Grok 4.1 Fast Reasoning

API model name: grok-4.1-fast-reasoning

Grok 4.1 Fast Reasoning is xAI's chat model, served on the Api.Airforce unified API. It has a 2M-token context window. Beyond text, it accepts image as input. Capabilities include Vision, Tool calling, Reasoning, Prompt caching. It is priced at $0.50 per million input tokens and $0.50 per million output tokens. That is below the provider's $0.20 official input rate. Knowledge cutoff: 2025-09. Access it through the OpenAI-compatible API with one key, alongside 65+ other models on Api.Airforce.

Pricing

Api.Airforce price vs. the provider's official rate.

Specifications

Provider

xAI

Type

chat model

Context window

2M tokens

Max output

33K tokens

Knowledge cutoff

2025-09

Input

text, image

Output

text

Capabilities

Use Grok 4.1 Fast Reasoning via the API

OpenAI-compatible — point any OpenAI SDK at https://api.airforce/v1 and pass grok-4.1-fast-reasoning as the model.

curl https://api.airforce/v1/chat/completions \
  -H "Authorization: Bearer $AIRFORCE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "grok-4.1-fast-reasoning",
    "messages": [{ "role": "user", "content": "Hello!" }]
  }'

from openai import OpenAI
client = OpenAI(base_url="https://api.airforce/v1", api_key="$AIRFORCE_API_KEY")
r = client.chat.completions.create(
    model="grok-4.1-fast-reasoning",
    messages=[{"role": "user", "content": "Hello!"}],
)
print(r.choices[0].message.content)

import OpenAI from "openai";
const client = new OpenAI({ baseURL: "https://api.airforce/v1", apiKey: process.env.AIRFORCE_API_KEY });
const r = await client.chat.completions.create({
  model: "grok-4.1-fast-reasoning",
  messages: [{ role: "user", content: "Hello!" }],
});
console.log(r.choices[0].message.content);

Related models