Side-by-side technical and economic comparison between Anthropic's Claude Fable 5.1 and OpenAI's OpenAI o3-pro.
| Metric | Claude Fable 5.1 | OpenAI o3-pro | Advantage |
|---|---|---|---|
| Provider Organization | Anthropic | OpenAI | — |
| Standard Input / 1M | $10.00 | $20.00 | Claude Fable 5.1 (50% lower) |
| Cached Input / 1M | $0.25 | None | Claude Fable 5.1 lower |
| Output / 1M | $50.00 | $80.00 | Claude Fable 5.1 lower |
| Context Window | 1M | 256k | Claude Fable 5.1 (1M) |
| Max Generation Tokens | 32k | 100k | OpenAI o3-pro |
| Tokenizer Family | Anthropic Claude BPE (~65k vocabulary) | OpenAI o200k_base (200k vocabulary) | — |
Opt for Claude Fable 5.1 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 $10/M input rate.
Opt for OpenAI o3-pro when looking for OpenAI's tooling integration, specific context window depth (256k tokens), or when output generation volume favors its $80/M rate.