9 ms·

Cursor's latest “browser experiment” implied success without evidence

724 points by embedding-shape 10mo ago

Related: Scaling long-running autonomous coding - https://news.ycombinator.com/item?id=46624541 https://news.ycombinator.com/item?id=46624541 - Jan 2026 (174 comments)

embedding-shape 10mo ago
I'm eager to find out if this was actually successfully compiled at one point (otherwise how did they get the screenshots?), so I'm running `cargo check` for each of the last 100 commits to see if anything works. Will update here with the results once it's ready. Edit: As mentioned, I ran `cargo check` on all the last 100 commits, and seems every single of them failed in some way: https://gist.github.com/embedding-shapes/f5d096dd10be44ff82b6e5ccdaf00b29 https://gist.github.com/embedding-shapes/f5d096dd10be44ff82b...
- techpression 10mo ago
  I wouldn’t be surprised if any form of screen shot is fake (as in not made the way it claims), in my experience Occam’s razor tends to lead that way when extraordinary claims are made regarding LLM’s.
  - deleted 10mo ago
    [deleted]
- leerob 10mo ago
  Should compile now: https://news.ycombinator.com/item?id=46650998 https://news.ycombinator.com/item?id=46650998
  - embedding-shape 10mo ago
    > Yeah, seems latest commit does let `cargo check` successfully run. I'm gonna write an update blog post once they've made their statement, because I'm guessing they're about to say something. > Sometime fishy is happening in their `git log`, it doesn't seem like it was the agents who "autonomously" actually made things compile in the end. Notice the git username and email addresses switching around, even a commit made inside a EC2 instance managed to get in there: https://gist.github.com/embedding-shapes/d09225180ea3236f18039ca7a24b7ecb https://gist.github.com/embedding-shapes/d09225180ea3236f180... Gonna need to look closer into it when I have time, but seems they manually patched it up in the end, so the original claim still doesn't stand :/
- saghm 10mo ago
  > otherwise how did they get the screenshots Their AI is probably better at producing images than writing code
josefritzishere 10mo ago
Key phrase "They never actually claim this browser is working and functional " This is what most AI "successes" turn out to be when you apply even a modicum of scrutiny.
- embedding-shape 10mo ago
  In my personal experience, Codex and Claude Code are definitively capable tools when used in certain ways. What Cursor did with their blogpost seems intentionally and outright misleading, since I'm not able to even run the thing. With Codex/Claude Codex it's relatively easy to download it and run it to try for yourself.
  - netdevphoenix 10mo ago
    "definitively capable tools when used in certain ways". This sounds like "if it doesn't work for you is because you don't use in the right way" imo. Reminds me of SAAP/Salesforce.
    - embedding-shape 10mo ago
      Yes, many tools work like that, especially professional tools. You think you can just fire up Ableton, Cubase or whatever and make as great music as a artist who done that for a long time? No, it requires practice and understanding. Every tool works like this, some different difficulties, some different skill levels, but all of them have it in some way.
      - immibis 10mo ago
        Not even the Ableton marketing team is telling me I can just fire up Ableton and make great music and if I can't do that I must be a brainwashed doomer.
        embedding-shape 10mo ago
        The argument isn't what OpenAI/Anthropic are selling their users, what I said was: > are definitively capable tools when used in certain ways Which I received pushback on. My reply is to that pushback, defending what I said, not what others told you. Edit: Besides the point, but Ableton (and others) constantly tell people how to learn how to use the tool, so they use it the right way. There is a whole industry of people (teachers) who specialize in specific software/hardware and teaching others "how to hold the tool correctly".
7777777phil 10mo ago
I wonder who they actually tried to impress with that? People who understand and appreciate the difficulty of building a browser from scratch would surely be interested to understand what you (or your Agent) did to a degree that they would understand if you didn’t.
- deleted 10mo ago
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- koolala 10mo ago
  It worked to impress people on Twitter...
- thewhitetulip 10mo ago
  You'll see countless posts on LinkedIn about how great LLM is. Nobody goes in depth these days - just superficial posts
- Snuggly73 10mo ago
  Not sure - if it works, then who needs Cursor (and all other IDEs). You just ask for a browser and it comes out of the thin air.
- fernandotakai 10mo ago
  >I wonder who they actually tried to impress with that? investors?
paulus_magnus2 10mo ago
The blog[0] is worded rather conservatively but on Twitter [2] the claim is pretty obvious and the hype effect is achieved [2] CEO stated "We built a browser with GPT-5.2 in Cursor" instead of "by dividing agents into planners and workers we managed to get them busy for weeks creating thousands of commits to the main branch, resolving merge conflicts along the way. The repo is 1M+ lines of code but the code does not work (yet)" [0] https://cursor.com/blog/scaling-agents https://cursor.com/blog/scaling-agents [1] https://x.com/kimmonismus/status/2011776630440558799 https://x.com/kimmonismus/status/2011776630440558799 [2] https://x.com/mntruell/status/2011562190286045552 https://x.com/mntruell/status/2011562190286045552 [3]https://www.reddit.com/r/singularity/comments/1qd541a/ceo_of_cursor_said_they_coordinated_hundreds_of/ https://www.reddit.com/r/singularity/comments/1qd541a/ceo_of...
- embedding-shape 10mo ago
  So clearly someone, at some point, managed to run this, surely? That's where the screenshots come from? I just don't understand how, given the code is riddled with errors.
  - deeth_starr_v 10mo ago
    Maybe they just asked an AI to create an image of a rendered webpage?
    - deleted 10mo ago
      [deleted]
  - nicoburns 10mo ago
    Somebody managed to get it to compile https://x.com/CanadaHonk/status/2011612084719796272 https://x.com/CanadaHonk/status/2011612084719796272 But apparently "some pages take a literal minute to load"
    - embedding-shape 10mo ago
      > to be clear those 2 hours were fixing compile errors and bugs, not compile time Seems like "I had to do the last mile myself", not "autonomous coding" which was Cursor's claim here.
emp17344 10mo ago
This is why AI skeptics exist. We’re now at the point where you can make entirely unsubstantiated claims about AI capability, and even many folks on HN will accept it with a complete lack of discernment. The hype is out of control.
- embedding-shape 10mo ago
  > folks on HN will accept it with a complete lack of discernment Well, I'm a heavy LLM user, I "believe" LLM helps me a lot for some tasks, but I'm also a developer with decades of experience, so I'm not gonna claim it'll help non-programmers to build software, or whatever. They're tools, not solutions in themselves. But even us "folks on HN" who generally keep up with where the ecosystem is going, have a limit I suppose. You need to substantiate what you're saying, and if you're saying you've managed to create a browser, better let others verify that somehow.
  - emp17344 10mo ago
    Take a look at this thread regarding the original claim: https://news.ycombinator.com/item?id=46624541 https://news.ycombinator.com/item?id=46624541 The top comment is indeed baseless hype without a hint of skepticism.
    - embedding-shape 10mo ago
      The second top comment is my own (skeptical) comment, with 20 points at this moment. Thanks to those 20 people, I felt compelled to write the blog-post in this submission, and try to ask a bit clearer "what is going on?", since apparently we're at least 20 people who is wondering about this. There is also clearly a lot of other skeptical people in that submission too. Also, simonw (from that top comment) told me themselves "it's not clear that what they built even runs": https://bsky.app/profile/simonwillison.net/post/3mckgw4mxoc2w https://bsky.app/profile/simonwillison.net/post/3mckgw4mxoc2...
    - dingnuts 10mo ago
      [dead]
geooff_ 10mo ago
I think the original post was just headline bait. There is such a fast news cycle around AI that many people would take "Thousands of AI agents collaborate to make a web browser" at face value.
- embedding-shape 10mo ago
  At least I now have something to link to, when this inevitable gets mentioned in some off-hand HN comment, about how "now AI agents can build whole browsers from scratch".
  - gusmally 10mo ago
    It's a great post, I will use it for the same. Thank you.
  - buggy6257 10mo ago
    Literally happened at work. Breathless thread of people saying how insane it was and then we got to link this and it immediately 180-ed and everyone was like “holy shit that’s messed up”
    - embedding-shape 10mo ago
      And I haven't even published part 2 yet!
    - fernandotakai 10mo ago
      yup, same. slack thread with a lot of comments with people praising it. others were quite skeptical, specially the ones that actually perused the code.
- themafia 10mo ago
  A fast news cycle around projects that don't actually work. It's a real bummer that "fake news" became politically charged because it's a perfect description of this segment.
nindalf 10mo ago
The CEO said > It's 3M+ lines of code across thousands of files. The rendering engine is from-scratch in Rust with HTML parsing, CSS cascade, layout, text shaping, paint, and a custom JS VM. "From scratch" sounds very impressive. "custom JS VM" is as well. So let's take a look at the dependencies [1], where we find - html5ever - cssparser - rquickjs That's just servo [2], a Rust based browser initially built by Mozilla (and now maintained by Igalia [3]) but with extra steps. So this supposed "from scratch" browser is just calling out to code written by humans. And after all that it doesn't even compile! It's just plain slop. [1] - https://github.com/wilsonzlin/fastrender/blob/main/Cargo.toml https://github.com/wilsonzlin/fastrender/blob/main/Cargo.tom... [2] - https://github.com/servo/servo https://github.com/servo/servo [3] - https://blogs.igalia.com/mrego/servo-2025-stats/ https://blogs.igalia.com/mrego/servo-2025-stats/
- zipy124 10mo ago
  Honestly as soon as I saw browser in rust I assumed it had just reproduced the servo source code in part, or utilised its libraries.
  - nindalf 10mo ago
    I thought they'd plagiarise, not import. Importing servo's code would make it obvious because it's so easy to look at their dependencies file. And yet ... they did. I really think they thought no one would check?
    - deleted 10mo ago
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    - satvikpendem 10mo ago
