four twenty one" is grammatically finished but obviously incomplete, so the agent waits longer. That helps, but it never eliminates the underlying guess.

Different questions deserve different patience

The mistake is one silence threshold for the whole call. The right threshold depends entirely on what was just asked.

• Yes/no and confirmations. Short window. Callers answer fast, and waiting feels sluggish.
• Addresses, model numbers, spelled names. Long window. People read these in chunks with real gaps between them.
• Open-ended problem descriptions. Longest window. "Tell me what's going on" invites a pause while the caller organizes the story.
• Anything asked while the caller is outdoors or driving. Longer still, because ambient noise makes the detector trip early and late unpredictably.

Barge-in is the other half of the problem

Barge-in means the caller can start talking while the agent is still speaking, and the agent stops. Without it, every long prompt becomes a hostage situation. With it badly configured, the agent's own audio bleeds back through a speakerphone and it interrupts itself.

There are a small number of places to deliberately turn barge-in off: a required disclosure at the start of the call, or a safety instruction. Everywhere else, leave it on. If you find yourself writing prompts long enough that barge-in matters, the prompt is too long. This is the sort of thing an integration team tunes against real recordings rather than in a settings panel.

How to find it in your own recordings

Do not guess from a handful of calls. Pull the transcripts and look for caller turns that end mid-word or mid-number, and for calls where the caller repeats the same information twice in a row. Both are signatures of a threshold set too tight. The opposite signature is dead air followed by the caller saying "hello?" before the agent responds.

Call analysis makes this measurable across every call instead of anecdotal. Sort by the count of caller re-statements per call and the worst configurations surface immediately.