GPT-5.5 vs GPT-5.6 Luna

Both models are evenly matched

Arena ELO

Tie

Cheaper

Tie

Faster

Tie

Detailed Comparison

Category	GPT-5.5	GPT-5.6 Luna
Provider	OpenAI	OpenAI
Context Window	128K	128K
Input Price ($/1M)	N/A	N/A
Output Price ($/1M)	N/A	N/A
Arena ELO	N/A	N/A
Coding	N/A	N/A
Reasoning	N/A	N/A
Speed (tokens/sec)	N/A	N/A
Open Source	No	No

Frequently Asked Questions

Which has a larger context window?

GPT-5.5 supports 128K context, while GPT-5.6 Luna supports 128K.

Is GPT-5.5 or GPT-5.6 Luna open source?

GPT-5.5 is proprietary. GPT-5.6 Luna is proprietary.

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More Comparisons

GPT-5.5 vs Claude Opus 4.5 GPT-5.5 vs Llama 4 Scout GPT-5.5 vs Claude Sonnet 4.6 GPT-5.5 vs Claude Haiku 4.5 GPT-5.5 vs GLM-5.2 GPT-5.5 vs Qwen 3.6 GPT-5.5 vs Claude Fable 5 GPT-5.5 vs Kimi K2.7 Code GPT-5.6 Luna vs Claude Opus 4.5 GPT-5.6 Luna vs Llama 4 Scout GPT-5.6 Luna vs Claude Sonnet 4.6 GPT-5.6 Luna vs Claude Haiku 4.5 GPT-5.6 Luna vs GLM-5.2 GPT-5.6 Luna vs Qwen 3.6 GPT-5.6 Luna vs Claude Fable 5 GPT-5.6 Luna vs Kimi K2.7 Code