Side-by-side technical and economic comparison between Anthropic's Claude Fable 5.1 and OpenAI's OpenAI o4-mini.
| Metric | Claude Fable 5.1 | OpenAI o4-mini | Advantage |
|---|---|---|---|
| Provider Organization | Anthropic | OpenAI | — |
| Standard Input / 1M | $10.00 | $1.10 | OpenAI o4-mini (89% lower) |
| Cached Input / 1M | $0.25 | $0.275 | Claude Fable 5.1 lower |
| Output / 1M | $50.00 | $4.40 | OpenAI o4-mini lower |
| Context Window | 1M | 200k | Claude Fable 5.1 (1M) |
| Max Generation Tokens | 32k | 64k | OpenAI o4-mini |
| Tokenizer Family | Anthropic Claude BPE (~65k vocabulary) | OpenAI o200k_base (200k vocabulary) | — |
| Workload (per month) | Claude Fable 5.1 | OpenAI o4-mini |
|---|---|---|
| Chatbot10k requests · 500 in / 200 out | $150.00 | $14.30 |
| RAG app100k requests · 8,000 in / 1,200 out | $14,000.00 | $1,408.00 |
| Coding agent100k requests · 12,000 in / 2,000 out | $22,000.00 | $2,200.00 |
Standard rates, no caching or batch discounts. Model your own numbers below.
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 o4-mini when looking for OpenAI's tooling integration, specific context window depth (200k tokens), or when output generation volume favors its $4.4/M rate.
At a typical 3:1 input-to-output token mix, OpenAI o4-mini is about 90% cheaper than Claude Fable 5.1. Claude Fable 5.1 costs $10 per 1M input and $50 per 1M output tokens; OpenAI o4-mini costs $1.1 and $4.4.
Claude Fable 5.1 has the larger context window: 1M tokens vs 200k.
Claude Fable 5.1: yes, cached input costs $0.25/1M. OpenAI o4-mini: yes, cached input costs $0.275/1M.