Fugu Ultra vs Claude Fable 5.1
Claude Fable 5.1 comes out ahead, 36 to 33 on our weighted score, though Fugu Ultra is 44% cheaper per token.
Sakana AI
Fugu Ultra
33/100- ECI—
- Price$5.00 / $30.00
- Context1M
- Our pick
AnthropicClaude Fable 5.1
36/100- ECI164.8
- Price$10.00 / $50.00
- Context1M
Add a model
Make it a three-way comparison.
Claude Fable 5.1 is our pick
Claude Fable 5.1 is the better all-round choice, scoring 36/100 against Fugu Ultra (33). It leads on inputs & features. 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 · Claude Fable 5.1 $20.00 per 1M tokens (3:1 blend)
- Longest contextAbout the sameFugu Ultra 1,000,000 · Claude Fable 5.1 1,000,000 tokens
- Widest inputsClaude Fable 5.1Fugu Ultra: Text, Images · Claude Fable 5.1: Text, Images, PDFs
- Self-hostingNo open weightsBoth are available only through APIs
| Measure | Weight | Fugu Ultra | Claude Fable 5.1 |
|---|---|---|---|
| Price | 50% | 0 | 0 |
| Inputs & features | 30% | 70 | 80 |
| Context window | 20% | 60 | 60 |
| Overall | 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 | Fugu UltraSakana AI | Claude Fable 5.1Anthropic |
|---|---|---|
| Capability | ||
| Capabilities Index (ECI) | — | 164.8 |
| ECI rank | — | #4 of 148 |
| FrontierMath Tiers 1–3Research-level mathematics | — | 90.2% |
| OTIS Mock AIME 2024–2025Competition mathematics | — | 100% |
| SimpleQA VerifiedShort factual questions | — | 70.8% |
| Price per million tokens | ||
| Input | $5.00 (best) | $10.00 |
| Output | $30.00 (best) | $50.00 |
| Cached input | $0.50 | $0.25 (best) |
| Blended (3:1) | $11.25 (best) | $20.00 |
| Long-context rate | Over 272K: $10.00 / $45.00 | Same rate |
| Price source | Official Sakana AI API | Official Anthropic API |
| Limits | ||
| Context window | 1,000,000 tokens | 1,000,000 tokens |
| Max output | — | 128,000 tokens |
| Inputs and features | ||
| Text | Yes | Yes |
| Images | Yes | Yes |
| PDFs | No | Yes |
| Audio | No | No |
| Video | No | No |
| Reasoning | Yeshigh · xhigh | Yeslow · medium · high · xhigh · max |
| Tool calling | Yes | Yes |
| Structured output | Yes | Yes |
| Availability | ||
| Weights | Proprietary | Proprietary |
| API model ID | fugu-ultra | claude-fable-5-1 |
| API providers | 11 | 29 (best) |
| Released | Jun 15, 2026 | Sep 1, 2026 |
| Knowledge cutoff | — | 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.
- Fugu Ultra$110.00
- Claude Fable 5.1$200.00
Which should you choose?
Which is better: Fugu Ultra or Claude Fable 5.1?
Claude Fable 5.1 is the better all-round choice, scoring 36/100 against Fugu Ultra (33). It leads on inputs & features. 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, 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). 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 Claude Fable 5.1 (1.8× as much).
Which scores higher on benchmarks?
There is no independent benchmark that covers both models yet. 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 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. Both support tool calling for agent workflows.
Which has the bigger context window?
Fugu Ultra and Claude Fable 5.1 share the same 1,000,000-token context window. Maximum output per response: Claude Fable 5.1 up to 128,000 tokens.
Which can read images, PDFs, audio or video?
Fugu Ultra accepts text and images; Claude Fable 5.1 accepts text, images and PDFs. Claude Fable 5.1 handles the widest range of inputs.
Are any of these open source?
No. Fugu Ultra and Claude Fable 5.1 are proprietary and only available through APIs and apps.
Which is newer?
Claude Fable 5.1 is the newest, released Sep 1, 2026. Fugu Ultra came out Jun 15, 2026. Knowledge cutoff: 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.
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