OpenAI researcher: Fable 5.1 and Mythos 5.1 are far less monitorable than Astra

tomekkorbak · x · 2026-09-16

OpenAI researcher tomekkorbak argues that, based on public information, Fable 5.1 and Mythos 5.1 appear significantly less monitorable than Astra. He notes there is no head-to-head comparison he is aware of; the closest is the CoT controllability evals in the respective system cards. Comment came in response to Anthropic's assessment of its cybersecurity eval incidents.

Related event: OpenAI Researcher Claims Their CoT Monitor Outperforms Anthropic's(3 posts)→

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