Anthropic releases Claude Fable 5 with Mythos-class capabilities at $10/$50 per million tokens

Anthropic released Claude Fable 5 to enterprise customers and paid subscribers on June 9, 2026, making Mythos-class AI capabilities broadly available two months after restricting its original Mythos model to a limited group of companies.

Pricing and performance

Claude Fable 5 costs $10 per million input tokens and $50 per million output tokens—double the price of Claude Opus 4.8, which Anthropic released in late May 2026. According to the company, the model scores more than 10% higher than Claude Opus 4.8 on some benchmarks and shows "exceptional performance" across software engineering and knowledge work tasks.

Safety guardrails enable public release

The broad release became possible through new safeguards that block responses in high-risk areas including cybersecurity and biology. When users ask high-risk questions—such as how to make ricin—the model blocks its response and falls back to Claude Opus 4.8 to deliver a safe answer.

"What we wanted to do was to be very intentional about building new types of classifiers and new types of safety guardrails in place for this launch," said Dianne Penn, Anthropic's head of product management for research.

Anthropic first unveiled Mythos in April 2026, a model that excels at identifying security flaws within software. The company limited that rollout to select companies through Project Glasswing due to concerns about the model's potential for misuse.

Updated Mythos model also released

Anthropic simultaneously launched Claude Mythos 5, which uses the same underlying model as Claude Fable 5 but with safeguards lifted in some areas. This model remains available only to the limited group in Project Glasswing.

Financial context

The release comes days after Anthropic confidentially filed its IPO prospectus with the SEC. The company said in May 2026 that its revenue run rate reached $47 billion, up from roughly $10 billion in annual revenue last year. Its most recent funding round valued the company at $965 billion, exceeding rival OpenAI's $852 billion valuation from March 2026.

What this means

Anthropic is attempting to commercialize highly capable AI models while maintaining safety controls—a balance competitors like OpenAI also face ahead of their IPOs. The 2x price premium over Claude Opus 4.8 suggests Anthropic believes enterprises will pay significantly more for incremental capability gains. The fallback mechanism to a less capable model for blocked queries is a novel safety approach, though its effectiveness at preventing sophisticated misuse attempts remains untested at scale. Early customer feedback indicating "higher ROI" and "improvement in spend per task" will be critical to justifying the premium pricing as competition intensifies.