Claude Fable 5.1 versus GPT-6 Astra
Claude Fable 5.1 (Anthropic) and GPT-6 Astra (OpenAI) compared point by point: measured performance, pricing, context and capabilities.
Data as of October 22, 2026
Side-by-side comparison
| Criterion | Claude Fable 5.1 | GPT-6 Astra |
|---|---|---|
| Developer | Anthropic | OpenAI |
| Released | September 1, 2026 | September 4, 2026 |
| Capability index | 92.6 / 100 | 94.7 / 100 |
| Input price | $10 | $10 |
| Output price | $50 | $50 |
| Cost of a typical task | $0.30 | $0.30 |
| Context window | 1,000,000 tokens | 1,050,000 tokens |
| Maximum output | 128,000 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 | June 2026 | April 30, 2026 |
What are we comparing?
This comparison pits two frontier models, the ones you pick when quality comes first against each other: Claude Fable 5.1 and GPT-6 Astra, one from Anthropic, the other from OpenAI. The first dates from September 1, 2026, the second from September 4, 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 5.1 scores 92.6 out of 100 and GPT-6 Astra 94.7. GPT-6 Astra leads by 2.1 points.
On the 5 benchmarks reported for both, Claude Fable 5.1 wins 1 time and GPT-6 Astra 3:
- OTIS Mock AIME (competition mathematics problems): Claude Fable 5.1 100%, GPT-6 Astra 100%
- FrontierMath (very hard research-level mathematics): Claude Fable 5.1 90.2%, GPT-6 Astra 93.7%
- FrontierCode (advanced programming tasks): Claude Fable 5.1 50.9%, GPT-6 Astra 53.3%
- APEX-Agents (professional tasks carried out by an agent): Claude Fable 5.1 68.6%, GPT-6 Astra 64.7%
- Humanity's Last Exam (multidisciplinary expert questions): Claude Fable 5.1 46.5%, GPT-6 Astra 54.8%
Pricing
Claude Fable 5.1 costs $10 per million input tokens and $50 per million output tokens; GPT-6 Astra costs $10 and $50.
For a typical agent task (read 20,000 tokens, write 2,000), expect $0.30 with Claude Fable 5.1 versus $0.30 with GPT-6 Astra. The cost is almost the same.
Run the numbers with your own volumes in the agent cost calculator.
Features and limits
GPT-6 Astra reads more in one go: 1,050,000 tokens of context (roughly 1,575 pages), versus 1,000,000 for Claude Fable 5.1.
Reasoning mode: Claude Fable 5.1 yes, GPT-6 Astra yes. Tool calling: Claude Fable 5.1 yes, GPT-6 Astra yes. Image input: Claude Fable 5.1 yes, GPT-6 Astra yes.
Neither publishes its weights: both are used through an API.
Knowledge cutoff: June 2026 for Claude Fable 5.1, April 30, 2026 for GPT-6 Astra.
In short
Our reading of the data:
- Choose GPT-6 Astra for a higher capability index.
This verdict relies on public figures; it does not replace a trial on your own tasks.
Other comparisons
Frequently asked questions
Claude Fable 5.1 or GPT-6 Astra: which is better?
On our index (Epoch AI data), Claude Fable 5.1 scores 92.6 and GPT-6 Astra 94.7 out of 100. The best choice also depends on price and on your use case.
Which one is cheaper?
Claude Fable 5.1. To read 20,000 tokens and write 2,000, expect $0.30 with Claude Fable 5.1 and $0.30 with GPT-6 Astra (prices as of October 22, 2026).
Which one has the larger context window?
GPT-6 Astra, with 1,050,000 tokens versus 1,000,000.
Can I run Claude Fable 5.1 or GPT-6 Astra 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
Report an error
Does a figure, a date or a fact look wrong? Tell us: every report is checked.