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Anthropic Advanced

Claude Fable 5.1

Claude Fable 5.1 is Anthropic's premium 1M-context model for demanding reasoning and long-horizon agents, priced at $10/M input and $50/M output.

General Purpose Language ModelTextImage Paid
In plain English

What is this model and why does it matter?

Claude Fable 5.1 is Anthropic's newest high-end model for demanding reasoning, long-running agents and complex professional artifact work.

Long-horizon agentsDeep reasoningAgentic codingMultistep researchDocumentsSpreadsheets
Model overview

Claude Fable 5.1: features, use cases and important details

Claude Fable 5.1 is Anthropic’s newest premium model for demanding reasoning and long-horizon agentic work.

Verified model facts

Anthropic documents a 1M-token context window, 128K maximum output, June 2026 knowledge cutoff, adaptive thinking, text and image input and $10/M input, $50/M output pricing.

Current status

Fable 5.1 is active and released September 1, 2026 across the Claude API and major cloud platforms.

Best fit

It is best for long-running coding agents, multistep research and professional document, spreadsheet and slide work.

Limitations

It is slower and substantially more expensive than Opus 5 or Sonnet 5, so it should be reserved for tasks that justify the extra capability.

Claude Fable 5.1 capabilities and use cases

In addition, its main capabilities include 1M context, 128K output, Adaptive thinking, Long-running agents, Coding and Research. For example, common use cases include Complex agents, Coding, Deep research, Professional documents and High-difficulty reasoning.

Who should consider Claude Fable 5.1?

In practice, this model may suit Long-horizon agents, Deep reasoning, Agentic coding, Multistep research, Documents and Spreadsheets. Also, notable strengths include Newest Anthropic high-end model, Very large context, Strong long-horizon agent performance and Improved cache-read pricing. However, review trade-offs such as High token cost, Always-on adaptive thinking can increase latency and May be unnecessary when Opus 5 meets task requirements before adopting it.

Claude Fable 5.1 pricing and access

Meanwhile, $10.00 per 1M input tokens and $50.00 per 1M output tokens. Cache reads cost $0.25/M and Batch API input/output receives a 50% discount. Fable 5.1 costs $10/M input and $50/M output, making it a premium model intended for workloads where Opus 5 is not enough.

Official resources and verification

Use the official model website, official documentation and pricing or release source to confirm current availability, limits and pricing. Product details can change after publication, so rely on primary documentation for final decisions.

Compare with other AI models

Next, continue your research in the AI models directory, Anthropic models and General Purpose Language Model models. Compare providers, pricing, modalities and practical limitations side by side to choose the right model for your workflow.

Get started

How to use this model

  1. Create a Claude API key.
  2. Call model claude-fable-5-1.
  3. Use the default high effort for difficult tasks.
  4. Add tools for long-running agent workflows.
  5. Use prompt caching and Batch API where cost savings matter.
Copy and try

Example prompts

  • Work through this long-running engineering task and report progress between tool calls.
  • Research this complex question across many sources and produce a decision memo.
  • Create and refine a professional spreadsheet and slide deck from these requirements.
Capabilities

What it can do

  • 1M context
  • 128K output
  • Adaptive thinking
  • Long-running agents
  • Coding
  • Research
  • Artifact creation
  • Tool use
Best for

Practical use cases

  • Complex agents
  • Coding
  • Deep research
  • Professional documents
  • High-difficulty reasoning
Pricing

What does it cost?

$10.00 per 1M input tokens and $50.00 per 1M output tokens. Cache reads cost $0.25/M and Batch API input/output receives a 50% discount.

Input$10.00 / 1M tokens
Output$50.00 / 1M tokens
Simple summaryFable 5.1 costs $10/M input and $50/M output, making it a premium model intended for workloads where Opus 5 is not enough.

What stands out

  • Newest Anthropic high-end model
  • Very large context
  • Strong long-horizon agent performance
  • Improved cache-read pricing

Things to consider

  • Very expensive
  • Slower than Opus/Sonnet
  • Proprietary
Limitations

Important restrictions and trade-offs

  • High token cost
  • Always-on adaptive thinking can increase latency
  • May be unnecessary when Opus 5 meets task requirements
SimplifyAITools verdict

Our editorial take

Anthropic’s specialist choice for the hardest long-horizon agent and reasoning workloads, but priced accordingly.

References

Primary sources

  1. Open source 1 ↗
  2. Open source 2 ↗
  3. Open source 3 ↗
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