Choose Anthropic: Claude Fable 5 if…
No advantage on the data we track — pick it for provider preference or output quality on your own prompts.
Anthropic: Claude Fable 5 vs Sakana: Fugu Ultra v2
Sakana: Fugu Ultra v2 comes out ahead on the data we track: 2 advantages and none for Anthropic: Claude Fable 5.
Key numbers
| Spec | Anthropic: Claude Fable 5 | Sakana: Fugu Ultra v2 |
|---|---|---|
| Provider | Anthropic | Sakana |
| Input price (per 1M tokens) | $10.00 | $5.00 |
| Output price (per 1M tokens) | $50.00 | $30.00 |
| Blended price (3:1 input/output) | $20.00 | $11.25 |
| Cheaper than … of all models we track | 3% | 5% |
| Context window | 1M tokens (~1,500 pages) | 1M tokens (~1,500 pages) |
| Larger context than … of all models | 68% | 68% |
| Max output per response | 128K tokens (~96,000 words) | 128K tokens (~96,000 words) |
| Input types | text, image, file | text, image, file |
| Output types | text | text |
| Free variant | No | No |
| Listed since | 2026-06-09 | 2026-09-11 |
Advertisement
What it costs for real workloads
Monthly cost at list price for five common workloads. Token counts per unit are stated so you can scale them to your own traffic. A workload that does not fit a model's context window is marked rather than priced.
| Workload (per month) | Anthropic: Claude Fable 5 | Sakana: Fugu Ultra v2 | Difference |
|---|---|---|---|
| Customer-support chatbot 50,000 conversations — each a 6-turn conversation (1,500 in / 400 out tokens) | $1,750 | $975 | Sakana: Fugu Ultra v2 saves $775 |
| RAG search over documents 20,000 questions — each a question answered from ~8 retrieved passages (6,000 in / 500 out tokens) | $1,700 | $900 | Sakana: Fugu Ultra v2 saves $800 |
| Coding / tool-using agent 2,000 tasks — each a multi-step task with tool calls and file context (60,000 in / 6,000 out tokens) | $1,800 | $960 | Sakana: Fugu Ultra v2 saves $840 |
| Batch summarisation 10,000 documents — each a 6,000-word report summarised to a page (8,000 in / 600 out tokens) | $1,100 | $580 | Sakana: Fugu Ultra v2 saves $520 |
| Long-document analysis 500 documents — each a 150-page contract or codebase read in one pass (100,000 in / 2,000 out tokens) | $550 | $280 | Sakana: Fugu Ultra v2 saves $270 |
Capabilities side by side
| Capability | Anthropic: Claude Fable 5 | Sakana: Fugu Ultra v2 | What it lets you do |
|---|---|---|---|
| Tool / function calling | ✓ Yes | ✓ Yes | call your APIs and run agent loops |
| Structured output (JSON schema) | ✓ Yes | ✓ Yes | return JSON that validates against your schema |
| Reasoning / thinking mode | ✓ Yes | ✓ Yes | spend extra tokens thinking before answering hard problems |
| Image input | ✓ Yes | ✓ Yes | read screenshots, charts and scanned pages |
| Audio input | — | — | take speech or audio directly |
| File / PDF input | ✓ Yes | ✓ Yes | accept documents without your own parsing step |
| Image output | — | — | generate images, not just text |
| Built-in web search | ✓ Yes | ✓ Yes | answer from live web results |
| Seed (reproducible sampling) | — | — | repeat a generation for tests and evals |
| Log-probabilities | — | — | read token confidence for classification and scoring |
From each model's published parameters and input/output types. “—” means not advertised, not proven absent.
Price history
- Anthropic: Claude Fable 5: price unchanged since we started tracking it on 2026-08-06.
- Sakana: Fugu Ultra v2: price unchanged since we started tracking it on 2026-09-12.
Which should you choose?
Choose Sakana: Fugu Ultra v2 if…
- cost matters at scale — it is 44% cheaper on a typical 3:1 input/output mix ($975 vs $1,750 a month for 50,000 support chats)
- you want the newer model — released 2026-09-11, 3 months after the other
Frequently asked questions
Is Anthropic: Claude Fable 5 better than Sakana: Fugu Ultra v2?
Sakana: Fugu Ultra v2 comes out ahead on the data we track: 2 advantages and none for Anthropic: Claude Fable 5.
Which is cheaper, Anthropic: Claude Fable 5 or Sakana: Fugu Ultra v2?
Sakana: Fugu Ultra v2 is cheaper: $11.25 vs $20.00 per 1M tokens at a typical 3:1 input/output mix, 44% less. For 50,000 support conversations a month that is $975 against $1,750.
How much do Anthropic: Claude Fable 5 and Sakana: Fugu Ultra v2 cost per million tokens?
Anthropic: Claude Fable 5 costs $10.00 per 1M input tokens and $50.00 per 1M output tokens; Sakana: Fugu Ultra v2 costs $5.00 input and $30.00 output. Output tokens are billed separately, so long answers shift the gap.
Which has the bigger context window, Anthropic: Claude Fable 5 or Sakana: Fugu Ultra v2?
Both take 1M tokens per request — roughly 1,500 pages of text.
Do Anthropic: Claude Fable 5 and Sakana: Fugu Ultra v2 support function calling and JSON output?
Tool calling — Anthropic: Claude Fable 5: yes, Sakana: Fugu Ultra v2: yes. JSON-schema structured output — Anthropic: Claude Fable 5: yes, Sakana: Fugu Ultra v2: yes.
Can Anthropic: Claude Fable 5 or Sakana: Fugu Ultra v2 read images?
Yes, both accept image input.
Is Anthropic: Claude Fable 5 or Sakana: Fugu Ultra v2 free to use?
No free variant is listed for either; both are pay-per-token.
What is the maximum output length of Anthropic: Claude Fable 5 and Sakana: Fugu Ultra v2?
Anthropic: Claude Fable 5 can write up to 128K tokens (about 96,000 words) per response; Sakana: Fugu Ultra v2 up to 128K (about 96,000 words).
When were Anthropic: Claude Fable 5 and Sakana: Fugu Ultra v2 released?
Anthropic: Claude Fable 5 was listed on 2026-06-09; Sakana: Fugu Ultra v2 on 2026-09-11.
About the two models
Anthropic: Claude Fable 5
Claude Fable 5 is a Mythos-class model from Anthropic, built for autonomous knowledge work and coding. It supports text, image, and file inputs with text output, with reasoning support and...
Full Anthropic: Claude Fable 5 specs →Sakana: Fugu Ultra v2
Fugu Ultra v2 is the higher-performance model in Sakana AI's Fugu family. Rather than a single monolithic model, Fugu is a learned multi-agent orchestration system: a language model trained to...
Full Sakana: Fugu Ultra v2 specs →