The short answer
Claude Opus 5.5 vs GPT-6 Luna: specs side by side
| Claude Opus 5.5 | GPT-6 Luna | |
|---|---|---|
| Made by | Anthropic | OpenAI |
| Released | September 22, 2026 | September 22, 2026 |
| API model ID | claude-opus-5.5 | gpt-6-luna |
| Context window | 1M tokens | 1.05M tokens (922K input) |
| Max output | 128,000 tokens | 128,000 tokens |
| Knowledge cutoff | Not published | May 18, 2026 |
| Inputs | Text, images and files | Text and images |
| API price | $4 input / $20 output per 1M tokens | $0.10 input / $0.50 output per 1M tokens |
| In AimiChat | Genius quality · Aimi Genius ($100/month) | Fast quality · Free ($0) |
Which to use for each task
Everyday chat and summaries
Luna is built for speed, costs a small fraction as much, and is free in AimiChat.
Complex analysis and strategy
Opus 5.5 is Anthropic's flagship and is far stronger on long, high-stakes reasoning.
Serious coding
Opus 5.5 leads Anthropic's agentic coding results and is built for multi-file work.
Recent facts without web search
Luna's knowledge runs to May 2026.
What to know before you choose
The API price difference is 40x on input and output, so the question is less which is better and more whether the task needs a flagship at all.
In AimiChat, GPT-6 Luna is on the Free plan and Claude Opus 5.5 on the Aimi Genius plan.
Published benchmarks
Each company reports different tests with different settings, so these are listed per model rather than head to head.
| Model | Benchmark | Score | Reported by |
|---|---|---|---|
| Claude Opus 5.5 | Terminal-Bench 4.0 (xhigh effort) | 66.4% | Anthropic launch post |
| Claude Opus 5.5 | GDPval-AA v2.1 (knowledge work) | 1846 | Anthropic launch post |
| Claude Opus 5.5 | Humanity's Last Exam (with tools) | 67.7% | Anthropic launch post |
| Claude Opus 5.5 | OSWorld 2.0 (partial credit) | 81.8% | Anthropic launch post |
| GPT-6 Luna | DeepSWE v1.1 (max effort) | 66.6% | OpenAI launch post, as reported by VentureBeat and Codersera |
Try both in AimiChat
Claude Opus 5.5 runs on the Genius quality and GPT-6 Luna on Fast. On a plan that includes both, you can send the same prompt twice in one chat, switching quality in between, and compare the answers directly. Read more about Claude Opus 5.5 and GPT-6 Luna, or see which plan includes which model.
Sources
Specifications and prices come from the model makers and API listings below. Benchmark figures are reported by the company that made the model and are not independent tests.