      > And yet ... they did. I really think they thought no one would check? I doubt even they checked, given they say they just let the agents run autonomously.
      - bonesss 10mo ago
user432678 10mo ago
Are you telling me AI bros lying about their products? No way that ever happened…
m00dy 10mo ago
Cursor CEO got grilled in HN for a good reason.
xcvxvdf 10mo ago
[dead]
deng 10mo ago
If you look at the original Cursor post, they say they are currently running similar experiments, for instance, this Excel clone: https://github.com/wilson-anysphere/formula https://github.com/wilson-anysphere/formula The Actions overview is impressive: There have been 160,469 workflow runs, of which 247 succeeded. The reason the workflows are failing is because they have exceeded their spending limit. Of course, the agents couldn't care less.
- felipeerias 10mo ago
  IMHO people are missing the forest for the trees. The point of this experiment is not to build a functional browser but to develop ways to make agents create large codebases from scratch over a very long time span. A Web browser is just a convenient target because there are lots of documentation, specs and tests available.
  - noodletheworld 10mo ago
    ...but it didn't develop ways of doing that did it? Any idiot can have cursor run for 2 weeks and produce a pile of crap that doesn't compile. You know the brilliant insight they came out with? > A surprising amount of the system's behavior comes down to how we prompt the agents. Getting them to coordinate well, avoid pathological behaviors, and maintain focus over long periods required extensive experimentation. The harness and models matter, but the prompts matter more. i.e. It's kind of hard and we didn't really come up with a better solution than 'make sure you write good prompts'. Wellll, geeeeeeeee! Thanks for that insight guys! Come on. This was complete BS. Planners and workers. Cool. Details? Any details? Annnnnnnyyyyy way to replicate it? What sort of prompts did you use? How did you solve the pathalogical behaviours? Nope. The vagueness in this post... it's not an experiment. It's just fund raising hype.
    - chrisandchris 10mo ago
      IMHO, this whole thing could be read with "human" instread of "agent" and would make the exact same amount of sense. "We put 200 human in a room and gave them instructions how to build a browser. They coded for hours, resolving merge conflicts and producing code that did not build in the end without intervention of seniors []. We think, giving them better instructions leads to better results" So they actually invented humans? And will it come down to either "managing humans" or "managing agents"? One of both will be more reliable, more predictable and more convenient to work with. And my guess is, it is not an agent... As it seemed in the git log, something is weird.
Matthyze 10mo ago
Out of curiosity, what is the most difficult thing about building a browser?
- MobiusHorizons 10mo ago
  The very long task list. Browsers contain several high complexity pieces each of could take a while to build on its own, and interconnect them with reasonably verbose APIs that need to be implemented or at least stubbed out for code to not crash. There is also the difficulty of matching existing implementations quirk for quirk. I guess the complexity is on-par with operating systems, but with the added compatibility problems that in order to be useful it doesn't just have to load sites intended to be compatible with it, it has to handle sites people actually use on the internet, and those are both a moving target, and tend to use lots of high complexity features that you have to build or at least stub out before the site will even work.
- deleted 10mo ago
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- asadotzler 10mo ago
  In all sincerity, this question is almost identical to "what's the most difficult thing about building an operating system" as a modern browser is tens of millions of lines of code that can run sophisticated applications. It has a network stack, half a dozen parsers, frame construction and reflow modules, composite, render and paint components, front end UI components, an extensibility framework, and more. Each one of these must enable supporting backward compatibility for 30 year old content as well as ridiculously complex contemporary web apps. And it has to load and render sites that a completely programming illiterate fool like me wrote. It must do this all in a performant and secure way using minimal system resources. Also, it probably also must run on Mac, Windows, Linux, Android, iOS, and maybe more.
- potamic 10mo ago
  Check out the list of all CSS specifications [1], and then open any one of them and see how lengthy and elaborate each is. Then do the same for each version of the spec published over the last thirty years. Before you can start, you must read and understand all of this at a great level of depth. Still, specifications never tell the complete story. You must be aware of all the nuances that are implied by each requirement in the spec and know how to handle the zillion corner cases that will crop up inevitably. And this is just one part. Not even considering the fully sandboxed, mini operating system for running webapps. [1] https://www.w3.org/Style/CSS/specs.en.html https://www.w3.org/Style/CSS/specs.en.html
deleted 10mo ago
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Pinus 10mo ago
I haven’t studied the project that this is a comment on, but: The article notices that something that compiles, runs, and renders a trivial HTML page might be a good starting point, and I would certainly agree with that when it’s humans writing the code. But is it the only way? Instead of maintaining “builds and runs” as a constant and varying what it does, can it make sense to have “a decent-sized subset of browser functionality” as a constant and varying the “builds and runs” bit? (Admittedly, that bit does not seem to be converging here, but I’m curious in more general terms.)
- madeofpalk 10mo ago
  ...What use is code if it doesn't build and run? What other way is there to build a browser that doesn't involved 'build and run'? Writing junk in a text file isn't the hard part.
  - Pinus 10mo ago
    Obviously, it has to eventually build and run if there’s to be any point to it, but is it necessary that every, or even any, step along the way builds and runs? I imagine some sort of iterative set-up where one component generates code, more or less "intelligently", and others check it against the C, HTML, JavaScript, CSS and what-have-you specs, and the whole thing iterates until all the checking components are happy. The components can’t be completely separate, of course, they’d have to be more or less intermingled or convergence would be very slow (like when lcamtuf had his fuzzer generate a JPEG out of an empty file), but isn’t that basically what (large) neural networks are; tangled messes of interconnected functions that do things in ways too complicated for anyone to bother figuring out?
    - malfist 10mo ago
      How do you iteratively improve a broken codebase that doesn't compile with more than 3 million lines of code?
      - brabel 10mo ago
thedelanyo 10mo ago
These are stories that solely exist just to sell shovels and would cause one uninformed CEO to layoff actual humans.
AIorNot 10mo ago
Lesson 1: Always take any pronouncement from an AI company (heavily dependent on VC and public sentiment on AI) with a heavy grain of salt.. hype over reality I’m building an AI startup myself and I know that world and its full of hypsters and hucksters unfortunately - also social media communication + low attention span + AI slop communication is a blight upon todays engineering culture
Snuggly73 10mo ago
The latest commit now builds and runs (at least on my Mac). It’s tragically broken and the code is…dunno…something. 3m lines of something. I couldn’t make it render the apple page that was on the Cursor promo. Maybe they’ve used some other build.
- embedding-shape 10mo ago
  Yeah, seems latest commit does let `cargo check` successfully run. I'm gonna write an update blog post once they've made their statement, because I'm guessing they're about to say something. Sometime fishy is happening in their `git log`, it doesn't seem like it was the agents who "autonomously" actually made things compile in the end. Notice the git username and email addresses switching around, even some commits made inside a EC2 instance managed to get in there: https://gist.github.com/embedding-shapes/d09225180ea3236f18039ca7a24b7ecb https://gist.github.com/embedding-shapes/d09225180ea3236f180...
  - Snuggly73 10mo ago
    Noticed that as well - I think it was “manual”
- torginus 10mo ago
  I am not an expert AI user, but one typical 'failure mode' I see constantly is the AI reimplementing features that already exist in the codebase, or breaking existing ones.
lifetimerubyist 10mo ago
> company claims they "built a browser" from scratch > looks inside > completely useless and busted 30 billion dollar VS Code fork everyone. When we do start looking at these people for what they are: snake oil salesmen. They slop laundered the FOSS Servo code into a broken mess and called it a browser, but dumbasses with money will make line go up based on lies. EFF right off.
- arresin 10mo ago
  30. Billion. Dollars. Man
  - lifetimerubyist 10mo ago
    It's absolutely absurd.
- ben_w 10mo ago
  When I tried it last year, the mac download of this particular VS Code fork was only available as an Intel build. This… was suggestive.
- ravenstine 10mo ago
  I recently was convinced by colleagues to try Cursor at work for project planning. At first I was excited for something even better than Copilot Chat, but then I quickly realized it's just a shitty VS Code fork with maybe a few improvements that are by no means a moat for that company. Worse yet, it makes lots of bizarre mistakes, deletes lines for no good reason, and sometimes even deletes the entire project plan. The scroll on the chat history gets laggy very quickly, and I've found the whole program to be glitchy as hell. The hype around Cursor is unreal. My suspicion is this company is little more than a parasite with no qualms about getting you to waste your tokens. It's one thing when a product is new, but Cursor has been around since 2023 I guess? The quality of their software is unacceptable.
pavlov 10mo ago
The comment that points out that this week-long experiment produced nothing more than a non-functional wrapper for Servo (an existing Rust browser) should be at the top: https://news.ycombinator.com/item?id=46649046 https://news.ycombinator.com/item?id=46649046
- pera 10mo ago
  Has anyone tried to rewrite some popular open source project with IA? I imagine modern LLMs can be very effective at license-washing/plagiarizing dependencies, it could be an interesting new benchmark too
  - benhoyt 10mo ago
