Side-by-side technical and economic comparison between OpenAI's GPT-5.6 Luna and Anthropic's Claude Opus 5.
| Metric | GPT-5.6 Luna | Claude Opus 5 | Advantage |
|---|---|---|---|
| Provider Organization | OpenAI | Anthropic | — |
| Standard Input / 1M | $0.20 | $15.00 | GPT-5.6 Luna (99% lower) |
| Cached Input / 1M | $0.10 | $0.50 | GPT-5.6 Luna lower |
| Output / 1M | $1.20 | $75.00 | GPT-5.6 Luna lower |
| Context Window | 128k | 200k | Claude Opus 5 (200k) |
| Max Generation Tokens | 16.4k | 16.4k | GPT-5.6 Luna |
| Tokenizer Family | OpenAI o200k_base (200k vocabulary) | Anthropic Claude BPE (~65k vocabulary) | — |
Opt for GPT-5.6 Luna when your engineering requirements prioritize OpenAI's ecosystem, specific tokenizer efficiencies (Exact BPE (o200k_base)), or when your expected prompt-to-completion ratios favor its $0.2/M input rate.
Opt for Claude Opus 5 when looking for Anthropic's tooling integration, specific context window depth (200k tokens), or when output generation volume favors its $75/M rate.