Configuration: Add default parameters for STT/TTS

[mdshamoon]

Summary

Currently, STT and TTS configs require users to explicitly provide all parameters. We should add sensible defaults for all parameters except the core input attributes:

• STT: audio input (the speech) should remain required, everything else should have defaults
• TTS: text input should remain required, everything else should have defaults

Proposed Defaults

STT (STTLLMParams)

Param	Current	Proposed Default
provider	required	"google"
model	required	"gemini-2.5-pro"
instructions	None	None (already optional)
input_language	None	"auto"
output_language	None	None (already optional)
response_format	None	"text"
temperature	None	None (already optional)

TTS (TTSLLMParams)

Param	Current	Proposed Default
provider	required	"google"
model	required	"gemini-2.5-pro"
voice	required	"Puck"
language	required	"en"
response_format	"wav"	"wav" (already has default)

Goal

Allow minimal API calls like:

STT:

{
  "query": { "input": { "type": "audio", "content": { "format": "base64", "value": "..." } } },
  "config": {
    "blob": {
      "completion": { "type": "stt", "params": {} }
    }
  }
}

TTS:

{
  "query": { "input": "Hello world" },
  "config": {
    "blob": {
      "completion": { "type": "tts", "params": {} }
    }
  }
}

Files to Update

• backend/app/models/llm/request.py — STTLLMParams, TTSLLMParams, CompletionConfig discriminator logic
• May need provider-specific default resolution in backend/app/services/llm/providers/gai.py and oai.py

[Prajna1999]

1. How will Glific create and maintain default configs (config_id/version through POST endpoint) way for all orgs? The current setup expects separate default configs for each project/org level even if the configs would be virtually identical.
2. If that's the pathway of storing config_id, version in db( it's far better way to make LLM_CALL since its traceable and have versions) and 4 months down the line the defaults change how would the older defaults be migrated at Glific's end?
   @mdshamoon

[mdshamoon]

We are not maintaining configs on our end for this. We are just sending the config blog for stt tts. So it will be just a one of request for any org from Glific.

[kartpop]

@mdshamoon do you want to put "en" as the default language? gemini-2.5-pro allows not putting any language, it will autodetect from the script. Although as I understand from @Prajna1999 other providers like sarvam need that param and don't autodetect - I don't agree that there should be a hardcoded language like en in such cases, because the TTS script will be other than English in most scenarios.

[mdshamoon]

[@mdshamoon](https://github.com/mdshamoon) do you want to put "en" as the default language? gemini-2.5-pro allows not putting any `language`, it will autodetect from the script. Although as I understand from [@Prajna1999](https://github.com/Prajna1999) other providers like sarvam need that param and don't autodetect - I don't agree that there should be a hardcoded language like `en` in such cases, because the TTS script will be other than English in most scenarios.

@kartpop if we are making gemini as default can we omit language in case if its not passed in the API

[Prajna1999]

Keeping Kore the default voice