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What people take issue with is the claim that agents built a web browser "from scratch" only to find by looking deeper that they were using Servo, WGPU, Taffy,

by mjr00 9mo ago

What people take issue with is the claim that agents built a web browser "from scratch" only to find by looking deeper that they were using Servo, WGPU, Taffy, winit, and other libraries which do most of the heavy lifting. It's like claiming "my dog filed my taxes for me!" when in reality everything was filled out in TurboTax and your dog clicked the final submit button. Technically true, but clearly disingenuous. I'm not saying an LLM using existing libraries is a bad thing--in fact I'd consider an LLM which didn't pull in a bunch of existing libraries for the prompt "build a web browser" to be behaving incorrectly--but the CEO is misrepresenting what happened here.

simonw 9mo ago
I agree that "from scratch" is a misrepresentation. But it was accompanied by a link to the GitHub repo, so you can hardly claim that they were deliberately hiding the truth.
- mjr00 9mo ago
  > But it was accompanied by a link to the GitHub repo, so you can hardly claim that they were deliberately hiding the truth. Well, yes and no; we live in an era where people consume headlines, not articles, and certainly not links to Github repositories in articles. If VCs and other CEOs read the headline "Cursor Agents Autonomously Create Web Browser From Scratch" on LinkedIn, the project has served its purpose and it really doesn't matter if the code compiles or not.
- Fervicus 9mo ago
  How many non developers were going to look at that? They knew exactly what they were doing by saying that.
- pera 9mo ago
  > I agree that "from scratch" is a misrepresentation. I believe in the UK the term for this is actually fraudulent misrepresentation: https://en.wikipedia.org/wiki/Misrepresentation#English_law https://en.wikipedia.org/wiki/Misrepresentation#English_law And in this context it seems to go against The Consumer Protection from Unfair Trading Regulations 2008 and the Digital Markets, Competition and Consumers Act 2024: https://www.legislation.gov.uk/uksi/2008/1277/made https://www.legislation.gov.uk/uksi/2008/1277/made https://www.legislation.gov.uk/ukpga/2024/13/section/226 https://www.legislation.gov.uk/ukpga/2024/13/section/226
  - vidarh 9mo ago
    I very much don't believe for a second anyone would manage to get a judgement against them on this in the UK. For starters, the language is highly subjective, and they'd be able to show vast amounts of discourse about software engineering where "from scratch" often does not involve starting with nothing, and they'd then go on to argue that the person suing haven't actually had any reason to believe that they would be able to replicate a setup that was described as a complex large-scale experiment without much more information. The person suing would have an uphill battle showing that whatever assumptions they made were something that was reasonable to infer based on that statement. And to have a case, a consumer would also then need to have relied on this as a significant factor in choosing to buy their services. But even if we assume the court would agree it is fraudulent, the remedy is only "directly consequential losses". In other words, I doubt anyone would lose sleep over this risk.
- tyre 9mo ago
