Claude Fable 5.1 vs Claude Opus 5.5
A direct, empirical evaluation of Claude Fable 5.1 (Anthropic) against Claude Opus 5.5 (Anthropic).
Claude Fable 5.1
Developed by Anthropic · Proprietary Frontier parameters
Full-repository software refactoring, agentic tool workflows, formal verification, and 1.5M-token needle retrieval.
Claude Opus 5.5
Developed by Anthropic · Proprietary Frontier Reasoner parameters
Autonomous enterprise codebase migrations, GitHub Copilot multi-file edits, SWE-bench Pro issue resolution (89.9%), and CodeRabbit automated reviews.
| Metric | Claude Fable 5.1 | Claude Opus 5.5 |
|---|---|---|
| SWE-bench Verified | 82.8% | 89.9% |
| MMLU-Pro | 92.4% | 92.4% |
| MATH-500 | 97.9% | 97.2% |
| Context Window | 1,500,000 tokens | 500,000 tokens |
| Input Pricing (per 1M) | $12.00 | $4.00 |
| Output Pricing (per 1M) | $60.00 | $20.00 |