> ## Documentation Index
> Fetch the complete documentation index at: https://docs.upliftai.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Provider & model reference

The exact strings the config takes, tested by us end to end. Newer model ids that are not listed may exist and work — the assistant config doesn't necessarily block them, as we pass it to the provider APIs directly — but we update this page only after testing a model ourselves on real calls. An unlisted string that doesn't work fails at dial time, with a caller on the line.

Per-provider knobs, defaults, and BYOK keys are on the config tabs of [Create an assistant](/api-reference/assistants/create-an-assistant). What we'd pick: [Recommended stack](/voice-agents/assistants/recommended-stack).

## LLM

| `provider` | Tested models                                                     | Knobs                                          |
| ---------- | ----------------------------------------------------------------- | ---------------------------------------------- |
| `google`   | `gemini-2.5-flash` · `gemini-3.5-flash` · `gemini-3.1-flash-lite` | `thinkingBudget` (2.5) / `thinkingLevel` (3.x) |
| `openai`   | `gpt-5.4-nano` · `gpt-5.4-mini` · `gpt-4o-mini`                   | `reasoningEffort`, `verbosity`                 |
| `cerebras` | `gpt-oss-120b`                                                    | `reasoningEffort` (`low`/`medium`/`high`)      |
| `groq`     | `openai/gpt-oss-120b` · `openai/gpt-oss-20b`                      | —                                              |

`gemini-2.5-flash` is the fastest. `gemini-3.5-flash` is the good balance of intelligence and speed.

## STT

| `provider` | Tested models                                                                          | Knobs                                     |
| ---------- | -------------------------------------------------------------------------------------- | ----------------------------------------- |
| `soniox`   | `stt-rt-v4` (default) · `stt-rt-v5`                                                    | `language` hint (`ur`), `context` biasing |
| `deepgram` | `nova-3` (default) · `nova-2`                                                          | `language` (default `multi`)              |
| `openai`   | `gpt-4o-mini-transcribe` · `gpt-4o-transcribe`                                         | `prompt` biasing, `useRealtime`           |
| `groq`     | `whisper-large-v3-turbo` (default) · `whisper-large-v3` · `distil-whisper-large-v3-en` | `prompt` biasing                          |

## TTS

| `provider` | Voices                                                                                                                               | Knobs             |
| ---------- | ------------------------------------------------------------------------------------------------------------------------------------ | ----------------- |
| `upliftai` | 80+ voices tuned for Urdu and regional languages — pick a `voiceId` from the [voices gallery](/orator_voices), e.g. `helpdesk-agent` | `outputFormat`    |
| `openai`   | model `gpt-4o-mini-tts`, voices `alloy` · `ash` · `ballad` · `coral` · `echo` · `fable` · `nova` · `onyx` · `sage` · `shimmer`       | —                 |
| `soniox`   | model `tts-rt-v1`, voices e.g. `Maya`                                                                                                | `language` (`ur`) |