    Not me personally, but a GitHub user wrote a replacement for Go's regexp library that was "up to 3-3000x+ faster than stdlib": https://github.com/coregx/coregex https://github.com/coregx/coregex ... at first I was impressed, so started testing it and reporting bugs, but as soon as I ran my own benchmarks, it all fell apart (https://github.com/coregx/coregex/issues/29 https://github.com/coregx/coregex/issues/29). After some mostly-bot updates, that issue was closed. But someone else opened a very similar one recently (https://github.com/coregx/coregex/issues/79 https://github.com/coregx/coregex/issues/79) -- same deal, "actually, it's slower than the stdlib in my tests". Basically AI slop with poor tests, poor benchmarks, and way oversold. How he's positioning these projects is the problematic bit, I reckon, not the use of AI. Same user did a similar thing by creating an AWK interpreter written in Go using LLMs: https://github.com/kolkov/uawk https://github.com/kolkov/uawk -- as the creator of (I think?) the only AWK interpreter written in Go (https://github.com/benhoyt/goawk https://github.com/benhoyt/goawk), I was curious. It turns out that if there's only one item in the training data (GoAWK), AI likes to copy and paste freely from the original. But again, it's poorly tested and poorly benchmarked. I just don't see how one can get quality like this, without being realistic about code review, testing, and benchmarking.
    - CuriouslyC 10mo ago
      To be fair, good benchmarking is hard, most people get it wrong. Scientific training helps.
chaosprint 10mo ago
I really doubt this marketing approach is effective. Isn't this just shooting themselves in the foot? My actual experience with Cursor has been: their design is excellent and the UX is great—it handles frontend work reasonably well. But as soon as you go deeper, it becomes very prone to serious bugs. While the addition of Claude's new models has helped somewhat, the results are still not as good as Google's Antigravity (despite its poor UX and numerous bugs). What's worse, even with this much-hyped Claude model, you can easily blow through the $20 subscription limit in just a few days. Maybe they're betting on models becoming 10x better and 10x cheaper, but that seems unlikely to happen anytime soon.
- bonesss 10mo ago
  Hitting my head into buggy apps made by these AI companies and seeing them all be amazed in parallel that skills/MCP would be necessary for real work has me pretty relaxed about ‘our jobs’. OpenAIs business-model floundering, degenerating inline to ads soon (lol), shows what can be done with infini-LLM, infini-capital, and all the smarts & connections on Earth… broadly speaking, I think the geniuses at Google who invented a lot of this shizz understand it and were leveraging it appropriately before ChatGPT blew up.
  - thewhitetulip 10mo ago
    We use mcp at work. Due to some typo the model ran absolutely random queries on our database most of the cases. We had initially kept ot open ended but after that, we wrote custom tools that took an input, gave an output and that was strictly mentioned in the prompt. Only then did it work fine.
ryanisnan 10mo ago
The amount of negativity in the original post was astounding. People were making all sorts of statements like: - “I cloned it and there were loads of compiler warnings” - “the commit build success rate was a joke” - “it used 3rd party libs” - “it is AI slop” What they all seem to be just glossing over is how the project unfolded: without human intervention, using computers, in an exceptionally accelerated time frame, working 24hr/day. If you are hung up on commit build quality, or code quality, you are completely missing the point, and I fear for your job prospects. These things will get better; they will get safer as the workflows get tuned; they will scale well beyond any of us. Don’t look at where the tech is. Look where it’s going.
- embedding-shape 10mo ago
  As mentioned elsewhere (I'm the author of this blogpost), I'm a heavy LLM user myself, use it everyday as a tool, get lots of benefits from it. It's not a "hit post" on using LLM tools for development, it's a post about Cursor making grand claims without being able to back them up. No one is hung up on the quality, but there is a ground fact if something "compiles" or "doesnt". No one is gonna claim a software project was successful if the end artifact doesn't compile.
  - ryanisnan 10mo ago
    I think for the point of the article, it appeared to, at some point, render homepages for select well known sites. I certainly did not expect this to be a serious browser, with any reliability or legs. I don’t think that is dishonest.
    - embedding-shape 10mo ago
      > I certainly did not expect this to be a serious browser, with any reliability or legs. Me neither, and I note so twice in the submission article. But I also didn't expect a project that for the last 100+ commits couldn't reliably be built and therefore tested and tried out.
noosphr 10mo ago
If this is what makes the AI bubble pop I'll laugh so hard.
- only-one1701 10mo ago
  Wishful thinking. They’re trying to (and maybe successfully) doing a military-industrial complex style thing with AI.
  - noosphr 10mo ago
    Probably, but this is one of the few cases where instead of being told how amazing some AI tool is we are shown just what it can do.
mikojan 10mo ago
Dear god please let AI get forever stuck at this point because it would be so funny
- themafia 10mo ago
  Just view the "input cost" vs "output accuracy" graph. It _is_ stuck at this point. There's so much money involved no one wants to admit it out loud. They have no path to the necessary exponential gains and no one is actually working on it.
  - arresin 10mo ago
    The greatest grift of all time. I don’t mean the tech itself—-which is kind of useful. I mean the 99% of the value inflation of a kind of useful tool (if you know what you’re doing).
    - tyre 10mo ago
      AI is not a bigger grift than crypto. Crypto produced basically nothing of value. If all model improvement stops today, Opus 4.5 with Claude Code is a huge leap in productivity building certain types of software.
      - mirsadm 10mo ago
        I would disagree on the huge boost to productivity but it is a very useful tool.
  - Kiro 10mo ago
    Hilarious thing to say when we've just had some of the biggest leaps ever with Gemini 3 and Opus 4.5.
  - lifetimerubyist 10mo ago
    Just one more new model bro the next one is AGI bro just give me a trillion dollars and I’ll build the datacenters and everything will be perfect bro I promise bro please
ankit219 10mo ago
Like it or not, it's a fundraising strategy. They have followed it mutliple times (eg: vague posts about how much their inhouse model is writing code, online RL, and lines of code etc. earlier) and it was less vague before. They released a model and did not give us the exact benchmarks or even tell us the base model for the same. This is not to imply there is no substance behind it, but they are not as public about their findings as one would like them to be. Not a criticism, just an observation.
- alfalfasprout 10mo ago
  Unfortunately all the major LLM companies have realized the truth doesn't really matter anymore. We even saw this with the GPT-5 launch with obviously vibe coded + nebulous metrics. Diminishing returns are starting to really set in and companies are desperate for any illusion to the contrary.
- themafia 10mo ago
  I don't like it. It's lying in order to capture more market value than they're entitled to. The ends do not justify the means. This is a criticism.
  - emp17344 10mo ago
    Basically, fraud. Low-level fraud, but still fraud.
    - csomar 10mo ago
      Low-level fraud? It’s used to raise billions that could have been used for other purposes.
    - nerdponx 10mo ago
      Fraud is just marketing in the 2020s now.
      - skciva 10mo ago
ironbound 10mo ago
Devin 2.0
heliumtera 10mo ago
Making it compile will considerably decrease productivity. PR number go up
logicallee 10mo ago
(this has been fixed)
- embedding-shape 10mo ago
  Thank you for telling me about the email, it had a typo :( Been fixed now. Regarding the downvotes, I think it's because it's feeling like you're pushing your project although it isn't really super relevant to the topic. The topic is specifically about Cursor failing to live up to their claims.
jonathanstrange 10mo ago
I think it's only a matter of time until this becomes reality. It's almost inevitable. My prediction last year was already that in the distant future - more than 10 years into the future - operating systems will create software on the fly. It will be a basic function of computers. However, there might remain a need for stable, deterministic software, the two human-machine interaction models can live together. There will be a need for software that does exactly what one wants in a dumb way and there will be a need for software that does complex things on the fly in an overall less reliable ad hoc way.
- falkensmaize 10mo ago
  We might cure cancer in 10 years. We could have Martian colonists in the next decade. Everyone might be commuting to work with a jet pack. Literally anything could happen, especially given a long enough time horizon.
  - jonathanstrange 10mo ago
    You do realize that AI can already today write fairly complex software autonomously, don't you? It's not as if I haven't tested that. It works quite well for certain tasks and with certain programming languages. Anyone who knows history knows that people initially tend to underestimate the impact of technologies, yet few people learn something from that lesson.
    - falkensmaize 10mo ago
      What fairly complex software has it written autonomously for you?
ares623 10mo ago
Can’t help but draw parallels to how working with AI feels like. Your coworker opens a giant impressive looking PR and marks it ready for review. Meanwhile it’s up to someone else in the team to do the actual work of checking. Meanwhile the PR author gets patted on the back by management for being forward thinking and pro-active while everyone else is “nitpicky” and holding progress back.
- callc 10mo ago
  I’m dealing with similar issues. It’s reasonable to come up with team rules like: - “if the reviewer finds more than 5 issues the PR shall be rejected immediately for the submitter to rework” - “if the reviewer needs to take more than 8 hours to thoroughly review the PR it must be rejected and sent back to split up into manageable change sets” Etc etc. let’s not make externalizing work for others appropriate behavior.
  - tyre 10mo ago
    Eight hours to review! Girlie how big are these PRs? I can’t imagine saying, “ah, only six hours of heads down time to review this. That’s reasonable.” A combination of peer reviewed architecture documentation and incremental PRs should prevent anything taking nearly 8 hours of review.
    - embedding-shape 10mo ago
      Agreed, if it takes 8 hours to review a PR, then the process is broken and you need to start talking before anyone starts writing code. I'd put the max window on maybe 30 minutes for a PR, otherwise we're doing something else, not a "last pass before merge into production".
