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Release notes

Telnyx Ultra Voices Upgraded With Better Naturalness and Multi-Lingual Support

15, Sep 2026

Telnyx Ultra voices have been upgraded with improved naturalness and stronger multi-lingual support. An auto language boost selector is now available in Mission Control for AI Assistants, and older voices that were not upgraded now carry a DEPRECATED tag.

What's new

  • Improved naturalness: All upgraded Ultra voices deliver more natural-sounding speech across their supported languages, with better prosody and intonation.
  • Better multi-lingual support: Ultra voices now handle code-switching and multi-lingual scenarios more accurately, with clearer pronunciation across language transitions.
  • Auto language boost selector: When configuring an AI Assistant with an Ultra voice, Mission Control now provides an automatic language boost selector, similar to the one available for Minimax voices. This sets the language_boost parameter without requiring a manual API call.
  • DEPRECATED voice tagging: Some older Ultra voices that were not upgraded now show a DEPRECATED tag in both the portal and the API. These voices remain selectable and functional, but will not receive future upgrades.

Why it matters

Voice AI agents live or die on how real they sound. A caller who notices the voice is synthetic loses trust in the conversation, and multi-lingual use cases have historically been where TTS engines break down first, dropping into accent drift or mispronunciation mid-sentence. Upgrading Ultra's core naturalness and multi-lingual handling addresses both failure modes in a single pass. The auto language boost selector removes the most common configuration error, teams no longer need to manually specify a language hint for every assistant. And by clearly marking deprecated voices, Telnyx makes it obvious which voices are current and which to migrate away from, without forcing an immediate switch.

Example use cases

  • Customer support agents serving multi-lingual regions where callers may switch between languages mid-conversation.
  • Global voice applications that need consistent voice quality across 44 languages without tuning per-language parameters.
  • Teams migrating from deprecated voices to upgraded ones, with full backward compatibility during the transition.

Getting started

  1. In Mission Control, navigate to AI and select your assistant.
  2. Go to the Voice tab and select a Telnyx Ultra voice.
  3. Use the new auto language boost selector to set the target language for your use case.
  4. To identify deprecated voices, look for the DEPRECATED tag in the voice selector or filter by status in the API.

Learn more in the Telnyx Ultra TTS docs or the TTS API docs.