# Grok 4.1 Fast

Grok 4.1 Fast is an AI model released by SpaceXSI on Nov 19 2025. It has a 2M context window. Tracked results include 19% on BullshitBench v2.

## Facts

| Field | Value |
| --- | --- |
| Model | Grok 4.1 Fast |
| Developer | SpaceXSI |
| Release date | Wednesday, Nov 19 2025 |
| Licensing | Closed |
| Context window | 2M |

## Tracked benchmark scores

| Benchmark | Score | Source | What it measures |
| --- | --- | --- | --- |
| BullshitBench v2 | 19% | [BullshitBench](https://github.com/petergpt/bullshit-benchmark) | Given a confidently-worded but nonsensical prompt, does the AI spot that it makes no sense and push back — instead of playing along and inventing an answer? The score is how often it clearly called out the nonsense. Higher is better. |

## About Grok 4.1 Fast

Grok 4.1 Fast launched on November 19, 2025 with xAI's Agent Tools API. It was built for enterprise agent workflows, with a two-million-token context window and training focused on tool calling over multiple turns. Example uses included customer-support processes where the assistant had to consult information, choose functions and continue working from the results.

The accompanying tools service supplied web and X search, remote code execution and other server-side capabilities. Those tools were surrounding infrastructure, rather than information permanently stored in the model. The release combined a model trained for long interactions with services that could carry out its actions, giving developers a more complete route to building agents than text generation alone.

## Questions and answers

### When was Grok 4.1 Fast released?

Grok 4.1 Fast was released by SpaceXSI on Wednesday, Nov 19 2025.

### Who made Grok 4.1 Fast?

Grok 4.1 Fast was built by SpaceXSI. Elon Musk's AI company building the Grok series of models. Founded in 2023 as xAI, merged into SpaceX as SpaceXAI in 2026 and renamed SpaceXSI (SpaceX Super Intelligence) that October. Cursor (Anysphere) and its Composer coding models were acquired in 2026 and are tracked here.

### What benchmark scores did Grok 4.1 Fast get?

Grok 4.1 Fast reports 1 tracked benchmark score — BullshitBench v2: 19%. Tracked scores may come from lab reports or independent benchmarks; source details accompany the benchmark data.

### What is the context window of Grok 4.1 Fast?

Grok 4.1 Fast has a context window of 2M. Providers may specify separate input and output token limits.

### Is Grok 4.1 Fast open source?

No. Grok 4.1 Fast is a closed model. The weights are not published — it is available only through the provider's own API, apps, or partner platforms.

### What came before and after Grok 4.1 Fast?

SpaceXSI's previous tracked release was Grok 4.1 on Nov 17 2025, 2 days earlier. It was followed by Composer 1.5 on Feb 9 2026.


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Canonical page: https://aireleasetracker.com/model/xai/grok-4.1-fast
Site index: https://aireleasetracker.com/llms.txt
Source: AI Release Tracker (https://aireleasetracker.com). Most benchmark scores come from lab launch material; gathered results identify the leaderboard that published them.