# Duplex conversation

**Source:** https://promtable.com/glossary/duplex-conversation

> Duplex conversation is the realtime-voice property where both parties (user + AI) can speak + listen simultaneously — supports natural interruption, backchanneling ('uh-huh'), and overlapping speech. The bar for voice agents to feel human in 2026.

---
Duplex conversation is the realtime-voice property where both parties (user + AI) can speak + listen simultaneously — supports natural interruption, backchanneling ('uh-huh'), and overlapping speech. The bar for voice agents to feel human in 2026.

Half-duplex voice (one party talks at a time, walkie-talkie style) feels robotic. Duplex flips this: continuous bidirectional audio, both parties can speak / interrupt / backchannel naturally. Engineering: audio streaming both ways simultaneously (WebRTC handles this natively), [[barge-in]] detection (stop AI playback when user starts speaking within ~100ms), backchanneling ('mm-hmm', 'right') without breaking the user's turn, turn-taking models that predict who should speak next. Realtime APIs (OpenAI, Gemini, ElevenLabs Conversational) ship duplex out of the box. The difference between voice that feels natural and voice that feels like calling a customer service IVR.

## When to use

- Voice agents in customer-facing apps.
- Phone agents, voice assistants.

## Common mistakes

- Building half-duplex voice apps in 2026 — feels dated immediately.
- Disabling barge-in for 'clean audio' — kills the natural feel.

## Related terms

- [barge-in](https://promtable.com/glossary/barge-in)
- [interrupt-handling](https://promtable.com/glossary/interrupt-handling)
- [voice-agent-platform](https://promtable.com/glossary/voice-agent-platform)

*Last updated: 2026-06-01*
---

Original page: https://promtable.com/glossary/duplex-conversation
Maintained by Promtable (https://promtable.com). Content: CC BY 4.0. Cite as "Promtable — https://promtable.com/glossary/duplex-conversation".
Contact: info@vibecodingturkey.com.