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An agent’s perceived quality is dominated by three choices: how it sounds (TTS), how it understands you (STT), and how it thinks (LLM).

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TTS — text to speech

Anyreach supports three TTS providers.

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Cartesia Sonic-3

The default and recommended choice for most use cases. Strong points: low latency, large voice catalog, expressive emotion control.

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ElevenLabs

Best for premium-sounding voices and voice cloning. Models: eleven_turbo_v2, eleven_turbo_v2_5 Trade-off: slightly higher latency than Cartesia in our measurements; usually worth it if you’ve cloned a brand voice.

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LiveKit Inference

Pass-through to any TTS available through LiveKit’s inference plane. Specify the model string explicitly. Useful if you have a contract with a provider not natively supported.

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STT — speech to text

Pick Deepgram nova-3-general for English-only agents. Pick Gladia solaria-1 when callers may switch languages mid-utterance (common in customer support). Use Anyreach Default if you don’t want to think about it.

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LLM — the model that drives the conversation

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How to choose

  • Default: gpt-4o (Azure) — best quality-per-latency trade-off for most use cases
  • Lowest latency: Cerebras llama-3.3-70b — sub-second time to first token, good for high call volumes where latency dominates UX
  • Highest quality reasoning: gpt-4.1 — pick when the agent needs to follow complex multi-step instructions or reason about KB content carefully
  • Compliance: prefer Azure OpenAI variants if you have data-residency requirements

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Stacks, fallbacks, and output format

A couple of structural choices apply across the stack:
  • Stack type. An agent uses either an stt_llm_tts pipeline (separate speech recognition, LLM, and speech synthesis) or a realtime stack. Most agents use the pipeline stack.
  • Fallbacks. Each of STT, LLM, and TTS accepts a model fallback list plus an on_failure policy (attempt_timeout, max_retry, retry_interval). If the primary model errors or times out, Anyreach fails over to the next model in the list.
  • Audio output format. TTS output format is set per channel — for example ElevenLabs emits pcm_8000 for telephony. You normally don’t touch this; the platform picks a sane format per channel.
Provider-specific extras worth knowing: Deepgram supports keywords/keyterms boosting (disabled in multi-language mode), and Gladia supports code-switching and a processing region (us-west/eu-west).

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Latency budget

A natural-feeling conversation needs end-to-end response latency under ~800ms. Latency stacks roughly as:
If your agent feels sluggish, the LLM is usually the culprit. Try Cerebras Llama before tuning anything else.

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Where to set this

All of these live in the Purpose & Personality section (voice + language) and Advanced Instructions section (model overrides) on the agent edit page.