Comment by jpollock | Hacker News Reader

Comment by jpollock | Hacker News Reader

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The last time I tried AI, I tested it with a stopwatch.

The group used feature flags...

    if (a) {
       // new code
    } else {
       // old code
    }

    void testOff() {
       disableFlag(a);
       // test it still works
    }
    
    void testOn() {
        enableFlag(a);
        // test it still works
    }

However, as with any cleanup, it doesn't happen. We have thousands of these things lying around taking up space. I thought "I can give this to the AI, it won't get bored or complain."

I can do one flag in ~3minutes. Code edit, pr prepped and sent.

The AI can do one in 10mins, but I couldn't look away. It kept trying to use find/grep to search through a huge repo to find symbols (instead of the MCP service).

Then it ignored instructions and didn't clean up one or the other test, left unused fields or parameters and generally made a mess.

Finally, I needed to review and fix the results, taking another 3-5 minutes, with no guarantee that it compiled.

At that point, a task that takes me 3 minutes has taken me 15.

Sure, it made code changes, and felt "cool", but it cost the company 5x the cost of not using the AI (before considering the token cost).

Even worse, the CI/CD system couldn't keep up the my individual velocity of cleaning these up, using an automated tool? Yeah, not going to be pleasant.

However, I need to try again, everyone's saying there was a step change in December.

I did my own experiment with Claude Code vs Cursor tab completion. The task was to convert an Excel file to a structured format. Nothing fancy at all.

Claude Code took 4 hours, with multiple prompts. At the end, it started to break the previous fixes in favor of new features. The code was spaghetti. There was no way I could fix it myself or steer Claude Code into fixing it the right way. Either it was a dead-end or a dice roll with every prompt.

Then I implemented my own version with Cursor tab completion. It took the same amount of time, 4 hours. The code had a clear object-oriented architecture, with a structure for evolution. Adding a new feature didn't require any prompts at all.

As a result, Claude Code was worse in terms of productivity: the same amount of time, worse quality output, no possibility of (or at best very high cost of) code evolution.

Are you able to share your prompts to Claude Code? I assume not, they are probably not saved - but this genuinely surprised me, it seems like exactly the type of task an LLM would excel at (no pun intended!). What model were you using OOI?

> this genuinely surprised me

Me too. After listening to all the claims about Claude Code's productivity benefits, I was surprised to get the result I got.

I'm not able to share details of my work. I was using Claude Opus 4.5, if I recall correctly.

The exact same prompt ? Everything depends on the prompt and it’s different tools. These days the quality and what’s build around the prompt matters as much as the code. We can’t feed generic query.

Similar happened to me just now. Claude whatever-is-the-latest-and-greatest, in Claude Code. I also tried out Windsurf's Arena Mode, with the same failure. To intercept the inevitable "holding it wrong" comments, we have all the AGENTS.md and RULES.md files and all the other snake oil you're told to include in the project. It has full context of the code, and even the ticket. It has very clear instructions on what to do (the kind of instructions I would trust an unpaid intern with, yet alone a tool marketed as the next coming of Cyber Jesus that we're paying for), in a chat with minimal context used up already. I manually review every command it runs, because I don't trust it running shell scripts unsupervised.

I wanted it to finish up some tests that I had already prefilled, basically all the AI had to do was convert my comments into the final assertions. A few minutes later of looping, I see it finishes and all tests are green.

A third of the tests were still unfilled, I guess left as an exercise for the reader. Another third was modified beyond what I told it to do, including hardcoding some things which made the test quite literally useless and the last third was fine, but because of all the miscellaneous changes it made I had to double check those anyways. This is about the bare minimum where I would expect these things to do good work, a simple take comment -> spit out the `assert()` block.

I ended up wasting more time arguing with it than if I had just done the menial task of filling out the tests myself. It sure did generate a shit ton of code though, and ran in an impressive looking loop for 5-10 minutes! And sure, the majority of the test cases were either not implemented or hardcoded so that they wouldn't actually catch a breakage, but it was all green!!

That's ultimately where this hype is leading us. It's a genuinely useful tool in some circumstances, but we've collectively lost the plot because untold billions have poured into these systems and we now have clueless managers and executives seeing "tests green -> code good" and making decisions based on that.

What model, what harness and about how long was your prompt to fire off this piece of work? All three matters a lot, but importantly missing from your experience.

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