Pyyan / Compare / Step 5 Preview vs Claude Fable 5.1
Step 5 Preview vs Claude Fable 5.1
2 of 5Language Models · verified 20 Sept 2026
Step 5 PreviewStepFuncurrentClaude Fable 5.1Anthropiccurrent
| Specification | Step 5 Preview | Claude Fable 5.1 |
|---|---|---|
| Summary | A frontier tier score at a tenth of the frontier price. | Same price as Fable 5, and cache reads cost a quarter of what they did. |
| Context | 1M | 1M |
| Input ($/Mtok) | $1 | $10 |
| Output ($/Mtok) | $2.7 | $50 |
| Licence | Proprietary | Proprietary |
| Max output | Not published | 128K |
| Parameters | 600B total, 27B active | Not published |
| Released | 18 Sep 2026 | 1 Sep 2026 |
| Model ID | step-5-preview | claude-fable-5-1 |
| Category | Language Models | Language Models |
| Official | StepFun ↗ | — |
Highlighted rows are where these differ.
Step 5 Preview
- 600B total parameters with 27B active per token, text and images in
- 24th of 200 models on the Artificial Analysis intelligence index
- Listings disagree on context: 1M on StepFun's API and Artificial Analysis, 100K on some trackers
Best for cheap reasoning at volume.
Claude Fable 5.1
- Matches or beats Fable 5 at low and medium effort, and pulls clear at high effort
- Cache reads cut to 25% of the old price, so re-reading a long context got much cheaper
- Identical model to Mythos 5.1 underneath; the difference is the safeguards
Best for coding and long-running work.