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Changes in the system prompt between Claude Opus 4.6 and 4.7

simonwillison.net

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Re: Changes in the system prompt between Claude Opus 4.6 and 4.7

#31

Post by [deleted] »

mysterydip wrote: post #10
sigmoid10 wrote: post #9

I knew these system prompts were getting big, but holy fuck. More than 60,000 words. With the 3/4 words per token rule of thumb, that's ~80k tokens. Even with 1M context window, that is approaching 10% and you haven't even had any user input yet. And it gets churned by every single request they receive. No wonder their infra costs keep ballooning. And most of it seems to be stable between claude version iterations to…

I assume the reason it’s not baked in is so they can “hotfix” it after release. but surely that many things don’t need updates afterwards. there’s novels that are shorter.

[deleted]

Re: Changes in the system prompt between Claude Opus 4.6 and 4.7

#32

Post by gausswho »

naasking wrote: post #30
embedding-shape wrote: post #6

> The new section includes: When a request leaves minor details unspecified, the person typically wants Claude to make a reasonable attempt now, not to be interviewed first. Uff, I've tried stuff like these in my prompts, and the results are never good, I much prefer the agent to prompt me upfront to resolve that before it "attempts" whatever it wants, kind of surprised to see that they added that

Seriously, when you're conversing with a person would you prefer they start rambling on their own interpretation or would you prefer they ask you to clarify? The latter seems pretty natural and obvious. Edit: That said, it's entirely possible that large and sophisticated LLMs can invent some pretty bizarre but technically possible interpretations, so maybe this is to curb that tendency.

Socrates would agree: https://en.wikipedia.org/wiki/Socratic_method

Re: Changes in the system prompt between Claude Opus 4.6 and 4.7

#33

Post by gchamonlive »

embedding-shape wrote: post #26
walthamstow wrote: post #24

The eating disorder section is kind of crazy. Are we going to incrementally add sections for every 'bad' human behaviour as time goes on?

Even better, adding it to the system prompt is a temporary fix, then they'll work it into post-training, so next model release will probably remove it from the system prompt. At least when it's in the system prompt we get some visibility into what's being censored, once it's in the model it'll be a lot harder to understand why "How many calories does 100g of Pasta have?" only returns "Sorry, I cannot divulge that inf…

Just assume each model iteration incorporates all the censorship prompts before and compile the possible list from the system prompt history. To validate it, design an adversary test against the items in the compiled list.

Re: Changes in the system prompt between Claude Opus 4.6 and 4.7

#34

Post by embedding-shape »

naasking wrote: post #30
embedding-shape wrote: post #6

> The new section includes: When a request leaves minor details unspecified, the person typically wants Claude to make a reasonable attempt now, not to be interviewed first. Uff, I've tried stuff like these in my prompts, and the results are never good, I much prefer the agent to prompt me upfront to resolve that before it "attempts" whatever it wants, kind of surprised to see that they added that

Seriously, when you're conversing with a person would you prefer they start rambling on their own interpretation or would you prefer they ask you to clarify? The latter seems pretty natural and obvious. Edit: That said, it's entirely possible that large and sophisticated LLMs can invent some pretty bizarre but technically possible interpretations, so maybe this is to curb that tendency.

> The latter seems pretty natural and obvious.

To me too, if something is ambigious or unclear when I'm getting something to do from someone, I need to ask them to clarify, anything else be borderline insane in my world.

But I know so many people whose approach is basically "Well, you didn't clearly state/say X so clearly that was up to me to interpret however I wanted, usually the easiest/shortest way for me", which is exactly how LLMs seem to take prompts with ambigiouity too, unless you strongly prompt them to not "reasonable attempt now without asking questions".

Re: Changes in the system prompt between Claude Opus 4.6 and 4.7

#36

Post by idiotsecant »

walthamstow wrote: post #24

The eating disorder section is kind of crazy. Are we going to incrementally add sections for every 'bad' human behaviour as time goes on?

Imagine the kind of human that never adapts their moral standpoints. Ever. They believe what they believed when they were 12 years old.

Letting the system improve over time is fine. System prompt is an inefficient place to do it, buts it's just a patch until the model can be updated.

Re: Changes in the system prompt between Claude Opus 4.6 and 4.7

#37

Post by ikidd »

I had seen reports that it was clamping down on security research and things like web-scraping projects were getting caught up in that and not able to use the model very easily anymore. But I don't see any changes mentioned in the prompt that seem likely to have affected that, which is where I would think such changes would have been implemented.

Re: Changes in the system prompt between Claude Opus 4.6 and 4.7

#38

Post by cma »

sigmoid10 wrote: post #9

I knew these system prompts were getting big, but holy fuck. More than 60,000 words. With the 3/4 words per token rule of thumb, that's ~80k tokens. Even with 1M context window, that is approaching 10% and you haven't even had any user input yet. And it gets churned by every single request they receive. No wonder their infra costs keep ballooning. And most of it seems to be stable between claude version iterations to…

> And it gets churned by every single request they receive

It gets pretty efficiently cached, but does eat the context window and RAM.

Re: Changes in the system prompt between Claude Opus 4.6 and 4.7

#39

Post by embedding-shape »

ikidd wrote: post #37

I had seen reports that it was clamping down on security research and things like web-scraping projects were getting caught up in that and not able to use the model very easily anymore. But I don't see any changes mentioned in the prompt that seem likely to have affected that, which is where I would think such changes would have been implemented.

I think it depends on how badly they want to avoid it. Stuff that is "We prefer if the model didn't do these things when the model is used here" goes into the system prompt, meanwhile stuff that is "We really need to avoid this ever being in any outputs, regardless of when/where the model is used" goes into post-training.

So I'm guessing they want none of the model users (webui + API) to be able to do those things, rather than not being able to do that just in the webui. The changes mentioned in the submission is just for claude.ai AFAIK, not API users, so the "disordered eating" stuff will only be prevented when API users would prompt against it in their system prompts, but not required.

Re: Changes in the system prompt between Claude Opus 4.6 and 4.7

#40

Post by dataviz1000 »

an0malous wrote: post #16
sigmoid10 wrote: post #9

I knew these system prompts were getting big, but holy fuck. More than 60,000 words. With the 3/4 words per token rule of thumb, that's ~80k tokens. Even with 1M context window, that is approaching 10% and you haven't even had any user input yet. And it gets churned by every single request they receive. No wonder their infra costs keep ballooning. And most of it seems to be stable between claude version iterations to…

I’m just surprised this works at all. When I was building AI automations for a startup in January, even 1,000 word system prompts would cause the model to start losing track of some of the rules. You could even have something simple like “never do X” and it would still sometimes do X.

I created a test evaluation (they friggen' stole the word harness) that runs a changed prompt comparing success pass / fail, the number of tokens and time of any change. It is an easy thing to do. The best part is I set up an orchestration pattern where one agent iterations updating the target agent prompts. Not only can it evaluate the outcome after the changes, it can update and rerun self-healing and fixing itself.
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