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Every Bolna agent uses three provider categories: a transcriber (speech-to-text), an LLM (language model), and a synthesizer (text-to-speech). This page helps you choose the right combination for your use case.
Provider model lineups change frequently. The specific model names here are current examples — always check the relevant LLM provider page or the provider’s own docs for the latest recommended model.

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Quick Decision Guide

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Transcribers (speech-to-text)

Language support is the primary selection factor — most transcribers are optimized for specific language families. Key settings: endpointing (silence detection), language (always set explicitly — auto-detection adds latency), encoding / sampling_rate (must match your telephony provider). For the exact provider and model values each takes, see Create Agent.

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LLMs (language models)

Quality tier and latency are the primary selection factors. See each provider’s page for current model names. LLM provider pages:

OpenAI

GPT-5.4-mini, GPT-5.4, GPT-5.5

Anthropic

Claude Sonnet 5, Haiku 4.5, Opus 4.8

Google Gemini

Gemini 2.5 Flash, Gemini 3.x

Azure OpenAI

GPT-5.x via Azure infrastructure

DeepSeek

DeepSeek V4 Flash, V4 Pro

OpenRouter

Unified gateway — all providers

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Synthesizers (text-to-speech)

Latency and language are the primary selection factors. Always enable stream: true. Key settings: stream: true (always enable), buffer_size (100–250 chars typical), audio_format (must match your telephony provider). For the exact provider and model values each takes, see Create Agent.
gemini appears as a synthesizer provider but cannot currently be used — no Gemini TTS model resolves.

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Telephony providers