grok-4-1-fast-reasoning — API, Pricing & Context Window | Vivgrid
grok-4-1-fast-reasoning on Vivgrid: xAI's fast reasoning model with a 2M-token context window and image input, via one unified API.
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.
Quick start
Call grok-4-1-fast-reasoning through Vivgrid's unified, OpenAI-compatible endpoint. Get an API key from the Vivgrid Console.
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 — lower-latency variant
- gpt-5.2 — alternative general-purpose model
- gemini-3.5-flash — large-context multimodal option