Detailed comparison of capabilities, features, and performance.
| Feature | GPT-5.1 codex max | Claude Fable 5 |
|---|---|---|
| AI Lab | OpenAI | Anthropic |
| Context Size | 400,000 tokens | 1,000,000 tokens |
| Max Output Size | 128,000 tokens | 128,000 tokens |
| Frontier Model | Yes | Yes |
| Vision Support | Yes | Yes |
| Description | A version of GPT-5.1 optimized for coding tasks set in max mode. | Anthropic's most capable widely released model, with a 1M token context window, 128k max output, and always-on adaptive thinking. |
View detailed specifications and capabilities
View model details →View detailed specifications and capabilities
View model details →Access both GPT-5.1 codex max and Claude Fable 5 in a single workspace without managing multiple API keys.
Create your workspace
