Claude Fable 5.1 vs GPT-Rosalind-6

Where it leads

• Lower input and output prices, $10 and $50 vs $15 and $75 per 1M tokens
• Accepts image input
• Cheaper cached input, $0.25 vs $1.50 per 1M tokens
• Batch pricing, $5 input and $25 output per 1M tokens

Best for

• Long-horizon agentic coding where a large prompt prefix is replayed across many turns
• Work where Claude Opus 5 at higher effort has already been evaluated and fell short

Watch out for

• Base input and output pricing is unchanged from Fable 5 at $10 / $50; the saving is entirely in cache reads, so a workload with little cache reuse sees no discount
• The 4.7-generation tokenizer produces roughly 30% more tokens for the same text than Claude Sonnet 4.6 and earlier, so per-token rates are not directly comparable across generations
• Anthropic’s launch comparisons are self-reported and were not reproduced independently here

Where it leads

No measured lead over Claude Fable 5.1 in this data.

Best for

• Drug discovery and life sciences research teams approved for OpenAI's trusted access
• Dual-use biology research that GPT-6 Astra is more likely to refuse

Watch out for

• Limited access: OpenAI offers it only through its trusted-access program, after reviewing each applicant's intended use, security controls and governance, for internal research
• OpenAI treats it as High capability in the biological and chemical domain, so access comes with security, monitoring and enforcement terms
• OpenAI publishes no context window for it and compares it only with GPT-Rosalind-5.5; no independent benchmark score is recorded here yet