AISystem

Claude Mythos 5

Anthropic's released Mythos-tier frontier model of mid-2026, the yardstick that the unreleased Model 2 beat by 12.5 points on CoBench v2.

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Welcome to August 15, 2026 (theinnermostloop.substack.com)

Claude Mythos 5 is the Mythos-tier model Anthropic shipped after the spring Claude Mythos preview, and through the summer of 2026 the strongest model it sells. In this corpus it is more often the yardstick than the subject: Model 2 beat it by 12.5 points on CoBench v2 in the saturated-evals disclosure, and Z.ai’s GLM-5.3 nearly matched it on vulnerability discovery in the same issue.

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2026-08-15: A lab reports its AI R&D evaluations have saturated

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Developed by

Anthropic

Evaluated on

CoBench v2

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Claude Mythos 5
Innermost Loop KB — secondary record
Reporting date: unknown
KB permalink: https://nicholsn.github.io/innermost-loop-kb/systems/claude-mythos-5
Attributed sources:
- Welcome to August 15, 2026 — https://theinnermostloop.substack.com/p/welcome-to-august-15-2026
This citation does not imply independent verification of linked-source claims.

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