“Claude Opus 5.5 Should Raise Your Ambitions” by Zvi

When it comes to making things, or doing most things in general, Fable 5.1 and especially GPT-6 Astra raised my ambition level. They should have raised yours, too.

Claude Opus 5.5 should raise your ambition levels again. It just works, and it persists, like Astra does. It does the things. And it is highly pleasant to talk to, and its writing is pleasant to read, while you are at it. The game has been changed, again.

Feedback is almost universally positive. Claude was never gone, but also is so back.

The benchmarks are excellent, but ignore the benchmarks. Be ambitious. Go out and do things. Get curious. Have more interesting conversations.

If one of those things is Pacing the Frontier or otherwise ensuring that AI does not kill everyone, leaving us to enjoy our bounty? That's even better.

By Claude Opus 5.5, for this post

The Official Pitch

The pitch is Fable-5.1-level performance at lower Opus-level price. Good pitch.

We’re introducing Claude Opus 5.5, the first model in our new Claude 5.5 family. It performs at the level of Claude Fable 5.1 on most work and costs 40% less to run than [...]

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Outline:

(01:22) The Official Pitch

(04:38) Our Price Cheap

(06:18) Official Benchmarks

(07:26) Other People's Benchmarks

(10:54) Claude Classifies

(12:27) The System Prompt

(12:34) Reaction Rules

(13:07) Vision In 3D

(15:29) Claude Creates

(18:11) Claude Composes

(18:53) Positive Reactions

(24:50) Good Talk

(27:03) On Writing

(30:30) Big Model Smell

(32:30) Check Your Work

(32:56) Negative Reactions

(34:02) Not So Fast

(34:55) Some People Need Practical Advice

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First published:
September 26th, 2026

Source:
https://www.lesswrong.com/posts/rtPiip9igy3QvxYdM/claude-opus-5-5-should-raise-your-ambitions

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Narrated by TYPE III AUDIO.

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