- thewhitetulip 10mo ago
  Not to mention the fact that juniors can now put the entire problem statement in AI chatbot which spits out _some_ code. The said juniors then don't understand half the code and run the code and raise the PR. They don't get a pat on the back but this raises countless bugs later on. This is much worse as they don't develop skills on their own. They blindly copy from AI.
LegitShady 10mo ago
AI hype is just lying until you get caught
jadenpeterson 10mo ago
For my 11th or 12th birthday, I got a pet porcupine and I was ecstatic. It was my first pet, and I spent hours researching what they eat, what habitats they like, etc. I carefully curated my room to accommodate him (him being 'Sonic'), even keeping it clean for the first time in forever so I wouldn't lose him amidst the mess of soiled undergarments and such. He loved it, and I loved him. Of course, it made no difference when my uncle sat on him on Christmas morning. We rushed him to the vet, but they told us his scans showed fractures on several vertebrae or something like that. We took him home, and waited for him to die, but the waiting was too painful. I'll spare the details, but what transpired next involved my dad, his shovel, and a lot of tears. About an hour later, we got a call from the vet - they'd misread the scan, and Sonic was gonna be fine. I think I was traumatized at the time, but the whole thing later became an inside joke (?) for my family - "Don't kill your porcupine before the vet calls" (a la "Don't count your chickens before they hatch"). I guess my point, as it pertains to Cursor, its AI offerings, and other corporations in the space is that we shouldn't jump the gun before a reasonable framework exists to evaluate such open-ended technologies. Of course Cursor reported this as a success, the incentive structure demands they do so. So remember - don't kill your porcupine before the vet calls.
- callc 10mo ago
  Welcome to HN, thanks for sharing. That’s a very sad story, I hope you aren’t traumatized still. A reasonable framework does exist. Since the claim is “we made a web browser from scratch” the framework is: 1. Does it actually f*** work? 2. Is it actually from scratch? It fails on both counts. Further, even when compiled successfully, as others have pointed out, it takes more than a minute to load some pages which is a fail for #1.
  - Shaanie 10mo ago
    If it loads pages, then it clearly works. Nobody claims it's a practical, competitive browser.
    - callc 10mo ago
      “I built a car from scratch” … “Nobody said it has brakes.” Taken at face value, everyone assumes when you say statement #1 that you are not speaking like a lawyer.
solid_fuel 10mo ago
This is par for the course with this AI slop. Most of the big claims about LLM productivity have completely lacked any backing evidence. Big claims require big evidence, but all I've seen so far is loud assertions and pathetic results.
- callc 10mo ago
  I’m happy that this shows that hard work, understanding your codebase, having performant software, having actually working software, rigorously measuring and proving proof of results still matters. There’s a huge difference between using LLMs to offload any hard work and for LLMs to be of some assistance while you are in control and take ownership of the output. Unfortunately, the general public probably didn’t try a git clone and cargo build, and took the article at face value.
sidgarimella 10mo ago
there’s a curve where something of a conservative middle in AI marketing stunts are held to a higher level of criticism than headlines on either side
wilsonzlin 10mo ago
Hey, Wilson here, author of the blog post and the engineer working on this project. I've been reading the responses here and appreciate the feedback. I've posted some follow up context on Twitter/X[0], which I'll also write here: The repo is a live incubator for the harness. We are actively researching the behavior of collaborative long running agents, and may in the future make the browser and other products this research produces more consumable by end users and developers, but it's not the goal for now. We made it public as we were excited by the early results and wanted to share; while far off from feature parity with the most popular production browsers today, we think it has made impressive progress in the last <1 week of wall time. Given the interest in trying out the current state of the project, I've merged a more up-to-date snapshot of the system's progress that resolves issues with builds and CI. The experimental harness can occasionally leave the repo in an incomplete state but does converge, which was the case at the time of the post. I'm here to answer any further questions you have. [0] https://x.com/wilsonzlin/status/2012398625394221537?s=20 https://x.com/wilsonzlin/status/2012398625394221537?s=20
- eloisius 10mo ago
  That doesn’t really address much of the criticism in this thread. No one is shocked that it’s not as good as production web browsers. It’s that it was billed as “from scratch” but upon deeper inspection it looks like it’s just gluing together Servo and some other dependencies, so it’s not really as impressive or interesting because the “agents” didn’t really create a browser engine.
  - M4v3R 10mo ago
    Upon deeper inspection? Someone checked the Cargo file and proclaimed it was just Servo and QuickJS glued together without actually bothering to look if these dependencies are even being used. In reality while project does indeed have Servo in its dependencies it only uses it for HTML tokenization, CSS selector matching and some low level structures. Javascript parsing and execution, DOM implementation & Layout engine was written from scratch with only one exception - Flexbox and Grid layouts are implemented using Taffy - a Rust layout library. So while “from scratch” is debatable it is still immensely impressive to be that AI was able to produce something that even just “kinda works” at this scale.
devmor 10mo ago
I am just so utterly tired of AI companies lying about everything, constantly without end. The things that modern machine learning can do are absolutely incredible, mindblowing and have myriad uses. But this culture of startup scams to siphon money out of the economy and into the bank accounts of a few investment firms and a couple "visionaries" has just turned what should be an exciting field full of technical advancement into a deluge of mental sewage that's constantly pumped into our faces.
DeathArrow 10mo ago
So they prove that if you have enough money to burn you can use AI to generate terabytes of useless junk? Who would have thought of that?
nubskr 10mo ago
That's actually the state of autonomous coding in 2026, scale the output, skip the verification.
- thewhitetulip 10mo ago
  Also since firefox is FOSS and any model has reasonably been trained on the code base of at least Firefox if not also Chromium, it's not a shock that agents are able to generate a similar code!
motbus3 10mo ago
If it just forks chromium because it found it on the web it would also claim it made a browser from scratch. LLM does not know. It is not a person, it is a thing, just an algorithm
orourke 10mo ago
I feel that getting anywhere into the neighborhood of “kind of working” for a project like this is noteworthy and a huge milestone. Maybe a better headline would be, however: Agents almost create a working browser.
- embedding-shape 10mo ago
  Yes, if Cursor claimed "We let autonomous agents run for weeks, and they produced millions of lines of code, and it kind of looks like a browser, and it kind of runs", then I wouldn't have written and published TFA. But their claim wasn't so nuanced, it was "hundreds of agents can work on a single codebase autonomously for weeks and build an entire browser from scratch that works (kinda)". Considering the hand-holding that seems to have been required to get it to compile, this claim doesn't seem to hold up to scrutiny.
  - Snuggly73 10mo ago
    I've watched them today work in the new repo - https://github.com/wilson-anysphere/fastrender/tree/main https://github.com/wilson-anysphere/fastrender/tree/main , adding another 50k lines trying to optimize scroll/rendering performance (spoiler: not really) At this point, its 1.5mlocs without the vendored crates (so basically excluding the js engine etc). If you compare that to Servo/Ladybird which are 300k locs each and actually happen to work, agents do love slinging slop.
elzbardico 10mo ago
I think that the companies that have the mindset "Let's give engineers tools that can leverage their strengths and eliminate toil" have way more success than those scammy "get-rich-fast let's automate software development and stop paying those sv salaries, invest in us!!!" gigs like Cursor and Devin. Their whole attitude leads to them wasting time with those Willy the Coyote Plans instead of building good products like Amp.
- embedding-shape 10mo ago
  Huge distinction between the two, one is about "Augmenting the human intellect" and the other is about "Get rich quick", but unfortunately it seems it's hard even for software developers to see which is which sometimes.
utopiah 10mo ago
That's kind of hilarious (...ly sad) to read knowing that I have on my desk https://browser.engineering https://browser.engineering so I literally went the opposite direction some months ago. Not only did I actually build a Web browser myself, from scratch (ok OK of course with a working OS and Python, and its libraries ;) but mine, did work! And it took me what, few hours, maybe few days if adding it altogether but, not only it did work (namely I did browse my own Website with it) but I had fun with it (!), I learned quite a bit with it (including the provable fact that I can indeed build a Web browser, woohoo!) and finally I did it on... I want say few kilowatts at most, including my computer (obviously) but also myself and the food I ate along the way. So... to each their own ̄\_ (ツ)_/ ̄
deleted 10mo ago
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TechDebtDevin 10mo ago
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simonw 10mo ago
They fixed FastRender so that CI passes and added build instructions to the README. I've tried it and it works surprisingly well - screenshots here: https://gist.github.com/simonw/53a725811db8e34f4f99226e8f45682b https://gist.github.com/simonw/53a725811db8e34f4f99226e8f456...
izucken 10mo ago
You people clearly don't understand how important lines of code are. Three millions is a lot of lines of code even if its broken, and you can't even appreciate that number. Clearly you are weak software developers who write very little lines of code, and can't even steal other's lines of code to keep up. I am very glad we are back to reporting results in lines of code which is a very informative metric hence now I can get my many lines of code appreciated.

