Development

A rival ships one model at two safeguard tiers

development2026-09-04

Claim

Anthropic answered with Claude Fable 5.1 and Mythos 5.1, the same model at two safeguard tiers, debuting by mapping a third of Venus, with Fable back on the frontier at 66, Mythos 5.1 on its lowest setting matching the previous model at maximum, and invisible EU watermarks carried throughout.

Reported metric: AAII 66

Reporting date: 2026-09-04 (not necessarily the event date)

Sources

Attribution and reporting linked by this record; links do not imply independent verification.

Welcome to September 4, 2026 (theinnermostloop.substack.com)

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Reported in

Welcome to September 4, 2026

Actor

Anthropic

Evidence for

Supersedes

Open weights ship under a license that security-screens large hosts

Referenced by

Welcome to September 4, 2026

Cite or correct this record

Citation formatCitation text

A rival ships one model at two safeguard tiers
Innermost Loop KB — secondary record
Reporting date: 2026-09-04
KB permalink: https://nicholsn.github.io/innermost-loop-kb/developments/2026-09-04-the-same-model-at-two-safeguard-tiers
Claim: Anthropic answered with Claude Fable 5.1 and Mythos 5.1, the same model at two safeguard tiers, debuting by mapping a third of Venus, with Fable back on the frontier at 66, Mythos 5.1 on its lowest setting matching the previous model at maximum, and invisible EU watermarks carried throughout.
Attributed sources:
- Welcome to September 4, 2026 — https://theinnermostloop.substack.com/p/welcome-to-september-4-2026
This citation does not imply independent verification of linked-source claims.

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