Model Comparison

GPT-5.6 Luna vs Nemotron 3 Ultra (550B A55B)Which is better in 2026?

GPT-5.6 Luna significantly outperforms across most benchmarks.

Verdict: GPT-5.6 Luna vs Nemotron 3 Ultra (550B A55B) — which is better?

GPT-5.6 Luna (by OpenAI) and Nemotron 3 Ultra (550B A55B) (by NVIDIA) 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 4 benchmarks (BrowseComp, GDPval-AA, GPQA, Terminal-Bench 2.1), while Nemotron 3 Ultra (550B A55B) 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 4 of 4 shared benchmarks
  • you want the most recent training data — it shipped Jul 2026

Choose Nemotron 3 Ultra (550B A55B) if…

  • you need open weights you can self-host or fine-tune

Performance Benchmarks

Comparative analysis across standard metrics

4 benchmarks

GPT-5.6 Luna outperforms in 4 benchmarks (BrowseComp, GDPval-AA, GPQA, Terminal-Bench 2.1), while Nemotron 3 Ultra (550B A55B) is better at 0 benchmarks.

GPT-5.6 Luna significantly outperforms across most benchmarks.

Tue Jul 28 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
NVIDIA
Nemotron 3 Ultra (550B A55B)
Input- tokens
Output- tokens
Tue Jul 28 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

GPT-5.6 Luna supports multimodal inputs, whereas Nemotron 3 Ultra (550B A55B) 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

Nemotron 3 Ultra (550B A55B)

Text
Images
Audio
Video

License

Usage and distribution terms

GPT-5.6 Luna is licensed under a proprietary license, while Nemotron 3 Ultra (550B A55B) uses OpenMDW License v1.1.

License differences may affect how you can use these models in commercial or open-source projects.

GPT-5.6 Luna

Proprietary

Closed source

Nemotron 3 Ultra (550B A55B)

OpenMDW License v1.1

Open weights

Release Timeline

When each model was launched

GPT-5.6 Luna was released on 2026-07-09, while Nemotron 3 Ultra (550B A55B) was released on 2026-06-04.

GPT-5.6 Luna is 1 month newer than Nemotron 3 Ultra (550B A55B).

GPT-5.6 Luna

Jul 9, 2026

2 weeks ago

1mo newer
Nemotron 3 Ultra (550B A55B)

Jun 4, 2026

1 months ago

Knowledge Cutoff

When training data ends

GPT-5.6 Luna has a knowledge cutoff of 2026-02-16, while Nemotron 3 Ultra (550B A55B) has a cutoff of 2025-09-30.

GPT-5.6 Luna has more recent training data (up to 2026-02-16), making it potentially better informed about events through that date compared to Nemotron 3 Ultra (550B A55B) (2025-09-30).

GPT-5.6 Luna

Feb 2026

5 mo newer
Nemotron 3 Ultra (550B A55B)

Sep 2025

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Key Takeaways

OpenAI
Larger context window (1,050,000 tokens)
Supports multimodal inputs
Higher BrowseComp score (83.3% vs 44.4%)
Higher GDPval-AA score (53.1% vs 39.4%)
Higher GPQA score (92.3% vs 87.0%)
Higher Terminal-Bench 2.1 score (84.7% vs 56.4%)
NVIDIA
Has open weights

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against GPT-5.6 Luna and Nemotron 3 Ultra (550B A55B) side-by-side, then vote on the output you prefer.

GPT-5.6 Luna
✓ Preferred
Nemotron 3 Ultra (550B A55B)
Open in Playground
AI Model Comparison Table
Feature
OpenAI
GPT-5.6 Luna
NVIDIA
Nemotron 3 Ultra (550B A55B)

FAQ

Common questions about GPT-5.6 Luna vs Nemotron 3 Ultra (550B A55B).

Which is better, GPT-5.6 Luna or Nemotron 3 Ultra (550B A55B)?

GPT-5.6 Luna significantly outperforms across most benchmarks. GPT-5.6 Luna is made by OpenAI and Nemotron 3 Ultra (550B A55B) is made by NVIDIA. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does GPT-5.6 Luna compare to Nemotron 3 Ultra (550B A55B) 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%. Nemotron 3 Ultra (550B A55B) scores RULER: 94.7%, IMO-AnswerBench: 92.3%, PinchBench: 90.0%, LiveCodeBench v6: 89.0%, GPQA: 87.0%.

What are the context window sizes for GPT-5.6 Luna and Nemotron 3 Ultra (550B A55B)?

GPT-5.6 Luna supports 1.1M tokens and Nemotron 3 Ultra (550B A55B) 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 Nemotron 3 Ultra (550B A55B)?

Key differences include multimodal support (yes vs no), licensing (Proprietary vs OpenMDW License v1.1). See the full comparison above for benchmark-by-benchmark results.

Who makes GPT-5.6 Luna and Nemotron 3 Ultra (550B A55B)?

GPT-5.6 Luna is developed by OpenAI and Nemotron 3 Ultra (550B A55B) is developed by NVIDIA.

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