# grok-4-1-fast-reasoning — API, Pricing & Context Window

`grok-4-1-fast-reasoning` is xAI's fast reasoning model, pairing an enormous **2M-token context window** with image input and an emphasis on quick, structured problem solving. The large context makes it well suited to sprawling documents and long agent histories.

On Vivgrid, `grok-4-1-fast-reasoning` is available through the unified, OpenAI-compatible API, so xAI slots into multi-provider agent stacks with a single key.

## Specifications

|     |     |
| --- | --- |
| **Provider** | xAI |
| **Model ID** | `grok-4-1-fast-reasoning` |
| **Best for** | General-purpose |
| **Context window** | 2,000,000 tokens |
| **Modalities** | Text, Image |
| **Tool / function calling** | Yes |
| **Knowledge cutoff** | 2025-06 |
| **Acceleration** | 🌐 Global (Centralized) |

## Pricing

Pricing for `grok-4-1-fast-reasoning` matches the provider's published rates. See live pricing in the [Vivgrid Console](https://console.vivgrid.com/).

## Quick start

Call `grok-4-1-fast-reasoning` through Vivgrid's unified, OpenAI-compatible endpoint. Get an API key from the [Vivgrid Console](https://console.vivgrid.com/).

```
curl https://api.vivgrid.com/v1/chat/completions \
  -H "Authorization: Bearer $VIVGRID_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "grok-4-1-fast-reasoning",
    "messages": [\
      { "role": "user", "content": "Say hello in English, Chinese and Spanish." }\
    ],
    "stream": true
  }'
```

## Ideal use cases

- Reasoning over very large contexts (up to 2M tokens)
- Analytical and multi-step problem solving
- Agents ingesting large document sets
- Mixed text-and-image reasoning tasks

## Related models

- [grok-4-1-fast-non-reasoning](/content/docs/models/grok-4-1-fast-non-reasoning/index.html) — lower-latency variant
- [gpt-5.2](/content/docs/models/gpt-5.2) — alternative general-purpose model
- [gemini-3.5-flash](/content/docs/models/gemini-3.5-flash/index.html) — large-context multimodal option