### Answer This error indicates that when using a custom STT configuration with Deepgram as the provider, the specific language you've selected for your agent isn't supported by that custom setup. [(1) ]() [(2) ]() [(3) ]() [(4) ]() When you set

stt_mode

to

custom

, you must provide a

custom_stt_config

object specifying the provider (e.g.,

"deepgram"

or

"azure"

) . However, not all custom STT providers support all the languages available in Retell's default

fast

or

accurate

modes. To resolve this, you have a few options: 1. **Switch to a supported STT mode**: Change

stt_mode

from

"custom"

to either

"fast"

or

"accurate"

, which have broader language support. 2. **Change the language**: If you need to use Deepgram specifically, select a language that Deepgram supports for your custom configuration. 3. **Use a different custom provider**: If Azure supports your required language, you could switch the custom STT provider to

"azure"

. The

language

setting specifies what language the speech recognition operates in (e.g.,

en-US

,

zh-CN

,

pt-PT

) , and this must be compatible with your chosen STT provider.

​ To learn more, see the sources I considered: [[1] Get Agent Versions](https://docs.retellai.com/api-references/get-agent-versions) [[2] Update Voice Agent](https://docs.retellai.com/api-references/update-agent) [[3] Create Voice Agent](https://docs.retellai.com/api-references/create-agent) [[4] Get Voice Agent](https://docs.retellai.com/api-references/get-agent) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.