# Grok 4.1 Fast

> xAI's agentic tool-calling model: 2M-token context, a low-latency non-reasoning mode and a deeper reasoning mode, shipped with the Agent Tools API.

- Maker: xAI (Grok)
- Line: Grok Fast
- Canonical page: https://ai-tldr.dev/models/grok-4-1-fast/
- Updated: 2026-06-18

## In short

Grok 4.1 Fast is xAI's agentic tool-calling model: 2M-token context, a low-latency non-reasoning mode and a deeper reasoning mode, shipped with the Agent Tools API. xAI (Grok) released it on 19 November 2025 as an API-only model. It has a 2M-token context window and costs $0.20 per million input tokens and $0.50 per million output tokens. You can use it through xAI API, OpenRouter and Oracle Cloud (OCI Generative AI).

## Facts

| Fact | Value | Source |
| --- | --- | --- |
| Context window | 2M | [1] |
| Input price | $0.20 / 1M tokens (cached $0.05 / 1M tokens) | [2] |
| Output price | $0.50 / 1M tokens | [2] |
| Licence | Proprietary · API only | [1] |
| Released | 19 November 2025 | [3] |

## Sources

1. [Grok 4.1 Model Card (PDF)](https://data.x.ai/2025-11-17-grok-4-1-model-card.pdf)
2. [Grok 4.1 Fast and Agent Tools API — official announcement](https://x.ai/news/grok-4-1-fast)
3. [xAI — official site](https://x.ai)

## Overview

Grok 4.1 Fast is a large language model from xAI, part of the Grok Fast line and released on November 19, 2025 alongside the Agent Tools API. It is positioned as xAI's best tool-calling and agentic model — built for high-volume, real-world tasks like customer support and deep research rather than as the absolute top "brain" (that role belongs to Grok 4 / Grok 4 Heavy). It is tuned from the Grok 4.1 base, which itself emphasized lower hallucination and stronger conversational quality.

The model carries a 2-million-token context window and accepts both text and images, returning text. It is offered as a single model in two modes: a low-latency non-reasoning mode (model ID grok-4-1-fast-non-reasoning) for instant replies, and a reasoning mode (grok-4-1-fast-reasoning) that emits thinking tokens for multi-step problems. The mode is selected through a reasoning parameter in the API, and pricing is the same either way.

xAI trained Grok 4.1 Fast with heavy reinforcement learning across many simulated tool-use environments, which is reflected in its agentic benchmark results. At launch xAI made the model and the bundled Agent Tools API free for a two-week window (through December 3, 2025) via partners such as OpenRouter, before settling into low per-token pricing.

## Benchmarks

- τ²-bench (Telecom) — agentic tool use: 100% ([source](https://x.ai/news/grok-4-1-fast))
- Berkeley Function Calling Leaderboard v4 (BFCL-V4): 72% ([source](https://x.ai/news/grok-4-1-fast))
- Long-context (2M window) retrieval: 67% ([source](https://www.hostzealot.com/blog/news/grok-41-fast-benchmark-results-and-details-about-the-agent-tools-api))

## Pricing

- Input: $0.20 / 1M tokens per 1M tokens
- Cached input: $0.05 / 1M tokens per 1M tokens
- Output: $0.50 / 1M tokens per 1M tokens

Same price for reasoning and non-reasoning modes. The bundled Agent Tools API is billed separately at no more than $5 per 1,000 successful tool calls. Model and Agent Tools API were free through Dec 3, 2025 at launch.

