Grok 4.1 Fast
Summary
Grok 4.1 Fast is a proprietary language model from xAI, released on 19 Nov 2025. It accepts text and images and generates text, with a 2M-token context window and up to 30K output tokens per response.
xAI's fast agentic tool-calling model with a 2M context window; non-reasoning variant for low-latency responses
Last verified 4 Oct 2026. Every figure on this page links to its source.
Specifications
| Developer | xAI |
|---|---|
| Release date | 19 Nov 2025 [models.dev] |
| Status | Generally available [models.dev] |
| Weights | Proprietary (API only) [models.dev] |
| Context window | 2M (2,000,000 tokens) [models.dev] |
| Max output | 30K tokens [models.dev] |
| Input | Text and images [models.dev] |
| Output | Text [models.dev] |
| Reasoning mode | No [models.dev] |
| Tool calling | Yes [models.dev] |
| Structured output | Yes [models.dev] |
Grok 4.1 Fast API pricing by provider
USD per million tokens. Sorted by input price.
We do not currently track a paid API listing for this model.
Frequently asked questions
What is the context window of Grok 4.1 Fast?
Grok 4.1 Fast has a context window of 2,000,000 tokens (2M) and can generate up to 30,000 tokens in a single response, according to models.dev.
Is Grok 4.1 Fast open source?
No. Grok 4.1 Fast is a proprietary model; xAI has not released its weights.
When was Grok 4.1 Fast released?
xAI released Grok 4.1 Fast on 19 Nov 2025, according to models.dev.
Change history
No changes detected since we started tracking this model. We re-check every source daily.