Claude Fable 5 API, pricing, playground & code

Name: Claude Fable 5 API
Brand: Anthropic

Overview

About Claude Fable 5

Claude Fable 5 is Anthropic's first Mythos-class model, a new tier above Opus, built for the hardest reasoning, research, and agentic work. Through CompanyFabric it runs behind the same OpenAI-compatible key as the rest of the Claude family, so escalating a task from Sonnet to Fable is a model-string change, not a new integration. Every model on CompanyFabric shares the same API key, billing balance, and rate-limit envelope, one integration covers the entire library.

Facts

At a glance

Availability

Live

Pricing

$10/Mtok in

Metered exactly per call

Context window

200k tokens

Commercial use

See license

Commercial use of outputs permitted per Anthropic's usage policies.

Variants

All endpoints

Claude Sonnet 4.5

$3/Mtok in

Frontier-quality text and reasoning through one OpenAI-compatible endpoint.

Chat Completions

Claude Haiku 4.5

$1/Mtok in

Fast, cheap frontier-family model for high-volume tasks.

Chat Completions

Claude Opus 4.6

$5/Mtok in

The frontier tier for the hardest reasoning and agentic work.

Chat Completions

Claude Fable 5

$10/Mtok in

Anthropic's first Mythos-class model, the new flagship tier above Opus, tuned for the hardest reasoning and agentic work.

Chat Completions

Claude Opus 5

$5/Mtok in

The Claude 5 generation's deep-work model, maximum-capability reasoning for research, architecture, and hard agentic tasks.

Chat Completions

Quickstart

How to use the Claude Fable 5 API

1
Create a free CompanyFabric account, starter credits are included, no card required.
2
Copy your API key from the dashboard. One key covers every model in the library.
3
Point any OpenAI SDK at api.companyfabric.com/v1 and set model to "anthropic/claude-fable-5".
4
Read the exact metered cost of the call from the response, the same number shown in the playground.

Use cases

What teams build with it

Frontier agent loops

The model you reach for when the agent must not be wrong, long multi-step plans, architecture decisions, high-stakes tool chains.

agentsreasoningfrontier

Escalation tier

Route routine turns to Sonnet or Haiku and escalate the hard 5% to Fable, the routing split is one config line on one balance.

model routingescalation

Research & synthesis

Deep document analysis and cross-source synthesis where reasoning depth beats speed.

researchanalysis

Get better output

Prompting tips

Give it the whole problem, not a decomposition, Fable-class models plan better than most humans decompose.
Budget output generously on hard tasks; cutting reasoning short is the main failure mode users cause.
Reserve it for the calls that matter and meter the difference, per-key usage shows exactly what the top tier buys you.

Exact, metered, prepaid

Claude Fable 5 pricing

Claude Fable 5 pricing is per token: $10 / M input · $50 / M output. Output tokens cost 5× input tokens, so long generations, not long prompts, are what actually drive most bills. A typical call with a 2k-token prompt and a 1k-token answer costs about $0.0700.

Every call is metered exactly and attributed to your key, the dashboard, the API usage response, and your invoice all read from the same ledger row. Cap any key's monthly spend with a budget cap, and bring your own provider key (BYOK) at 0% platform fee if you already have a direct contract.

Endpoint	Type	Price
Claude Sonnet 4.5	Chat	$3 / M input · $15 / M output
Claude Haiku 4.5	Chat	$1 / M input · $5 / M output
Claude Opus 4.6	Chat	$5 / M input · $25 / M output
Claude Fable 5	Chat	$10 / M input · $50 / M output
Claude Opus 5	Chat	$5 / M input · $25 / M output

Starter credits

Use Claude Fable 5 free

Your CompanyFabric starter credits cover your first Claude Fable 5 calls at no cost, create a free account, no card required, and the credits apply to Claude Fable 5 and every other model on the key. When they run out, prepaid credits or BYOK (0% fee) take over with no plan to pick.

All ways to use AI models free →

Production-grade

Code samples

import OpenAI from "openai"

const client = new OpenAI({
  baseURL: "https://api.companyfabric.com/v1",
  apiKey: process.env.COMPANYFABRIC_API_KEY,
})

const res = await client.chat.completions.create({
  model: "anthropic/claude-fable-5",
  max_tokens: 1024,
  temperature: 0.7,
  messages: [{ role: "user", content: "Say hello from the fabric." }],
})

console.log(res.choices[0].message.content)

Playground

Try it in the browser

Playground$10 in / $50 out per 1M tokens

Model

Max output

Prompt

Comparisons

Claude Fable 5 vs the alternatives

Claude Fable 5 vs GPT-5.5

Both sit at the top of their families. GPT-5.5 is priced aggressively on input tokens; Fable 5 is the pick where tool-use reliability and long-horizon agentic work decide the outcome. Behind one key, the honest answer is: run your own eval, switching is a string.

Claude Fable 5 vs Gemini 3.1 Pro (preview)

Gemini 3.1 Pro counters with a giant context window and multimodal input; Fable 5 leads on deep reasoning and agentic reliability. Massive-context ingestion to Gemini, hardest-reasoning steps to Fable, same balance either way.

FAQ

Frequently asked questions

How much does the Claude Fable 5 API cost?

$10 / M input · $50 / M output. Every call is metered exactly and shown before you run it.

How do I get a Claude Fable 5 API key?

Create a CompanyFabric account, and one key unlocks Claude Fable 5 and every other model in the library. Free starter credits are included, no subscription, no card required to try it.

Why use Claude Fable 5 on CompanyFabric instead of going direct?

One key, one prepaid balance, and one rate-limit envelope across the whole library, at pricing at parity with or below the direct API. Model switching is a one-line change, and BYOK routing is 0% fee.

Is the API OpenAI-compatible?

Yes, point any OpenAI SDK at api.companyfabric.com/v1 and set model to "anthropic/claude-fable-5".

Can I use the output commercially?

Commercial use of outputs permitted per Anthropic's usage policies.

How does billing work?

Prepaid credits via card, or BYOK with your own provider keys at 0% platform fee. No subscription required; balances never expire.

What is the difference between Claude Fable 5 and Claude Mythos 5?

They share the same underlying model. Fable 5 is the generally available variant with additional safety measures for dual-use capabilities; Mythos 5 is available only to approved organizations. The gateway serves Fable 5.

Fable 5 or Opus 5, which should I default to?

Opus 5 is the deep-work model of the Claude 5 generation; Fable 5 sits above it as the new flagship tier. Start with Opus 5 for heavy analysis and step up to Fable 5 where results still fall short, both are one string apart on the same key.

Provider

About Anthropic

Anthropic publishes the claude family. Also in this family: Claude Sonnet 4.5, Claude Haiku 4.5, Claude Opus 4.6, Claude Opus 5. License: Commercial use of outputs permitted per Anthropic's usage policies.

Explore

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Google's stable Pro tier, the non-preview reasoning model.

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Gemini 3.1 Pro (preview)

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Google's newest Pro tier, shipped as a preview.

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