“If Mythos actually made Anthropic employees 4x more productive, I would radically shorten my timelines” by Ryan Greenblatt

Subtitle: Better estimates of uplift at AI companies seem helpful.

Anthropic's system card for Mythos Preview says:

It's unclear how we should interpret this. What do they mean by productivity uplift? To what extent is Anthropic's institutional view that the uplift is 4x? (Like, what do they mean by “We take this seriously and it is consistent with our own internal experience of the model.”)

One straightforward interpretation is: AI systems improve the productivity of Anthropic so much that Anthropic would be indifferent between the current situation and a situation where all of their technical employees magically work 4 hours for every 1 hour (at equal productivity without burnout) but they get zero AI assistance. In other words, AI assistance is as useful as having their employees operate at 4x faster speeds for all activities (meetings, coding, thinking, writing, etc.) I’ll call this “4x serial labor acceleration”1 (see here for more discussion of this idea2 ).

I currently think it's very unlikely that Anthropic's AIs are yielding 4x serial labor acceleration, but if I did come to believe it was true, I would update towards radically shorter timelines. (I tentatively think my median to Automated Coder would go [...]

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Outline:

(08:25) Appendix: Estimating AI progress speed up from serial labor acceleration

(11:06) Appendix: Different notions of uplift

The original text contained 4 footnotes which were omitted from this narration.

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First published:
April 11th, 2026

Source:
https://blog.redwoodresearch.org/p/if-mythos-actually-made-anthropic

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Narrated by TYPE III AUDIO.

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