Pyyan / Compare / GPT-6 Luna vs Claude Opus 5.5
GPT-6 Luna vs Claude Opus 5.5
2 of 5Language Models · verified 24 Sept 2026
GPT-6 LunaOpenAIcurrentClaude Opus 5.5Anthropiccurrent
| Specification | GPT-6 Luna | Claude Opus 5.5 |
|---|---|---|
| Summary | Ten cents a million in, for the work that does not need thinking. | Fable 5.1's level of work on most tasks, at 40% less to run than Opus 5. |
| Context | 1.05M | 1M |
| Input ($/Mtok) | $0.1 | $4 |
| Output ($/Mtok) | $0.5 | $20 |
| Licence | Proprietary | Proprietary |
| Max output | 128K | 128K |
| Parameters | Not published | Not published |
| Released | 22 Sep 2026 | 22 Sep 2026 |
| Model ID | gpt-6-luna | claude-opus-5-5 |
| Category | Language Models | Language Models |
| Official | OpenAI ↗ | Anthropic ↗ |
Highlighted rows are where these differ.
GPT-6 Luna
- Half the price of GPT-5.6 Luna, which it replaces at the bottom of the family
- Beats or matches GPT-5.6 Luna on all five benchmarks OpenAI published
- Same 1.05M context window as the tiers above it
Best for classification and high-volume chat.
Claude Opus 5.5
- 66.4% on Terminal-Bench 4.0 against 52.3% for Opus 5, on Anthropic's own harness
- Cache reads cut 60% to $0.20, and output more than 30% faster than Opus 5
- Attempts to work around its boundaries 85% less often than Opus 5, Anthropic reports
Best for agentic coding at flagship quality.