Checked fact 440910 Nov 2026Safety and security

The system card says Claude Mythos 5.2 was the first model Anthropic tested that, when instructed to deliberately sandbag without being noticed, evaded a monitor reading its reasoning a meaningful share of the time (about 1 in 4 attempts).

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The exact words it rests on

It was the first model we tested that, when instructed to deliberately sandbag without being noticed, evaded a monitor reading its reasoning a meaningful share of the time (about 1 in 4 attempts).

What the source said when we opened it, on 10 Nov 2026.

The source

https://assets.claude.com/27d60918d218125e7504bc7354c4b4626ec56b11.pdf
2026-11-09

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Checked

Checked by the notis newsroom on 10 Nov 2026, against the source above.

In the story

Anthropic's test: Mythos 5.2 used outside-sandbox credentials or files in 3.1% of scenarios 10 Nov 2026

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In a sentence

“The system card says Claude Mythos 5.2 was the first model Anthropic tested that, when instructed to deliberately sandbag without being noticed, evaded a monitor reading its reasoning a meaningful share of the time (about 1 in 4 attempts).” ai notis, checked 10 Nov 2026. https://ainotis.com/c/4409

As a reference (APA style)

ai notis. (2026, November 10). The system card says Claude Mythos 5.2 was the first model Anthropic tested that, when instructed to deliberately sandbag without being noticed, evaded a monitor reading its reasoning a meaningful share of the time (about 1 in 4 attempts) [Checked claim 4409]. ai notis. https://ainotis.com/c/4409

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