Claude Fable 5

What is Claude Fable 5?

Claude Fable 5 is a Mythos-class model from Anthropic that has been made safe for general use. It exceeds the capabilities of any previous Anthropic model, demonstrating state-of-the-art performance across nearly all tested benchmarks of AI capability, including software engineering, vision, and scientific research. It is designed to handle long and complex tasks with a high degree of autonomy and reliability.

Feature 1: Software Engineering

Fable 5 excels at agentic coding and codebase migrations. It can perform codebase-wide migrations in a fraction of the time required by human teams and scores highest among frontier models on difficult coding evaluations.

Feature 2: State-of-the-art Vision

The model can extract precise data from detailed scientific figures and rebuild web application source code from screenshots alone. It has demonstrated the ability to play complex games like Pokémon FireRed using vision-only inputs.

Feature 3: Memory and Long-context

Fable 5 stays focused across millions of tokens in long-running tasks. It utilizes persistent file-based memory to improve its performance and can refine its own outputs using its own notes.

Use Case 1: Codebase Migration

Stripe used Fable 5 to perform a codebase-wide migration on a 50-million-line Ruby codebase in a single day, a task that would have normally taken a team over two months.

Use Case 2: Life Sciences and Drug Design

Using the related Mythos 5 model, internal experts accelerated drug design processes by approximately ten times, successfully identifying protein targets for further investigation.

Use Case 3: Financial Reasoning

Fable 5 shows strong performance on complex analytical tasks, including document-based reasoning, chart interpretation, and root-cause analysis for trading firms.

Claude Fable 5 Pricing

Claude Fable 5 and Claude Mythos 5 are offered at $10 per million input tokens and $50 per million output tokens, which is less than half the price of the previous Claude Mythos Preview.