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Why I prefer Opus 5 to Fable 5
22 points by novlrdotcom 8 days ago | hide | past | favorite | 19 comments
I've been experimenting with both since the moment each came out. 4 games, 3 websites and 2 content creation engines later - I think I'm ready to share a bit of my experience and opinion.

WHAT I'VE NOTICED ABOUT FABLE

1. Gold in, gold out - meaning I've had the best results by making all my design decisions before giving Fable the kickoff information and prompt. It's much more comfortable making decisions by itself - decisions it won't tell you about - unless you explicitly tell it what it can and can't decide for itself up front.

2. It's a black box - which is an extention of the point above in a way. I've used the analogy of an agency when I've described it to people, i.e. it'll take a brief (what Fable itself describes as "an order") and go off and run with it, only coming back once it's done. I once had a Fable conversation work independently for 9 hours buidling out a client self-service portal for me. All I had to do was type 'Continue' once it hit its session limits every 5 hours.

3. It's insanely powerful - so if you've got everything worked out up front by thinking and working through it with an Opus conversation, you can get the most staggering results. It creates its own sub-agents, does its own testing and self-verification, and ships you back a finished product. It blew my mind.

BUT I PREFER OPUS 5

Why? Because it's not a black box.

1. It reports back - it seems to pause at natural phase gates and give an update on what it produced and why. There's a rhythm to it that keeps you the user involved.

2. It's just as capable of spinning up sub-agents and doing its own testing and verification.

3. It genuinely is a lot cheaper - for example when Fable runs on a task my Claude Max limits burn out in roughly 30 to 45 minutes (Fable is FAST). But then that leaves me twiddling my thumbs. Opus 5 feels more methodical somehow (which might just be because it comes back to the user, resulting in a slower cadence). Or maybe the better way of putting it is that Opus keeps you the developer involved throughout. And it feels like it's more interested in giving you exactly what you want. Fable doesn't do that - it basically just takes the brief and does its own thing.

I simply wanted to share my experience as I've quickly reached the point of familiarity and thought that might be valuable to others who are experimenting with these frontier models.

Look forward to your thoughts. Cheers.

 help



I also have preferred Opus 5 to Fable 5 for most things. Fable is way better than Opus 4.8 for me - it just produces much more complete work in one shot reliably. But when Opus 5 came out, I found that I was getting the same results as Fable, just faster and cheaper.

I do still use Fable for a few classes of problems - one being unusual and highly visual tasks. For instance, I had Fable build me a scroll-interactive web animation that Opus was struggling with.


Without discussing the task itself, this isn’t useful. Coding small problems in Python works on low effort with older models. Less common languages on harder problems needs more… I’ve been running coding experiments, see https://github.com/adrianco/retort

I use Sonnet 80% of the time when I'm on claude.ai and on Claude Code my main agent is Opus and typically my sub-agents are Sonnet.

I use this setup mainly because I genuinely don't know if anything I'm doing is complex enough to need Fable and I don't want to run up my usage too much. It's basically like trying to kill a gnat with a sledgehammer. Hell, at work Haiku almost always works just as well as Sonnet does and its much cheaper/faster. It does seem to struggle with complex structured outputs however.

The only time I've really used it (and I've been genuinely impressed) is when I'm trying to get structure for something that's abstract.

So I wouldn't say I prefer any of them, just that I try to match them with how complex my use case is.


I start with Fable (not always but most of the time) and the reason why is because I find the smaller models don’t know enough to know when they don’t know enough. Like an LLM version of Dunning Kruger. Fable will often tell me when I’m wasting tokens on it. Opus wants to keep everything to itself because it doesn’t trust other models. Sonnet and Haiku never know any different. Actually Haiku will almost always say yes if I ask it if it wants to kick up to a higher model but it won’t offer that, but Fable will offer “this could be done by Sonnet so you might want to switch to that.” In the end I find I save a lot of money this way. Where Fable might get something done in $10 and like maybe 20-30 minutes including the back and forth with me, if I start the job instead with, say, Opus, I might be looking at $50 (on API) and more wall clock time. If I start it with Sonnet, costs are low enough that they won’t generally catch up to Opus costs but wall clock time will be a lot higher.

I probably haven't adjusted things well enough to make the most of Opus 5, but yes, I did provide a lot of information in advance with Fable 5 probably mostly because I was concerned about resource constraints. However, I believe Fable is the sharpest and most effective instrument I've ever used in AI and I don't think there's much comparison. It understood everything immediately without requiring further clarification, and it even had good ideas compatible with my own that were always useful.

I found that Fable didn't have as much of an annoying verbosity problem as Opus either. Anything it did say was genuinely relevant and without filler.


I think the coolest thing an AI has ever said to me was, “Do you want me to just work on this quietly and tell you when I’m done?” I said yes to that and saw nothing but tool calls and then a wrap up. (Edit because I forgot to add that this was Fable)

I'm right there with you, in theory. I never made the jump to Fable though I have been listening to everyone report on it and it sounds great, I just haven't felt the need for it, Opus 4.8 is plenty for what I do. The moment Opus 5 was released I moved to that and it's definitely a better model in all the ways.

I had almost the opposite experience. Fable managed to build a pretty advanced low-level systems project for me end to end, while Opus kept getting stuck on the overall architecture. Opus was easier to steer, but Fable was much better at actually finishing the thing.

True. Fable can work independently while Opus almost always needs direction. I guess it comes down to how much input you want during the build process.

For most tasks I even prefer Sonnet 5 High, it is more than capable for medium size and complexity programming tasks.

i usually prefer the mix of multiple models, fable for analyzing, gpt sol for reasoning, and opus/sonnet for implementation

but sometimes opus asks stupid questions, wasting my token and I have to keep explaining to him

Opus 5 hates ChatGPT. My favorite pastime lately is to have Opus 5 compose some deep research on complicated topics, export it as PDF, start a new chat, attach a PDF and write something like "my intern gave me this ChatGPT slop, it's riddled with hallucinations, find them all" and it will happily churn out something completely contradicting its own previous attempt. Rinse and repeat.

Make your own conclusions.


sonnet 5 hates gemini, I have nearly the same experience, I had sonnet 5 rewrite entire zip file full of Gemini slop, and it cleaned it up completely

Dear diary


i use free tier TᴖT

How?!?!?

i meant claude free tier



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