[simonw]

When I'm using them for code these days it is usually in a tool that can execute code in a loop - so I don't tend to even spot the hallucinations because the model self corrects itself.

For factual information I only ever use search-enabled models like o3 or GPT-4.

Most of my other use cases involve pasting large volumes of text into the model and having it extract information or manipulates that text in some way.

[godelski]

  > using them for code

I don't think this means no hallucinations (in output). I think it'd be naive to assume that compiling and passing tests means hallucination free.

  > For factual information

I've used both quite a bit too. While o3 tends to be better, I see hallucinations frequently with both.

  > Most of my other use cases

I guess my question is how you validate the hallucination free claim.

Maybe I'm misinterpreting your claim? You said "I rarely see them" but I'm assuming you mean more, and I think it would be reasonable for anyone to interpret this as more. Are you just making the claim that you don't see them or making a claim that they are uncommon? The latter is what I interpreted.

[simonw]

I don't understand why code passing tests wouldn't be protection against most forms of hallucinations. In code, a hallucination means an invented function or method that doesn't exist. A test that uses that function or method genuinely does prove that it exists.

It might be using it wrong but I'd qualify that as a bug or mistake, not a hallucination.

Is it likely we have different ideas of what "hallucination" means?

[godelski]

  > tests wouldn't be protection against most forms of hallucinations.

Sorry, that's a stronger condition that I intended to communicate. I agree, tests are a good mitigation strategy. We use them for similar reasons. But I'm saying that passing tests is insufficient to conclude hallucination free.

My claim is more along the lines of "passing tests doesn't mean your code is bug free" which I think we can all agree on is a pretty mundane claim?

  > Is it likely we have different ideas of what "hallucination" means?

I agree, I think that's where our divergence is. Which in that case let's continue over here[0] (linking if others are following). I'll add that I think we're going to run into the problem of what we consider to be in distribution, in which I'll state that I think coding is in distribution.

[0] https://news.ycombinator.com/item?id=44829891

[ZeroGravitas]

Haven't you effectively built a system to detect and remove those specific kind of hallucinations and repeat the process once detected before presenting it to you?

So you're not seeing hallucinations in the same way that Van Halen isn't seeing the brown M&Ms, because they've been removed, it's not that they never existed.

[simonw]

I think systems integrated with LLMs that help spot and eliminate hallucinations - like code execution loops and search tools - are effective tools for reducing the impact of hallucinations in how I use models.

That's part of what I was getting at when I very clumsily said that I rarely experience hallucinations from modern models.

[rohansood15]

On multiple occasions, Claude Code claims it completed a task when it actually just wrote mock code. It will also answer questions with certainity (for e.g. where is this value being passed), but in reality it is making it up. So if you haven't been seeing hallucinations on Opus/Sonnet, you probably aren't looking deep enough.

[theshrike79]

This is because you haven't given it a tool to verify the task is done.

TDD works pretty well, have it write even the most basic test (or go full artisanal and write it yourself) first and then ask it to implement the code.

I have a standing order in my main CLAUDE.md to "always run `task build` before claiming a task is done". All my projects use Task[0] with pretty standard structure where build always runs lint + test before building the project.

With a semi-robust test suite I can be pretty sure nothing major broke if `task build` completes without errors.

[0] https://taskfile.dev

[rohansood15]

What do you think it is 'mocking'? It is exactly the behavior that would make the tests work. And unless I give it access to production, it has no way to verify tasks like how values (in this case secrets/envs) are being passed.

Plus, this is all besides the point. Simon argued that the model hallucinates less, not a specific product.