724 points by embedding-shape 10mo ago

Related: Scaling long-running autonomous coding - https://news.ycombinator.com/item?id=46624541 https://news.ycombinator.com/item?id=46624541 - Jan 2026 (174 comments)

embedding-shape 10mo ago

I'm eager to find out if this was actually successfully compiled at one point (otherwise how did they get the screenshots?), so I'm running `cargo check` for each of the last 100 commits to see if anything works. Will update here with the results once it's ready. Edit: As mentioned, I ran `cargo check` on all the last 100 commits, and seems every single of them failed in some way: https://gist.github.com/embedding-shapes/f5d096dd10be44ff82b6e5ccdaf00b29 https://gist.github.com/embedding-shapes/f5d096dd10be44ff82b...

techpression 10mo ago
I wouldn’t be surprised if any form of screen shot is fake (as in not made the way it claims), in my experience Occam’s razor tends to lead that way when extraordinary claims are made regarding LLM’s.
- deleted 10mo ago
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leerob 10mo ago
Should compile now: https://news.ycombinator.com/item?id=46650998 https://news.ycombinator.com/item?id=46650998
- embedding-shape 10mo ago
  > Yeah, seems latest commit does let `cargo check` successfully run. I'm gonna write an update blog post once they've made their statement, because I'm guessing they're about to say something. > Sometime fishy is happening in their `git log`, it doesn't seem like it was the agents who "autonomously" actually made things compile in the end. Notice the git username and email addresses switching around, even a commit made inside a EC2 instance managed to get in there: https://gist.github.com/embedding-shapes/d09225180ea3236f18039ca7a24b7ecb https://gist.github.com/embedding-shapes/d09225180ea3236f180... Gonna need to look closer into it when I have time, but seems they manually patched it up in the end, so the original claim still doesn't stand :/
saghm 10mo ago
> otherwise how did they get the screenshots Their AI is probably better at producing images than writing code

josefritzishere 10mo ago

Key phrase "They never actually claim this browser is working and functional " This is what most AI "successes" turn out to be when you apply even a modicum of scrutiny.

embedding-shape 10mo ago
In my personal experience, Codex and Claude Code are definitively capable tools when used in certain ways. What Cursor did with their blogpost seems intentionally and outright misleading, since I'm not able to even run the thing. With Codex/Claude Codex it's relatively easy to download it and run it to try for yourself.
- netdevphoenix 10mo ago
  "definitively capable tools when used in certain ways". This sounds like "if it doesn't work for you is because you don't use in the right way" imo. Reminds me of SAAP/Salesforce.
  - embedding-shape 10mo ago
    Yes, many tools work like that, especially professional tools. You think you can just fire up Ableton, Cubase or whatever and make as great music as a artist who done that for a long time? No, it requires practice and understanding. Every tool works like this, some different difficulties, some different skill levels, but all of them have it in some way.
    - immibis 10mo ago
      Not even the Ableton marketing team is telling me I can just fire up Ableton and make great music and if I can't do that I must be a brainwashed doomer.
      - embedding-shape 10mo ago
        The argument isn't what OpenAI/Anthropic are selling their users, what I said was: > are definitively capable tools when used in certain ways Which I received pushback on. My reply is to that pushback, defending what I said, not what others told you. Edit: Besides the point, but Ableton (and others) constantly tell people how to learn how to use the tool, so they use it the right way. There is a whole industry of people (teachers) who specialize in specific software/hardware and teaching others "how to hold the tool correctly".

7777777phil 10mo ago

I wonder who they actually tried to impress with that? People who understand and appreciate the difficulty of building a browser from scratch would surely be interested to understand what you (or your Agent) did to a degree that they would understand if you didn’t.

deleted 10mo ago
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koolala 10mo ago
It worked to impress people on Twitter...
thewhitetulip 10mo ago
You'll see countless posts on LinkedIn about how great LLM is. Nobody goes in depth these days - just superficial posts
Snuggly73 10mo ago
Not sure - if it works, then who needs Cursor (and all other IDEs). You just ask for a browser and it comes out of the thin air.
fernandotakai 10mo ago
>I wonder who they actually tried to impress with that? investors?

paulus_magnus2 10mo ago

The blog[0] is worded rather conservatively but on Twitter [2] the claim is pretty obvious and the hype effect is achieved [2] CEO stated "We built a browser with GPT-5.2 in Cursor" instead of "by dividing agents into planners and workers we managed to get them busy for weeks creating thousands of commits to the main branch, resolving merge conflicts along the way. The repo is 1M+ lines of code but the code does not work (yet)" [0] https://cursor.com/blog/scaling-agents https://cursor.com/blog/scaling-agents [1] https://x.com/kimmonismus/status/2011776630440558799 https://x.com/kimmonismus/status/2011776630440558799 [2] https://x.com/mntruell/status/2011562190286045552 https://x.com/mntruell/status/2011562190286045552 [3]https://www.reddit.com/r/singularity/comments/1qd541a/ceo_of_cursor_said_they_coordinated_hundreds_of/ https://www.reddit.com/r/singularity/comments/1qd541a/ceo_of...

embedding-shape 10mo ago
So clearly someone, at some point, managed to run this, surely? That's where the screenshots come from? I just don't understand how, given the code is riddled with errors.
- deeth_starr_v 10mo ago
  Maybe they just asked an AI to create an image of a rendered webpage?
  - deleted 10mo ago
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- nicoburns 10mo ago
  Somebody managed to get it to compile https://x.com/CanadaHonk/status/2011612084719796272 https://x.com/CanadaHonk/status/2011612084719796272 But apparently "some pages take a literal minute to load"
  - embedding-shape 10mo ago
    > to be clear those 2 hours were fixing compile errors and bugs, not compile time Seems like "I had to do the last mile myself", not "autonomous coding" which was Cursor's claim here.

emp17344 10mo ago

This is why AI skeptics exist. We’re now at the point where you can make entirely unsubstantiated claims about AI capability, and even many folks on HN will accept it with a complete lack of discernment. The hype is out of control.

embedding-shape 10mo ago
> folks on HN will accept it with a complete lack of discernment Well, I'm a heavy LLM user, I "believe" LLM helps me a lot for some tasks, but I'm also a developer with decades of experience, so I'm not gonna claim it'll help non-programmers to build software, or whatever. They're tools, not solutions in themselves. But even us "folks on HN" who generally keep up with where the ecosystem is going, have a limit I suppose. You need to substantiate what you're saying, and if you're saying you've managed to create a browser, better let others verify that somehow.
- emp17344 10mo ago
  Take a look at this thread regarding the original claim: https://news.ycombinator.com/item?id=46624541 https://news.ycombinator.com/item?id=46624541 The top comment is indeed baseless hype without a hint of skepticism.
  - embedding-shape 10mo ago
    The second top comment is my own (skeptical) comment, with 20 points at this moment. Thanks to those 20 people, I felt compelled to write the blog-post in this submission, and try to ask a bit clearer "what is going on?", since apparently we're at least 20 people who is wondering about this. There is also clearly a lot of other skeptical people in that submission too. Also, simonw (from that top comment) told me themselves "it's not clear that what they built even runs": https://bsky.app/profile/simonwillison.net/post/3mckgw4mxoc2w https://bsky.app/profile/simonwillison.net/post/3mckgw4mxoc2...
  - dingnuts 10mo ago
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geooff_ 10mo ago

I think the original post was just headline bait. There is such a fast news cycle around AI that many people would take "Thousands of AI agents collaborate to make a web browser" at face value.

embedding-shape 10mo ago
At least I now have something to link to, when this inevitable gets mentioned in some off-hand HN comment, about how "now AI agents can build whole browsers from scratch".
- gusmally 10mo ago
  It's a great post, I will use it for the same. Thank you.
- buggy6257 10mo ago
  Literally happened at work. Breathless thread of people saying how insane it was and then we got to link this and it immediately 180-ed and everyone was like “holy shit that’s messed up”
  - embedding-shape 10mo ago
    And I haven't even published part 2 yet!
  - fernandotakai 10mo ago
    yup, same. slack thread with a lot of comments with people praising it. others were quite skeptical, specially the ones that actually perused the code.
themafia 10mo ago
A fast news cycle around projects that don't actually work. It's a real bummer that "fake news" became politically charged because it's a perfect description of this segment.

nindalf 10mo ago

The CEO said > It's 3M+ lines of code across thousands of files. The rendering engine is from-scratch in Rust with HTML parsing, CSS cascade, layout, text shaping, paint, and a custom JS VM. "From scratch" sounds very impressive. "custom JS VM" is as well. So let's take a look at the dependencies [1], where we find - html5ever - cssparser - rquickjs That's just servo [2], a Rust based browser initially built by Mozilla (and now maintained by Igalia [3]) but with extra steps. So this supposed "from scratch" browser is just calling out to code written by humans. And after all that it doesn't even compile! It's just plain slop. [1] - https://github.com/wilsonzlin/fastrender/blob/main/Cargo.toml https://github.com/wilsonzlin/fastrender/blob/main/Cargo.tom... [2] - https://github.com/servo/servo https://github.com/servo/servo [3] - https://blogs.igalia.com/mrego/servo-2025-stats/ https://blogs.igalia.com/mrego/servo-2025-stats/

zipy124 10mo ago
Honestly as soon as I saw browser in rust I assumed it had just reproduced the servo source code in part, or utilised its libraries.
- nindalf 10mo ago
  I thought they'd plagiarise, not import. Importing servo's code would make it obvious because it's so easy to look at their dependencies file. And yet ... they did. I really think they thought no one would check?
  - deleted 10mo ago
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  - satvikpendem 10mo ago
    > And yet ... they did. I really think they thought no one would check? I doubt even they checked, given they say they just let the agents run autonomously.
    - bonesss 10mo ago

user432678 10mo ago

Are you telling me AI bros lying about their products? No way that ever happened…

m00dy 10mo ago

Cursor CEO got grilled in HN for a good reason.

