# Grok 4 Heavy

> xAI's top-tier multi-agent version of Grok 4 that runs several reasoning agents in parallel for the hardest problems.

- Maker: xAI (Grok)
- Line: Grok Heavy
- Canonical page: https://ai-tldr.dev/models/grok-4-heavy/
- Updated: 2026-06-17

## In short

Grok 4 Heavy is the most powerful configuration of xAI's Grok 4, launched on July 9, 2025 alongside the standard Grok 4. It has a 256K-token context window.

## Facts

| Fact | Value | Source |
| --- | --- | --- |
| Context window | 256K | [1] |
| Licence | Proprietary · API only | [1] |
| Released | 9 July 2025 | [2] |
| Knowledge cutoff | November 2024 | [1] |

## Sources

1. [xAI API & models docs](https://docs.x.ai/developers/models)
2. [Grok 4 announcement (xAI)](https://x.ai/news/grok-4)

## Overview

Grok 4 Heavy is the most powerful configuration of xAI's Grok 4, launched on July 9, 2025 alongside the standard Grok 4. Where ordinary Grok 4 answers with a single reasoning pass, Grok 4 Heavy spawns several Grok 4 agents that work on the same problem in parallel and then compare notes, picking the strongest answer. xAI markets this "test-time compute" approach as its highest-capability offering for the most demanding reasoning, math, and coding tasks.

Grok 4 Heavy is not a separate set of weights — it is the same underlying Grok 4 model run in a multi-agent mode, with a 256,000-token context window and text plus image (vision) input. At launch it set state-of-the-art numbers across several frontier benchmarks: it was the first model publicly reported to clear 50% on Humanity's Last Exam (50.7% on the text-only subset with tools) and posted 15.9% on ARC-AGI-2, 100% on AIME 2025, and 61.9% on the USAMO 2025 math-proof benchmark.

Crucially, Grok 4 Heavy is a consumer-only product. It is available exclusively through the SuperGrok Heavy subscription at $300/month (or $3,000/year) and was never exposed to developers as a standalone API model ID — the xAI API offered the regular Grok 4 model instead. The parallel multi-agent idea later resurfaced as a documented API mode in xAI's newer Grok 4.20 line.

## Benchmarks

- Humanity's Last Exam (text-only, with tools): 50.7% ([source](https://www.datacamp.com/blog/grok-4))
- ARC-AGI-2: 15.9% ([source](https://www.datacamp.com/blog/grok-4))
- GPQA: 88.9% ([source](https://www.datacamp.com/blog/grok-4))
- AIME 2025: 100% ([source](https://www.datacamp.com/blog/grok-4))
- USAMO 2025: 61.9% ([source](https://www.datacamp.com/blog/grok-4))
- HMMT 2025: 96.7% ([source](https://www.datacamp.com/blog/grok-4))
- LiveCodeBench (Jan-May): 79.4% ([source](https://www.datacamp.com/blog/grok-4))

## Strengths

- Highest benchmark scores in the Grok 4 family — first model to break 50% on Humanity's Last Exam (50.7% with tools)
- Parallel multi-agent reasoning improves reliability on long, multi-step math and coding chains
- State-of-the-art on ARC-AGI-2 (15.9%) for closed models at launch
- Near-saturated competition-math performance (AIME 2025 100%, HMMT 2025 96.7%)
- 256K-token context window for long documents and large codebases
- Native tool use and live web/X search integrated into reasoning

## Best for

- Hardest research-grade reasoning and STEM problem solving
- Competition-level mathematics and formal proof drafting
- Complex multi-step coding and debugging tasks
- Deep research that benefits from cross-checking multiple agent answers
- High-stakes analysis where extra accuracy justifies the premium tier

## Grok Heavy versions

- Grok 4 Heavy (9 July 2025) — this page

## FAQ

### What is the difference between Grok 4 and Grok 4 Heavy?

Standard Grok 4 answers with a single reasoning pass. Grok 4 Heavy runs several Grok 4 agents in parallel on the same problem and cross-evaluates their outputs to pick the best answer, which raises accuracy on the hardest tasks. Both share the same 256K context window and knowledge cutoff.

### How much does Grok 4 Heavy cost?

Grok 4 Heavy is available only on the SuperGrok Heavy plan, priced at $300/month or $3,000/year. It was xAI's most expensive consumer tier at launch.

### Can I use Grok 4 Heavy through the xAI API?

No. Grok 4 Heavy was a consumer-only feature with no standalone API model ID. Developers could call the regular Grok 4 model through the API, but the multi-agent Heavy mode was exclusive to the SuperGrok Heavy subscription.

### How well does Grok 4 Heavy do on benchmarks?

At launch it was the first model publicly reported to top 50% on Humanity's Last Exam (50.7% with tools), and it posted 15.9% on ARC-AGI-2, 88.9% on GPQA, 100% on AIME 2025, and 61.9% on USAMO 2025.

## Links

- [Grok 4 announcement (xAI)](https://x.ai/news/grok-4)
- [xAI API & models docs](https://docs.x.ai/developers/models)
- [xAI API overview](https://x.ai/api)
- [Grok 4 benchmarks & tests (DataCamp)](https://www.datacamp.com/blog/grok-4)
- [Grok 4 on Artificial Analysis](https://artificialanalysis.ai/models/grok-4)
- [Grok pricing guide (Fello AI)](https://felloai.com/grok-pricing/)
- [Grok 4 on LLM-Stats](https://llm-stats.com/models/grok-4)

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