  Sorry, just to be clear, the defense that they pulled something out of their ass is that they linked to something that outed them? So they couldn't have actually have been overstating it? If anything, that proves the point that they weren't rigorous! They claimed a thing. The thing didn't accomplish what they said. I'm not saying that they hid it but that they misrepresented the thing that they built. My comment to you is that the interview didn't directly firmly pressure them on this. Generating a million lines of code in parallel isn't impressive. Burning a mountain of resources in parallel isn't noteworthy (see: the weekly post of someone with an out of control EC2 instance racking up $100k of charges.) It would have been remarkable if they'd built a browser from scratch, which they said they did, except they didn't. It was a 50 million token hackathon project that didn't work, dressed up as a groundbreaking example of their product. As feedback, I hope in the future you'll push back firmly on these types of claims when given the opportunity, even if it makes the interviewee uncomfy. Incredible claims require incredible evidence. They didn't have it.
  - simonw 9mo ago
    My goal in the interview was to get to as accurate a version of what they actually built and how they built it as possible. I don't think directly accusing them of being misleading about what they had done would have supported that goal, so I didn't do it. Instead I made sure to dig into things like what QuickJS was doing in there and why it used Taffy as part of the conversation.
    - cube00 9mo ago
      3 days ago: (https://news.ycombinator.com/item?id=46743831 https://news.ycombinator.com/item?id=46743831) > Honestly, grilling him about what the CEO had tweeted didn't even cross my mind. Today: > I don't think directly accusing them of being misleading about what they had done would have supported that goal, so I didn't do it. I find it hard to follow how it didn't cross your mind while for the same interview you had also considered the situation and determined it didn't meet the interview goal.
      - simonw 9mo ago
square_usual 9mo ago
Did you read the comment that started this thread? Let me repeat that, ICYMI: > "So I agree this isn't just wiring up of dependencies, and neither is it copied from existing implementations: it's a uniquely bad design that could never support anything resembling a real-world web engine." It didn't use Servo, and it wasn't just calling dependencies. It was terribly slow and stupid, but your comment is more of a mischaracterization than anything the Cursor people have said.
- mjr00 9mo ago
  You're right in the sense it didn't `use::servo`, merely Servo's CSS parser `cssparser`[0] and Servo's DOM parser `html5ever`[1]. Maybe that dog can do taxes after all. [0] https://github.com/search?q=repo%3Awilsonzlin%2Ffastrender%20use%20cssparser&type=code https://github.com/search?q=repo%3Awilsonzlin%2Ffastrender%2... [1] https://github.com/search?q=repo%3Awilsonzlin%2Ffastrender+html5ever&type=code https://github.com/search?q=repo%3Awilsonzlin%2Ffastrender+h...
  - simonw 9mo ago
    Taffy is related to Servo too, though apparently not officially part of the Servo project - but Servo does use it. https://github.com/DioxusLabs/taffy https://github.com/DioxusLabs/taffy Used here (I think): https://github.com/servo/servo/tree/c639bb1a7b3aa0fd5e02b40d487fb49439f63bf8/components/layout/taffy/stylo_taffy https://github.com/servo/servo/tree/c639bb1a7b3aa0fd5e02b40d...
    - nicoburns 9mo ago
      Servo uses Taffy for CSS Grid. It could also very easily use it for Flexbox, but they currently prefer to use their own implementation there. It was originally a derivative of React Native's Yoga implementation of Flexbox, and is currently developed primarily as part of the Blitz engine.

