Claude Opus 5.5 writes 30% faster and thinks more per turn
Prompting Claude Opus 5.5
Anthropic's guide to prompting Claude Opus 5.5 covers the model's behavioral shifts from Opus 5 and the patterns that address them: effort calibration, thinking behavior, progress updates, unattended and multiagent tasks, safeguard refusals, frontend design, complex visual inputs, multi-app workflows, and pasted text in user messages. Opus 5.5 generates output tokens over 30% faster, finishes tasks with fewer tokens, and at medium effort matches Opus 5 at high effort on coding and knowledge work.
At a given level, Claude Opus 5.5 tends to think more per turn than Claude Opus 5, especially at xhigh and max. If you keep the effort value you set for Claude Opus 5, expect longer turns and more output tokens.
- skeledrew
All that keeps jumping out at me is how they've set it to refuse giving users thinking tokens and prompts for full reasoning in output. Just drives me further away; I may not stop using Claude completely for now, but I'll be moving even more of my primary workload to Chinese providers. That's where openness and freedom is now at.
- bluegatty
This is a failure of the AI foundries; if we have to use totally different prompting techniques for every model, this wont work.
AI is rapidly saturating it's ability to be useful and these products need to start to mature.
It's not 'fun' to manage 50 different broken MCPs and their variety of ways in which they are broken.
It was 'fun' at the start, now it's just 'broken technology'.
Astra and Opus 5.5 are the 'starting point' for the next era of AI where we expect robust tooling.
- prodigycorp
Opus 5.5 is a good model, but I've tried to understand the extreme hype about it on social media about Opus' ability to do 2d work, as we got with Astra doing 3d work. In both releases, the models required extensive access to third party apis to generate assets for it, and a lot of the models work was essentially coordinating everything.
There's so many "x generated this in one shot, this is agi" stuff that gives you the impression that you can vibe operate modern models the same way you operated last year's models. There's so much more to it than that. It requires you to put a faith in the leap in the capability of models, one that would've surely been a waste of time in previous models.
Not sure where i'm going with this other than I think most can relate that it's exhausting keeping up with. I cant imagine what it'd be like parenting a kid that went from toddler to puberty in the span of a year and planning for them to go to college the next year. This industry is moving so fast that it's becoming fact that it's the user that's "holding it wrong" every six months.
- jryan49
I just tested it over the weekend and I had a 33h claude session completely unattended, with minimal prompting. All the stuff it generated looks good too. It's crazy.
- silversmith
"the biology safeguards are the same as Claude Fable 5.1's ... Everyday health and educational questions are unaffected"
Yet here we are, "why my calves hurt more than any other muscle after training" being classified as a naughty question.
- bob1029
> Fourth, if long tool-calling turns still go quiet for longer than you want, have your harness ask for an update
I'm not sure I understand this complexity. In all harnesses I've ever used, tool calls themselves are surfaced to the user as an indication of progress. When the UI/UX around this is engineered well, the user should be able to infer roughly what is going on. Different tools have different ideal presentations. You can't reduce everything to plaintext blobs.
If I absolutely needed intra-turn progress updates, I'd accumulate a separate per-turn transcript and feed it into a cheaper model at deterministic intervals.
- bronlund
First thing it did when I tried it, was roaming through files in directories way outside of the project. I tried to get it to explain why it did it multiple times, but I never got anything resembling an explanation.
- _superposition_
Anthropic is the new Microsoft.
Just my gut. I'll be staying away from their products. Hopefully it will benefit my career the same way by focusing on open standards, instead of some proprietary bullshit that changes every 3 months.