Long-horizon coding
Engineering teams that need a model to inspect a codebase, use tools, make coordinated changes and keep a detailed implementation brief in view.
Independent tool overview
Claude Fable 5.1 at a glance
Claude Fable 5.1 is Anthropic’s high-capability model for coding, knowledge work and long-running problem solving across Claude apps, developer tools and the API.
Visit the official Claude Fable 5.1 site ↗
- Best for
- Coding, knowledge work and long-running agents
- API model
- claude-fable-5-1
- API price
- $10 input / $50 output per 1M tokens
- Access
- Claude apps, Claude Code, Cowork, API and cloud platforms
- Default effort
- High in Claude Code; Medium in Cowork and claude.ai
Overview
What Claude Fable 5.1 is
Anthropic positions Claude Fable 5.1 as a model for sustained, multi-step work rather than only short chat responses. It is designed to plan, use tools, work through large tasks and preserve instructions across coding and knowledge-work workflows.
The model is available through Claude’s consumer and work surfaces, Claude Code, Claude Cowork, the Claude API and supported cloud platforms. Developers can select the claude-fable-5-1 API model, while Claude products choose an effort level suited to the experience.
Use cases
Who Claude Fable 5.1 is best for
The strongest fit depends on the job you need the product to complete, not the size of its feature list.
Research and knowledge work
Analysts and operators working through complex source material, structured reasoning and multi-part deliverables that benefit from sustained attention.
Agent builders
Developers building tool-using workflows where the model needs to plan, execute, check its work and continue across a longer task.
Claude-centered teams
Organizations already using Claude Code, Claude Cowork or Anthropic’s API and cloud integrations that want the flagship Fable model in the same ecosystem.
Capabilities
Core Claude Fable 5.1 features
Long-running problem solving
Built for tasks that require multiple steps, tool calls and revisions instead of a single prompt-and-response exchange.
Advanced coding workflows
Targets software-development work that spans code understanding, implementation, debugging and verification across a larger task.
Adjustable effort
Claude experiences can vary the amount of reasoning effort, with higher defaults in Claude Code and medium defaults in Cowork and claude.ai.
Tool and agent support
Works in Anthropic’s agentic products and through the API for workflows that combine model reasoning with external tools and application context.
Cross-platform availability
Available across Anthropic products and through AWS, Google Cloud and Microsoft Azure in addition to the direct Claude API.
Lower-cost prompt-cache reads
Anthropic lists cache reads at $0.25 per million tokens, which can reduce repeated-input cost in workflows with a stable prompt prefix.
Process
How the Claude Fable 5.1 workflow works
Step 1
Choose the Claude surface
Use claude.ai or Cowork for knowledge work, Claude Code for repository tasks, or the API and cloud platforms for an application workflow.
Step 2
Provide the goal and context
Describe the outcome, constraints, source material and permissions clearly so the model can plan the work without guessing at consequential choices.
Step 3
Set an appropriate effort level
Use greater effort for difficult, high-value work and a lighter setting when latency and token use matter more than maximum depth.
Step 4
Review the result and tool actions
Check generated code, research claims and external actions before they become production changes or business decisions.
Cost
Claude Fable 5.1 pricing and free plan
Anthropic prices Claude Fable 5.1 API usage by tokens. Consumer and team access depends on the Claude plan and product surface; API applications should also account for reasoning effort and cache use.
Claude products
Available through Claude plans
Use Fable 5.1 in supported Claude experiences without building a direct API integration.
- Available across Claude product surfaces
- High effort is the default in Claude Code
- Medium effort is the default in Cowork and claude.ai
Claude API
$10 input · $50 output / 1M tokens
Usage-based access for developers building Fable 5.1 into products and automated workflows.
- Model identifier: claude-fable-5-1
- Token use can rise at higher effort levels
- Also available through supported cloud platforms
Prompt caching
$0.25 / 1M cache-read tokens
A lower read rate for repeated prompt context in eligible API workflows.
- Useful for large, stable system instructions or shared context
- Cache writes and other API charges should be checked separately
- Savings depend on how often the same prefix is reused
Pricing checked . Check current pricing at the source ↗
Assessment
Claude Fable 5.1 strengths and limitations
Where it stands out
- Designed for demanding coding and knowledge-work tasks that unfold over many steps.
- Available across consumer, coding, coworking, API and major cloud-platform surfaces.
- Adjustable effort gives teams a way to trade additional reasoning for latency and token cost.
- Low cache-read pricing can improve the economics of repeated-context agent workflows.
What to consider
- Its $10 input and $50 output token rates are materially higher than low-cost Flash-class models.
- Higher effort can use more tokens, so teams should measure complete task cost rather than only the published unit rate.
- Anthropic says exploit generation, penetration testing and binary scanning are redirected to Claude Opus even though Fable 5.1 can identify software vulnerabilities.
- Enhanced safeguards are planned for later in the fall; until then, zero-data-retention access is limited to eligible customers described by Anthropic.
Compare
Claude Fable 5.1 alternatives
The right alternative depends on the specific output, workflow, controls and budget your project requires.
Consumer
Gemini 3.8 Flash
Choose Gemini 3.8 Flash when lower token pricing and Google’s developer or Workspace ecosystem matter more than staying in Claude.
Explore Gemini 3.8 Flash →Consumer
GPT 5.5
Choose GPT 5.5 when your applications and team workflows are already centered on OpenAI’s model and product ecosystem.
Explore GPT 5.5 →Consumer
Claude Opus 4.8
Choose Claude Opus 4.8 when you need Anthropic’s Opus tier or security workflows that Fable redirects to Opus.
Explore Claude Opus 4.8 →Questions
Claude Fable 5.1 FAQs
What is Claude Fable 5.1?
Claude Fable 5.1 is an Anthropic model built for advanced coding, knowledge work and long-running problem solving across Claude products and the API.
How much does the Claude Fable 5.1 API cost?
Anthropic lists API pricing at $10 per million input tokens and $50 per million output tokens. Prompt-cache reads are listed at $0.25 per million tokens.
Where can I use Claude Fable 5.1?
Anthropic says it is available across Claude platforms, including Claude Code and Cowork, through the Claude API, and on AWS, Google Cloud and Microsoft Azure.
What is the Claude Fable 5.1 API model name?
The model identifier published by Anthropic is claude-fable-5-1.
What effort level does Fable 5.1 use?
Anthropic says Claude Code defaults to High effort, while Claude Cowork and claude.ai default to Medium. The right setting depends on the task, latency target and budget.
Is Claude Fable 5.1 suitable for security work?
It can help identify software vulnerabilities, but Anthropic says exploit generation, penetration testing and binary scanning are redirected to Claude Opus.
Is this a hands-on Claude Fable 5.1 review?
No. This is an independent editorial overview based on Anthropic’s announcement and system-card materials; The Rundown has not completed a controlled hands-on model comparison for this page.
Bottom line
Our Claude Fable 5.1 verdict
Claude Fable 5.1 is a strong fit for teams that value sustained coding and knowledge-work performance and already operate in Anthropic’s ecosystem. Its broad availability and cache-read economics help agent builders, but the premium output-token price makes task-level cost testing important. Teams optimizing first for lower unit cost should compare Gemini 3.8 Flash or Muse Spark 1.3, while specialized security work may call for Claude Opus.
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