Model Comparison

GPT-5.6 Luna vs Grok-1.5Which is better in 2026?

GPT-5.6 Luna significantly outperforms across most benchmarks.

Verdict: GPT-5.6 Luna vs Grok-1.5 — which is better?

GPT-5.6 Luna (by OpenAI) and Grok-1.5 (by xAI) are two of the AI models people compare most. Here is how they stack up on benchmarks, price and capabilities, and which one to pick in 2026.

GPT-5.6 Luna outperforms in 1 benchmarks (GPQA), while Grok-1.5 is better at 0 benchmarks. GPT-5.6 Luna significantly outperforms across most benchmarks.

Choose GPT-5.6 Luna if…

  • you want the strongest raw capability — it leads on 1 of 1 shared benchmarks
  • you want the most recent training data — it shipped Jul 2026

Choose Grok-1.5 if…

  • you are already invested in the xAI ecosystem

Performance Benchmarks

Comparative analysis across standard metrics

1 benchmarks

GPT-5.6 Luna outperforms in 1 benchmarks (GPQA), while Grok-1.5 is better at 0 benchmarks.

GPT-5.6 Luna significantly outperforms across most benchmarks.

Sat Jul 18 2026 • llm-stats.com

Arena Performance

Human preference votes

Context Window

Maximum input and output token capacity

Only GPT-5.6 Luna specifies input context (1,050,000 tokens). Only GPT-5.6 Luna specifies output context (128,000 tokens).

OpenAI
GPT-5.6 Luna
Input1,050,000 tokens
Output128,000 tokens
xAI
Grok-1.5
Input- tokens
Output- tokens
Sat Jul 18 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

GPT-5.6 Luna supports multimodal inputs, whereas Grok-1.5 does not.

GPT-5.6 Luna can handle both text and other forms of data like images, making it suitable for multimodal applications.

GPT-5.6 Luna

Text
Images
Audio
Video

Grok-1.5

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-5.6 Luna

Proprietary

Closed source

Grok-1.5

Proprietary

Closed source

Release Timeline

When each model was launched

GPT-5.6 Luna was released on 2026-07-09, while Grok-1.5 was released on 2024-03-28.

GPT-5.6 Luna is 28 months newer than Grok-1.5.

GPT-5.6 Luna

Jul 9, 2026

1 weeks ago

2.3yr newer
Grok-1.5

Mar 28, 2024

2.3 years ago

Knowledge Cutoff

When training data ends

GPT-5.6 Luna has a documented knowledge cutoff of 2026-02-16, while Grok-1.5's cutoff date is not specified.

We can confirm GPT-5.6 Luna's training data extends to 2026-02-16, but cannot make a direct comparison without Grok-1.5's cutoff date.

GPT-5.6 Luna

Feb 2026

Grok-1.5

—

Outputs Comparison

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Key Takeaways

OpenAI
Larger context window (1,050,000 tokens)
Supports multimodal inputs
Higher GPQA score (92.3% vs 35.9%)
xAI

No standout differentiators in the data we have for this pair.

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against GPT-5.6 Luna and Grok-1.5 side-by-side, then vote on the output you prefer.

GPT-5.6 Luna
✓ Preferred
Grok-1.5
Open in Playground
AI Model Comparison Table
Feature
OpenAI
GPT-5.6 Luna
xAI
Grok-1.5

FAQ

Common questions about GPT-5.6 Luna vs Grok-1.5.

Which is better, GPT-5.6 Luna or Grok-1.5?

GPT-5.6 Luna significantly outperforms across most benchmarks. GPT-5.6 Luna is made by OpenAI and Grok-1.5 is made by xAI. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does GPT-5.6 Luna compare to Grok-1.5 in benchmarks?

GPT-5.6 Luna scores Connectors: 99.9%, HealthBench Consensus: 95.1%, GPQA: 92.3%, Search and Function-Calling: 89.7%, Capture-the-Flag Challenges (Internal): 85.2%. Grok-1.5 scores GSM8k: 90.0%, DocVQA: 85.6%, MMLU: 81.3%, HumanEval: 74.1%, MMMU: 53.6%.

What are the context window sizes for GPT-5.6 Luna and Grok-1.5?

GPT-5.6 Luna supports 1.1M tokens and Grok-1.5 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-5.6 Luna and Grok-1.5?

Key differences include multimodal support (yes vs no). See the full comparison above for benchmark-by-benchmark results.

Who makes GPT-5.6 Luna and Grok-1.5?

GPT-5.6 Luna is developed by OpenAI and Grok-1.5 is developed by xAI.

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