xcvxvdf 10mo ago

[dead]

deng 10mo ago

If you look at the original Cursor post, they say they are currently running similar experiments, for instance, this Excel clone: https://github.com/wilson-anysphere/formula https://github.com/wilson-anysphere/formula The Actions overview is impressive: There have been 160,469 workflow runs, of which 247 succeeded. The reason the workflows are failing is because they have exceeded their spending limit. Of course, the agents couldn't care less.

felipeerias 10mo ago
IMHO people are missing the forest for the trees. The point of this experiment is not to build a functional browser but to develop ways to make agents create large codebases from scratch over a very long time span. A Web browser is just a convenient target because there are lots of documentation, specs and tests available.
- noodletheworld 10mo ago
  ...but it didn't develop ways of doing that did it? Any idiot can have cursor run for 2 weeks and produce a pile of crap that doesn't compile. You know the brilliant insight they came out with? > A surprising amount of the system's behavior comes down to how we prompt the agents. Getting them to coordinate well, avoid pathological behaviors, and maintain focus over long periods required extensive experimentation. The harness and models matter, but the prompts matter more. i.e. It's kind of hard and we didn't really come up with a better solution than 'make sure you write good prompts'. Wellll, geeeeeeeee! Thanks for that insight guys! Come on. This was complete BS. Planners and workers. Cool. Details? Any details? Annnnnnnyyyyy way to replicate it? What sort of prompts did you use? How did you solve the pathalogical behaviours? Nope. The vagueness in this post... it's not an experiment. It's just fund raising hype.
  - chrisandchris 10mo ago
    IMHO, this whole thing could be read with "human" instread of "agent" and would make the exact same amount of sense. "We put 200 human in a room and gave them instructions how to build a browser. They coded for hours, resolving merge conflicts and producing code that did not build in the end without intervention of seniors []. We think, giving them better instructions leads to better results" So they actually invented humans? And will it come down to either "managing humans" or "managing agents"? One of both will be more reliable, more predictable and more convenient to work with. And my guess is, it is not an agent... As it seemed in the git log, something is weird.

Matthyze 10mo ago

Out of curiosity, what is the most difficult thing about building a browser?

MobiusHorizons 10mo ago
The very long task list. Browsers contain several high complexity pieces each of could take a while to build on its own, and interconnect them with reasonably verbose APIs that need to be implemented or at least stubbed out for code to not crash. There is also the difficulty of matching existing implementations quirk for quirk. I guess the complexity is on-par with operating systems, but with the added compatibility problems that in order to be useful it doesn't just have to load sites intended to be compatible with it, it has to handle sites people actually use on the internet, and those are both a moving target, and tend to use lots of high complexity features that you have to build or at least stub out before the site will even work.
deleted 10mo ago
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asadotzler 10mo ago
In all sincerity, this question is almost identical to "what's the most difficult thing about building an operating system" as a modern browser is tens of millions of lines of code that can run sophisticated applications. It has a network stack, half a dozen parsers, frame construction and reflow modules, composite, render and paint components, front end UI components, an extensibility framework, and more. Each one of these must enable supporting backward compatibility for 30 year old content as well as ridiculously complex contemporary web apps. And it has to load and render sites that a completely programming illiterate fool like me wrote. It must do this all in a performant and secure way using minimal system resources. Also, it probably also must run on Mac, Windows, Linux, Android, iOS, and maybe more.
potamic 10mo ago
Check out the list of all CSS specifications [1], and then open any one of them and see how lengthy and elaborate each is. Then do the same for each version of the spec published over the last thirty years. Before you can start, you must read and understand all of this at a great level of depth. Still, specifications never tell the complete story. You must be aware of all the nuances that are implied by each requirement in the spec and know how to handle the zillion corner cases that will crop up inevitably. And this is just one part. Not even considering the fully sandboxed, mini operating system for running webapps. [1] https://www.w3.org/Style/CSS/specs.en.html https://www.w3.org/Style/CSS/specs.en.html

deleted 10mo ago

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Pinus 10mo ago

I haven’t studied the project that this is a comment on, but: The article notices that something that compiles, runs, and renders a trivial HTML page might be a good starting point, and I would certainly agree with that when it’s humans writing the code. But is it the only way? Instead of maintaining “builds and runs” as a constant and varying what it does, can it make sense to have “a decent-sized subset of browser functionality” as a constant and varying the “builds and runs” bit? (Admittedly, that bit does not seem to be converging here, but I’m curious in more general terms.)

madeofpalk 10mo ago
...What use is code if it doesn't build and run? What other way is there to build a browser that doesn't involved 'build and run'? Writing junk in a text file isn't the hard part.
- Pinus 10mo ago
  Obviously, it has to eventually build and run if there’s to be any point to it, but is it necessary that every, or even any, step along the way builds and runs? I imagine some sort of iterative set-up where one component generates code, more or less "intelligently", and others check it against the C, HTML, JavaScript, CSS and what-have-you specs, and the whole thing iterates until all the checking components are happy. The components can’t be completely separate, of course, they’d have to be more or less intermingled or convergence would be very slow (like when lcamtuf had his fuzzer generate a JPEG out of an empty file), but isn’t that basically what (large) neural networks are; tangled messes of interconnected functions that do things in ways too complicated for anyone to bother figuring out?
  - malfist 10mo ago
    How do you iteratively improve a broken codebase that doesn't compile with more than 3 million lines of code?
    - brabel 10mo ago

thedelanyo 10mo ago

These are stories that solely exist just to sell shovels and would cause one uninformed CEO to layoff actual humans.

AIorNot 10mo ago

Lesson 1: Always take any pronouncement from an AI company (heavily dependent on VC and public sentiment on AI) with a heavy grain of salt.. hype over reality I’m building an AI startup myself and I know that world and its full of hypsters and hucksters unfortunately - also social media communication + low attention span + AI slop communication is a blight upon todays engineering culture

Snuggly73 10mo ago

The latest commit now builds and runs (at least on my Mac). It’s tragically broken and the code is…dunno…something. 3m lines of something. I couldn’t make it render the apple page that was on the Cursor promo. Maybe they’ve used some other build.

embedding-shape 10mo ago
Yeah, seems latest commit does let `cargo check` successfully run. I'm gonna write an update blog post once they've made their statement, because I'm guessing they're about to say something. Sometime fishy is happening in their `git log`, it doesn't seem like it was the agents who "autonomously" actually made things compile in the end. Notice the git username and email addresses switching around, even some commits made inside a EC2 instance managed to get in there: https://gist.github.com/embedding-shapes/d09225180ea3236f18039ca7a24b7ecb https://gist.github.com/embedding-shapes/d09225180ea3236f180...
- Snuggly73 10mo ago
  Noticed that as well - I think it was “manual”
torginus 10mo ago
I am not an expert AI user, but one typical 'failure mode' I see constantly is the AI reimplementing features that already exist in the codebase, or breaking existing ones.

lifetimerubyist 10mo ago

> company claims they "built a browser" from scratch > looks inside > completely useless and busted 30 billion dollar VS Code fork everyone. When we do start looking at these people for what they are: snake oil salesmen. They slop laundered the FOSS Servo code into a broken mess and called it a browser, but dumbasses with money will make line go up based on lies. EFF right off.

arresin 10mo ago
30. Billion. Dollars. Man
- lifetimerubyist 10mo ago
  It's absolutely absurd.
ben_w 10mo ago
When I tried it last year, the mac download of this particular VS Code fork was only available as an Intel build. This… was suggestive.
ravenstine 10mo ago
I recently was convinced by colleagues to try Cursor at work for project planning. At first I was excited for something even better than Copilot Chat, but then I quickly realized it's just a shitty VS Code fork with maybe a few improvements that are by no means a moat for that company. Worse yet, it makes lots of bizarre mistakes, deletes lines for no good reason, and sometimes even deletes the entire project plan. The scroll on the chat history gets laggy very quickly, and I've found the whole program to be glitchy as hell. The hype around Cursor is unreal. My suspicion is this company is little more than a parasite with no qualms about getting you to waste your tokens. It's one thing when a product is new, but Cursor has been around since 2023 I guess? The quality of their software is unacceptable.

