Model Comparison

GPT-5.6 Luna vs U2Which is better in 2026?

Comparing GPT-5.6 Luna and U2 across benchmarks, pricing, and capabilities.

Verdict: GPT-5.6 Luna vs U2 — which is better?

GPT-5.6 Luna (by OpenAI) and U2 (by Unisound) 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.

On price, U2 is roughly 12.0x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Choose GPT-5.6 Luna if…

  • you want the most recent training data — it shipped Jul 2026

Choose U2 if…

  • cost matters — it's about 12.0x cheaper per token

Performance Benchmarks

Comparative analysis across standard metrics

No common benchmarks found

GPT-5.6 Luna and U2don't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.

Arena Performance

Human preference votes

Pricing Analysis

Price comparison per million tokens

U2 costs less

For input processing, GPT-5.6 Luna ($1.00/1M tokens) is 6.7x more expensive than U2 ($0.15/1M tokens).

For output processing, GPT-5.6 Luna ($6.00/1M tokens) is 20.0x more expensive than U2 ($0.30/1M tokens).

In conclusion, GPT-5.6 Luna is more expensive than U2.*

* 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
Unisound
U2
Input tokens$0.15
Output tokens$0.30
Best providerUnisound
Notice missing or incorrect data?Start an Issue→

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
Unisound
U2
Input- 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 U2 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

U2

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

U2

Proprietary

Closed source

Release Timeline

When each model was launched

GPT-5.6 Luna was released on 2026-07-09, while U2 was released on 2026-06-05.

GPT-5.6 Luna is 1 month newer than U2.

GPT-5.6 Luna

Jul 9, 2026

1 weeks ago

1mo newer
U2

Jun 5, 2026

1 months ago

Knowledge Cutoff

When training data ends

GPT-5.6 Luna has a knowledge cutoff of 2026-02-16, while U2 has a cutoff of 2026-01-31.

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 U2 (2026-01-31).

GPT-5.6 Luna

Feb 2026

1 mo newer
U2

Jan 2026

Provider Availability

GPT-5.6 Luna is available from OpenAI. U2 is available from Unisound.

GPT-5.6 Luna

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

U2

unisound logo
Unisound
Input Price:Input: $0.15/1MOutput Price:Output: $0.30/1M
* 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
Unisound
Less expensive input tokens
Less expensive output tokens

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against GPT-5.6 Luna and U2 side-by-side, then vote on the output you prefer.

GPT-5.6 Luna
✓ Preferred
U2
Open in Playground
AI Model Comparison Table
Feature
OpenAI
GPT-5.6 Luna
Unisound
U2

FAQ

Common questions about GPT-5.6 Luna vs U2.

Which is better, GPT-5.6 Luna or U2?

GPT-5.6 Luna (OpenAI) and U2 (Unisound) each have strengths in different areas. Compare their benchmark scores, pricing, context windows, and capabilities above to determine which fits your needs.

How does GPT-5.6 Luna compare to U2 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%.

Is GPT-5.6 Luna cheaper than U2?

U2 is 6.7x cheaper for input tokens. GPT-5.6 Luna costs $1.00/M input and $6.00/M output via openai. U2 costs $0.15/M input and $0.30/M output via unisound.

What are the context window sizes for GPT-5.6 Luna and U2?

GPT-5.6 Luna supports 1.1M tokens and U2 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 U2?

Key differences include input pricing ($1.00 vs $0.15/M), multimodal support (yes vs no). See the full comparison above for benchmark-by-benchmark results.

Who makes GPT-5.6 Luna and U2?

GPT-5.6 Luna is developed by OpenAI and U2 is developed by Unisound.

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