Claude Fable 5 Economy

Claude Fable 5 is Anthropic’s officially released Mythos-tier model, designed for autonomous knowledge work, advanced reasoning, and long-horizon coding. It supports text, image, and file inputs and produces text output. It features a 1-million-token context window, up to 128,000 output tokens, and built-in always-on adaptive thinking, tool use, and structured outputs. The model shares the same underlying model family as Claude Mythos 5 but was released publicly with stronger safety safeguards. It is suitable for complex software engineering, multi-step agentic workflows, enterprise research, document analysis, and professional tasks requiring sustained reasoning and high reliability.

claude-fable-5

1 Authentication

The API uses an API Key for authentication.

Get your API Key

Get your API key from https://icreat.ai/hub/keys .

2 Calling the API

This model provides an HTTP API that is compatible with Anthropic's /messages API. You can use any SDK that is compatible with this API to call the llm.

2.1 curl

curl --fail-with-body --connect-timeout 10 --max-time 60 \
  -X POST https://api.icreat.ai/llm/anthropic/v1/messages \
  -H "Authorization: Bearer ${ICREAT_API_KEY}" \
  -H "Content-Type: application/json" \
  -d '{
  "model": "claude-fable-5",
  "messages": [
    {"role": "system", "content": "You are a helpful assistant."},
    {"role": "user", "content": "Which is healthier, coffee or tea?"}
  ],
  "stream": false
}'

2.2 python

import anthropic

client = anthropic.Anthropic(
  base_url="https://api.icreat.ai/llm/anthropic", 
  api_key="ICREAT_API_KEY"
)

message = client.messages.create(
    model="claude-fable-5",
    system="You are a helpful assistant.",
    messages=[
        {
            "role": "user",
            "content": [
                {
                    "type": "text",
                    "text": "Hi, how are you?"
                }
            ]
        }
    ]
)

for block in message.content:
    if block.type == "thinking":
        print(f"Thinking:\n{block.thinking}\n")
    elif block.type == "text":
        print(f"Text:\n{block.text}\n")

2.3 node.js

const client = new Anthropic({
  baseURL: "https://api.icreat.ai/llm/anthropic"
  apiKey: "ICREAT_API_KEY"
});

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

for (const block of message.content) {
  if (block.type === "text") {
    console.log(block.text);
  }
}

3 API Protocol

3.1 Stream output

Set stream parameter to true to request a stream output.

{
  "model": "claude-fable-5",
  "messages": [
    {
      "role": "user",
      "content": "Please explain what recursion is and give a Python example."
    }
  ],
  "stream": true
}