We, or at least ‘more than 100 American institutions,’ got Mythos back this week.

What we the people do not have is Fable or Sol.

While we wait for both Claude Fable 5 and GPT-5.6-Sol, today we instead got Claude Sonnet 5. As usual it will take a few days to get a handle on the new model. In this case, Anthropic is representing it as a cheaper and faster version of Opus 4.8, so even though the number says 5 this is a relatively minor development.

This post expands the Fable series to cover all further developments this week surrounding the Mythos Moment, and the various aspects of handling our new ad hoc licensing regime and figuring out policy going forward, and other aspects of policy as well.

This includes my notes on various rhetoric being pulled out, where I fear I end up saying similar things every so often, because we are doomed to repeat the cycle. I have accepted my role in that, but those are sections many of you can skip, and are marked in italics accordingly as per usual.

Table of Contents

You Should See The Other [...]

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Outline:

(01:12) You Should See The Other Guy

(01:54) DeepMind Coders Of The World, Unite

(02:45) Report Your Incidents

(03:04) Good Guy With An AI

(04:49) Free As In To Give It A Shot

(08:21) Everything Is Both Speech And Computer

(11:10) Lambs To The Slaughter

(15:43) A Sign Saying Beware Of The Leopard

(16:52) The Once And Present Mythos

(20:26) What Is To Be Done

(24:00) Distillation

(26:24) What Would Banning Open Source Even Mean

(27:20) Open Weight Models Are Unsafe And Nothing Can Fix This

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First published:
June 30th, 2026

Source:
https://www.lesswrong.com/posts/phxgfwGNGbanumMMv/the-once-and-future-fable-5

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Narrated by TYPE III AUDIO.

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Images from the article:

Meme showing two people on a bus with overlapping text about powerful models.

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