Claude Fable 5.5 (Leaked Checkpoint) vs GPT-6 Luna
A direct, empirical evaluation of Claude Fable 5.5 (Leaked Checkpoint) (Anthropic) against GPT-6 Luna (OpenAI).
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.
GPT-6 Luna
Developed by OpenAI · Proprietary High-Throughput Distillation parameters
High-throughput document extraction, sub-second routing, customer service triage, code autocomplete, and cost-optimized reasoning via Luna Pro mode.
| Metric | Claude Fable 5.5 (Leaked Checkpoint) | GPT-6 Luna |
|---|---|---|
| SWE-bench Verified | 84.2% | 48.2% |
| MMLU-Pro | 94.6% | 74.6% |
| MATH-500 | 98.4% | 84.1% |
| Context Window | 1,500,000 tokens | 1,050,000 tokens |
| Input Pricing (per 1M) | $3.50 | $0.10 |
| Output Pricing (per 1M) | $17.50 | $0.50 |