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Claude Opus 5

anthropic.com

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Re: Claude Opus 5

#461

Post by consumer451 »

roboyoshi wrote: post #439
consumer451 wrote: post #390

I have a side project that I always run a simple security analysis prompt on in CC, at each model release. Obviously, Fable 5 would downgrade to Opus 4.8 on any such request. Nothing since Opus 4.6 has found anything interesting. Just ran it using Opus 5, and it found a genuine issue that I verified. Neato!

Do you have a skill for that or do you (or anyone else here) just prompt with "try to find security issues"?

I have a project-specific prompt saved as a text file. It is very basic, just focusing on the app's most important security issues. I kept it broad, so as not to over-specify.

Something along the lines of: "Please run a full security analysis on the entire project. Make sure user documents are secure."

Just something like that prompt found a vector in my web app's MCP server that I never would have considered. It was very much an edge case, but it did exist.

Being broad allows the model and harness to do the work. Giving too many instructions can apparently work against you in many cases.

Of course, when dealing with new PRs, I use the /security-review and /code-review skills.

Re: Claude Opus 5

#462

Post by winwang »

deet wrote: post #446

I compared the writing style of Opus 5 vs Fable 5, and Opus 5 continues many of the "Claude-isms" of its 4.8 predecessor in a way that Fable broke away from. Opus 5 still uses "carry the argument", "worth stating plainly", ", and the trap", "The X matters more", the use of "move" We need an "annoying English" benchmark. - Fable 5 Max: https://gist.github.com/deet/3d97f854b48eac6658d642fa18bb24d... - Opus 5 Max: https…

I found 4.6 more amenable than 4.8 to style directions, we'll see how 5.0 does. Super-small-sample-size: I think part of its "Claude-ism" style comes from its propensity to try and "proactively" move the conversation/work along. Not sure how this would fare in non-obviously-productive environments, I'd guess "it's still annoying" considering your evidence.

I'm also thinking of another benchmark: (quantified) stylistic range across different prompts. Just putting it out there if anyone wants to do the work for me :D

Re: Claude Opus 5

#463

Post by winwang »

acmnrs wrote: post #46

From the prompting guide https://platform.claude.com/docs/en/build-with-claude/prompt... >: > Claude Opus 5's default user-facing responses run longer than prior Opus models'. The benchmarks do show Opus 5 as slightly more expensive than 4.8, although the scores are much higher. This still feels like a step in the wrong direction, though, especially with OpenAI making so much progress with the efficiency of their mod…

Almost completely disagree. Slightly more expensive, but significant better on a per-prompt basis? For non-trivial projects, the former is a small linear increase, the latter is a (somewhat-)exponential(-ish) cost/time/sanity savings.

Re: Claude Opus 5

#464

Post by Kwpolska »

deet wrote: post #446

I compared the writing style of Opus 5 vs Fable 5, and Opus 5 continues many of the "Claude-isms" of its 4.8 predecessor in a way that Fable broke away from. Opus 5 still uses "carry the argument", "worth stating plainly", ", and the trap", "The X matters more", the use of "move" We need an "annoying English" benchmark. - Fable 5 Max: https://gist.github.com/deet/3d97f854b48eac6658d642fa18bb24d... - Opus 5 Max: https…

Fable might be using those phrases less, but its writing is still terrible and exhausting to read.

Re: Claude Opus 5

#465

Post by owenthejumper »

paxys wrote: post #41

Looking at all these releases it’s not a surprise that model routing is the fastest growing segment in AI right now. There are 10+ LLM companies, each with dozens of models of different modalities, each model with multiple size variants, then different “thinking” levels, then agentic modes, “pro” modes, a “fast” option, standard vs flex vs batch execution. And of course each end combination has a different input/outp…

I am not convinced this will end up being a domain of the ‘routers’ vs the clients, as in harnesses themselves. Thoughts?

Re: Claude Opus 5

#467

Post by slices »

wuhhh wrote: post #457

It really feels as though my 20 year career as a front end developer is coming to a very abrupt end; at least as I have know it these past two decades.

really? I have yet to see fable or 5.6 reliably generate front end code with correct a11y, for one thing -- does that not matter to the work you do?

Re: Claude Opus 5

#469

Post by furyofantares »

mulhoon wrote: post #353

As a coder, I’ve had no desire to use Fable. In fact I switched from Opus models to sonnet 5 and haven’t noticed any drop in quality on large repos. It seems the gap at the top is very small and not hugely noticeable for backed/frontend. Has anyone else had this experience?

If I'm using medium or low reasoning, I use Sonnet 5. If high or above, I use Opus 4.8. (Before 5, I was never using Sonnet. This is a Sonnet 5 vs Opus 4.8 comparison.)

Sonnet 5 and Opus 4.8 seem about the same to me - the reason I switch between the two is I'd read that it's cheaper to use Sonnet 5 on those reasoning levels, and cheaper to use Opus 4.8 above them. This is due to them using different token quantities.

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