I don't know, maybe I'm doing it wrong but I feel LLMs add a slop debt, and each agent pass just exuberates it.

Like I had an LLM implement a spec and said it was done... Except it had a ton of `casts` everywhere. Okay, my bad, I should have been clear "NO CASTS", so I use the LLM to remove the casts, except it just kept making things more and more complicated and ugly.

It took me taking a break and having a shower thought to realize all the ugliness is because one type should have been broken up into 2, which would remove a ton of generics and code. But Claude never suggested that, it was always "we need at least one cast here, or we need 1000 LOC of generic factories". I tried multiple new sessions with various prompts too.

Maybe one day soon LLMs could pay off their own slop debt but at least right now I don't trust them to write code unseen.

Edit: Maybe the correct action should have been to delete everything and make it re-write everything from scratch with the clear "NO CASTS EVER" rule. But still the point is feels like having LLM clean up after an LLM doesn't work well enough to just have keep it in a loop and never look at what it does.

If you want hard rules, use deterministic tools. Prompts are for fuzzy guidance.

This matches my experience.

I've had to put a fair chunk of effort in to skills that will run deterministic mechanisms to unslop a codebase (cyclomatic complexity grading has been really helpful here) as invariably some amount of guidance around principles will be missed over time. I've found it does help, though. Certainly I'm getting overall better results from Flash and Sonnet over multiple runs for fairly modest token increases. GPT 5.5 less so, but that's because it scores better in a first pass. I won't really know until I gauge it at the end of my sub month which has been more cost efficient for me all things considered.

The problem is that we have an ever growing and large number of constraints, and not following even a single one means the result is sloppy.

I don’t see them fixing this any time soon, and thus human in the loop is a requirement to use these tools effectively. That is unless you love your slot machine dopamine rush enough to ignore quality gates and respect for your peers time.

I've been reading writing Rust for a long while now, since before 1.0. I'm capable of critically evaluating Rust code. I'm also a happy Claude Code user, mostly for lightweight uses like generating scaffolding, prototyping, and debugging.

The pure LLM, no human intervention vibe-coded PRs on Bun since the vibe-rewrite to Rust contain the worst coding horrors I've seen in 20 years of programming.

Setting aside the quality of the change itself (I would have done it differently, for sure: it is pretty straightforward to build a safe abstraction out of this type), the utterly pointless "source-text consistency test" added here is easily the worst example of "test repeats implementation" I have seen in my career:

https://github.com/oven-sh/bun/pull/30728/files#diff-863477b...

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