ConversationRelay

What it does

ConversationRelay takes live caller speech from phone calls, converts it to text, sends it to the language model you choose, and returns that model's replies as synthesized speech. It runs over a WebSocket API and includes speech-to-text, text-to-speech, Deepgram Flux turn detection, automatic language detection, and SSML tags for pacing and intonation. The output is a spoken phone conversation with the caller.

Teams use it to build voice agents for self-service support, lead qualification, appointment scheduling, and proactive reminders or callback options. A Studio Widget provides drag-and-drop flow design, while code builds use the WebSocket API with a TwiML <ConversationRelay> element. Its main distinction is bring-your-own-LLM and bring-your-own-TTS, plus adjustable interruption sensitivity for noisy environments.

It fits developers and teams already building on Twilio who want control over the model, voice, and conversation logic. Access requires a Twilio account. Code builds also need your own WebSocket server and LLM, and regulated-industry deployments such as HIPAA-eligible or PCI-compliant setups depend on how you architect and configure them.

What it can do

• Real-time speech-to-text for live caller audio
• Text-to-speech with natural pronunciation and SSML tags
• Bring-your-own-LLM orchestration over a WebSocket API
• Adjustable interruption handling for barge-in and noisy environments
• Automatic language detection and multilingual responses within a call
• Escalation to live agents and transcript storage via Conversational Intelligence

Works with

• Twilio Conversational Intelligence
• Twilio Studio Widget

Example workflows

Appointment reminder with callback

Input: a patient's appointment record. Steps: the system places an outbound call, the voice agent confirms the time and answers questions, and it routes to a live agent if asked. Output: a confirmed or rescheduled appointment and a stored transcript.

Lead qualification call

Input: an inbound caller asking about a service. Steps: the agent gathers contact details and needs, qualifies the lead against your criteria, and books a follow-up. Output: a qualified lead record and a scheduled sales call.

Before you choose

• Published latency figures (median under 0.5 seconds, 95th percentile under 0.725 seconds) come from internal benchmarks and may vary by model.
• Support plan response-time guarantees do not cover every product, and plan terms are billed separately from ConversationRelay usage.
• Regulated-industry use depends on how you architect and configure your deployment.

Listed under

• Support
• Voice and phone agents
• Appointment scheduling
• Conversational AI
• Customer support
• Developers
• Lead qualification
• Phone calls

Get started

Create a Twilio account, then build with the Studio Widget or the API and docs.

1. Create a Twilio account and open the Twilio Console.
2. Build a call flow in the Studio Widget or add a TwiML <ConversationRelay> element pointing to your WebSocket server URL.
3. Connect your chosen LLM and speech settings, then test the flow and review the onboarding guide and webhook security documentation.

Billing is usage-based. Consult Twilio's pricing page for current ConversationRelay meters and rates. Support plans are billed separately.

Source: twilio.com/en-us/support-plans, checked 29 Oct 2026. Prices can change; check before you buy.

Sources for this overview

Product pages, documentation, and pricing checked 29 Oct 2026. Each source supports part of the overview; availability and prices can change.

• Conversation Relay | Twilio ↗www.twilio.com
• Support Plans for Text, VoIP & Voice APIs - Twilio | Twilio ↗www.twilio.com

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Last checked 29 Oct 2026. Every field keeps its source and date; unknown means we couldn’t confirm it.