Source: https://x.ai/news/grok-4-1-fast

## Strengths

- Frontier-level tool calling and agentic workflows — top results on τ²-bench Telecom and Berkeley Function Calling v4
- 2M-token context window that holds up on long-context retrieval far better than Grok 4
- Two modes from one model: pick instant non-reasoning replies or deeper reasoning via a single API parameter
- Roughly half the hallucination rate of the earlier Grok 4 Fast, at similar task accuracy
- Very low, predictable pricing ($0.20/$0.50 per million tokens) with cheap cached input for high-volume agents
- Ships with a bundled Agent Tools API (web/code/file tools) capped at no more than $5 per 1,000 successful tool calls

## Best for

- Customer-support and helpdesk agents that chain many tool calls
- Deep-research assistants that fan out web search and synthesize long contexts
- Multi-step agentic automation and orchestration over external tools/APIs
- High-volume API workloads where latency and per-token cost matter
- Long-document analysis and retrieval over codebases or large corpora (up to 2M tokens)
- Vision-assisted agent steps that read screenshots, charts, or scanned pages (JPG/PNG)

## How to access

- [xAI API](https://docs.x.ai/developers/release-notes) — model id `grok-4-1-fast-reasoning / grok-4-1-fast-non-reasoning`
- [OpenRouter](https://openrouter.ai/x-ai/grok-4.1-fast) — model id `x-ai/grok-4.1-fast`
- [Oracle Cloud (OCI Generative AI)](https://docs.oracle.com/en-us/iaas/Content/generative-ai/xai-grok-4-1-fast.htm) — model id `xai.grok-4-1-fast-reasoning / xai.grok-4-1-fast-non-reasoning`

## Grok Fast versions

- Grok 4.1 Fast (19 November 2025) — this page
- [Grok 4 Fast](https://ai-tldr.dev/models/grok-4-fast/) (September 2025)

## FAQ

### What is Grok 4.1 Fast?

Grok 4.1 Fast is xAI's agentic, tool-calling LLM released November 19, 2025. It is tuned for high-volume, real-world tasks like customer support and deep research, carries a 2M-token context window, and shipped together with xAI's Agent Tools API.

### What is the difference between the reasoning and non-reasoning modes?

It is one model offered in two modes selected by an API parameter. The non-reasoning mode (grok-4-1-fast-non-reasoning) gives instant, low-latency replies; the reasoning mode (grok-4-1-fast-reasoning) emits thinking tokens for multi-step problems. Per-token pricing is the same for both.

### How much does Grok 4.1 Fast cost?

Per xAI, it is $0.20 per million input tokens, $0.05 per million cached input tokens, and $0.50 per million output tokens. The bundled Agent Tools API is billed separately at no more than $5 per 1,000 successful tool calls. Both were free through December 3, 2025 at launch.

### How good is Grok 4.1 Fast at tool calling?

xAI reports it scores 100% on τ²-bench Telecom and 72% on the Berkeley Function Calling Leaderboard v4, beating models like Claude Sonnet 4.5, GPT-5.1, and Grok 4 on those agentic benchmarks, and it sustains long-context quality (67%) far above Grok 4 (22%).

## Links

- [Grok 4.1 Fast and Agent Tools API — official announcement](https://x.ai/news/grok-4-1-fast)
- [xAI — official site](https://x.ai)
- [Grok 4.1 — model line announcement](https://x.ai/news/grok-4-1)
- [Grok 4.1 Model Card (PDF)](https://data.x.ai/2025-11-17-grok-4-1-model-card.pdf)
- [xAI API — release notes](https://docs.x.ai/developers/release-notes)
- [Grok 4.1 Fast on OpenRouter — API pricing](https://openrouter.ai/x-ai/grok-4.1-fast)
- [Grok 4.1 Fast — Artificial Analysis benchmarks](https://artificialanalysis.ai/models/grok-4-1-fast)
- [Grok 4.1 Fast benchmark results & Agent Tools API — HostZealot](https://www.hostzealot.com/blog/news/grok-41-fast-benchmark-results-and-details-about-the-agent-tools-api)
- [xAI Grok 4.1 Fast on Oracle OCI — specs](https://docs.oracle.com/en-us/iaas/Content/generative-ai/xai-grok-4-1-fast.htm)

Source: AI/TLDR LLM registry, https://ai-tldr.dev/models/grok-4-1-fast/