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The agent transcribes any supported language automatically and code-switches natively, so a caller can move between, say, English and Spanish mid-sentence with no configuration. When you know which language(s) a line serves, set input.language_codes to steer transcription toward them for a bit more accuracy. Omit it for automatic detection. Set it when you create or update the agent.
  • Global or mixed-language line: omit language_codes. The agent detects and code-switches on its own.
  • Region-specific line: pin the language(s) you expect. A Spanish support line set to ["es"] won’t drift into look-alike transcriptions of another language.

Supported language codes

Universal-3.5 Pro Streaming code-switches across all 18 languages below. Pass any of these codes in language_codes:
Set the input language and a matching voice together: transcribing Spanish while replying in an English voice is jarring. The example above pairs ["es"] with the Spanish voice lola.
language_codes is applied when the speech-to-text connection opens; a mid-session change takes effect on the next reconnect, not the current turn. For how native code-switching works, see Multilingual transcription.