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Bolna supports multiple languages, letting you deploy voice agents globally. Language support is integrated across all components: transcription, LLM processing, and voice synthesis.
Bolna Languages Tab configuration showing English marked as the default language, with Dutch and Hindi alongside it

Language selection in the Languages Tab showing English as the default language, with Dutch and Hindi alongside it

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How Multilingual Agents Work

A multilingual agent can understand and respond in multiple languages within a single call. Here is how the pieces fit together:

Languages

Add languages in the Agent Tab. The Languages Tab shows the same set for per-language audio settings.

Per-Language Prompts

Each language gets its own prompt tab. Write a dedicated prompt for every language your agent supports.

Language Switching

A dropdown in the Languages Tab controls when the agent is allowed to switch mid-call.

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Setting Up Languages

Setting up a multilingual agent touches two tabs: languages are added, defaulted, and prompted per-language in the Agent Tab, and each language gets its own voice, transcription, and hand-in message in the Languages Tab. See the Agent Tab guide for the step-by-step walkthrough of adding, defaulting, and removing languages.

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Language Switching

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When the Agent May Switch

In the Languages Tab, the summary under the language strip — “Starts in English, can move to Hindi, Dutch when …” — ends in a dropdown that sets when a switch is allowed:
For exactly what counts as “the caller speaking another language” — and why a stray English word or a read-out order number won’t trip a switch — see How Language Switching Works. It’s best not to write language-switching instructions into your prompt; the system handles switching itself.

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Auto-Switching System Messages

Beyond the conversation itself, Bolna’s built-in system messages (user-online check, hangup, tool-call wait) also follow the agent’s active language automatically. See Auto-Switch Languages for the full guide.

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Per-Language Configuration

Each language you add gets its own independent configuration:
Canvas with English marked as the default language, Hindi and Dutch language tabs, prompt editor showing Personality and Identity sections

Canvas with English as the default language and Hindi and Dutch language tabs

Each language can use a different transcription and voice provider. For example, use Deepgram for English transcription and Sarvam for Hindi, or ElevenLabs for English voice and Sarvam for Hindi voice. Select a language in the Languages Tab to configure its providers independently.
Settings are independent per language. The agent name, hand-in message, transcription provider, and voice provider for Hindi do not affect English.

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Configuration Best Practices

A few configuration choices make a bigger difference than they might seem:
  • Give every language a distinct, native voice. Never reuse one language’s voice for another — an English voice on a Hindi or Tamil slot is one of the most common reasons an agent sounds “off” in that language, even when the words themselves are correct.
  • Match your TTS and transcription provider to the language. Coverage and quality vary by provider and language; if one provider sounds noticeably worse on a specific language, try a different provider for just that language slot rather than the whole agent.
  • Set the language switch trigger deliberately, rather than leaving it at the default. See When the Agent May Switch above for what each option changes.
  • Consider a graph agent for multi-stage multilingual flows. A graph agent’s conversation flow (the nodes and routing) stays identical across languages — only the spoken line inside each node changes per language — so one graph can cleanly serve every language your agent supports, instead of duplicating logic per language.
  • Keep temperature low for scripted, per-language lines. Once the wording is pre-written and the flow is deterministic, a lower temperature keeps the model from paraphrasing away from the exact lines you wrote — see Best Practices for Production-Grade Multilingual Prompts for more on writing those lines.

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Supported Languages

This is the full set of languages Bolna can be configured with, provider support permitting. Mid-call automatic detection — the engine that decides on its own whether a caller has switched — is tuned for English plus the ten Indian languages in this list; see How Language Switching Works for that narrower set.

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Writing Effective Multilingual Prompts

Use Native Script

Write prompts in the language’s native script, not phonetic English. “नमस्ते” not “Namaste”.

Include Accented Characters

Use proper accents for European languages. “Cómo estás?” not “Como estas?”
Read the full guide for writing prompts in non-English languages for native-script examples and detailed best practices.

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Multilingual Knowledge Bases

If your agent uses knowledge bases with non-English documents, enable multilingual support when creating the knowledge base. This supports 100+ languages, allowing your agent to retrieve information regardless of document or query language.
Learn more in the Knowledge Base documentation.

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Next Steps

Agent Tab

Add languages and configure per-language prompts

Languages Tab

Set up voices, transcription, and hand-in messages

How Language Switching Works

The decision engine behind mid-call switching, and what triggers it

Auto-Switch Languages

Auto-detect and switch system messages by language

Non-English Prompts Guide

Best practices for writing multilingual prompts

Multilingual Agent Quickstart

Build the same setup over the API instead