Choose Anthropic: Claude Fable 5.1 if…
No advantage on the data we track — pick it for provider preference or output quality on your own prompts.
Anthropic: Claude Fable 5.1 vs Claude Opus 5 (Fast)
Anthropic: Claude Fable 5.1 and Claude Opus 5 (Fast) are near-identical on price, context and listed capabilities — choose on provider, latency in your region, and output quality on your own prompts.
Key numbers
| Spec | Anthropic: Claude Fable 5.1 | Claude Opus 5 (Fast) |
|---|---|---|
| Provider | Anthropic | Anthropic |
| Input price (per 1M tokens) | $10.00 | $10.00 |
| Output price (per 1M tokens) | $50.00 | $50.00 |
| Blended price (3:1 input/output) | $20.00 | $20.00 |
| Cheaper than … of all models we track | 3% | 3% |
| 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, file |
| Output types | text | text |
| Free variant | No | No |
| Listed since | 2026-09-01 | 2026-07-24 |
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 5.1 | Claude Opus 5 (Fast) | Difference |
|---|---|---|---|
| Customer-support chatbot 50,000 conversations — each a 6-turn conversation (1,500 in / 400 out tokens) | $1,750 | $1,750 | — |
| RAG search over documents 20,000 questions — each a question answered from ~8 retrieved passages (6,000 in / 500 out tokens) | $1,700 | $1,700 | — |
| 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 | $1,800 | — |
| Batch summarisation 10,000 documents — each a 6,000-word report summarised to a page (8,000 in / 600 out tokens) | $1,100 | $1,100 | — |
| Long-document analysis 500 documents — each a 150-page contract or codebase read in one pass (100,000 in / 2,000 out tokens) | $550 | $550 | — |
Capabilities side by side
| Capability | Anthropic: Claude Fable 5.1 | Claude Opus 5 (Fast) | 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 5.1: price unchanged since we started tracking it on 2026-09-02.
- Claude Opus 5 (Fast): price unchanged since we started tracking it on 2026-08-06.
Which should you choose?
Choose Claude Opus 5 (Fast) if…
No advantage on the data we track — pick it for provider preference or output quality on your own prompts.
Frequently asked questions
Is Anthropic: Claude Fable 5.1 better than Claude Opus 5 (Fast)?
Anthropic: Claude Fable 5.1 and Claude Opus 5 (Fast) are near-identical on price, context and listed capabilities — choose on provider, latency in your region, and output quality on your own prompts.
Which is cheaper, Anthropic: Claude Fable 5.1 or Claude Opus 5 (Fast)?
They cost the same: $20.00 per 1M tokens at a 3:1 input/output mix.
How much do Anthropic: Claude Fable 5.1 and Claude Opus 5 (Fast) cost per million tokens?
Anthropic: Claude Fable 5.1 costs $10.00 per 1M input tokens and $50.00 per 1M output tokens; Claude Opus 5 (Fast) costs $10.00 input and $50.00 output. Output tokens are billed separately, so long answers shift the gap.
Which has the bigger context window, Anthropic: Claude Fable 5.1 or Claude Opus 5 (Fast)?
Both take 1M tokens per request — roughly 1,500 pages of text.
Do Anthropic: Claude Fable 5.1 and Claude Opus 5 (Fast) support function calling and JSON output?
Tool calling — Anthropic: Claude Fable 5.1: yes, Claude Opus 5 (Fast): yes. JSON-schema structured output — Anthropic: Claude Fable 5.1: yes, Claude Opus 5 (Fast): yes.
Can Anthropic: Claude Fable 5.1 or Claude Opus 5 (Fast) read images?
Yes, both accept image input.
Is Anthropic: Claude Fable 5.1 or Claude Opus 5 (Fast) 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 5.1 and Claude Opus 5 (Fast)?
Anthropic: Claude Fable 5.1 can write up to 128K tokens (about 96,000 words) per response; Claude Opus 5 (Fast) up to 128K (about 96,000 words).
When were Anthropic: Claude Fable 5.1 and Claude Opus 5 (Fast) released?
Anthropic: Claude Fable 5.1 was listed on 2026-09-01; Claude Opus 5 (Fast) on 2026-07-24.
About the two models
Anthropic: Claude Fable 5.1
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...
Full Anthropic: Claude Fable 5.1 specs →Claude Opus 5 (Fast)
Fast-mode variant of [Opus 5](/anthropic/claude-opus-5) - identical capabilities with higher output speed at 2x pricing relative to regular Opus 5. Learn more in Anthropic's docs: https://platform.claude.com/docs/en/build-with-claude/fast-mode
Full Claude Opus 5 (Fast) specs →