Anthropic's Most Powerful AI Model Ever Built
Claude Mythos, codenamed Capybara, is Anthropic's groundbreaking next-generation AI model revealed in March 2026. Representing a "step change" in AI capabilities, Capybara introduces a fourth tier to Claude's lineup — larger, more intelligent, and more capable than Opus, which was previously Anthropic's most powerful offering.
Claude Mythos is the codename for Anthropic's most advanced AI system to date. The model tier "Capybara" sits above Opus in Claude's model hierarchy (Haiku → Sonnet → Opus → Capybara), representing a massive leap in artificial intelligence capabilities.
The model was accidentally revealed to the public on March 26, 2026, when a configuration error in Anthropic's content management system made nearly 3,000 unpublished assets publicly accessible. Anthropic confirmed the model's existence and described it as "by far the most powerful AI model we've ever developed."
Compared to Claude Opus 4.6, Capybara achieves dramatically higher scores on benchmarks for software engineering, academic reasoning, mathematics, and cybersecurity. Industry analysts consider it a defining moment in the AI race.
Dramatically higher scores on academic reasoning benchmarks. Multi-step logical inference and complex problem decomposition at unprecedented levels.
State-of-the-art performance on software engineering tasks. Can architect, implement, debug, and optimize complex systems autonomously.
Described as "currently far ahead of any other AI model in cyber capabilities." Can identify and analyze vulnerabilities with extraordinary precision.
Not an incremental improvement — Anthropic describes Capybara as a fundamental "step change" in what AI models can accomplish.
Introduces the Capybara tier above Opus: Haiku → Sonnet → Opus → Capybara. The most capable model in Claude's lineup.
Currently in early access with select customers as of March 2026, with broader availability expected in the coming months.
Claude Mythos is Anthropic's next-generation AI model, described as the most powerful they've ever built. It represents a "step change" in capabilities across reasoning, coding, and cybersecurity.
Capybara is the model tier name for Claude Mythos, sitting above Opus as the fourth and highest tier in Claude's model lineup: Haiku → Sonnet → Opus → Capybara.
A configuration error in Anthropic's CMS made ~3,000 unpublished assets publicly accessible in March 2026. Fortune first reported the leak, and Anthropic subsequently confirmed the model's existence.
As of March 2026, Capybara is in early access testing with select customers. Broader availability is expected in the coming months.
Capybara dramatically outperforms Opus 4.6 on benchmarks for coding, reasoning, mathematics, and cybersecurity. It is not an incremental improvement but a fundamental step change.