pavlov 10mo ago

The comment that points out that this week-long experiment produced nothing more than a non-functional wrapper for Servo (an existing Rust browser) should be at the top: https://news.ycombinator.com/item?id=46649046 https://news.ycombinator.com/item?id=46649046

pera 10mo ago
Has anyone tried to rewrite some popular open source project with IA? I imagine modern LLMs can be very effective at license-washing/plagiarizing dependencies, it could be an interesting new benchmark too
- benhoyt 10mo ago
  Not me personally, but a GitHub user wrote a replacement for Go's regexp library that was "up to 3-3000x+ faster than stdlib": https://github.com/coregx/coregex https://github.com/coregx/coregex ... at first I was impressed, so started testing it and reporting bugs, but as soon as I ran my own benchmarks, it all fell apart (https://github.com/coregx/coregex/issues/29 https://github.com/coregx/coregex/issues/29). After some mostly-bot updates, that issue was closed. But someone else opened a very similar one recently (https://github.com/coregx/coregex/issues/79 https://github.com/coregx/coregex/issues/79) -- same deal, "actually, it's slower than the stdlib in my tests". Basically AI slop with poor tests, poor benchmarks, and way oversold. How he's positioning these projects is the problematic bit, I reckon, not the use of AI. Same user did a similar thing by creating an AWK interpreter written in Go using LLMs: https://github.com/kolkov/uawk https://github.com/kolkov/uawk -- as the creator of (I think?) the only AWK interpreter written in Go (https://github.com/benhoyt/goawk https://github.com/benhoyt/goawk), I was curious. It turns out that if there's only one item in the training data (GoAWK), AI likes to copy and paste freely from the original. But again, it's poorly tested and poorly benchmarked. I just don't see how one can get quality like this, without being realistic about code review, testing, and benchmarking.
  - CuriouslyC 10mo ago
    To be fair, good benchmarking is hard, most people get it wrong. Scientific training helps.

chaosprint 10mo ago

I really doubt this marketing approach is effective. Isn't this just shooting themselves in the foot? My actual experience with Cursor has been: their design is excellent and the UX is great—it handles frontend work reasonably well. But as soon as you go deeper, it becomes very prone to serious bugs. While the addition of Claude's new models has helped somewhat, the results are still not as good as Google's Antigravity (despite its poor UX and numerous bugs). What's worse, even with this much-hyped Claude model, you can easily blow through the $20 subscription limit in just a few days. Maybe they're betting on models becoming 10x better and 10x cheaper, but that seems unlikely to happen anytime soon.

bonesss 10mo ago
Hitting my head into buggy apps made by these AI companies and seeing them all be amazed in parallel that skills/MCP would be necessary for real work has me pretty relaxed about ‘our jobs’. OpenAIs business-model floundering, degenerating inline to ads soon (lol), shows what can be done with infini-LLM, infini-capital, and all the smarts & connections on Earth… broadly speaking, I think the geniuses at Google who invented a lot of this shizz understand it and were leveraging it appropriately before ChatGPT blew up.
- thewhitetulip 10mo ago
  We use mcp at work. Due to some typo the model ran absolutely random queries on our database most of the cases. We had initially kept ot open ended but after that, we wrote custom tools that took an input, gave an output and that was strictly mentioned in the prompt. Only then did it work fine.

ryanisnan 10mo ago

The amount of negativity in the original post was astounding. People were making all sorts of statements like: - “I cloned it and there were loads of compiler warnings” - “the commit build success rate was a joke” - “it used 3rd party libs” - “it is AI slop” What they all seem to be just glossing over is how the project unfolded: without human intervention, using computers, in an exceptionally accelerated time frame, working 24hr/day. If you are hung up on commit build quality, or code quality, you are completely missing the point, and I fear for your job prospects. These things will get better; they will get safer as the workflows get tuned; they will scale well beyond any of us. Don’t look at where the tech is. Look where it’s going.

embedding-shape 10mo ago
As mentioned elsewhere (I'm the author of this blogpost), I'm a heavy LLM user myself, use it everyday as a tool, get lots of benefits from it. It's not a "hit post" on using LLM tools for development, it's a post about Cursor making grand claims without being able to back them up. No one is hung up on the quality, but there is a ground fact if something "compiles" or "doesnt". No one is gonna claim a software project was successful if the end artifact doesn't compile.
- ryanisnan 10mo ago
  I think for the point of the article, it appeared to, at some point, render homepages for select well known sites. I certainly did not expect this to be a serious browser, with any reliability or legs. I don’t think that is dishonest.
  - embedding-shape 10mo ago
    > I certainly did not expect this to be a serious browser, with any reliability or legs. Me neither, and I note so twice in the submission article. But I also didn't expect a project that for the last 100+ commits couldn't reliably be built and therefore tested and tried out.

noosphr 10mo ago

If this is what makes the AI bubble pop I'll laugh so hard.

only-one1701 10mo ago
Wishful thinking. They’re trying to (and maybe successfully) doing a military-industrial complex style thing with AI.
- noosphr 10mo ago
  Probably, but this is one of the few cases where instead of being told how amazing some AI tool is we are shown just what it can do.

mikojan 10mo ago

Dear god please let AI get forever stuck at this point because it would be so funny

themafia 10mo ago
Just view the "input cost" vs "output accuracy" graph. It _is_ stuck at this point. There's so much money involved no one wants to admit it out loud. They have no path to the necessary exponential gains and no one is actually working on it.
- arresin 10mo ago
  The greatest grift of all time. I don’t mean the tech itself—-which is kind of useful. I mean the 99% of the value inflation of a kind of useful tool (if you know what you’re doing).
  - tyre 10mo ago
    AI is not a bigger grift than crypto. Crypto produced basically nothing of value. If all model improvement stops today, Opus 4.5 with Claude Code is a huge leap in productivity building certain types of software.
    - mirsadm 10mo ago
      I would disagree on the huge boost to productivity but it is a very useful tool.
- Kiro 10mo ago
  Hilarious thing to say when we've just had some of the biggest leaps ever with Gemini 3 and Opus 4.5.
- lifetimerubyist 10mo ago
  Just one more new model bro the next one is AGI bro just give me a trillion dollars and I’ll build the datacenters and everything will be perfect bro I promise bro please

ankit219 10mo ago

Like it or not, it's a fundraising strategy. They have followed it mutliple times (eg: vague posts about how much their inhouse model is writing code, online RL, and lines of code etc. earlier) and it was less vague before. They released a model and did not give us the exact benchmarks or even tell us the base model for the same. This is not to imply there is no substance behind it, but they are not as public about their findings as one would like them to be. Not a criticism, just an observation.

alfalfasprout 10mo ago
Unfortunately all the major LLM companies have realized the truth doesn't really matter anymore. We even saw this with the GPT-5 launch with obviously vibe coded + nebulous metrics. Diminishing returns are starting to really set in and companies are desperate for any illusion to the contrary.
themafia 10mo ago
I don't like it. It's lying in order to capture more market value than they're entitled to. The ends do not justify the means. This is a criticism.
- emp17344 10mo ago
  Basically, fraud. Low-level fraud, but still fraud.
  - csomar 10mo ago
    Low-level fraud? It’s used to raise billions that could have been used for other purposes.
  - nerdponx 10mo ago
    Fraud is just marketing in the 2020s now.
    - skciva 10mo ago

ironbound 10mo ago

Devin 2.0

heliumtera 10mo ago

Making it compile will considerably decrease productivity. PR number go up

logicallee 10mo ago

(this has been fixed)

embedding-shape 10mo ago
Thank you for telling me about the email, it had a typo :( Been fixed now. Regarding the downvotes, I think it's because it's feeling like you're pushing your project although it isn't really super relevant to the topic. The topic is specifically about Cursor failing to live up to their claims.

jonathanstrange 10mo ago

I think it's only a matter of time until this becomes reality. It's almost inevitable. My prediction last year was already that in the distant future - more than 10 years into the future - operating systems will create software on the fly. It will be a basic function of computers. However, there might remain a need for stable, deterministic software, the two human-machine interaction models can live together. There will be a need for software that does exactly what one wants in a dumb way and there will be a need for software that does complex things on the fly in an overall less reliable ad hoc way.

falkensmaize 10mo ago
We might cure cancer in 10 years. We could have Martian colonists in the next decade. Everyone might be commuting to work with a jet pack. Literally anything could happen, especially given a long enough time horizon.
- jonathanstrange 10mo ago
  You do realize that AI can already today write fairly complex software autonomously, don't you? It's not as if I haven't tested that. It works quite well for certain tasks and with certain programming languages. Anyone who knows history knows that people initially tend to underestimate the impact of technologies, yet few people learn something from that lesson.
  - falkensmaize 10mo ago
    What fairly complex software has it written autonomously for you?

ares623 10mo ago

Can’t help but draw parallels to how working with AI feels like. Your coworker opens a giant impressive looking PR and marks it ready for review. Meanwhile it’s up to someone else in the team to do the actual work of checking. Meanwhile the PR author gets patted on the back by management for being forward thinking and pro-active while everyone else is “nitpicky” and holding progress back.

callc 10mo ago
I’m dealing with similar issues. It’s reasonable to come up with team rules like: - “if the reviewer finds more than 5 issues the PR shall be rejected immediately for the submitter to rework” - “if the reviewer needs to take more than 8 hours to thoroughly review the PR it must be rejected and sent back to split up into manageable change sets” Etc etc. let’s not make externalizing work for others appropriate behavior.
- tyre 10mo ago
  Eight hours to review! Girlie how big are these PRs? I can’t imagine saying, “ah, only six hours of heads down time to review this. That’s reasonable.” A combination of peer reviewed architecture documentation and incremental PRs should prevent anything taking nearly 8 hours of review.
  - embedding-shape 10mo ago
    Agreed, if it takes 8 hours to review a PR, then the process is broken and you need to start talking before anyone starts writing code. I'd put the max window on maybe 30 minutes for a PR, otherwise we're doing something else, not a "last pass before merge into production".
thewhitetulip 10mo ago
Not to mention the fact that juniors can now put the entire problem statement in AI chatbot which spits out _some_ code. The said juniors then don't understand half the code and run the code and raise the PR. They don't get a pat on the back but this raises countless bugs later on. This is much worse as they don't develop skills on their own. They blindly copy from AI.

