Claude Mythos 5.1 is Anthropic’s invitation-only model for long-horizon research in areas like cybersecurity and biology, with a 1M context and $10/M input pricing.
Claude Mythos 5.1 is Anthropic's September 2026 specialized Project Glasswing model, sharing Fable 5.1-class capabilities for demanding long-horizon reasoning while using always-on adaptive thinking.
Claude Mythos 5.1 is a current AI model verified from first-party Anthropic sources.
Claude Mythos 5.1 is Anthropic’s September 2026 specialized Project Glasswing model, sharing Fable 5.1-class capabilities for demanding long-horizon reasoning while using always-on adaptive thinking. Its verified context or usage limit is 1000000 tokens, with 128000 tokens maximum output.
Claude Mythos 5.1 costs $10 per 1M input tokens and $50 per 1M output tokens. Cache reads cost $0.25/M tokens and Batch API input/output receives a 50% discount. Access is invitation-only.
Advanced research, Cybersecurity research, Biology research, Long-horizon agents, Complex reasoning.
Not generally available, Always-on thinking can increase output usage, Access depends on Project Glasswing eligibility.
In addition, its main capabilities include 1M context, 128K output, Always-on adaptive thinking, Vision, Tool use and Structured outputs. For example, common use cases include Specialized research, Long-running agents, Deep analysis and High-complexity knowledge work.
In practice, this model may suit Advanced research, Cybersecurity research, Biology research, Long-horizon agents and Complex reasoning. Also, notable strengths include Newest specialized Claude model, 1M context, 128K output and Strong long-horizon reasoning. However, review trade-offs such as Not generally available, Always-on thinking can increase output usage and Access depends on Project Glasswing eligibility before adopting it.
Meanwhile, Claude Mythos 5.1 costs $10 per 1M input tokens and $50 per 1M output tokens. Cache reads cost $0.25/M tokens and Batch API input/output receives a 50% discount. Access is invitation-only. Premium $10/M input and $50/M output pricing; access requires invitation through Project Glasswing.
Use the official model website, official documentation, pricing or release source and additional primary source to confirm current availability, limits and pricing. Product details can change after publication, so rely on primary documentation for final decisions.
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Analyze this complex research problem and identify the strongest evidence.Plan this multistep expert workflow.Review these technical documents and surface high-confidence findings.Claude Mythos 5.1 costs $10 per 1M input tokens and $50 per 1M output tokens. Cache reads cost $0.25/M tokens and Batch API input/output receives a 50% discount. Access is invitation-only.
A very fresh September 2026 Claude model with strong high-intent interest around Anthropic’s most specialized research tier.
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