Choose Anthropic: Claude Fable 5.1 if…
- you generate long outputs in one go — up to 128K tokens (about 96,000 words) per response
- you want the newer model — released 2026-09-01, 6 months after the other
Anthropic: Claude Fable 5.1 vs Google: Gemini 3.1 Pro Preview
Neither wins outright: Anthropic: Claude Fable 5.1 is the pick when you generate long outputs in one go, Google: Gemini 3.1 Pro Preview when cost matters at scale.
Key numbers
| Spec | Anthropic: Claude Fable 5.1 | Google: Gemini 3.1 Pro Preview |
|---|---|---|
| Provider | Anthropic | |
| Input price (per 1M tokens) | $10.00 | $2.00 |
| Output price (per 1M tokens) | $50.00 | $12.00 |
| Blended price (3:1 input/output) | $20.00 | $4.50 |
| Cheaper than … of all models we track | 3% | 12% |
| Context window | 1M tokens (~1,500 pages) | 1.0M tokens (~1,573 pages) |
| Larger context than … of all models | 69% | 81% |
| Max output per response | 128K tokens (~96,000 words) | 66K tokens (~49,200 words) |
| Input types | text, image, file | audio, file, image, text, video |
| Output types | text | text |
| Free variant | No | No |
| Listed since | 2026-09-01 | 2026-02-19 |
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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 | Google: Gemini 3.1 Pro Preview | Difference |
|---|---|---|---|
| Customer-support chatbot 50,000 conversations — each a 6-turn conversation (1,500 in / 400 out tokens) | $1,750 | $390 | Google: Gemini 3.1 Pro Preview saves $1,360 |
| RAG search over documents 20,000 questions — each a question answered from ~8 retrieved passages (6,000 in / 500 out tokens) | $1,700 | $360 | Google: Gemini 3.1 Pro Preview saves $1,340 |
| 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 | $384 | Google: Gemini 3.1 Pro Preview saves $1,416 |
| Batch summarisation 10,000 documents — each a 6,000-word report summarised to a page (8,000 in / 600 out tokens) | $1,100 | $232 | Google: Gemini 3.1 Pro Preview saves $868 |
| Long-document analysis 500 documents — each a 150-page contract or codebase read in one pass (100,000 in / 2,000 out tokens) | $550 | $112 | Google: Gemini 3.1 Pro Preview saves $438 |
Capabilities side by side
| Capability | Anthropic: Claude Fable 5.1 | Google: Gemini 3.1 Pro Preview | 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 | — | ✓ Yes | 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) | — | ✓ Yes | 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.
- Google: Gemini 3.1 Pro Preview: price unchanged since we started tracking it on 2026-03-10.
Which should you choose?
Choose Google: Gemini 3.1 Pro Preview if…
- cost matters at scale — it is 78% cheaper on a typical 3:1 input/output mix ($390 vs $1,750 a month for 50,000 support chats)
- you need audio input — to take speech or audio directly; Anthropic: Claude Fable 5.1 does not advertise it
- you need seed (reproducible sampling) — to repeat a generation for tests and evals; Anthropic: Claude Fable 5.1 does not advertise it
Frequently asked questions
Is Anthropic: Claude Fable 5.1 better than Google: Gemini 3.1 Pro Preview?
Neither wins outright: Anthropic: Claude Fable 5.1 is the pick when you generate long outputs in one go, Google: Gemini 3.1 Pro Preview when cost matters at scale. In short: Anthropic: Claude Fable 5.1 when you generate long outputs in one go, you want the newer model; Google: Gemini 3.1 Pro Preview when cost matters at scale, you need audio input, you need seed (reproducible sampling).
Which is cheaper, Anthropic: Claude Fable 5.1 or Google: Gemini 3.1 Pro Preview?
Google: Gemini 3.1 Pro Preview is cheaper: $4.50 vs $20.00 per 1M tokens at a typical 3:1 input/output mix, 78% less. For 50,000 support conversations a month that is $390 against $1,750.
How much do Anthropic: Claude Fable 5.1 and Google: Gemini 3.1 Pro Preview cost per million tokens?
Anthropic: Claude Fable 5.1 costs $10.00 per 1M input tokens and $50.00 per 1M output tokens; Google: Gemini 3.1 Pro Preview costs $2.00 input and $12.00 output. Output tokens are billed separately, so long answers shift the gap.
Which has the bigger context window, Anthropic: Claude Fable 5.1 or Google: Gemini 3.1 Pro Preview?
Google: Gemini 3.1 Pro Preview: 1.0M tokens, about 1,573 pages, against 1M (about 1,500 pages) for Anthropic: Claude Fable 5.1.
Do Anthropic: Claude Fable 5.1 and Google: Gemini 3.1 Pro Preview support function calling and JSON output?
Tool calling — Anthropic: Claude Fable 5.1: yes, Google: Gemini 3.1 Pro Preview: yes. JSON-schema structured output — Anthropic: Claude Fable 5.1: yes, Google: Gemini 3.1 Pro Preview: yes.
Can Anthropic: Claude Fable 5.1 or Google: Gemini 3.1 Pro Preview read images?
Yes, both accept image input.
Is Anthropic: Claude Fable 5.1 or Google: Gemini 3.1 Pro Preview 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 Google: Gemini 3.1 Pro Preview?
Anthropic: Claude Fable 5.1 can write up to 128K tokens (about 96,000 words) per response; Google: Gemini 3.1 Pro Preview up to 66K (about 49,200 words).
When were Anthropic: Claude Fable 5.1 and Google: Gemini 3.1 Pro Preview released?
Anthropic: Claude Fable 5.1 was listed on 2026-09-01; Google: Gemini 3.1 Pro Preview on 2026-02-19.
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 →Google: Gemini 3.1 Pro Preview
Gemini 3.1 Pro Preview is Google’s frontier reasoning model, delivering enhanced software engineering performance, improved agentic reliability, and more efficient token usage across complex workflows. Building on the multimodal foundation...
Full Google: Gemini 3.1 Pro Preview specs →