Claude Fable 5.1 vs GPT-6 Astra vs GPT-6 Astra (Fast)
Too close to call on our weighted score (GPT-6 Astra 36, GPT-6 Astra (Fast) 36, Claude Fable 5.1 36). The right pick depends on what you value most.
AnthropicClaude Fable 5.1
36/100- ECI164.8
- Price$10.00 / $50.00
- Context1M
OpenAIGPT-6 Astra
36/100- ECI166.5
- Price$10.00 / $50.00
- Context1.05M
- OpenAI
GPT-6 Astra (Fast)
36/100- ECI—
- Price$20.00 / $100.00
- Context1.05M
Too close to call
It is close. Our weighted score puts them within a point (GPT-6 Astra 36/100, GPT-6 Astra (Fast) 36/100, Claude Fable 5.1 36/100), so choose by what matters most for your work: Claude Fable 5.1 on price. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.
- CapabilityNot enough dataNo independent benchmark covers every model here yet
- Lowest priceClaude Fable 5.1 and GPT-6 AstraClaude Fable 5.1 $20.00 · GPT-6 Astra $20.00 · GPT-6 Astra (Fast) $40.00 per 1M tokens (3:1 blend)
- Longest contextGPT-6 Astra and GPT-6 Astra (Fast)GPT-6 Astra 1,050,000 · GPT-6 Astra (Fast) 1,050,000 · Claude Fable 5.1 1,000,000 tokens
- Widest inputsSame inputsClaude Fable 5.1: Text, Images, PDFs · GPT-6 Astra: Text, Images, PDFs · GPT-6 Astra (Fast): Text, Images, PDFs
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | Claude Fable 5.1 | GPT-6 Astra | GPT-6 Astra (Fast) |
|---|---|---|---|---|
| Price | 50% | 0 | 0 | 0 |
| Inputs & features | 30% | 80 | 80 | 80 |
| Context window | 20% | 60 | 61 | 61 |
| Overall | 100% | 36/100 | 36/100 | 36/100 |
Left out because at least one model lacks the data: capability. The remaining weights were rescaled.
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | Claude Fable 5.1Anthropic | GPT-6 AstraOpenAI | GPT-6 Astra (Fast)OpenAI |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 164.8 | 166.5 (best) | — |
| ECI rank | #4 of 148 | #2 of 148 (best) | — |
| GPQA DiamondGraduate-level science questions | — | 95.8% | — |
| FrontierMath Tiers 1–3Research-level mathematics | 90.2% | 93.7% (best) | — |
| OTIS Mock AIME 2024–2025Competition mathematics | 100% | 100% | — |
| SimpleQA VerifiedShort factual questions | 70.8% | 75.6% (best) | — |
| Price per million tokens | |||
| Input | $10.00 (best) | $10.00 (best) | $20.00 |
| Output | $50.00 (best) | $50.00 (best) | $100.00 |
| Cached input | $0.25 (best) | $1.00 | — |
| Blended (3:1) | $20.00 (best) | $20.00 (best) | $40.00 |
| Long-context rate | Same rate | Over 272K: $20.00 / $75.00 | Same rate |
| Price source | Official Anthropic API | Official OpenAI API | Median of 1 providers |
| Limits | |||
| Context window | 1,000,000 tokens | 1,050,000 tokens (best) | 1,050,000 tokens (best) |
| Max output | 128,000 tokens | 128,000 tokens | 128,000 tokens |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | Yes | Yes | Yes |
| Audio | No | No | No |
| Video | No | No | No |
| Reasoning | Yeslow · medium · high · xhigh · max | Yeslow · medium · high · xhigh · max | Yes |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | Yes |
| Availability | |||
| Weights | Proprietary | Proprietary | Proprietary |
| API model ID | claude-fable-5-1 | gpt-6-astra | — |
| API providers | 29 (best) | 26 | 1 |
| Released | Sep 1, 2026 | Sep 4, 2026 | Sep 4, 2026 |
| Knowledge cutoff | Jun 2026 | Apr 30, 2026 | — |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- Claude Fable 5.1$200.00
- GPT-6 Astra$200.00
- GPT-6 Astra (Fast)$400.00
Which should you choose?
Which is better: Claude Fable 5.1, GPT-6 Astra or GPT-6 Astra (Fast)?
It is close. Our weighted score puts them within a point (GPT-6 Astra 36/100, GPT-6 Astra (Fast) 36/100, Claude Fable 5.1 36/100), so choose by what matters most for your work: Claude Fable 5.1 on price. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.
Which is cheaper, Claude Fable 5.1, GPT-6 Astra or GPT-6 Astra (Fast)?
Claude Fable 5.1 is cheaper at $10.00 input / $50.00 output per million tokens (official Anthropic API price). GPT-6 Astra costs $10.00 input / $50.00 output per million tokens (official OpenAI API price); GPT-6 Astra (Fast) costs $20.00 input / $100.00 output per million tokens (median across 1 API provider). At a typical mix of three input tokens to one output token, that is $20.00 per million tokens for Claude Fable 5.1 versus $20.00 for GPT-6 Astra (1× as much) and $40.00 for GPT-6 Astra (Fast) (2× as much).
Which scores higher on benchmarks?
There is no independent benchmark that covers all three models yet. Claude Fable 5.1 has an ECI of 164.8, GPT-6 Astra has an ECI of 166.5 and GPT-6 Astra (Fast) has not been scored yet.
Which is better for coding?
There are no published SWE-bench Verified results for Claude Fable 5.1, GPT-6 Astra and GPT-6 Astra (Fast) yet, so there is no like-for-like coding score. Test both on a sample of your own tasks. All three support tool calling for agent workflows.
Which has the bigger context window?
GPT-6 Astra and GPT-6 Astra (Fast) have the largest context windows (1,050,000 and 1,050,000 tokens), against 1,000,000 for Claude Fable 5.1. Maximum output per response: Claude Fable 5.1 up to 128,000, GPT-6 Astra up to 128,000, GPT-6 Astra (Fast) up to 128,000 tokens.
Which can read images, PDFs, audio or video?
Claude Fable 5.1 accepts text, images and PDFs; GPT-6 Astra accepts text, images and PDFs; GPT-6 Astra (Fast) accepts text, images and PDFs. They handle the same number of input types.
Are any of these open source?
No. Claude Fable 5.1, GPT-6 Astra and GPT-6 Astra (Fast) are proprietary and only available through APIs and apps.
Which is newer?
GPT-6 Astra is the newest, released Sep 4, 2026. GPT-6 Astra (Fast) came out Sep 4, 2026; Claude Fable 5.1 came out Sep 1, 2026. Knowledge cutoff: Claude Fable 5.1 Jun 2026, GPT-6 Astra Apr 30, 2026.
How do you decide the winner?
Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.
