Claude Opus 5.5 vs Mythos 5: Similar Cyber Capability, Very Different Price and Access

Anthropic’s Claude Opus 5.5 is substantially cheaper and easier to access than the company’s restricted Claude Mythos 5 line, even as Anthropic says the newer public flagship offers comparable capabilities in areas including cybersecurity and biology. Opus 5.5 is priced at $4 per million input tokens and $20 per million output tokens, while Mythos 5 carries a $10 and $50 rate, making the restricted model 2.5 times more expensive at list price. Pasted markdown Claude Mythos 5, released on June 9, 2026, is available only through Anthropic’s verification programmes. A refreshed Mythos 5.1 followed on September 1. Claude Opus 5.5, released on September 22, is generally available and can be accessed through Anthropic’s API as well as major cloud platforms.

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