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GPT-6 Luna vs Grok-4 Heavy

GPT-6 Luna and Grok-4 Heavy are closely matched at 44.5 and 40.7 on the LLM Stats Score.

OpenAI · xAI · Updated for 2026

Which is better?

GPT-6 Luna and Grok-4 Heavy are closely matched on the overall LLM Stats Score at 44.5 and 40.7.

Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.

Choose GPT-6 Luna

  • you want predictable pricing at $0.10/M input and $0.50/M output

Choose Grok-4 Heavy

  • you are already invested in the xAI ecosystem

At a glance

The differences that matter most.

GPT-6 Luna
OpenAI
Grok-4 Heavy
xAI
Core performance indexes
LLM Stats Score
44.5
#40
40.7
#59
Reasoning
40.0
#58
39.0
#63
Coding
31.4
#47
17.7
#121
Cost, coverage & limits
Benchmark wins
—
—
Input price
$0.10 / M
— / M
Output price
$0.50 / M
— / M
Context window
1,050,000
—

Individual benchmarks

5 reported for GPT-6 Luna · 6 for Grok-4 Heavy

No common benchmarks found

GPT-6 Luna and Grok-4 Heavydon't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.

Human preference

Blind head-to-head votes and playground preference scores

Context Window

Maximum input and output token capacity

Only GPT-6 Luna specifies input context (1,050,000 tokens). Only GPT-6 Luna specifies output context (128,000 tokens).

OpenAI
GPT-6 Luna
Input1,050,000 tokens
Output128,000 tokens
xAI
Grok-4 Heavy
Input- tokens
Output- tokens
Tue Sep 22 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Both GPT-6 Luna and Grok-4 Heavy support multimodal inputs.

They are both capable of processing various types of data, offering versatility in application.

GPT-6 Luna

Text
Images
Audio
Video

Grok-4 Heavy

Text
Images
Audio
Video

License

Usage and distribution terms

Both models are licensed under proprietary licenses.

Both models have usage restrictions defined by their respective organizations.

GPT-6 Luna

Proprietary

Closed source

Grok-4 Heavy

Proprietary

Closed source

Release Timeline

When each model was launched

GPT-6 Luna was released on 2026-09-22, while Grok-4 Heavy's release date is not specified.

We can confirm GPT-6 Luna's release timeline, but cannot make a direct age comparison without Grok-4 Heavy's release date.

GPT-6 Luna

Sep 22, 2026

0 days ago

Grok-4 Heavy

—

Knowledge Cutoff

When training data ends

GPT-6 Luna has a knowledge cutoff of 2026-05-18, while Grok-4 Heavy has a cutoff of 2024-12-31.

GPT-6 Luna has more recent training data (up to 2026-05-18), making it potentially better informed about events through that date compared to Grok-4 Heavy (2024-12-31).

GPT-6 Luna

May 2026

1.4 yr newer
Grok-4 Heavy

Dec 2024

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Judge for yourself.

Run your own prompts against GPT-6 Luna and Grok-4 Heavy side-by-side, then vote on the output you prefer.

GPT-6 Luna
✓ Preferred
Grok-4 Heavy
Open in Playground

FAQ

Common questions about GPT-6 Luna vs Grok-4 Heavy.

Which is better, GPT-6 Luna or Grok-4 Heavy?

GPT-6 Luna and Grok-4 Heavy are closely matched on the LLM Stats Score at 44.5 and 40.7. GPT-6 Luna is made by OpenAI and Grok-4 Heavy is made by xAI. The best choice depends on your use case — compare their capability indexes, individual benchmarks, pricing, and limits above.

How does GPT-6 Luna compare to Grok-4 Heavy in benchmarks?

GPT-6 Luna scores DeepSWE 1.1: 66.6%, OSWorld 2.0: 52.7%, Agents' Last Exam: 50.9%, FrontierCode 1.1: 42.4%, AutomationBench v1.0.6: 20.7%. Grok-4 Heavy scores AIME 2025: 100.0%, HMMT25: 96.7%, GPQA: 88.4%, LiveCodeBench: 79.4%, USAMO25: 61.9%.

What are the context window sizes for GPT-6 Luna and Grok-4 Heavy?

GPT-6 Luna supports 1.1M tokens and Grok-4 Heavy supports an unknown number of tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between GPT-6 Luna and Grok-4 Heavy?

Key differences include LLM Stats Score (44.5 vs 40.7). See the full comparison above for benchmark-by-benchmark results.

Who makes GPT-6 Luna and Grok-4 Heavy?

GPT-6 Luna is developed by OpenAI and Grok-4 Heavy is developed by xAI.

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