Compare models
Put models side by side on price, context, capabilities, and benchmarks.
This is OpenRouter's auto-updating alias to OpenAI's current 'Luna' model, always resolving to the newest release in that family (1.05M-token context) rather than a pinned snapshot. Luna is the cheapest and fastest tier in OpenAI's Sol/Terra/Luna/Astra alias family, priced roughly ten times below Sol and suited to high-volume, latency-sensitive chat and lightweight agent work.
Claude Sonnet 5.5 is Anthropic's Sonnet-class model (1M-token context, 128K max output, $2/$10 per million input/output tokens), released September 28, 2026 as a direct upgrade to Sonnet 5 and a faster, lower-cost complement to Opus 5.5. It generates output over 30% faster with fewer tokens per task, and is strongest at well-scoped everyday work such as building features, fixing bugs, and producing polished documents, slides, and spreadsheets.
Benchmarks
Head-to-head scores across reasoning, coding, and agentic indices, plus per-domain rankings.
Intelligence
Coding
GPT Luna Latest has no data
Claude Sonnet 5.5 has no data
Automation & Tool Use
GPT Luna Latest has no data
Claude Sonnet 5.5 has no data
Intelligence, coding & agentic scores from Artificial Analysis.
Software & IT Services
arena.aiPopular comparisons
Claude Sonnet 5.5 vs GPT-6.1 Sol
Qwen3.8 Max Prime vs Kimi K3
Grok 4.7 vs GPT-6.1 Sol
Claude Haiku 5.5 vs GPT-6 Luna
GPT-6.1 Sol vs Claude Opus 5.5
Gemini 4 Argon vs GPT-6.1 Sol
Kimi K3 vs Claude Fable 5.1
DeepSeek V4 Pro 0813 vs GPT-6.1 Sol
Claude Opus 5.5 vs Gemini 4 Argon
Mistral Large 4 vs Llama 4 Maverick

Ling 3.1 Flash vs DeepSeek V4.1 Flash
Gemini 3.8 Flash vs Claude Haiku 5.5
GLM 5.3 vs DeepSeek V4 Pro 0813
DeepSeek V4 Pro 0813 vs Claude Opus 5.5
Claude Fable 5.1 vs GPT-6 Astra
Claude Opus 5.5 vs Claude Sonnet 5.5