Voice

telnyx-acp set voice.greeting "Hello, how can I help?"
telnyx-acp set voice.harness true

support-agent/
├── agent.json                                         ◀
├── instructions.md
└── .telnyx/                        written by deploy
    ├── index.ts                                       ◀
    ├── telnyx.toml
    ├── telnyx-env.d.ts
    └── package.json

@telnyx/acp/                      the package
├── managed/
│   ├── index.ts
│   ├── agent.ts
│   ├── model.ts
│   ├── memory.ts
│   ├── tools.ts
│   ├── mcp.ts
│   ├── voice.ts                                       ◀
│   ├── direct-turn.ts                                 ◀
│   └── filler.ts                                      ◀
├── channels/
│   ├── index.ts
│   ├── phone.ts
│   ├── email.ts
│   ├── web.ts
│   └── wire.ts
├── synth/
│   ├── index.ts
│   ├── code-entry.ts
│   └── vendor.ts
└── spec/
    ├── schema.ts
    ├── model.ts
    ├── phone.ts
    ├── project.ts
    └── io.ts

voice is written by set voice.*, or its greeting by the wizard when the project has a number. It becomes spec.voice in .telnyx/index.ts, and four functions in managed/voice.ts read it:

// managed/voice.ts
export function answerOptions(spec) {
  const v = spec.voice ?? {};
  return { eager: v.eager ?? true, ...(v.bargeIn !== undefined ? { bargeIn: v.bargeIn } : {}),
           ...(v.keypressInterrupts !== undefined ? { keypressInterrupts: v.keypressInterrupts } : {}) };
}
export function speechOptionsFor(spec) {
  const v = spec.voice ?? {};
  return { recognizer: { ...(v.stt ?? {}) },
           synthesizer: { voice: v.tts?.voice ?? DEFAULT_TTS_VOICE, ...(v.tts?.voiceSettings ? { voiceSettings: v.tts.voiceSettings } : {}) } };
}
export function defaultGreeting(spec) {
  return spec.voice?.greeting?.trim() || `Hi, this is ${spec.name.replace(/[-_]+/g, " ")}. How can I help?`;
}
export function harnessOnCalls(spec) {
  return spec.voice?.harness === true;
}

answerOptions is what the voice class passes to the voice() mixin’s answer when the media socket opens, as The Call Webhook shows.
speechOptionsFor feeds speechProvidersFor, which builds the STT and TTS providers.
defaultGreeting is returned by the voice class’s greeting, and spoken when the call is answered.
harnessOnCalls chooses the turn engine, the direct engine in managed/direct-turn.ts by default and the harness when voice.harness is true.

answerOptions(spec) sets the mixin’s call options.

eager is on unless voice.eager is false. A turn then starts on STT’s first guess that the caller has finished, and its audio is held until the guess is confirmed.
bargeIn and keypressInterrupts are passed only when voice sets them, and the mixin’s own defaults apply otherwise.

speechProvidersFor hands the speech options to the runtime SDK:

// managed/voice.ts
export function speechProvidersFor(spec, make = telnyxSpeechProviders) {
  return make(speechOptionsFor(spec));
}

telnyxSpeechProviders(options) is the Telnyx STT and TTS pair from @telnyx/edge-runtime/voice. Its recognizer option tunes STT and its synthesizer option tunes TTS. Both reach Telnyx over the runtime’s own connection, with no credential in the class. A fifth, fillerOptions in managed/filler.ts, reads voice.filler:

// managed/filler.ts
export function fillerOptions(spec) {
  const f = spec.voice?.filler;
  if (f === false) return undefined;
  return { afterMs: f?.afterMs ?? DEFAULT_FILLER_AFTER_MS,
           phrases: f?.phrases?.length ? f.phrases : DEFAULT_FILLER_PHRASES,
           maxPerCall: f?.maxPerCall ?? 0 };
}

fillerOptions is what the voice class’s reply uses to say one short phrase when the model is slow to start. DEFAULT_FILLER_AFTER_MS is 700, and the default phrases are “One moment.”, “Let me check that for you.” and “Sure, just a second.”. The Voice Loop is where the phrase is spoken. Voice is the user-facing side of the same fields.

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