Claude Fable 5.1 API
About
Build advanced reasoning agents with Claude Fable 5.1, a specialized AI model optimized for complex logic and chain-of-thought tasks. This model delivers cost-effective pricing at $10.00/1M input and $50.00/1M output tokens, native tool calling support. Access Claude Fable 5.1 via the Vertex API with up to 128K output tokens.
Capabilities
Input Modalities
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Output Modalities
text
Reasoning
Yes
Structured Output
Yes
Tool Use
Yes
WeightsClosed
Temperature
Fixed
Attachment
Supported
Limits
Context Window
1.0M
Tokens
Input Limit
1.0M
Tokens
Max Output
128K
Tokens
Pricing
Standard (per 1M tokens)
Input
$10.00
Output
$50.00
Caching (per 1M tokens)
Read
$0.25
Write
$12.50
Frequently Asked Questions
Claude Fable 5.1 by Vertex costs $10.00 per 1M input tokens and $50.00 per 1M output tokens. Cached reads cost $0.25 per 1M tokens. Cache writes cost $12.50 per 1M tokens.
Model Details
ID
claude-fable-5-1@default
Provider
VertexFamily
claude-fable
Release Date
Sep 1, 2026
Knowledge Cutoff
Jun 1, 2026
API Integration
NPM Package
@ai-sdk/google-vertex
Environment Variables
GOOGLE_VERTEX_PROJECT
GOOGLE_VERTEX_LOCATION
GOOGLE_APPLICATION_CREDENTIALS