Anthropic

Claude Fable 5.1

Anthropic's most capable widely released model — the first Mythos-class tier above Opus, built for the most demanding reasoning and long-horizon agentic work

Category Text Model ID claude-fable-5-1

Context Length1M tokens

Model TypeLarge Language Model (LLM)

MultimodalText, Image Input

Pricing & Specs

💰 Pricing

Input$10 / M tokens

Output$50 / M tokens

Cache Write5m: $12.50 / MTok; 1h: $20 / MTok

Cache Hit$0.25 / MTok

⚙️ Specs

Context Length1M tokens

Model TypeLarge Language Model (LLM)

MultimodalText, Image Input

Adaptive ThinkingAlways on (cannot be disabled)

Max Output128K tokens

Release DateSeptember 1, 2026

Knowledge CutoffJune 2026

API CompatibilityClaude API, Claude Code, OpenAI API

API Examples

Python

import anthropic

client = anthropic.Anthropic(
    api_key="YOUR_API_KEY",
    base_url="https://api.zairouter.com"
)

message = client.messages.create(
    model="claude-fable-5-1",
    max_tokens=1024,
    messages=[
        {"role": "user", "content": "Hello, Claude!"}
    ]
)

for block in message.content:
    if block.type == "text":
        print(block.text)

cURL

curl https://api.zairouter.com/v1/messages \
  -H "x-api-key: YOUR_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "Content-Type: application/json" \
  -d '{"model":"claude-fable-5-1","max_tokens":4096,"messages":[{"role":"user","content":"Hello, Claude!"}]}'

Developer Assist

# Set environment variables in terminal
export ANTHROPIC_AUTH_TOKEN=sk-Xvs...  # Your API Key
export ANTHROPIC_BASE_URL=https://api.zairouter.com

# Start Claude Code
claude --model claude-fable-5-1

# Now you can use claude-fable-5-1 model directly for development

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