> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://developers.deepgram.com/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://developers.deepgram.com/_mcp/server.

## LLM Model Updates & Cartesia Speed Control

### GPT-5.5 LLM Model Support

OpenAI's GPT-5.5 model is now available as a managed LLM in the Voice Agent API. GPT-5.5 is an Advanced tier model.

Set the model in your agent configuration:

```json
{
  "agent": {
    "think": {
      "provider": {
        "type": "open_ai",
        "model": "gpt-5.5",
        "temperature": 0.7
      }
    }
  }
}
```

For the full list of supported models and pricing tiers, see the [Voice Agent LLM Models documentation](/docs/voice-agent-llm-models).

### Llama Nemotron Super 49B Removed

The `llama-nemotron-super-49B` (Llama Nemotron Super 49B) model has been removed from the NVIDIA provider due to poor performance. The `nemotron-3-nano-30B-A3B` model remains available. See the [NVIDIA models table](/docs/voice-agent-llm-models#nvidia) for current options.

### Cartesia TTS Speed Control

The `agent.speak.provider.speed` parameter now supports Cartesia TTS in addition to Deepgram TTS. For Cartesia, the parameter accepts the following preset values:

- `slowest`
- `slow`
- `normal`
- `fast`
- `fastest`

You can also pass a numerical value for more granular control. See the [Cartesia speed documentation](https://docs.cartesia.ai/build-with-cartesia/capability-guides/control-speed-and-emotion#api) for details.

```json
{
  "agent": {
    "speak": {
      "provider": {
        "type": "cartesia",
        "model_id": "sonic-2",
        "voice": {
          "mode": "id",
          "id": "a167e0f3-df7e-4d52-a9c3-f949145efdab"
        },
        "speed": "fast"
      }
    }
  }
}
```

For more details, see the [TTS Models documentation](/docs/voice-agent-tts-models#deepgram-managed-cartesia-tts-models).