Model Comparison

GPT-5.6 Luna vs GPT OSS 20BWhich is better in 2026?

GPT-5.6 Luna significantly outperforms across most benchmarks. GPT OSS 20B is 25.7x cheaper per token.

Verdict: GPT-5.6 Luna vs GPT OSS 20B — which is better?

GPT-5.6 Luna (by OpenAI) and GPT OSS 20B (by OpenAI) 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 3 benchmarks (GPQA, HealthBench, HealthBench Hard), while GPT OSS 20B is better at 0 benchmarks. GPT-5.6 Luna significantly outperforms across most benchmarks.

On price, GPT OSS 20B is roughly 25.7x 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 3 of 3 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 GPT OSS 20B if…

  • cost matters — it's about 25.7x cheaper per token
  • you need open weights you can self-host or fine-tune

Performance Benchmarks

Comparative analysis across standard metrics

3 benchmarks

GPT-5.6 Luna outperforms in 3 benchmarks (GPQA, HealthBench, HealthBench Hard), while GPT OSS 20B is better at 0 benchmarks.

GPT-5.6 Luna significantly outperforms across most benchmarks.

Sat Jul 25 2026 • llm-stats.com

Arena Performance

Human preference votes

Pricing Analysis

Price comparison per million tokens

GPT OSS 20B costs less

For input processing, GPT-5.6 Luna ($1.00/1M tokens) is 20.0x more expensive than GPT OSS 20B ($0.05/1M tokens).

For output processing, GPT-5.6 Luna ($6.00/1M tokens) is 30.0x more expensive than GPT OSS 20B ($0.20/1M tokens).

In conclusion, GPT-5.6 Luna is more expensive than GPT OSS 20B.*

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

Lowest available price from all providers
Sat Jul 25 2026 • llm-stats.com
OpenAI
GPT-5.6 Luna
Input tokens$1.00
Output tokens$6.00
Best providerOpenAI
OpenAI
GPT OSS 20B
Input tokens$0.05
Output tokens$0.20
Best providerNovita
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 GPT OSS 20B's 131,072 tokens. GPT-5.6 Luna can generate longer responses up to 128,000 tokens, while GPT OSS 20B is limited to 32,768 tokens.

OpenAI
GPT-5.6 Luna
Input1,050,000 tokens
Output128,000 tokens
OpenAI
GPT OSS 20B
Input131,072 tokens
Output32,768 tokens
Sat Jul 25 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

GPT-5.6 Luna supports multimodal inputs, whereas GPT OSS 20B 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

GPT OSS 20B

Text
Images
Audio
Video

License

Usage and distribution terms

GPT-5.6 Luna is licensed under a proprietary license, while GPT OSS 20B uses Apache 2.0.

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

GPT-5.6 Luna

Proprietary

Closed source

GPT OSS 20B

Apache 2.0

Open weights

Release Timeline

When each model was launched

GPT-5.6 Luna was released on 2026-07-09, while GPT OSS 20B was released on 2025-08-05.

GPT-5.6 Luna is 11 months newer than GPT OSS 20B.

GPT-5.6 Luna

Jul 9, 2026

2 weeks ago

11mo newer
GPT OSS 20B

Aug 5, 2025

11 months ago

Knowledge Cutoff

When training data ends

GPT-5.6 Luna has a documented knowledge cutoff of 2026-02-16, while GPT OSS 20B'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 GPT OSS 20B's cutoff date.

GPT-5.6 Luna

Feb 2026

GPT OSS 20B

—

Provider Availability

GPT-5.6 Luna is available from OpenAI. GPT OSS 20B is available from Novita, Fireworks, Groq, OpenAI.

GPT-5.6 Luna

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

GPT OSS 20B

novita logo
Novita
Input Price:Input: $0.05/1MOutput Price:Output: $0.20/1M
fireworks logo
Fireworks
Input Price:Input: $0.10/1MOutput Price:Output: $0.50/1M
groq logo
Groq
Input Price:Input: $0.10/1MOutput Price:Output: $0.50/1M
openai logo
OpenAI
Input Price:Input: $0.10/1MOutput Price:Output: $0.50/1M
* 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
Higher GPQA score (92.3% vs 71.5%)
Higher HealthBench score (55.8% vs 42.5%)
Higher HealthBench Hard score (32.0% vs 10.8%)
OpenAI
Less expensive input tokens
Less expensive output tokens
Has open weights

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against GPT-5.6 Luna and GPT OSS 20B side-by-side, then vote on the output you prefer.

GPT-5.6 Luna
✓ Preferred
GPT OSS 20B
Open in Playground
AI Model Comparison Table
Feature
OpenAI
GPT-5.6 Luna
OpenAI
GPT OSS 20B

FAQ

Common questions about GPT-5.6 Luna vs GPT OSS 20B.

Which is better, GPT-5.6 Luna or GPT OSS 20B?

GPT-5.6 Luna significantly outperforms across most benchmarks. GPT-5.6 Luna is made by OpenAI and GPT OSS 20B is made by OpenAI. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does GPT-5.6 Luna compare to GPT OSS 20B 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%. GPT OSS 20B scores MMLU: 85.3%, CodeForces: 74.3%, GPQA: 71.5%, TAU-bench Retail: 54.8%, HealthBench: 42.5%.

Is GPT-5.6 Luna cheaper than GPT OSS 20B?

GPT OSS 20B is 20.0x cheaper for input tokens. GPT-5.6 Luna costs $1.00/M input and $6.00/M output via openai. GPT OSS 20B costs $0.05/M input and $0.20/M output via novita.

What are the context window sizes for GPT-5.6 Luna and GPT OSS 20B?

GPT-5.6 Luna supports 1.1M tokens and GPT OSS 20B supports 131K 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 GPT OSS 20B?

Key differences include context window (1.1M vs 131K), input pricing ($1.00 vs $0.05/M), multimodal support (yes vs no), licensing (Proprietary vs Apache 2.0). See the full comparison above for benchmark-by-benchmark results.

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