Claude Fable 5 or Claude Fable 5.1: which to choose?
Claude Fable 5 (Anthropic) and Claude Fable 5.1 (Anthropic) compared point by point: measured performance, pricing, context and capabilities.
Data as of October 22, 2026
Side-by-side comparison
| Criterion | Claude Fable 5 | Claude Fable 5.1 |
|---|---|---|
| Developer | Anthropic | Anthropic |
| Released | June 9, 2026 | September 1, 2026 |
| Capability index | 90.8 / 100 | 92.6 / 100 |
| Input price | $10 | $10 |
| Output price | $50 | $50 |
| Cost of a typical task | $0.30 | $0.30 |
| Context window | 1,000,000 tokens | 1,000,000 tokens |
| Maximum output | 50,000 tokens | 128,000 tokens |
| Reasoning mode | Yes | Yes |
| Tool calling | Yes | Yes |
| Accepted inputs | text, image, PDF | text, image, PDF |
| Open weights | No | No |
| Knowledge cutoff | January 31, 2026 | June 2026 |
The match-up at a glance
Claude Fable 5 and Claude Fable 5.1 are two frontier models, the ones you pick when quality comes first, both built by Anthropic. Claude Fable 5 was released on June 9, 2026, Claude Fable 5.1 on September 1, 2026.
All figures below come from public sources checked on October 22, 2026: models.dev and OpenRouter for prices and capabilities, Epoch AI for scores.
What the benchmarks say
On our capability index, Claude Fable 5 scores 90.8 out of 100 and Claude Fable 5.1 92.6. Claude Fable 5.1 leads by 1.8 points.
On the 4 benchmarks reported for both, Claude Fable 5 wins 1 time and Claude Fable 5.1 2:
- OTIS Mock AIME (competition mathematics problems): Claude Fable 5 100%, Claude Fable 5.1 100%
- FrontierMath (very hard research-level mathematics): Claude Fable 5 87%, Claude Fable 5.1 90.2%
- FrontierCode (advanced programming tasks): Claude Fable 5 53.5%, Claude Fable 5.1 50.9%
- APEX-Agents (professional tasks carried out by an agent): Claude Fable 5 63.6%, Claude Fable 5.1 68.6%
Which one costs less?
Claude Fable 5 costs $10 per million input tokens and $50 per million output tokens; Claude Fable 5.1 costs $10 and $50.
For a typical agent task (read 20,000 tokens, write 2,000), expect $0.30 with Claude Fable 5 versus $0.30 with Claude Fable 5.1. The cost is almost the same.
Run the numbers with your own volumes in the agent cost calculator.
Context and capabilities
Both models have the same context window: 1,000,000 tokens, roughly 1,500 pages.
Reasoning mode: Claude Fable 5 yes, Claude Fable 5.1 yes. Tool calling: Claude Fable 5 yes, Claude Fable 5.1 yes. Image input: Claude Fable 5 yes, Claude Fable 5.1 yes.
Neither publishes its weights: both are used through an API.
Knowledge cutoff: January 31, 2026 for Claude Fable 5, June 2026 for Claude Fable 5.1.
In short
Our reading of the data:
- Choose Claude Fable 5.1 for a higher capability index and a more recent release.
This verdict relies on public figures; it does not replace a trial on your own tasks.
Other comparisons
Frequently asked questions
Claude Fable 5 or Claude Fable 5.1: which is better?
On our index (Epoch AI data), Claude Fable 5 scores 90.8 and Claude Fable 5.1 92.6 out of 100. The best choice also depends on price and on your use case.
Which one is cheaper?
Claude Fable 5. To read 20,000 tokens and write 2,000, expect $0.30 with Claude Fable 5 and $0.30 with Claude Fable 5.1 (prices as of October 22, 2026).
Which one has the larger context window?
Neither: both accept 1,000,000 tokens.
Can I run Claude Fable 5 or Claude Fable 5.1 on my own servers?
No: both are closed models, available through an API.
Data sources
- Models.dev — Model data: models.dev (open-source project)
- OpenRouter — Market prices cross-checked with OpenRouter
- Epoch AI — AI Benchmarking Hub — Epoch AI, “AI Benchmarking Hub”, epoch.ai, CC BY 4.0
Data as of October 22, 2026
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