> ## Documentation Index
> Fetch the complete documentation index at: https://dialnexa.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# How DialNexa Voice AI Works

> Learn how DialNexa voice AI turns caller audio into transcription, model responses, synthesized speech, actions, and Call History evidence.

DialNexa Voice AI works by moving each call through a loop: receive audio, transcribe speech, decide the next response with the configured agent version, optionally call tools, synthesize speech, and store the result in Call History.

<Tip>
  If you can follow the loop, you can debug most calls without guessing. Guessing is dramatic, but logs are cheaper.
</Tip>

## How DialNexa Voice AI Works During A Call

<Steps>
  <Step title="Caller audio arrives">
    Audio enters through a Plivo number, SIP trunk, web call, batch call, workflow call node, API call, or test call.
  </Step>

  <Step title="The transcriber listens">
    Deepgram or Soniox converts speech into text. The transcript is later shown in Call History as realtime and, where available, post-call text.
  </Step>

  <Step title="The agent decides">
    The published agent version supplies prompt, system prompt, language, LLM model, dynamic variables, functions, and safety settings.
  </Step>

  <Step title="Tools may run">
    Functions and integrations can end a call, book a calendar event, call an API, send a WhatsApp message, send an email, or trigger another configured action.
  </Step>

  <Step title="The voice speaks">
    ElevenLabs or Cartesia synthesizes the response. Audio Cache can reduce latency for repeated exact phrases.
  </Step>

  <Step title="Evidence is saved">
    Call History receives status, summary, transcript, recording URL, post-call analysis, transfer details, Audio Cache data, and metadata.
  </Step>
</Steps>

## Provider Work At Each Runtime Layer

| Layer            | Provider choices                                                                                                                                                         | Why users should care                                                                            |
| ---------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------ |
| Audio route      | Plivo, SIP trunking, web call.                                                                                                                                           | Changes number ownership, audio quality, routing, and whether phone network issues are involved. |
| Speech to text   | Deepgram or Soniox.                                                                                                                                                      | Changes transcript accuracy, language fit, turn timing, and Response Eagerness support.          |
| Reasoning        | OpenAI, Google, or Groq. Speech-to-Speech agents use a realtime model (OpenAI gpt-realtime-2 or Gemini 3.1 Flash Live) that replaces the separate transcriber and voice. | Changes instruction following, latency, structured behavior, and fallback strategy.              |
| Text to speech   | ElevenLabs or Cartesia.                                                                                                                                                  | Changes voice identity, pronunciation, streaming behavior, and cache compatibility.              |
| External actions | Wati, Resend, Custom Functions, webhooks.                                                                                                                                | Changes what the call or workflow can do outside DialNexa.                                       |

## Runtime Input Versus Saved Evidence

Do not confuse what starts a call with what proves it happened.

| Layer         | Examples                                                                                          | Where reviewed                                               |
| ------------- | ------------------------------------------------------------------------------------------------- | ------------------------------------------------------------ |
| Input         | Recipient number, metadata, dynamic variables, workflow lead variables, selected outbound number. | Batch setup, workflow lead, API request, or test call modal. |
| Agent version | Prompt, model, voice, transcriber, welcome mode, functions, post-call fields, fallback settings.  | Agent builder and version history.                           |
| Call result   | Status, duration, sentiment, end reason, transcript, summary, recording, extracted fields.        | Call History and call detail page.                           |

## What Can Change A Reply

The same caller sentence can lead to different behavior when these settings change.

<CardGroup cols={2}>
  <Card title="Prompt and system prompt" icon="message-square" href="/docs/agents/prompts-and-welcome-messages">
    Instruction wording decides goal, boundaries, escalation rules, and acceptable answers.
  </Card>

  <Card title="Dynamic variables" icon="braces" href="/docs/agents/dynamic-variables">
    Caller-specific values can change greeting, eligibility, due date, location, or transfer destination.
  </Card>

  <Card title="Functions" icon="settings" href="/docs/agent-settings/functions">
    Tools add actions the model can call during the conversation.
  </Card>

  <Card title="LLM and temperature" icon="brain" href="/docs/voice-ai/llms-and-conversation-behavior">
    Model choice and temperature affect reasoning style and consistency.
  </Card>
</CardGroup>

## Debug By Layer

<AccordionGroup>
  <Accordion title="Audio sounds bad">
    Check recording quality, phone path, SIP trunk behavior, web microphone, and Denoising Mode.
  </Accordion>

  <Accordion title="Transcript is wrong">
    Check language, Deepgram or Soniox selection, background noise, and whether the caller spoke over the agent.
  </Accordion>

  <Accordion title="Transcript is right but answer is wrong">
    Check prompt, dynamic variables, functions, knowledge source, model family, and temperature.
  </Accordion>

  <Accordion title="Answer is right but late">
    Check Response Eagerness, Audio Cache, fallback LLM, function latency, and integration action placement.
  </Accordion>
</AccordionGroup>

## Related Reading

<CardGroup cols={2}>
  <Card title="Speech To Text" icon="file-text" href="/docs/voice-ai/speech-to-text-and-transcription">
    Understand Deepgram and Soniox behavior.
  </Card>

  <Card title="LLM Behavior" icon="brain" href="/docs/voice-ai/llms-and-conversation-behavior">
    Tune reasoning and fallback behavior.
  </Card>

  <Card title="Provider Selection Guide" icon="sliders-horizontal" href="/docs/voice-ai/provider-selection-guide">
    Choose the complete provider stack.
  </Card>

  <Card title="Text To Speech" icon="volume-2" href="/docs/voice-ai/text-to-speech-and-voices">
    Choose ElevenLabs or Cartesia.
  </Card>

  <Card title="Integrations" icon="plug" href="/docs/dashboard-integrations/overview">
    Understand Wati, Resend, and workflow actions.
  </Card>
</CardGroup>