feat(ultravox): support server-side external TTS voices via externalVoice - #6850
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ssgutierrez42 wants to merge 5 commits into
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feat(ultravox): support server-side external TTS voices via externalVoice#6850ssgutierrez42 wants to merge 5 commits into
ssgutierrez42 wants to merge 5 commits into
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longcw
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Aug 14, 2026
longcw
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looks good to me. something nit:
| voice : str | UltravoxVoice | ||
| The voice to use for TTS. | ||
| external_voice : dict[str, Any], optional | ||
| The Ultravox configuration for an external TTS provider. Mutually exclusive with ``voice``. |
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should we log a warning when both voice and external_voice are given?
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external_voice cannot work with output_medium="text" too?
| "selectedTools": parse_tools(list(self._tools.function_tools.values())), | ||
| } | ||
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| if is_given(self._realtime_model._opts.external_voice): |
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should we skip a given but empty external_voice or raise an error, or fallback to voice?
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Summary
external_voiceparameter toRealtimeModelto pass an external TTS provider configuration (e.g. ElevenLabs, Cartesia, MiniMax) through Ultravox's/callsAPI via theexternalVoicefieldexternal_voiceis provided, theexternalVoicekey is sent in the/callspayload instead ofvoice, keeping the model in voice mode so native barge-in is preserveddict[str, Any]to accommodate all provider variants without coupling to Ultravox's evolving schemaWhy
Ultravox's
output_medium="text"path (text-out half-cascade) cannot support barge-in — the plugin's interruption signal (playback_clear_buffer) only fires in voice mode, and Ultravox exposes no input-side speech-onset event. Server-sideexternalVoicesolves this by having Ultravox call the TTS provider directly, keeping the session in voice mode with working interruption.Changes
_UltravoxOptions: addedexternal_voice: NotGivenOr[dict[str, Any]]RealtimeModel.__init__: addedexternal_voicekeyword argument (defaults toNOT_GIVEN), documented as mutually exclusive withvoice/callspayload construction:voiceis now conditional — whenexternal_voiceis given,externalVoiceis sent insteadReferences
/callsAPI: https://docs.ultravox.ai/api-reference/calls/calls-post