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Anthropic · New 2026 Frontier Model · ASL-4

Claude Fable 5.1 API Pricing & Token Cost Calculator (2026)

Anthropic Claude Fable 5.1 costs $10.00 per million input tokensand $50.00 per million output tokens. With prompt caching, cached input drops to just $0.25/M — a 97.5% discount. Use our free Claude Fable 5.1 token cost calculator to model your exact API spend.

Input$10.00 / 1M
Output$50.00 / 1M
Cached$0.25 / 1M 🔥
Context1,000,000 tok
Batch50% off
SafetyASL-4

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Claude Fable 5.1 API Pricing Breakdown

All prices per million tokens as of September 2026. Note the exceptional 97.5% caching discount — one of the largest of any frontier model.

TierInput /1MOutput /1MType
Claude Fable 5.1 (Standard)$10.00$50.00Flagship
Claude Fable 5.1 (Batch)$5.00$25.0050% off
Claude Fable 5.1 (Cached)$0.25$50.0097.5% off!

* Verify latest prices at anthropic.com/pricing

What Makes Claude Fable 5.1 Different?

🧠

Enhanced Reasoning Engine

Tuned for deep logical leaps without hallucinating intermediate steps. Ideal for complex multi-step agentic workflows, legal analysis, and research tasks.

📄

1,000,000 Token Context

Process ~3,000 pages of text in one prompt. Full codebase ingestion, entire legal documents, or massive research corpora — all in a single API call.

💰

97.5% Prompt Caching Discount

One of the industry's deepest caching discounts at $0.25/M for cached tokens. Any app with large repeated context (RAG, agents, doc analysis) benefits massively.

🔒

ASL-4 Constitutional AI Safety

First Anthropic model at ASL-4 safety level. Built on Anthropic's constitutional AI framework — the most safety-aligned frontier model available.

98.4%
MMLU Score
15x
Fewer Hallucinations
< 0.2s
Time to First Token
ASL-4
Safety Rating

Claude Fable 5.1 Real-World Cost Examples

Full codebase ingestion (1M tokens)

In: 1,000,000 tokensOut: 15,000 tokens
per call$10.75

~$107.50 at 10 reviews/mo (fully cached: ~$10.00)

Legal contract deep analysis

In: 200,000 tokensOut: 8,000 tokens
per call$2.40

~$240.00 at 100 contracts/mo

Multi-step agentic coding workflow

In: 80,000 tokensOut: 30,000 tokens
per call$2.30

~$230.00 at 100 runs/mo

Large-doc RAG with cached context

In: 500,000 tokensOut: 5,000 tokens
per call$0.375

~$37.50 at 100 queries/mo (with caching)

Claude Fable 5.1 vs Other 2026 LLMs — Cost Comparison

Standard on-demand pricing. Claude Fable 5.1's effective cost advantage comes from caching, not sticker price.

ModelProviderInput /1MOutput /1MContext
Claude Fable 5.1this pageAnthropic$10.00$50.001,000,000
GPT-6 AstraOpenAI$10.00$50.001,050,000
Claude Sonnet 5Anthropic$2.00$10.001,000,000
GPT-4oOpenAI$2.50$10.00128,000
Gemini 3.8 FlashGoogle$0.75$3.751,000,000
→ Compare all 50+ models in the full LLM token cost calculator

Claude Fable 5.1 Pricing — Frequently Asked Questions

How much does Claude Fable 5.1 cost per token?
Claude Fable 5.1 costs $10.00 per million input tokens and $50.00 per million output tokens at standard pricing. With the Batch API, costs drop 50% to $5.00/M input and $25.00/M output. Prompt-cached input tokens cost only $0.25/M — a 97.5% discount, making Claude Fable 5.1 extremely cost-effective for applications with large repeated context windows.
Is Claude Fable 5.1 more expensive than GPT Astra 6?
Claude Fable 5.1 and GPT Astra 6 are priced identically at $10.00/M input and $50.00/M output. The key cost differentiator is caching: Claude Fable 5.1 offers 97.5% off cached tokens ($0.25/M) vs GPT Astra 6's 90% off ($1.00/M). For RAG pipelines, agents with large system prompts, or repeated document contexts, Claude Fable 5.1 is significantly cheaper in practice.
What is Claude Fable 5.1's context window?
Claude Fable 5.1 supports a 1,000,000-token context window — equivalent to approximately 3,000 pages of text in a single prompt. This enables full codebase ingestion, entire legal documents, or massive research papers in one API call. Combined with prompt caching at $0.25/M, large-context workloads become far more affordable.
What is the difference between Claude Fable 5.1 and Claude Sonnet 5?
Claude Fable 5.1 is Anthropic's 2026 frontier flagship, while Claude Sonnet 5 is the mid-tier model. Fable 5.1 has the same 1,000,000-token context window, significantly deeper reasoning capabilities, and costs 5× more ($10.00 vs $2.00/M input). Use Claude Sonnet 5 for standard production workloads; use Claude Fable 5.1 only where frontier reasoning or massive context is required.
How does Claude Fable 5.1 prompt caching work?
Anthropic's prompt caching for Claude Fable 5.1 charges cached input tokens at just $0.25/M — a 97.5% discount vs the $10.00/M standard rate. Cache writes cost $12.50/M (a one-time fee). Caching activates for prompt prefixes exceeding ~1,024 tokens that appear in multiple consecutive API calls within a session. For any app with a large, reused system prompt or document context, caching is the single highest-impact cost optimization.
What is Claude Fable 5.1's safety rating?
Claude Fable 5.1 is the first Anthropic model rated at ASL-4 (AI Safety Level 4) under Anthropic's Responsible Scaling Policy. ASL-4 indicates capabilities that require significant additional safety measures before deployment. Despite this, it is publicly available via the Anthropic API with enhanced usage monitoring.

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