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61% Positive

Analyzed from 958 words in the discussion.

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#opus#fable#space#medium#maybe#more#high#models#system#code

Discussion (28 Comments)Read Original on HackerNews

sothatsitabout 1 hour ago
This matches my experience of Opus 5 being a nice improvement over Opus 4.8, but not being revolutionary like Fable felt.

I’ve now replaced my use of Opus 4.8 xhigh with Opus 5 medium, and I’m using less tokens and it’s quicker. I can understand people being annoyed by its writing style but for getting work done that really doesn’t bother me. I’ve been really enjoying using it.

fastball38 minutes ago
Medium vs High? Why? From all the charts I've seen the performance jump is pretty large from med -> high (not as noticeable from high -> xhigh).
sothatsit14 minutes ago
If I need something smarter I use Fable. Medium works well and is quick. Opus 5 medium feels much better to me than Opus 4.8 medium.
dhorthy4 minutes ago
yeah someone will have to re-run this bench on various effort levels. unfortunately it is not cheap
rubicon3337 minutes ago
I think they neutered Fable. When it first came out it was indeed revolutionary. But what we have today, is not what we had before the ban.
swader99913 minutes ago
Noticed that too. I wonder if these things just degrade over time, perhaps with the way it writes memories about my project as it goes
Espressosaurus7 minutes ago
I’ve observed the degradation, but I suspect what’s happening is they’re tuning it for lower inference costs. Maybe turning down the amount of thinking, maybe quantizing, maybe something else.

It seems like there’s a week by week and sometimes day by day change in performance when on a subscription plan using their harnesses.

Johnny_Bonkabout 2 hours ago
I haven't joined your chats in a while but glad to see you put this together, I truly feel as though opus 5 is not much of an improvement. The only time i ever felt a wow factor was opus 4, 4.6 and fable pre trump admin lobotimizing
dhorthyabout 2 hours ago
yeah this was just a start - the fastest cheapest thing we could try for a brand new model.

I'm hoping to do some more work with sol/fable in the mix as well as exploring more languages and curating the problem set to include more of the benchmark

I also kinda felt like opus4.5 was dumber than 4.1 personally, maybe a little biased since 4.5 was 2.5x faster and 2.5x cheaper seems to indicate its a smaller model

Johnny_Bonkabout 2 hours ago
yeah i agree
dan_geeabout 2 hours ago
As someone who doesn't use AI, this is totally incomprehensible to me.

You might as well be talking about the difference between smoking Maui Wowie and Grandaddy Purp.

scrollawayabout 2 hours ago
How is this useful or insightful?

You ever go to forums full of entomology specialists and tell them you don’t understand their fancy terms?

dan_geeabout 2 hours ago
My point is that the differences between these models are so minor that obsessively benchmarking them comes across as navel-gazing.
ajwin37 minutes ago
To what degree is this a harness/system prompt problem? Models maybe should implement new stuff with as little impact on the existing stuff as possible by default? A simple system prompt for it to always check the code after task completion for proper simplifications, abstractions and cleanups before returning to the user? Instructions to retain "story like" readability of the code.
igregoryca15 minutes ago
At least for Claude Code, putting "run /simplify at the end" in an "implement the plan" skill helps a little. It still often leaves new code in bizarre places, and/or with bad/alien-sounding names and comments.
dhorthy28 minutes ago
I agree this is an option, and the next thing on my radar is to try with a more realistic "factory-shaped" harness where you have feedback from linters and other models after each coding episode that refines the architecture.

For readability specifically, I've found it hard to get the models to do this with prompting. If you've talked to opus/fable for a long time on prose writing you probably felt this too

killingtime74about 2 hours ago
Did you not benchmark latest GPT 5.6 or GLM 5.1/Kimi K3 because of cost? I can run them if you share how you ran them
dhorthyabout 2 hours ago
no i'm spinning those up at some point this week. here's the first few prompts I used (claude opus 5 as the research orchestrator), (these were interspersed with lots of tools and assistant messages but it should get you kicked off.

> fetch this article for slopcodebench and help me run an eval on a subset of problems with opus 5 https://arxiv.org/html/2603.24755v1 > Get all the context, fetch any mentioned repos, and then propose a plan to me.

> i have an anthropic API key in .... > Let's do the three challenges with Opus 4.8 and Opus 5 and Fable please. I like your minimal set. Let's try it. What do you need from me?

> Actually I changed my mind. I want to do two of the easy ones you picked and then I want you to pick the one with more checkpoints, maybe one of the harder ones, not the very hardest one but one with a higher number of checkpoints.

> Actually let's do one easy, one medium, and one hard problem please. If we have a hard problem I'd like to see that.

> lets rock - i think lets just do opus 4.8 and sonnet 5 and opus 5 since we our ZDR will block fable

Vgooseabout 1 hour ago
Nice! I actually ran across this paper+benchmark recently, too. It's the first I've found that start to aim at some of the non-functional and longitudinal requirements that I think have always been an important part of writing production code.

It's especially relevant now that models are good enough to solve ~most point-in-time problems.

Some relevant but disconnected thoughts:

- deterministic scores are so nice

- what "maintainable" is is probably some high dimensional space described by these signals; it'd probably require some human labeling to figure out where this space is

- another signal I've been thinking about and I'm seeing increasingly get brought up is the state space of a system; I'm seeing formal methods pop up a lot recently

dhorthyabout 1 hour ago
> - what "maintainable" is is probably some high dimensional space described by these signals; it'd probably require some human labeling to figure out where this space is

this is a nicely succinct way to put this - a multi-dimensional space where no single metric is really useful

state space of the system is interesting too. I would guess that for any production software with dependencies like databases/third parties that might be too hard to measure, but if you can silo off parts of your system into bounded state machines, it may be a value metric on some module behind a clean interface.

I think the kubernetes control loop model is a great instance of this, a handful of scoped components that own a control loop across a well-defined state machine, that can operate / recover in the face of most network partitions or downtime - the promise of CRDTs but rather more a pragmatic approach to it

dclabout 2 hours ago
finally the benchmark for me
dhorthyabout 2 hours ago
i hope that is because you hate slop and not because you write it
knighthackerabout 1 hour ago
This is where Opus 5 shines
cute_boiabout 1 hour ago
Opus 5 is an overconfident stupid model. It tries to generate too much slop, tries to act like everything will fall. I have reversed back to fable and codex sol.
dhorthyabout 1 hour ago
yes sol is still my daily driver for most coding tasks

I did find opus 5 quite handy for general knowledge work and visual design, without the cost of fable (e.g. the graphics in this post are made by opus 5)

but its not noticeably better than opus 4.8 in those regards, and I would not miss it if forced to go back to 4.8

roncesvalles41 minutes ago
I almost prefer Opus 4.8. Opus 5.0 has the overly scholastic tone of Fable but without the intelligence.