LLM

OpenAI GPT LLM for Bolna AI voice agents

OpenAI GPT models write your Bolna voice agent's replies. gpt-5.4-mini is the recommended default, with fast first tokens, function calling and low cost.

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Official Documentation

At a glance

How OpenAI fits in the stack

Best for

Reasoning, policy handling, tool use, and response generation.

Use this layer when

You want to tune quality, cost, latency, or function-calling behavior.

Connects to

Transcribed caller input upstream and voice or actions downstream.

Voice Stack

The LLM is the reasoning layer

This provider decides how the agent interprets intent, selects next actions, calls tools, and formulates responses. It is the decision engine inside the voice stack.

TelephonyPhone Network

→

STTListener

→

LLMReasoning

→

TTSVoice

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ToolsActions

Last updated 11 October 2026

What is OpenAI used for in a Bolna voice agent?

OpenAI's GPT models are the LLM in a Bolna voice agent: they understand what the caller said, decide the next reply and call your tools, and gpt-5.4-mini is Bolna's default recommendation for its low time to first token and cost. Pick OpenAI when you want the simplest setup and the models that sit inside Bolna's flat per-minute rate.

How do I set up OpenAI with Bolna?

Open your agent in Agent Studio at platform.bolna.ai and go to the Intelligence tab.
Under Choose LLM model, set the provider to OpenAI and the model to gpt-5.4-mini.
In Model Parameters, keep the token limit around 150 and reasoning effort at the lowest setting for fast replies.
Optional: connect your own key at platform.bolna.ai/auth/openai to bill the LLM to your OpenAI account.

The OpenAI setup guide in the Bolna docs covers every model, reasoning effort values and the API config.

Which GPT models does Bolna support?

Model	Context	Best for on Bolna	On the flat rate
`gpt-5.4-mini`	400K tokens	Most voice agents. Recommended: fastest time to first token, lowest cost	Yes
`gpt-5.6-luna`	1M tokens	Fast, low-cost everyday agents on the newest generation	Yes
`gpt-5.6-terra`	1M tokens	High-volume production agents, balanced quality and cost	No
`gpt-5.4`	1M tokens	General-purpose production agents	No
`gpt-5.6-sol`	1M tokens	Hardest multi-step reasoning	No
`gpt-5.5`	1M tokens	Most demanding reasoning and quality	No

gpt-4.1, gpt-4.1-mini and gpt-4o are still available for agents already built on them. Models off the flat rate are billed by usage; see pricing.

What can you build with OpenAI and Bolna?

Hindi and Hinglish calling agents. Pair gpt-5.4-mini with Sarvam text-to-speech and Sarvam speech-to-text, the combination the Bolna docs suggest for Indian languages.

Appointment booking and reminders. Function calling lets the agent check and book slots or update a record while the caller is on the line.

Lead qualification at scale. gpt-5.4-mini keeps replies quick and costs low across large outbound batches.

Complex support or financial calls. Move to gpt-5.4, gpt-5.5 or gpt-5.6-sol when the agent has to reason through several steps.

FAQ

OpenAI on Bolna: frequently asked questions

Use gpt-5.4-mini for most agents. Step up to gpt-5.6-luna or gpt-5.6-terra for newer models at moderate cost, or gpt-5.6-sol and gpt-5.5 for the hardest tasks. Avoid gpt-5.5-pro on live calls, as its latency is too high.

Yes. The Bolna docs recommend gpt-5.4-mini as the LLM for Indian-language agents, paired with Sarvam for speech-to-text and text-to-speech.

Yes. Connect it at platform.bolna.ai/auth/openai. The LLM cost is then charged to your OpenAI account instead of your Bolna wallet.

GPT-5 models accept only a temperature of 1, and any other value fails with a 400 error. Make the agent consistent through the prompt instead, with exact wording, a sentence limit and a fallback line.

Other providers in this layer

LLM

Anthropic

Anthropic Claude writes your Bolna voice agent's replies. Use claude-sonnet-5 for most agents, or claude-haiku-4-5 for faster, high-volume calls.

LLM

Azure OpenAI

Azure OpenAI runs GPT models for your Bolna voice agent inside your own Azure account, for teams that need regional data residency and private networking.

LLM

DeepSeek

DeepSeek V4 runs the conversation in a Bolna voice agent at low cost per token. deepseek-v4-flash suits high-volume calls, with a 1M token context window.

Browse this layer

Keep exploring the voice stack

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Large Language Models

The LLM is the brain of your voice agent. It understands what callers say and decides how to respond. Bolna lets you switch between models like GPT-5.4 mini, Claude and DeepSeek by changing the provider and model in your agent LLM settings, so you can tune for speed, cost or reasoning depth.

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Telephony

Telephony providers connect your voice agents to the phone network so they can make and receive real calls. Bolna supports managed integrations with major carriers as well as bring-your-own-carrier via SIP trunking, giving you full control over call routing, number provisioning, and cost.

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Speech-to-Text

Speech-to-text converts what callers say into text that your LLM can process. Transcription accuracy and latency directly affect how natural a conversation feels. Bolna supports streaming STT providers optimized for telephony audio, including specialized models for Indian languages.

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Text-to-Speech

Text-to-speech turns your agent responses into spoken audio. Voice quality shapes how callers perceive your brand. Flat, robotic speech kills trust while natural, expressive voices build it. Bolna integrates with the fastest TTS providers so responses sound human and arrive without awkward pauses.

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Tools & Workflows

Tools let your voice agents take action during a call, not just talk. Book a calendar slot, look up an order through your own API, push a lead into your CRM, or trigger a multi-step automation in Zapier. These integrations turn voice agents from answering machines into workflow engines.

See where OpenAI fits in your production workflow

Use the demo to walk through provider selection, stack tradeoffs, and the exact workflow you want Bolna to automate.

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