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Claude Fable 5

AnthropicReleased Jun 9, 2026

Claude Fable 5 is a Mythos-class model from Anthropic, built for autonomous knowledge work and coding. It supports text, image, and file inputs with text output, with reasoning support and...

Try in playground
Context window
1M tokens
Max output
128K tokens
Input
text, image, file
Output
text
Tokenizer
Claude
Released
Jun 9, 2026
Reasoning
always on

Pricing

Per 1M tokens. The provider price and our flat 3% fee are separate columns — what you pay is their sum.

Per 1M tokensProvider+ 3% feeYou pay
Input$10.00$0.300$10.30
Output$50.00$1.50$51.50
Cache read$1.00$0.030$1.03
Cache write$12.50$0.375$12.88

Benchmarks

Artificial Analysis

Intelligence index
59.9
Coding index
76.5
Agentic index
52.8

Design Arena

CategoryEloWin rateRank
agentichtmlslidesagents125459.4%#1
agenticslides(html)agents125259.5%#1
htmlslidesagents125960.6%#1
3Dmodels136867.2%#2
ASCII artmodels137070.1%#1
Codemodels134963.3%#2
Data vizmodels138170.2%#1
Game devmodels137965.1%#1
SVGmodels137171.8%#1
UI componentsmodels141671.3%#1
Websitesmodels134162.5%#2

Head-to-head preference voting. How we filter and rank

Supported parameters

  • include_reasoning
  • max_completion_tokens
  • max_tokens
  • reasoning
  • response_format
  • stop
  • structured_outputs
  • tool_choice
  • tools
  • verbosity

Call it

OpenAI-compatible: point your SDK at api.openkey.ai/v1 and use model anthropic/claude-fable-5.

Code sample language
curl https://api.openkey.ai/v1/chat/completions \
  -H "Authorization: Bearer $OPENKEY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "anthropic/claude-fable-5",
    "messages": [{"role": "user", "content": "Hello"}]
  }'
import os
from openai import OpenAI

client = OpenAI(
    base_url="https://api.openkey.ai/v1",
    api_key=os.environ["OPENKEY_API_KEY"],
)

completion = client.chat.completions.create(
    model="anthropic/claude-fable-5",
    messages=[{"role": "user", "content": "Hello"}],
)
print(completion.choices[0].message.content)
import OpenAI from "openai";

const client = new OpenAI({
  baseURL: "https://api.openkey.ai/v1",
  apiKey: process.env.OPENKEY_API_KEY,
});

const completion = await client.chat.completions.create({
  model: "anthropic/claude-fable-5",
  messages: [{ role: "user", content: "Hello" }],
});
console.log(completion.choices[0].message.content);

Questions

How much does Claude Fable 5 cost via API?
Through OpenKey, Claude Fable 5 costs $10.30 per 1M input tokens and $51.50 per 1M output tokens. That is the provider price ($10.00 / $50.00) plus a flat 3% fee — nothing else.
What is Claude Fable 5's context window?
Claude Fable 5 accepts up to 1M tokens of context and returns up to 128K tokens per request.
Is Claude Fable 5 OpenAI-compatible?
Yes. Send requests to OpenKey's /v1/chat/completions endpoint with model "anthropic/claude-fable-5" using any OpenAI SDK — only the base URL and API key change.
What inputs does Claude Fable 5 support?
Claude Fable 5 accepts text, image, file input and produces text output.

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