Side-by-side technical and economic comparison between Anthropic's Claude Fable 5.1 and Anthropic's Claude Opus 5.
| Metric | Claude Fable 5.1 | Claude Opus 5 | Advantage |
|---|---|---|---|
| Provider Organization | Anthropic | Anthropic | — |
| Standard Input / 1M | $10.00 | $5.00 | Claude Opus 5 (50% lower) |
| Cached Input / 1M | $0.25 | $0.50 | Claude Fable 5.1 lower |
| Output / 1M | $50.00 | $25.00 | Claude Opus 5 lower |
| Context Window | 1M | 1M | Equal |
| Max Generation Tokens | 32k | 16.4k | Claude Fable 5.1 |
| Tokenizer Family | Anthropic Claude BPE (~65k vocabulary) | Anthropic Claude BPE (~65k 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 Claude Opus 5 when looking for Anthropic's tooling integration, specific context window depth (1M tokens), or when output generation volume favors its $25/M rate.