Anthropic: Claude Fable 5.1

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anthropic/claude-fable-5.1
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Claude Fable 5.1 is Anthropic's Mythos-class frontier model and the successor to Fable 5, released on 2026-09-01. It targets ambitious coding, long-horizon agents, and enterprise knowledge work, with adaptive thinking always on rather than toggled per request. It supports vision, tool use, PDF input, and prompt caching. Context window: 1M tokens, output: 128K. The 1M-token context together with PDF input makes it practical to load whole document sets or repositories into a single session, while prompt caching keeps the repeated context affordable across long agentic runs. Available via Anthropic and OpenAI protocols through Ofox.

Context Window
1M
Max Output Tokens
128K
Released
2026-09-01
Capabilities
VisionFunction CallingReasoningPrompt CachingPDF Input
Available Providers
Bedrock
Supported Protocols
openaianthropic

Providers

Bedrock
Input Tokens
$10/M
Output Tokens
$50/M
Cache Read
$0.25/M
Cache Write (5 min)
$12.5/M
Cache Write (1 hour)
$20/M
Web Search
$0.01/R
Protocols
openai/v1/chat/completions/v1/responses
anthropic

Code Examples

import anthropic


client = anthropic.Anthropic(
    base_url="https://api.ofox.run/anthropic",
    api_key="YOUR_OFOX_API_KEY",
)


message = client.messages.create(
    model="anthropic/claude-fable-5.1",
    max_tokens=1024,
    messages=[
        {"role": "user", "content": "Hello!"}
    ],
)


print(message.content[0].text)

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Frequently Asked Questions

Anthropic: Claude Fable 5.1 on Ofox.ai costs $10/M per million input tokens and $50/M per million output tokens. Pay-as-you-go, no monthly fees.