LegitShady 10mo ago

AI hype is just lying until you get caught

jadenpeterson 10mo ago

For my 11th or 12th birthday, I got a pet porcupine and I was ecstatic. It was my first pet, and I spent hours researching what they eat, what habitats they like, etc. I carefully curated my room to accommodate him (him being 'Sonic'), even keeping it clean for the first time in forever so I wouldn't lose him amidst the mess of soiled undergarments and such. He loved it, and I loved him. Of course, it made no difference when my uncle sat on him on Christmas morning. We rushed him to the vet, but they told us his scans showed fractures on several vertebrae or something like that. We took him home, and waited for him to die, but the waiting was too painful. I'll spare the details, but what transpired next involved my dad, his shovel, and a lot of tears. About an hour later, we got a call from the vet - they'd misread the scan, and Sonic was gonna be fine. I think I was traumatized at the time, but the whole thing later became an inside joke (?) for my family - "Don't kill your porcupine before the vet calls" (a la "Don't count your chickens before they hatch"). I guess my point, as it pertains to Cursor, its AI offerings, and other corporations in the space is that we shouldn't jump the gun before a reasonable framework exists to evaluate such open-ended technologies. Of course Cursor reported this as a success, the incentive structure demands they do so. So remember - don't kill your porcupine before the vet calls.

callc 10mo ago
Welcome to HN, thanks for sharing. That’s a very sad story, I hope you aren’t traumatized still. A reasonable framework does exist. Since the claim is “we made a web browser from scratch” the framework is: 1. Does it actually f*** work? 2. Is it actually from scratch? It fails on both counts. Further, even when compiled successfully, as others have pointed out, it takes more than a minute to load some pages which is a fail for #1.
- Shaanie 10mo ago
  If it loads pages, then it clearly works. Nobody claims it's a practical, competitive browser.
  - callc 10mo ago
    “I built a car from scratch” … “Nobody said it has brakes.” Taken at face value, everyone assumes when you say statement #1 that you are not speaking like a lawyer.

solid_fuel 10mo ago

This is par for the course with this AI slop. Most of the big claims about LLM productivity have completely lacked any backing evidence. Big claims require big evidence, but all I've seen so far is loud assertions and pathetic results.

callc 10mo ago
I’m happy that this shows that hard work, understanding your codebase, having performant software, having actually working software, rigorously measuring and proving proof of results still matters. There’s a huge difference between using LLMs to offload any hard work and for LLMs to be of some assistance while you are in control and take ownership of the output. Unfortunately, the general public probably didn’t try a git clone and cargo build, and took the article at face value.

sidgarimella 10mo ago

there’s a curve where something of a conservative middle in AI marketing stunts are held to a higher level of criticism than headlines on either side

wilsonzlin 10mo ago

Hey, Wilson here, author of the blog post and the engineer working on this project. I've been reading the responses here and appreciate the feedback. I've posted some follow up context on Twitter/X[0], which I'll also write here: The repo is a live incubator for the harness. We are actively researching the behavior of collaborative long running agents, and may in the future make the browser and other products this research produces more consumable by end users and developers, but it's not the goal for now. We made it public as we were excited by the early results and wanted to share; while far off from feature parity with the most popular production browsers today, we think it has made impressive progress in the last <1 week of wall time. Given the interest in trying out the current state of the project, I've merged a more up-to-date snapshot of the system's progress that resolves issues with builds and CI. The experimental harness can occasionally leave the repo in an incomplete state but does converge, which was the case at the time of the post. I'm here to answer any further questions you have. [0] https://x.com/wilsonzlin/status/2012398625394221537?s=20 https://x.com/wilsonzlin/status/2012398625394221537?s=20

eloisius 10mo ago
That doesn’t really address much of the criticism in this thread. No one is shocked that it’s not as good as production web browsers. It’s that it was billed as “from scratch” but upon deeper inspection it looks like it’s just gluing together Servo and some other dependencies, so it’s not really as impressive or interesting because the “agents” didn’t really create a browser engine.
- M4v3R 10mo ago
  Upon deeper inspection? Someone checked the Cargo file and proclaimed it was just Servo and QuickJS glued together without actually bothering to look if these dependencies are even being used. In reality while project does indeed have Servo in its dependencies it only uses it for HTML tokenization, CSS selector matching and some low level structures. Javascript parsing and execution, DOM implementation & Layout engine was written from scratch with only one exception - Flexbox and Grid layouts are implemented using Taffy - a Rust layout library. So while “from scratch” is debatable it is still immensely impressive to be that AI was able to produce something that even just “kinda works” at this scale.

devmor 10mo ago

I am just so utterly tired of AI companies lying about everything, constantly without end. The things that modern machine learning can do are absolutely incredible, mindblowing and have myriad uses. But this culture of startup scams to siphon money out of the economy and into the bank accounts of a few investment firms and a couple "visionaries" has just turned what should be an exciting field full of technical advancement into a deluge of mental sewage that's constantly pumped into our faces.

DeathArrow 10mo ago

So they prove that if you have enough money to burn you can use AI to generate terabytes of useless junk? Who would have thought of that?

nubskr 10mo ago

That's actually the state of autonomous coding in 2026, scale the output, skip the verification.

thewhitetulip 10mo ago
Also since firefox is FOSS and any model has reasonably been trained on the code base of at least Firefox if not also Chromium, it's not a shock that agents are able to generate a similar code!

motbus3 10mo ago

If it just forks chromium because it found it on the web it would also claim it made a browser from scratch. LLM does not know. It is not a person, it is a thing, just an algorithm

orourke 10mo ago

I feel that getting anywhere into the neighborhood of “kind of working” for a project like this is noteworthy and a huge milestone. Maybe a better headline would be, however: Agents almost create a working browser.

embedding-shape 10mo ago
Yes, if Cursor claimed "We let autonomous agents run for weeks, and they produced millions of lines of code, and it kind of looks like a browser, and it kind of runs", then I wouldn't have written and published TFA. But their claim wasn't so nuanced, it was "hundreds of agents can work on a single codebase autonomously for weeks and build an entire browser from scratch that works (kinda)". Considering the hand-holding that seems to have been required to get it to compile, this claim doesn't seem to hold up to scrutiny.
- Snuggly73 10mo ago
  I've watched them today work in the new repo - https://github.com/wilson-anysphere/fastrender/tree/main https://github.com/wilson-anysphere/fastrender/tree/main , adding another 50k lines trying to optimize scroll/rendering performance (spoiler: not really) At this point, its 1.5mlocs without the vendored crates (so basically excluding the js engine etc). If you compare that to Servo/Ladybird which are 300k locs each and actually happen to work, agents do love slinging slop.

elzbardico 10mo ago

I think that the companies that have the mindset "Let's give engineers tools that can leverage their strengths and eliminate toil" have way more success than those scammy "get-rich-fast let's automate software development and stop paying those sv salaries, invest in us!!!" gigs like Cursor and Devin. Their whole attitude leads to them wasting time with those Willy the Coyote Plans instead of building good products like Amp.

embedding-shape 10mo ago
Huge distinction between the two, one is about "Augmenting the human intellect" and the other is about "Get rich quick", but unfortunately it seems it's hard even for software developers to see which is which sometimes.

utopiah 10mo ago

That's kind of hilarious (...ly sad) to read knowing that I have on my desk https://browser.engineering https://browser.engineering so I literally went the opposite direction some months ago. Not only did I actually build a Web browser myself, from scratch (ok OK of course with a working OS and Python, and its libraries ;) but mine, did work! And it took me what, few hours, maybe few days if adding it altogether but, not only it did work (namely I did browse my own Website with it) but I had fun with it (!), I learned quite a bit with it (including the provable fact that I can indeed build a Web browser, woohoo!) and finally I did it on... I want say few kilowatts at most, including my computer (obviously) but also myself and the food I ate along the way. So... to each their own ̄\_ (ツ)_/ ̄

deleted 10mo ago

[deleted]

TechDebtDevin 10mo ago

[dead]

simonw 10mo ago

They fixed FastRender so that CI passes and added build instructions to the README. I've tried it and it works surprisingly well - screenshots here: https://gist.github.com/simonw/53a725811db8e34f4f99226e8f45682b https://gist.github.com/simonw/53a725811db8e34f4f99226e8f456...

izucken 10mo ago

You people clearly don't understand how important lines of code are. Three millions is a lot of lines of code even if its broken, and you can't even appreciate that number. Clearly you are weak software developers who write very little lines of code, and can't even steal other's lines of code to keep up. I am very glad we are back to reporting results in lines of code which is a very informative metric hence now I can get my many lines of code appreciated.