Claude Fable 5.1

Claude Fable 5.1 is Anthropic's generally available frontier model for demanding coding, research, and long-running agent workflows, with lower cache-read pricing and several API migration changes from Fable 5.

Platform: Replicate

Reasoning AICoding AssistantLong-horizon AgentsMultimodal AI

Input: $10 per million tokens; Cache read: $0.25 per million tokens; Output: $50 per million tokens

Commercial

🚀Function Overview

A high-capability text-and-image input model with adaptive thinking, a 1M-token context window, and controls for long-running agent work.

Key Features

Stable Claude API model ID claude-fable-5-1
1M-token context window and 128K-token maximum output
Adaptive thinking is always on, with high effort as the documented API default
Text and image input with text output
Per-message effort, turn-scoped system messages, and progress display are available as beta controls
Cache reads cost $0.25 per million tokens, below Fable 5's cache-read rate

Use Cases

•Long-running repository-scale coding and difficult debugging
•Multistep research and document-heavy analysis
•Spreadsheet, presentation, and structured artifact creation
•Agent workflows that need large context and visible progress updates
•Defensive vulnerability discovery within Anthropic's safeguard boundaries

⚙️Input Parameters

prompt

string

Text instructions and context for the model

image

string

Optional image input for multimodal analysis

system_prompt

string

System-level instructions; turn-scoped system messages are available in beta

effort

string

Reasoning effort control for adaptive thinking

max_tokens

integer

Maximum output length, up to 128K tokens

💡Usage Examples

Example 1

Input Parameters

{
  "prompt": "Investigate this intermittent repository failure, identify the root cause, implement the smallest safe fix, and summarize the evidence.",
  "system_prompt": "Work methodically. Preserve unrelated changes and verify every claimed fix.",
  "effort": "high",
  "max_tokens": 8192
}

Output Results

I will first reproduce the failure and map the affected execution path.

I will distinguish the root cause from secondary symptoms, make the narrowest bounded change, and run the relevant tests.

The final summary will separate observed evidence, the implemented fix, verification results, and remaining risk.

Quick Actions

Use NowView Documentation

Technical Specifications

Hardware Type
Commercial Use: Supported
Pricing: Input: $10 per million tokens; Cache read: $0.25 per million tokens; Output: $50 per million tokens
Platform: Replicate

Related Keywords

Claude Fable 5.1 APIClaude Fable 5.1 pricingclaude-fable-5-1Fable 5.1 vs Fable 5Anthropic frontier modellong-horizon coding model

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