Claude Fable 5.1 vs GPT-5.5
Claude Fable 5.1 vs GPT-5.5: which AI model is cheaper, has the larger context window and more capabilities? Side-by-side comparison updated daily.
Quick verdict
- GPT-5.5 is 1.8× cheaper than Claude Fable 5.1 for the same mix of input and output tokens.
- GPT-5.5 has the larger context window (1.1M), useful for long documents and big codebases.
- Claude Fable 5.1 is the more recent release (Sep 1, 2026).
- Claude Fable 5.1 scores higher on independent tests (overall index 165.0 vs 159.3).
- Choose GPT-5.5 if cost matters most; choose Claude Fable 5.1 if you need its specific strengths above. For the best results, test both on your own prompts.
| Claude Fable 5.1 | GPT-5.5 | |
|---|---|---|
| Company | Anthropic | OpenAI |
| Released | Sep 1, 2026 ● | Apr 24, 2026 |
| Overall index | 165.0 ● | 159.3 |
| GPQA Diamond | — | 90.7% |
| AIME math | 100% ● | 84.4% |
| FrontierMath | 90.2% ● | 85.3% |
| SimpleQA Verified | 70.8% ● | 63.0% |
| Input (per 1M tokens) | $10 | $5 ● |
| Output (per 1M tokens) | $50 | $30 ● |
| Cost for 1M input + 1M output tokens | $60.00 | $35.00 ● |
| Providers | 4 | 7 ● |
| Context | 1M | 1.1M ● |
| Max output | 128K | 128K |
| Inputs | Text, Image, Files | Files, Image, Text |
| Outputs | Text | Text |
| Reasoning | ✓ | ✓ |
| Tool use | ✓ | ✓ |
| Structured output | ✓ | ✓ |
| Open weights | — | — |