Claude Fable 5.5 (Leaked Checkpoint) vs Claude Opus 5.5
A direct, empirical evaluation of Claude Fable 5.5 (Leaked Checkpoint) (Anthropic) against Claude Opus 5.5 (Anthropic).
Claude Fable 5.5 (Leaked Checkpoint)
Developed by Anthropic · Proprietary Frontier Dynamic Reasoner parameters
Terminal-Bench 4.0 autonomous shell execution (78.5% target), recursive self-critique, and 1.5M-token repository refactoring.
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 5.5 (Leaked Checkpoint) | Claude Opus 5.5 |
|---|---|---|
| SWE-bench Verified | 84.2% | 89.9% |
| MMLU-Pro | 94.6% | 92.4% |
| MATH-500 | 98.4% | 97.2% |
| Context Window | 1,500,000 tokens | 500,000 tokens |
| Input Pricing (per 1M) | $3.50 | $4.00 |
| Output Pricing (per 1M) | $17.50 | $20.00 |