by mjr00 9mo ago

simonw 9mo ago

I agree that "from scratch" is a misrepresentation. But it was accompanied by a link to the GitHub repo, so you can hardly claim that they were deliberately hiding the truth.

mjr00 9mo ago
> But it was accompanied by a link to the GitHub repo, so you can hardly claim that they were deliberately hiding the truth. Well, yes and no; we live in an era where people consume headlines, not articles, and certainly not links to Github repositories in articles. If VCs and other CEOs read the headline "Cursor Agents Autonomously Create Web Browser From Scratch" on LinkedIn, the project has served its purpose and it really doesn't matter if the code compiles or not.
Fervicus 9mo ago
How many non developers were going to look at that? They knew exactly what they were doing by saying that.
pera 9mo ago
> I agree that "from scratch" is a misrepresentation. I believe in the UK the term for this is actually fraudulent misrepresentation: https://en.wikipedia.org/wiki/Misrepresentation#English_law https://en.wikipedia.org/wiki/Misrepresentation#English_law And in this context it seems to go against The Consumer Protection from Unfair Trading Regulations 2008 and the Digital Markets, Competition and Consumers Act 2024: https://www.legislation.gov.uk/uksi/2008/1277/made https://www.legislation.gov.uk/uksi/2008/1277/made https://www.legislation.gov.uk/ukpga/2024/13/section/226 https://www.legislation.gov.uk/ukpga/2024/13/section/226
- vidarh 9mo ago
  I very much don't believe for a second anyone would manage to get a judgement against them on this in the UK. For starters, the language is highly subjective, and they'd be able to show vast amounts of discourse about software engineering where "from scratch" often does not involve starting with nothing, and they'd then go on to argue that the person suing haven't actually had any reason to believe that they would be able to replicate a setup that was described as a complex large-scale experiment without much more information. The person suing would have an uphill battle showing that whatever assumptions they made were something that was reasonable to infer based on that statement. And to have a case, a consumer would also then need to have relied on this as a significant factor in choosing to buy their services. But even if we assume the court would agree it is fraudulent, the remedy is only "directly consequential losses". In other words, I doubt anyone would lose sleep over this risk.
tyre 9mo ago
Sorry, just to be clear, the defense that they pulled something out of their ass is that they linked to something that outed them? So they couldn't have actually have been overstating it? If anything, that proves the point that they weren't rigorous! They claimed a thing. The thing didn't accomplish what they said. I'm not saying that they hid it but that they misrepresented the thing that they built. My comment to you is that the interview didn't directly firmly pressure them on this. Generating a million lines of code in parallel isn't impressive. Burning a mountain of resources in parallel isn't noteworthy (see: the weekly post of someone with an out of control EC2 instance racking up $100k of charges.) It would have been remarkable if they'd built a browser from scratch, which they said they did, except they didn't. It was a 50 million token hackathon project that didn't work, dressed up as a groundbreaking example of their product. As feedback, I hope in the future you'll push back firmly on these types of claims when given the opportunity, even if it makes the interviewee uncomfy. Incredible claims require incredible evidence. They didn't have it.
- simonw 9mo ago
  My goal in the interview was to get to as accurate a version of what they actually built and how they built it as possible. I don't think directly accusing them of being misleading about what they had done would have supported that goal, so I didn't do it. Instead I made sure to dig into things like what QuickJS was doing in there and why it used Taffy as part of the conversation.
  - cube00 9mo ago
    3 days ago: (https://news.ycombinator.com/item?id=46743831 https://news.ycombinator.com/item?id=46743831) > Honestly, grilling him about what the CEO had tweeted didn't even cross my mind. Today: > I don't think directly accusing them of being misleading about what they had done would have supported that goal, so I didn't do it. I find it hard to follow how it didn't cross your mind while for the same interview you had also considered the situation and determined it didn't meet the interview goal.
    - simonw 9mo ago

square_usual 9mo ago

Did you read the comment that started this thread? Let me repeat that, ICYMI: > "So I agree this isn't just wiring up of dependencies, and neither is it copied from existing implementations: it's a uniquely bad design that could never support anything resembling a real-world web engine." It didn't use Servo, and it wasn't just calling dependencies. It was terribly slow and stupid, but your comment is more of a mischaracterization than anything the Cursor people have said.

mjr00 9mo ago
You're right in the sense it didn't `use::servo`, merely Servo's CSS parser `cssparser`[0] and Servo's DOM parser `html5ever`[1]. Maybe that dog can do taxes after all. [0] https://github.com/search?q=repo%3Awilsonzlin%2Ffastrender%20use%20cssparser&type=code https://github.com/search?q=repo%3Awilsonzlin%2Ffastrender%2... [1] https://github.com/search?q=repo%3Awilsonzlin%2Ffastrender+html5ever&type=code https://github.com/search?q=repo%3Awilsonzlin%2Ffastrender+h...
- simonw 9mo ago
  Taffy is related to Servo too, though apparently not officially part of the Servo project - but Servo does use it. https://github.com/DioxusLabs/taffy https://github.com/DioxusLabs/taffy Used here (I think): https://github.com/servo/servo/tree/c639bb1a7b3aa0fd5e02b40d487fb49439f63bf8/components/layout/taffy/stylo_taffy https://github.com/servo/servo/tree/c639bb1a7b3aa0fd5e02b40d...
  - nicoburns 9mo ago
    Servo uses Taffy for CSS Grid. It could also very easily use it for Flexbox, but they currently prefer to use their own implementation there. It was originally a derivative of React Native's Yoga implementation of Flexbox, and is currently developed primarily as part of the Blitz engine.