Model Comparison

GPT-5.6 Luna vs Seed 2.0 ProWhich is better in 2026?

GPT-5.6 Luna significantly outperforms across most benchmarks. Seed 2.0 Pro is 2.0x cheaper per token.

Verdict: GPT-5.6 Luna vs Seed 2.0 Pro — which is better?

GPT-5.6 Luna (by OpenAI) and Seed 2.0 Pro (by ByteDance) 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 2 benchmarks (BrowseComp, GPQA), while Seed 2.0 Pro is better at 0 benchmarks. GPT-5.6 Luna significantly outperforms across most benchmarks.

On price, Seed 2.0 Pro is roughly 2.0x 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 2 of 2 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 Seed 2.0 Pro if…

  • cost matters — it's about 2.0x cheaper per token

Performance Benchmarks

Comparative analysis across standard metrics

2 benchmarks

GPT-5.6 Luna outperforms in 2 benchmarks (BrowseComp, GPQA), while Seed 2.0 Pro is better at 0 benchmarks.

GPT-5.6 Luna significantly outperforms across most benchmarks.

Tue Jul 21 2026 • llm-stats.com

Arena Performance

Human preference votes

Pricing Analysis

Price comparison per million tokens

Seed 2.0 Pro costs less

For input processing, GPT-5.6 Luna ($1.00/1M tokens) is 2.0x more expensive than Seed 2.0 Pro ($0.50/1M tokens).

For output processing, GPT-5.6 Luna ($6.00/1M tokens) is 2.0x more expensive than Seed 2.0 Pro ($3.00/1M tokens).

In conclusion, GPT-5.6 Luna is more expensive than Seed 2.0 Pro.*

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

Lowest available price from all providers
Tue Jul 21 2026 • llm-stats.com
OpenAI
GPT-5.6 Luna
Input tokens$1.00
Output tokens$6.00
Best providerOpenAI
ByteDance
Seed 2.0 Pro
Input tokens$0.50
Output tokens$3.00
Best providerDeepinfra
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 Seed 2.0 Pro's 256,000 tokens. GPT-5.6 Luna can generate longer responses up to 128,000 tokens, while Seed 2.0 Pro is limited to 65,536 tokens.

OpenAI
GPT-5.6 Luna
Input1,050,000 tokens
Output128,000 tokens
ByteDance
Seed 2.0 Pro
Input256,000 tokens
Output65,536 tokens
Tue Jul 21 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Both GPT-5.6 Luna and Seed 2.0 Pro support multimodal inputs.

They are both capable of processing various types of data, offering versatility in application.

GPT-5.6 Luna

Text
Images
Audio
Video

Seed 2.0 Pro

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

Seed 2.0 Pro

Proprietary

Closed source

Release Timeline

When each model was launched

GPT-5.6 Luna was released on 2026-07-09, while Seed 2.0 Pro was released on 2026-02-14.

GPT-5.6 Luna is 5 months newer than Seed 2.0 Pro.

GPT-5.6 Luna

Jul 9, 2026

1 weeks ago

4mo newer
Seed 2.0 Pro

Feb 14, 2026

5 months ago

Knowledge Cutoff

When training data ends

GPT-5.6 Luna has a knowledge cutoff of 2026-02-16, while Seed 2.0 Pro has a cutoff of 2024-01-01.

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 Seed 2.0 Pro (2024-01-01).

GPT-5.6 Luna

Feb 2026

2.1 yr newer
Seed 2.0 Pro

Jan 2024

Provider Availability

GPT-5.6 Luna is available from OpenAI. Seed 2.0 Pro is available from DeepInfra.

GPT-5.6 Luna

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

Seed 2.0 Pro

deepinfra logo
Deepinfra
Input Price:Input: $0.50/1MOutput Price:Output: $3.00/1M
* 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)
Higher BrowseComp score (83.3% vs 77.3%)
Higher GPQA score (92.3% vs 88.9%)
ByteDance
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 Seed 2.0 Pro side-by-side, then vote on the output you prefer.

GPT-5.6 Luna
✓ Preferred
Seed 2.0 Pro
Open in Playground
AI Model Comparison Table
Feature
OpenAI
GPT-5.6 Luna
ByteDance
Seed 2.0 Pro

FAQ

Common questions about GPT-5.6 Luna vs Seed 2.0 Pro.

Which is better, GPT-5.6 Luna or Seed 2.0 Pro?

GPT-5.6 Luna significantly outperforms across most benchmarks. GPT-5.6 Luna is made by OpenAI and Seed 2.0 Pro is made by ByteDance. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does GPT-5.6 Luna compare to Seed 2.0 Pro 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%. Seed 2.0 Pro scores AIME 2025: 98.3%, AIME 2026: 94.2%, GPQA: 88.9%, LiveCodeBench v6: 87.8%, BrowseComp: 77.3%.

Is GPT-5.6 Luna cheaper than Seed 2.0 Pro?

Seed 2.0 Pro is 2.0x cheaper for input tokens. GPT-5.6 Luna costs $1.00/M input and $6.00/M output via openai. Seed 2.0 Pro costs $0.50/M input and $3.00/M output via deepinfra.

What are the context window sizes for GPT-5.6 Luna and Seed 2.0 Pro?

GPT-5.6 Luna supports 1.1M tokens and Seed 2.0 Pro supports 256K 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 Seed 2.0 Pro?

Key differences include context window (1.1M vs 256K), input pricing ($1.00 vs $0.50/M). See the full comparison above for benchmark-by-benchmark results.

Who makes GPT-5.6 Luna and Seed 2.0 Pro?

GPT-5.6 Luna is developed by OpenAI and Seed 2.0 Pro is developed by ByteDance.

Related comparisons