Anthropic: Claude Fable 5.1 (batch) comes out ahead on the data we track: 2 advantages and none for Sakana: Fugu Ultra.
| Spec | Anthropic: Claude Fable 5.1 (batch) | Sakana: Fugu Ultra |
|---|---|---|
| Provider | Anthropic | Sakana |
| Input price (per 1M tokens) | $5.00 | $5.00 |
| Output price (per 1M tokens) | $25.00 | $30.00 |
| Blended price (3:1 input/output) | $10.00 | $11.25 |
| Cheaper than … of all models we track | 5% | 5% |
| Context window | 1M tokens (~1,500 pages) | 1M tokens (~1,500 pages) |
| Larger context than … of all models | 69% | 69% |
| Max output per response | 128K tokens (~96,000 words) | 128K tokens (~96,000 words) |
| Input types | text, image, file | text, image |
| Output types | text | text |
| Free variant | No | No |
| Listed since | 2026-09-01 | 2026-06-24 |
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 5.1 (batch) | Sakana: Fugu Ultra | Difference |
|---|---|---|---|
| Customer-support chatbot 50,000 conversations — each a 6-turn conversation (1,500 in / 400 out tokens) | $875 | $975 | Anthropic: Claude Fable 5.1 (batch) saves $100.00 |
| RAG search over documents 20,000 questions — each a question answered from ~8 retrieved passages (6,000 in / 500 out tokens) | $850 | $900 | Anthropic: Claude Fable 5.1 (batch) saves $50.00 |
| 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) | $900 | $960 | Anthropic: Claude Fable 5.1 (batch) saves $60.00 |
| Batch summarisation 10,000 documents — each a 6,000-word report summarised to a page (8,000 in / 600 out tokens) | $550 | $580 | Anthropic: Claude Fable 5.1 (batch) saves $30.00 |
| Long-document analysis 500 documents — each a 150-page contract or codebase read in one pass (100,000 in / 2,000 out tokens) | $275 | $280 | Anthropic: Claude Fable 5.1 (batch) saves $5.00 |
| Capability | Anthropic: Claude Fable 5.1 (batch) | Sakana: Fugu Ultra | 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 | — | 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.
No advantage on the data we track — pick it for provider preference or output quality on your own prompts.
Anthropic: Claude Fable 5.1 (batch) comes out ahead on the data we track: 2 advantages and none for Sakana: Fugu Ultra.
Anthropic: Claude Fable 5.1 (batch) is cheaper: $10.00 vs $11.25 per 1M tokens at a typical 3:1 input/output mix, 11% less. For 50,000 support conversations a month that is $875 against $975.
Anthropic: Claude Fable 5.1 (batch) costs $5.00 per 1M input tokens and $25.00 per 1M output tokens; Sakana: Fugu Ultra costs $5.00 input and $30.00 output. Output tokens are billed separately, so long answers shift the gap.
Both take 1M tokens per request — roughly 1,500 pages of text.
Tool calling — Anthropic: Claude Fable 5.1 (batch): yes, Sakana: Fugu Ultra: yes. JSON-schema structured output — Anthropic: Claude Fable 5.1 (batch): yes, Sakana: Fugu Ultra: yes.
Yes, both accept image input.
No free variant is listed for either; both are pay-per-token.
Anthropic: Claude Fable 5.1 (batch) can write up to 128K tokens (about 96,000 words) per response; Sakana: Fugu Ultra up to 128K (about 96,000 words).
Anthropic: Claude Fable 5.1 (batch) was listed on 2026-09-01; Sakana: Fugu Ultra on 2026-06-24.
Claude Fable 5.1 improves on Claude Fable 5 across the board, with the biggest gains in agentic coding, long-running agentic workflows, and knowledge work: long code refactors, front-end and visual...
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Full Sakana: Fugu Ultra specs →