Head-to-head · Anthropic vs OpenAI
Claude Opus 5.5 vs GPT-6 Luna
Quick answer: Claude Opus 5.5 stands out for matches Claude Fable 5.1 on most work at a much lower price. GPT-6 Luna stands out for extremely cheap for bulk processing. Reviewed September 2026.
Overview
Claude Opus 5.5: Claude Opus 5.5, released on 22 September 2026, is Anthropic's newest Opus model. Anthropic reports it performs at the level of Claude Fable 5.1 on most work while costing about 40% less to run than Opus 5, with a focus on agentic coding, computer use and knowledge work.
GPT-6 Luna: GPT-6 Luna, launched on 22 September 2026, is the small, low-cost member of the GPT-6 family at $0.10 and $0.50 per million tokens. It targets high-volume tasks where cost and speed matter most.
At a glance
| Dimension | Claude Opus 5.5 | GPT-6 Luna |
|---|---|---|
| Vendor | Anthropic | OpenAI |
| Starting price | API: $4 in / $20 out per M tokens | API: $0.10 in / $0.50 out per M tokens |
| Pricing model | Paid | Paid |
| Free tier | No | No |
| Category | Generative AI | Generative AI |
Strengths and limits
Claude Opus 5.5
- Matches Claude Fable 5.1 on most work at a much lower price
- Faster output than Opus 5
- Strong on coding and knowledge work such as financial analysis
Watch out for
- Newest release, so fewer independent long-term evaluations
- Output still costs $20 per million tokens
- Sonnet or Haiku are cheaper for routine tasks
GPT-6 Luna
- Extremely cheap for bulk processing
- Fast responses
- Good fit for classification and extraction
Watch out for
- Not suited to the hardest reasoning tasks
- Newest release with limited track record
- Quality varies by task, so test on your own data
Key features
Claude Opus 5.5
- 1M-token context window at standard pricing
- Agentic coding, code review and bug detection
- Computer use and complex multi-step tasks
- Clearer, more direct communication style
- Available in Claude apps, the API, Claude Code, AWS, Google Cloud and Microsoft Azure
GPT-6 Luna
- Very low per-token pricing
- Built for high-volume and latency-sensitive work
- Shares GPT-6 family technology
- Available through the OpenAI API
Pricing compared
Claude Opus 5.5 is priced by usage rather than by seat: API: $4 in / $20 out per M tokens. That means cost scales with how much text you send and receive, so estimate your monthly volume before committing.
GPT-6 Luna is priced by usage rather than by seat: API: $0.10 in / $0.50 out per M tokens. That means cost scales with how much text you send and receive, so estimate your monthly volume before committing.
Frequently asked questions
Which is better, Claude Opus 5.5 or GPT-6 Luna?
It depends on the work. Claude Opus 5.5 stands out for matches Claude Fable 5.1 on most work at a much lower price. GPT-6 Luna stands out for extremely cheap for bulk processing.
How do Claude Opus 5.5 and GPT-6 Luna compare on price?
Claude Opus 5.5 is priced by usage rather than by seat: API: $4 in / $20 out per M tokens. That means cost scales with how much text you send and receive, so estimate your monthly volume before committing. GPT-6 Luna is priced by usage rather than by seat: API: $0.10 in / $0.50 out per M tokens. That means cost scales with how much text you send and receive, so estimate your monthly volume before committing.
Is there a free option between Claude Opus 5.5 and GPT-6 Luna?
Neither lists a permanent free tier. Look for trials or usage-based pricing to test on real work first.