Side-by-side technical and economic comparison between Anthropic's Claude Opus 5 and OpenAI's GPT-5.6 Luna.
| Metric | Claude Opus 5 | GPT-5.6 Luna | Advantage |
|---|---|---|---|
| Provider Organization | Anthropic | OpenAI | — |
| Standard Input / 1M | $5.00 | $0.20 | GPT-5.6 Luna (96% lower) |
| Cached Input / 1M | $0.50 | $0.02 | GPT-5.6 Luna lower |
| Output / 1M | $25.00 | $1.20 | GPT-5.6 Luna lower |
| Context Window | 1M | 1.05M | GPT-5.6 Luna (1.05M) |
| Max Generation Tokens | 16.4k | 16.4k | Claude Opus 5 |
| Tokenizer Family | Anthropic Claude BPE (~65k vocabulary) | OpenAI o200k_base (200k vocabulary) | — |
Opt for Claude Opus 5 when your engineering requirements prioritize Anthropic's ecosystem, specific tokenizer efficiencies (Calibrated Claude Tokenizer (±3%)), or when your expected prompt-to-completion ratios favor its $5/M input rate.
Opt for GPT-5.6 Luna when looking for OpenAI's tooling integration, specific context window depth (1.05M tokens), or when output generation volume favors its $1.2/M rate.