GPT-6 Astra vs Fugu Ultra vs Claude Fable 5.1
Too close to call on our weighted score (GPT-6 Astra 36, Claude Fable 5.1 36, Fugu Ultra 33). The right pick depends on what you value most.
OpenAIGPT-6 Astra
36/100- ECI166.5
- Price$10.00 / $50.00
- Context1.05M
Sakana AI
Fugu Ultra
33/100- ECI—
- Price$5.00 / $30.00
- Context1M
AnthropicClaude Fable 5.1
36/100- ECI164.8
- Price$10.00 / $50.00
- Context1M
Too close to call
It is close. Our weighted score puts them within a point (GPT-6 Astra 36/100, Claude Fable 5.1 36/100, Fugu Ultra 33/100), so choose by what matters most for your work: Fugu Ultra on price and GPT-6 Astra for long inputs. 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 priceFugu UltraFugu Ultra $11.25 · GPT-6 Astra $20.00 · Claude Fable 5.1 $20.00 per 1M tokens (3:1 blend)
- Longest contextGPT-6 AstraGPT-6 Astra 1,050,000 · Fugu Ultra 1,000,000 · Claude Fable 5.1 1,000,000 tokens
- Widest inputsGPT-6 Astra and Claude Fable 5.1GPT-6 Astra: Text, Images, PDFs · Fugu Ultra: Text, Images · Claude Fable 5.1: Text, Images, PDFs
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | GPT-6 Astra | Fugu Ultra | Claude Fable 5.1 |
|---|---|---|---|---|
| Price | 50% | 0 | 0 | 0 |
| Inputs & features | 30% | 80 | 70 | 80 |
| Context window | 20% | 61 | 60 | 60 |
| Overall | 100% | 36/100 | 33/100 | 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 | GPT-6 AstraOpenAI | Fugu UltraSakana AI | Claude Fable 5.1Anthropic |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 166.5 (best) | — | 164.8 |
| ECI rank | #2 of 148 (best) | — | #4 of 148 |
| GPQA DiamondGraduate-level science questions | 95.8% | — | — |
| FrontierMath Tiers 1–3Research-level mathematics | 93.7% (best) | — | 90.2% |
| OTIS Mock AIME 2024–2025Competition mathematics | 100% | — | 100% |
| SimpleQA VerifiedShort factual questions | 75.6% (best) | — | 70.8% |
| Price per million tokens | |||
| Input | $10.00 | $5.00 (best) | $10.00 |
| Output | $50.00 | $30.00 (best) | $50.00 |
| Cached input | $1.00 | $0.50 | $0.25 (best) |
| Blended (3:1) | $20.00 | $11.25 (best) | $20.00 |
| Long-context rate | Over 272K: $20.00 / $75.00 | Over 272K: $10.00 / $45.00 | Same rate |
| Price source | Official OpenAI API | Official Sakana AI API | Official Anthropic API |
| Limits | |||
| Context window | 1,050,000 tokens (best) | 1,000,000 tokens | 1,000,000 tokens |
| Max output | 128,000 tokens | — | 128,000 tokens |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | Yes | No | Yes |
| Audio | No | No | No |
| Video | No | No | No |
| Reasoning | Yeslow · medium · high · xhigh · max | Yeshigh · xhigh | Yeslow · medium · high · xhigh · max |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | Yes |
| Availability | |||
| Weights | Proprietary | Proprietary | Proprietary |
| API model ID | gpt-6-astra | fugu-ultra | claude-fable-5-1 |
| API providers | 26 | 11 | 29 (best) |
| Released | Sep 4, 2026 | Jun 15, 2026 | Sep 1, 2026 |
| Knowledge cutoff | Apr 30, 2026 | — | Jun 2026 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- GPT-6 Astra$200.00
- Fugu Ultra$110.00
- Claude Fable 5.1$200.00
Which should you choose?
Which is better: GPT-6 Astra, Fugu Ultra or Claude Fable 5.1?
It is close. Our weighted score puts them within a point (GPT-6 Astra 36/100, Claude Fable 5.1 36/100, Fugu Ultra 33/100), so choose by what matters most for your work: Fugu Ultra on price and GPT-6 Astra for long inputs. 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, GPT-6 Astra, Fugu Ultra or Claude Fable 5.1?
Fugu Ultra is cheaper at $5.00 input / $30.00 output per million tokens (official Sakana AI API price). GPT-6 Astra costs $10.00 input / $50.00 output per million tokens (official OpenAI API price); Claude Fable 5.1 costs $10.00 input / $50.00 output per million tokens (official Anthropic API price). At a typical mix of three input tokens to one output token, that is $11.25 per million tokens for Fugu Ultra versus $20.00 for GPT-6 Astra (1.8× as much) and $20.00 for Claude Fable 5.1 (1.8× as much).
Which scores higher on benchmarks?
There is no independent benchmark that covers all three models yet. GPT-6 Astra has an ECI of 166.5, Fugu Ultra has not been scored yet and Claude Fable 5.1 has an ECI of 164.8.
Which is better for coding?
There are no published SWE-bench Verified results for GPT-6 Astra, Fugu Ultra and Claude Fable 5.1 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 has the largest context window at 1,050,000 tokens, against 1,000,000 for Fugu Ultra and 1,000,000 for Claude Fable 5.1. Maximum output per response: GPT-6 Astra up to 128,000, Claude Fable 5.1 up to 128,000 tokens.
Which can read images, PDFs, audio or video?
GPT-6 Astra accepts text, images and PDFs; Fugu Ultra accepts text and images; Claude Fable 5.1 accepts text, images and PDFs. GPT-6 Astra handles the widest range of inputs.
Are any of these open source?
No. GPT-6 Astra, Fugu Ultra and Claude Fable 5.1 are proprietary and only available through APIs and apps.
Which is newer?
GPT-6 Astra is the newest, released Sep 4, 2026. Claude Fable 5.1 came out Sep 1, 2026; Fugu Ultra came out Jun 15, 2026. Knowledge cutoff: GPT-6 Astra Apr 30, 2026, Claude Fable 5.1 Jun 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.
