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Conversation behavior

The Engine tab (labeled Behavior in the agent builder) controls how your agent handles the timing and pacing of a live phone call — interruptions, silence and pauses. Set this in the agent builder at /agent/setup.

The prompt and messages are on the Agent tab

The system prompt, the greeting, and the end / fallback / busy / voicemail messages are configured on the Agent tab, not here. This tab is purely about how the agent paces a call, not what it says. See the agents overview.

Barge-in and interrupts​

The Behavior tab The Behavior tab: interruption settings (barge-in, stop-TTS-on-interrupt, sensitivity) and silence detection.

Barge-in lets the caller interrupt the agent mid-sentence. Two related controls govern it:

  • Allow barge-in — whether the caller can interrupt at all.
  • Stop TTS on interrupt — whether the agent immediately stops speaking when interrupted.
  • Interrupt sensitivity — how easily an interruption triggers (low / medium / high). Higher sensitivity makes the agent yield quickly, which feels responsive but can trip on background noise; lower sensitivity holds its turn but can feel like it's talking over the caller.

Tune this to your callers' environment.

Voice-activity-detection padding​

The VAD settings shape turn-taking by detecting when speech starts and stops:

  • Speech detection padding (prefix_padding_ms) — how much audio before detected speech to keep, so the start of a word isn't clipped.
  • Silence duration (silence_duration_ms) — how long the caller must be silent before the turn is considered complete.

Response delay​

Response delay (response_delay_ms) inserts a brief pause before the agent replies, so it doesn't jump in the instant the caller stops — a small delay sounds more natural and avoids stepping on a caller who's only pausing.

Silence handling​

These settings decide what the agent does when the caller goes quiet — the silence timeout, the maximum silence duration, and the maximum silence count (how many times the agent re-prompts before ending). Sensible values keep dead air from making the call feel broken without ending it too soon.

Filler words​

Enable filler words to let the agent use natural conversational sounds and brief acknowledgements during pauses and turn-taking, and optionally provide your own list. These small touches make the agent feel more human and less robotic.

Memory and post-call analysis​

The Engine tab also exposes a few cross-cutting toggles:

  • Call history memory — let the agent recall previous calls with the same contact.
  • Auto-summarize and sentiment analysis — opt-in post-call analysis (also surfaced on the Guardrails tab).
tip

Pacing only really shows up in voice. Confirm barge-in, silence handling and filler words in the voice test at /agent/interface, since timing is hard to judge on paper.

Next steps​