Model Comparison

GPT-5.6 Luna vs Grok 4.3Which is better in 2026?

GPT-5.6 Luna significantly outperforms across most benchmarks. Grok 4.3 is 1.4x cheaper per token.

Verdict: GPT-5.6 Luna vs Grok 4.3 — which is better?

GPT-5.6 Luna (by OpenAI) and Grok 4.3 (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 (GDPval-AA), while Grok 4.3 is better at 0 benchmarks. GPT-5.6 Luna significantly outperforms across most benchmarks.

On price, Grok 4.3 is roughly 1.4x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

GPT-5.6 Luna also accepts a larger context window (1,050,000 input tokens), making it the stronger choice for long documents and large codebases.

Choose GPT-5.6 Luna if…

  • you want the strongest raw capability — it leads on 1 of 1 shared benchmarks
  • you process long inputs — it offers a 1,050,000 token context window
  • you want the most recent training data — it shipped Jul 2026

Choose Grok 4.3 if…

  • cost matters — it's about 1.4x cheaper per token

Performance Benchmarks

Comparative analysis across standard metrics

1 benchmarks

GPT-5.6 Luna outperforms in 1 benchmarks (GDPval-AA), while Grok 4.3 is better at 0 benchmarks.

GPT-5.6 Luna significantly outperforms across most benchmarks.

Fri Jul 17 2026 • llm-stats.com

Arena Performance

Human preference votes

Pricing Analysis

Price comparison per million tokens

Grok 4.3 costs less

For input processing, GPT-5.6 Luna ($1.00/1M tokens) is 1.3x cheaper than Grok 4.3 ($1.25/1M tokens).

For output processing, GPT-5.6 Luna ($6.00/1M tokens) is 2.4x more expensive than Grok 4.3 ($2.50/1M tokens).

In conclusion, GPT-5.6 Luna is more expensive than Grok 4.3.*

* Using a 3:1 ratio of input to output tokens

Lowest available price from all providers
Fri Jul 17 2026 • llm-stats.com
OpenAI
GPT-5.6 Luna
Input tokens$1.00
Output tokens$6.00
Best providerOpenAI
xAI
Grok 4.3
Input tokens$1.25
Output tokens$2.50
Best providerxAI
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

GPT-5.6 Luna accepts 1,050,000 input tokens compared to Grok 4.3's 1,000,000 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 4.3
Input1,000,000 tokens
Output- tokens
Fri Jul 17 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

GPT-5.6 Luna supports multimodal inputs, whereas Grok 4.3 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 4.3

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 4.3

Proprietary

Closed source

Release Timeline

When each model was launched

GPT-5.6 Luna was released on 2026-07-09, while Grok 4.3 was released on 2026-05-06.

GPT-5.6 Luna is 2 months newer than Grok 4.3.

GPT-5.6 Luna

Jul 9, 2026

1 weeks ago

2mo newer
Grok 4.3

May 6, 2026

2 months ago

Knowledge Cutoff

When training data ends

GPT-5.6 Luna has a documented knowledge cutoff of 2026-02-16, while Grok 4.3'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 4.3's cutoff date.

GPT-5.6 Luna

Feb 2026

Grok 4.3

—

Provider Availability

GPT-5.6 Luna is available from OpenAI. Grok 4.3 is available from xAI.

GPT-5.6 Luna

openai logo
OpenAI
Input Price:Input: $1.00/1MOutput Price:Output: $6.00/1M

Grok 4.3

xai logo
xAI
Input Price:Input: $1.25/1MOutput Price:Output: $2.50/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Key Takeaways

OpenAI
Larger context window (1,050,000 tokens)
Supports multimodal inputs
Less expensive input tokens
Higher GDPval-AA score (53.1% vs 36.7%)
xAI
Less expensive output tokens

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against GPT-5.6 Luna and Grok 4.3 side-by-side, then vote on the output you prefer.

GPT-5.6 Luna
✓ Preferred
Grok 4.3
Open in Playground
AI Model Comparison Table
Feature
OpenAI
GPT-5.6 Luna
xAI
Grok 4.3

FAQ

Common questions about GPT-5.6 Luna vs Grok 4.3.

Which is better, GPT-5.6 Luna or Grok 4.3?

GPT-5.6 Luna significantly outperforms across most benchmarks. GPT-5.6 Luna is made by OpenAI and Grok 4.3 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 4.3 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 4.3 scores Finance Agent v2: 37.7%, GDPval-AA: 36.7%.

Is GPT-5.6 Luna cheaper than Grok 4.3?

GPT-5.6 Luna is 1.3x cheaper for input tokens. GPT-5.6 Luna costs $1.00/M input and $6.00/M output via openai. Grok 4.3 costs $1.25/M input and $2.50/M output via xai.

What are the context window sizes for GPT-5.6 Luna and Grok 4.3?

GPT-5.6 Luna supports 1.1M tokens and Grok 4.3 supports 1.0M 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 4.3?

Key differences include context window (1.1M vs 1.0M), input pricing ($1.00 vs $1.25/M), multimodal support (yes vs no). See the full comparison above for benchmark-by-benchmark results.

Who makes GPT-5.6 Luna and Grok 4.3?

GPT-5.6 Luna is developed by OpenAI and Grok 4.3 is developed by xAI.

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