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Language models/Anthropic/Claude Fable 5.1
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Claude Fable 5.1

Anthropic's model for demanding reasoning and long-horizon agentic work.

claude-fable-5-1Get API key

Pricing USD per million tokens

TokensPer 1M tokens
Input$3.50
Cached input$0.0875
Cache write (5 min)$4.375
Cache write (1 hour)$7.00
Output$17.50

A request at reasoning effort max is billed at 3× these rates. Reasoning tokens are billed as output. Each answer's usage carries cost_usd, the amount taken from your balance; a request with no answer costs $0.00.

Request

curl
curl https://api.revana.si/v1/chat/completions \
  -H "Authorization: Bearer $REVANA_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model":"claude-fable-5-1","messages":[{"role":"user","content":"Write a haiku about routing."}]}'
Python
import os
from openai import OpenAI

client = OpenAI(base_url="https://api.revana.si/v1", api_key=os.environ["REVANA_API_KEY"])
reply = client.chat.completions.create(
    model="claude-fable-5-1",
    messages=[{"role": "user", "content": "Write a haiku about routing."}],
)
print(reply.choices[0].message.content)

Any OpenAI SDK works: set the base URL to https://api.revana.si/v1. Streaming, tools and the rest are in the chat completions docs.

Details

Model id
claude-fable-5-1
Maker
Anthropic
Endpoint
POST /v1/chat/completions
Context window
1M tokens
Max output
128K tokens
Streaming
Yes (server-sent events)
Routes
2 (falls back automatically)

2 routes

Every request starts on the cheapest route. A busy or failed route hands it to the next before any answer is sent.

About the Claude Fable 5.1 API

How much does the Claude Fable 5.1 API cost?

Claude Fable 5.1 costs $3.50 per million input tokens, $0.0875 per million cached input tokens and $17.50 per million output tokens on Revana. A request at reasoning effort max is billed at 3× these rates. You pay from prepaid credit for the tokens each request used, with no subscription or minimum.

How do I call Claude Fable 5.1 from code?

Use any OpenAI SDK with base URL https://api.revana.si/v1 and your Revana API key, and set model to "claude-fable-5-1". POST /v1/chat/completions takes the OpenAI request body, streamed or not.

What happens if a request fails?

Revana has 2 routes for Claude Fable 5.1 and moves a request to the next one when a route is busy or down. A request that gets no answer costs nothing.

Is Claude Fable 5.1 on Revana the same model?

Yes. Revana passes your request to Anthropic's model unchanged and returns its answer in the OpenAI format, with the usage it reported and what the request cost.

More from Anthropic

Also as markdown for agents. Every language model and price: llms.json.