Grok 4.1 Fast
xAI's cost-efficient high-throughput model. 2M context, optional reasoning, optimized for agentic loops and real-time apps.
Grok 4.1 Fast is multimodal AI model from xAI, priced at €0.000 per 1M input tokens with a 2M tokens context window.
About this model
0.7
Pricing
API Integration
Use our OpenAI-compatible API to integrate Grok 4.1 Fast into your application.
npm install railwailimport railwail from "railwail";
const rw = railwail("YOUR_API_KEY");
// Simple — just pass a string
const reply = await rw.run("grok-4-1-fast", "Hello! What can you do?");
console.log(reply);
// With message history
const reply2 = await rw.run("grok-4-1-fast", [
{ role: "system", content: "You are a helpful assistant." },
{ role: "user", content: "Explain quantum computing simply." },
]);
console.log(reply2);
// Full response with usage info
const res = await rw.chat("grok-4-1-fast", [
{ role: "user", content: "Hello!" },
], { temperature: 0.7, max_tokens: 500 });
console.log(res.choices[0].message.content);
console.log(res.usage);Deep dive — xAI's Grok 4.1 Fast
xAI was founded in March 2023 by Elon Musk together with senior researchers from DeepMind, OpenAI, Google Research, Microsoft Research and Tesla. The company's stated mission is to build maximally truth-seeking AI. The Grok lineage spans Grok 1 (open-source 314B MoE, November 2023), Grok 1.5, Grok 2, Grok 3 (February 2025), Grok 4 (mid-2025), Grok 4.1 Fast (late 2025), Grok 4.20 (early 2026) and Grok 4.3 (May 2026). The Fast variants are xAI's high-throughput, cost-optimized tier. xAI raised over $20 billion across multiple funding rounds and operates the Colossus supercluster in Memphis.
Visit xAI →Grok 4.1 Fast was released as xAI's cost-efficient mid-tier model and refreshed throughout 2026. Architecturally it is a smaller and sparser variant of the Grok 4.x family, designed for high-throughput production workloads. The model is available in both reasoning and non-reasoning modes - developers can choose to enable test-time thinking on demand. Pretraining used the same multi-trillion-token mixture as Grok 4.3 (web text, code, X posts) on the Colossus supercluster, with heavy distillation from larger Grok teacher models. Post-training combined RLHF and reinforcement learning against verifiable rewards on math, code and tool-use trajectories. Grok 4.1 Fast supports a class-leading 2M-token context window with 2M-token max output, native vision input, and the upgraded DeepSearch retrieval agent. xAI positions it as the cost-efficient alternative to GPT-5.4 mini and Gemini 3 Flash.
- Parameters
- Undisclosed (smaller and sparser than Grok 4.3)
- Context
- 2M tokens
- 2M token context window and 2M token max output
- Available in reasoning and non-reasoning modes
- Vision input for images and screenshots
- Native DeepSearch agent for X + web retrieval
- Function calling and structured JSON output
- Lowest per-token pricing in the Grok 4.x family
- Strong throughput for production workloads
- Available via xAI API and OpenRouter
- Compatible with the same tool-use API as Grok 4.3
- $175/month free API credits via data-sharing programme
- Best for: production agents, real-time chat, RAG pipelines, high-concurrency workloads.
Multi-trillion-token pretraining mixture of web text, code and X public posts; heavy distillation from larger Grok 4.x teacher models. Post-training combines RLHF and RL against verifiable rewards. Knowledge cutoff updated continuously through retrieval.
License: Proprietary commercial license via xAI API and partner platforms. Weights not publicly released.
Known limitations
- Below Grok 4.3 on the hardest reasoning and coding benchmarks
- Lower refusal rate increases risk of harmful or biased output
- Limited published third-party safety evaluations
- Real-time retrieval depends heavily on the X corpus
- Weights not released; reproducibility limited
Frequently asked questions
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